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| author |   hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 03:10:21 -0500 |
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| committer | hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 03:10:21 -0500 |
| commit | c0b7206652b2852bc574694e7ba07ba1c2acdc00 (patch) | |
| tree | 5cb95cb0e19e03610525903df46279df2c3b7eb1 /rubbos/app/httpd-2.0.64/srclib/pcre/doc | |
| parent | b6d3d6e668b793220f2d3af1bc3e828553dc3fe6 (diff) | |
delete app
Change-Id: Id4c572809969ebe89e946e88063eaed262cff3f2
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
Diffstat (limited to 'rubbos/app/httpd-2.0.64/srclib/pcre/doc')
17 files changed, 0 insertions, 9302 deletions
diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/Tech.Notes b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/Tech.Notes deleted file mode 100644 index f5ca2801..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/Tech.Notes +++ /dev/null @@ -1,253 +0,0 @@ -Technical Notes about PCRE --------------------------- - -Many years ago I implemented some regular expression functions to an algorithm -suggested by Martin Richards. These were not Unix-like in form, and were quite -restricted in what they could do by comparison with Perl. The interesting part -about the algorithm was that the amount of space required to hold the compiled -form of an expression was known in advance. The code to apply an expression did -not operate by backtracking, as the Henry Spencer and Perl code does, but -instead checked all possibilities simultaneously by keeping a list of current -states and checking all of them as it advanced through the subject string. (In -the terminology of Jeffrey Friedl's book, it was a "DFA algorithm".) When the -pattern was all used up, all remaining states were possible matches, and the -one matching the longest subset of the subject string was chosen. This did not -necessarily maximize the individual wild portions of the pattern, as is -expected in Unix and Perl-style regular expressions. - -By contrast, the code originally written by Henry Spencer and subsequently -heavily modified for Perl actually compiles the expression twice: once in a -dummy mode in order to find out how much store will be needed, and then for -real. The execution function operates by backtracking and maximizing (or, -optionally, minimizing in Perl) the amount of the subject that matches -individual wild portions of the pattern. This is an "NFA algorithm" in Friedl's -terminology. - -For the set of functions that forms PCRE (which are unrelated to those -mentioned above), I tried at first to invent an algorithm that used an amount -of store bounded by a multiple of the number of characters in the pattern, to -save on compiling time. However, because of the greater complexity in Perl -regular expressions, I couldn't do this. In any case, a first pass through the -pattern is needed, in order to find internal flag settings like (?i) at top -level. So PCRE works by running a very degenerate first pass to calculate a -maximum store size, and then a second pass to do the real compile - which may -use a bit less than the predicted amount of store. The idea is that this is -going to turn out faster because the first pass is degenerate and the second -pass can just store stuff straight into the vector. It does make the compiling -functions bigger, of course, but they have got quite big anyway to handle all -the Perl stuff. - -The compiled form of a pattern is a vector of bytes, containing items of -variable length. The first byte in an item is an opcode, and the length of the -item is either implicit in the opcode or contained in the data bytes which -follow it. A list of all the opcodes follows: - -Opcodes with no following data ------------------------------- - -These items are all just one byte long - - OP_END end of pattern - OP_ANY match any character - OP_SOD match start of data: \A - OP_CIRC ^ (start of data, or after \n in multiline) - OP_NOT_WORD_BOUNDARY \W - OP_WORD_BOUNDARY \w - OP_NOT_DIGIT \D - OP_DIGIT \d - OP_NOT_WHITESPACE \S - OP_WHITESPACE \s - OP_NOT_WORDCHAR \W - OP_WORDCHAR \w - OP_EODN match end of data or \n at end: \Z - OP_EOD match end of data: \z - OP_DOLL $ (end of data, or before \n in multiline) - OP_RECURSE match the pattern recursively - - -Repeating single characters ---------------------------- - -The common repeats (*, +, ?) when applied to a single character appear as -two-byte items using the following opcodes: - - OP_STAR - OP_MINSTAR - OP_PLUS - OP_MINPLUS - OP_QUERY - OP_MINQUERY - -Those with "MIN" in their name are the minimizing versions. Each is followed by -the character that is to be repeated. Other repeats make use of - - OP_UPTO - OP_MINUPTO - OP_EXACT - -which are followed by a two-byte count (most significant first) and the -repeated character. OP_UPTO matches from 0 to the given number. A repeat with a -non-zero minimum and a fixed maximum is coded as an OP_EXACT followed by an -OP_UPTO (or OP_MINUPTO). - - -Repeating character types -------------------------- - -Repeats of things like \d are done exactly as for single characters, except -that instead of a character, the opcode for the type is stored in the data -byte. The opcodes are: - - OP_TYPESTAR - OP_TYPEMINSTAR - OP_TYPEPLUS - OP_TYPEMINPLUS - OP_TYPEQUERY - OP_TYPEMINQUERY - OP_TYPEUPTO - OP_TYPEMINUPTO - OP_TYPEEXACT - - -Matching a character string ---------------------------- - -The OP_CHARS opcode is followed by a one-byte count and then that number of -characters. If there are more than 255 characters in sequence, successive -instances of OP_CHARS are used. - - -Character classes ------------------ - -OP_CLASS is used for a character class, provided there are at least two -characters in the class. If there is only one character, OP_CHARS is used for a -positive class, and OP_NOT for a negative one (that is, for something like -[^a]). Another set of repeating opcodes (OP_NOTSTAR etc.) are used for a -repeated, negated, single-character class. The normal ones (OP_STAR etc.) are -used for a repeated positive single-character class. - -OP_CLASS is followed by a 32-byte bit map containing a 1 bit for every -character that is acceptable. The bits are counted from the least significant -end of each byte. - - -Back references ---------------- - -OP_REF is followed by two bytes containing the reference number. - - -Repeating character classes and back references ------------------------------------------------ - -Single-character classes are handled specially (see above). This applies to -OP_CLASS and OP_REF. In both cases, the repeat information follows the base -item. The matching code looks at the following opcode to see if it is one of - - OP_CRSTAR - OP_CRMINSTAR - OP_CRPLUS - OP_CRMINPLUS - OP_CRQUERY - OP_CRMINQUERY - OP_CRRANGE - OP_CRMINRANGE - -All but the last two are just single-byte items. The others are followed by -four bytes of data, comprising the minimum and maximum repeat counts. - - -Brackets and alternation ------------------------- - -A pair of non-capturing (round) brackets is wrapped round each expression at -compile time, so alternation always happens in the context of brackets. - -Non-capturing brackets use the opcode OP_BRA, while capturing brackets use -OP_BRA+1, OP_BRA+2, etc. [Note for North Americans: "bracket" to some English -speakers, including myself, can be round, square, curly, or pointy. Hence this -usage.] - -Originally PCRE was limited to 99 capturing brackets (so as not to use up all -the opcodes). From release 3.5, there is no limit. What happens is that the -first ones, up to EXTRACT_BASIC_MAX are handled with separate opcodes, as -above. If there are more, the opcode is set to EXTRACT_BASIC_MAX+1, and the -first operation in the bracket is OP_BRANUMBER, followed by a 2-byte bracket -number. This opcode is ignored while matching, but is fished out when handling -the bracket itself. (They could have all been done like this, but I was making -minimal changes.) - -A bracket opcode is followed by two bytes which give the offset to the next -alternative OP_ALT or, if there aren't any branches, to the matching KET -opcode. Each OP_ALT is followed by two bytes giving the offset to the next one, -or to the KET opcode. - -OP_KET is used for subpatterns that do not repeat indefinitely, while -OP_KETRMIN and OP_KETRMAX are used for indefinite repetitions, minimally or -maximally respectively. All three are followed by two bytes giving (as a -positive number) the offset back to the matching BRA opcode. - -If a subpattern is quantified such that it is permitted to match zero times, it -is preceded by one of OP_BRAZERO or OP_BRAMINZERO. These are single-byte -opcodes which tell the matcher that skipping this subpattern entirely is a -valid branch. - -A subpattern with an indefinite maximum repetition is replicated in the -compiled data its minimum number of times (or once with a BRAZERO if the -minimum is zero), with the final copy terminating with a KETRMIN or KETRMAX as -appropriate. - -A subpattern with a bounded maximum repetition is replicated in a nested -fashion up to the maximum number of times, with BRAZERO or BRAMINZERO before -each replication after the minimum, so that, for example, (abc){2,5} is -compiled as (abc)(abc)((abc)((abc)(abc)?)?)?. The 99 and 200 bracket limits do -not apply to these internally generated brackets. - - -Assertions ----------- - -Forward assertions are just like other subpatterns, but starting with one of -the opcodes OP_ASSERT or OP_ASSERT_NOT. Backward assertions use the opcodes -OP_ASSERTBACK and OP_ASSERTBACK_NOT, and the first opcode inside the assertion -is OP_REVERSE, followed by a two byte count of the number of characters to move -back the pointer in the subject string. When operating in UTF-8 mode, the count -is a character count rather than a byte count. A separate count is present in -each alternative of a lookbehind assertion, allowing them to have different -fixed lengths. - - -Once-only subpatterns ---------------------- - -These are also just like other subpatterns, but they start with the opcode -OP_ONCE. - - -Conditional subpatterns ------------------------ - -These are like other subpatterns, but they start with the opcode OP_COND. If -the condition is a back reference, this is stored at the start of the -subpattern using the opcode OP_CREF followed by two bytes containing the -reference number. Otherwise, a conditional subpattern will always start with -one of the assertions. - - -Changing options ----------------- - -If any of the /i, /m, or /s options are changed within a parenthesized group, -an OP_OPT opcode is compiled, followed by one byte containing the new settings -of these flags. If there are several alternatives in a group, there is an -occurrence of OP_OPT at the start of all those following the first options -change, to set appropriate options for the start of the alternative. -Immediately after the end of the group there is another such item to reset the -flags to their previous values. Other changes of flag within the pattern can be -handled entirely at compile time, and so do not cause anything to be put into -the compiled data. - - -Philip Hazel -August 2001 diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.3 b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.3 deleted file mode 100644 index 738f76b4..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.3 +++ /dev/null @@ -1,1991 +0,0 @@ -.TH PCRE 3 -.SH NAME -pcre - Perl-compatible regular expressions. -.SH SYNOPSIS -.B #include <pcre.h> -.PP -.SM -.br -.B pcre *pcre_compile(const char *\fIpattern\fR, int \fIoptions\fR, -.ti +5n -.B const char **\fIerrptr\fR, int *\fIerroffset\fR, -.ti +5n -.B const unsigned char *\fItableptr\fR); -.PP -.br -.B pcre_extra *pcre_study(const pcre *\fIcode\fR, int \fIoptions\fR, -.ti +5n -.B const char **\fIerrptr\fR); -.PP -.br -.B int pcre_exec(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR," -.ti +5n -.B "const char *\fIsubject\fR," int \fIlength\fR, int \fIstartoffset\fR, -.ti +5n -.B int \fIoptions\fR, int *\fIovector\fR, int \fIovecsize\fR); -.PP -.br -.B int pcre_copy_substring(const char *\fIsubject\fR, int *\fIovector\fR, -.ti +5n -.B int \fIstringcount\fR, int \fIstringnumber\fR, char *\fIbuffer\fR, -.ti +5n -.B int \fIbuffersize\fR); -.PP -.br -.B int pcre_get_substring(const char *\fIsubject\fR, int *\fIovector\fR, -.ti +5n -.B int \fIstringcount\fR, int \fIstringnumber\fR, -.ti +5n -.B const char **\fIstringptr\fR); -.PP -.br -.B int pcre_get_substring_list(const char *\fIsubject\fR, -.ti +5n -.B int *\fIovector\fR, int \fIstringcount\fR, "const char ***\fIlistptr\fR);" -.PP -.br -.B void pcre_free_substring(const char *\fIstringptr\fR); -.PP -.br -.B void pcre_free_substring_list(const char **\fIstringptr\fR); -.PP -.br -.B const unsigned char *pcre_maketables(void); -.PP -.br -.B int pcre_fullinfo(const pcre *\fIcode\fR, "const pcre_extra *\fIextra\fR," -.ti +5n -.B int \fIwhat\fR, void *\fIwhere\fR); -.PP -.br -.B int pcre_info(const pcre *\fIcode\fR, int *\fIoptptr\fR, int -.B *\fIfirstcharptr\fR); -.PP -.br -.B char *pcre_version(void); -.PP -.br -.B void *(*pcre_malloc)(size_t); -.PP -.br -.B void (*pcre_free)(void *); - - - -.SH DESCRIPTION -The PCRE library is a set of functions that implement regular expression -pattern matching using the same syntax and semantics as Perl 5, with just a few -differences (see below). The current implementation corresponds to Perl 5.005, -with some additional features from later versions. This includes some -experimental, incomplete support for UTF-8 encoded strings. Details of exactly -what is and what is not supported are given below. - -PCRE has its own native API, which is described in this document. There is also -a set of wrapper functions that correspond to the POSIX regular expression API. -These are described in the \fBpcreposix\fR documentation. - -The native API function prototypes are defined in the header file \fBpcre.h\fR, -and on Unix systems the library itself is called \fBlibpcre.a\fR, so can be -accessed by adding \fB-lpcre\fR to the command for linking an application which -calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to -contain the major and minor release numbers for the library. Applications can -use these to include support for different releases. - -The functions \fBpcre_compile()\fR, \fBpcre_study()\fR, and \fBpcre_exec()\fR -are used for compiling and matching regular expressions. A sample program that -demonstrates the simplest way of using them is given in the file -\fIpcredemo.c\fR. The last section of this man page describes how to run it. - -The functions \fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and -\fBpcre_get_substring_list()\fR are convenience functions for extracting -captured substrings from a matched subject string; \fBpcre_free_substring()\fR -and \fBpcre_free_substring_list()\fR are also provided, to free the memory used -for extracted strings. - -The function \fBpcre_maketables()\fR is used (optionally) to build a set of -character tables in the current locale for passing to \fBpcre_compile()\fR. - -The function \fBpcre_fullinfo()\fR is used to find out information about a -compiled pattern; \fBpcre_info()\fR is an obsolete version which returns only -some of the available information, but is retained for backwards compatibility. -The function \fBpcre_version()\fR returns a pointer to a string containing the -version of PCRE and its date of release. - -The global variables \fBpcre_malloc\fR and \fBpcre_free\fR initially contain -the entry points of the standard \fBmalloc()\fR and \fBfree()\fR functions -respectively. PCRE calls the memory management functions via these variables, -so a calling program can replace them if it wishes to intercept the calls. This -should be done before calling any PCRE functions. - - -.SH MULTI-THREADING -The PCRE functions can be used in multi-threading applications, with the -proviso that the memory management functions pointed to by \fBpcre_malloc\fR -and \fBpcre_free\fR are shared by all threads. - -The compiled form of a regular expression is not altered during matching, so -the same compiled pattern can safely be used by several threads at once. - - -.SH COMPILING A PATTERN -The function \fBpcre_compile()\fR is called to compile a pattern into an -internal form. The pattern is a C string terminated by a binary zero, and -is passed in the argument \fIpattern\fR. A pointer to a single block of memory -that is obtained via \fBpcre_malloc\fR is returned. This contains the compiled -code and related data. The \fBpcre\fR type is defined for the returned block; -this is a typedef for a structure whose contents are not externally defined. It -is up to the caller to free the memory when it is no longer required. - -Although the compiled code of a PCRE regex is relocatable, that is, it does not -depend on memory location, the complete \fBpcre\fR data block is not -fully relocatable, because it contains a copy of the \fItableptr\fR argument, -which is an address (see below). - -The size of a compiled pattern is roughly proportional to the length of the -pattern string, except that each character class (other than those containing -just a single character, negated or not) requires 33 bytes, and repeat -quantifiers with a minimum greater than one or a bounded maximum cause the -relevant portions of the compiled pattern to be replicated. - -The \fIoptions\fR argument contains independent bits that affect the -compilation. It should be zero if no options are required. Some of the options, -in particular, those that are compatible with Perl, can also be set and unset -from within the pattern (see the detailed description of regular expressions -below). For these options, the contents of the \fIoptions\fR argument specifies -their initial settings at the start of compilation and execution. The -PCRE_ANCHORED option can be set at the time of matching as well as at compile -time. - -If \fIerrptr\fR is NULL, \fBpcre_compile()\fR returns NULL immediately. -Otherwise, if compilation of a pattern fails, \fBpcre_compile()\fR returns -NULL, and sets the variable pointed to by \fIerrptr\fR to point to a textual -error message. The offset from the start of the pattern to the character where -the error was discovered is placed in the variable pointed to by -\fIerroffset\fR, which must not be NULL. If it is, an immediate error is given. - -If the final argument, \fItableptr\fR, is NULL, PCRE uses a default set of -character tables which are built when it is compiled, using the default C -locale. Otherwise, \fItableptr\fR must be the result of a call to -\fBpcre_maketables()\fR. See the section on locale support below. - -This code fragment shows a typical straightforward call to \fBpcre_compile()\fR: - - pcre *re; - const char *error; - int erroffset; - re = pcre_compile( - "^A.*Z", /* the pattern */ - 0, /* default options */ - &error, /* for error message */ - &erroffset, /* for error offset */ - NULL); /* use default character tables */ - -The following option bits are defined in the header file: - - PCRE_ANCHORED - -If this bit is set, the pattern is forced to be "anchored", that is, it is -constrained to match only at the start of the string which is being searched -(the "subject string"). This effect can also be achieved by appropriate -constructs in the pattern itself, which is the only way to do it in Perl. - - PCRE_CASELESS - -If this bit is set, letters in the pattern match both upper and lower case -letters. It is equivalent to Perl's /i option. - - PCRE_DOLLAR_ENDONLY - -If this bit is set, a dollar metacharacter in the pattern matches only at the -end of the subject string. Without this option, a dollar also matches -immediately before the final character if it is a newline (but not before any -other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is -set. There is no equivalent to this option in Perl. - - PCRE_DOTALL - -If this bit is set, a dot metacharater in the pattern matches all characters, -including newlines. Without it, newlines are excluded. This option is -equivalent to Perl's /s option. A negative class such as [^a] always matches a -newline character, independent of the setting of this option. - - PCRE_EXTENDED - -If this bit is set, whitespace data characters in the pattern are totally -ignored except when escaped or inside a character class, and characters between -an unescaped # outside a character class and the next newline character, -inclusive, are also ignored. This is equivalent to Perl's /x option, and makes -it possible to include comments inside complicated patterns. Note, however, -that this applies only to data characters. Whitespace characters may never -appear within special character sequences in a pattern, for example within the -sequence (?( which introduces a conditional subpattern. - - PCRE_EXTRA - -This option was invented in order to turn on additional functionality of PCRE -that is incompatible with Perl, but it is currently of very little use. When -set, any backslash in a pattern that is followed by a letter that has no -special meaning causes an error, thus reserving these combinations for future -expansion. By default, as in Perl, a backslash followed by a letter with no -special meaning is treated as a literal. There are at present no other features -controlled by this option. It can also be set by a (?X) option setting within a -pattern. - - PCRE_MULTILINE - -By default, PCRE treats the subject string as consisting of a single "line" of -characters (even if it actually contains several newlines). The "start of line" -metacharacter (^) matches only at the start of the string, while the "end of -line" metacharacter ($) matches only at the end of the string, or before a -terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as -Perl. - -When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs -match immediately following or immediately before any newline in the subject -string, respectively, as well as at the very start and end. This is equivalent -to Perl's /m option. If there are no "\\n" characters in a subject string, or -no occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no -effect. - - PCRE_UNGREEDY - -This option inverts the "greediness" of the quantifiers so that they are not -greedy by default, but become greedy if followed by "?". It is not compatible -with Perl. It can also be set by a (?U) option setting within the pattern. - - PCRE_UTF8 - -This option causes PCRE to regard both the pattern and the subject as strings -of UTF-8 characters instead of just byte strings. However, it is available only -if PCRE has been built to include UTF-8 support. If not, the use of this option -provokes an error. Support for UTF-8 is new, experimental, and incomplete. -Details of exactly what it entails are given below. - - -.SH STUDYING A PATTERN -When a pattern is going to be used several times, it is worth spending more -time analyzing it in order to speed up the time taken for matching. The -function \fBpcre_study()\fR takes a pointer to a compiled pattern as its first -argument, and returns a pointer to a \fBpcre_extra\fR block (another typedef -for a structure with hidden contents) containing additional information about -the pattern; this can be passed to \fBpcre_exec()\fR. If no additional -information is available, NULL is returned. - -The second argument contains option bits. At present, no options are defined -for \fBpcre_study()\fR, and this argument should always be zero. - -The third argument for \fBpcre_study()\fR is a pointer to an error message. If -studying succeeds (even if no data is returned), the variable it points to is -set to NULL. Otherwise it points to a textual error message. - -This is a typical call to \fBpcre_study\fR(): - - pcre_extra *pe; - pe = pcre_study( - re, /* result of pcre_compile() */ - 0, /* no options exist */ - &error); /* set to NULL or points to a message */ - -At present, studying a pattern is useful only for non-anchored patterns that do -not have a single fixed starting character. A bitmap of possible starting -characters is created. - - -.SH LOCALE SUPPORT -PCRE handles caseless matching, and determines whether characters are letters, -digits, or whatever, by reference to a set of tables. The library contains a -default set of tables which is created in the default C locale when PCRE is -compiled. This is used when the final argument of \fBpcre_compile()\fR is NULL, -and is sufficient for many applications. - -An alternative set of tables can, however, be supplied. Such tables are built -by calling the \fBpcre_maketables()\fR function, which has no arguments, in the -relevant locale. The result can then be passed to \fBpcre_compile()\fR as often -as necessary. For example, to build and use tables that are appropriate for the -French locale (where accented characters with codes greater than 128 are -treated as letters), the following code could be used: - - setlocale(LC_CTYPE, "fr"); - tables = pcre_maketables(); - re = pcre_compile(..., tables); - -The tables are built in memory that is obtained via \fBpcre_malloc\fR. The -pointer that is passed to \fBpcre_compile\fR is saved with the compiled -pattern, and the same tables are used via this pointer by \fBpcre_study()\fR -and \fBpcre_exec()\fR. Thus for any single pattern, compilation, studying and -matching all happen in the same locale, but different patterns can be compiled -in different locales. It is the caller's responsibility to ensure that the -memory containing the tables remains available for as long as it is needed. - - -.SH INFORMATION ABOUT A PATTERN -The \fBpcre_fullinfo()\fR function returns information about a compiled -pattern. It replaces the obsolete \fBpcre_info()\fR function, which is -nevertheless retained for backwards compability (and is documented below). - -The first argument for \fBpcre_fullinfo()\fR is a pointer to the compiled -pattern. The second argument is the result of \fBpcre_study()\fR, or NULL if -the pattern was not studied. The third argument specifies which piece of -information is required, while the fourth argument is a pointer to a variable -to receive the data. The yield of the function is zero for success, or one of -the following negative numbers: - - PCRE_ERROR_NULL the argument \fIcode\fR was NULL - the argument \fIwhere\fR was NULL - PCRE_ERROR_BADMAGIC the "magic number" was not found - PCRE_ERROR_BADOPTION the value of \fIwhat\fR was invalid - -Here is a typical call of \fBpcre_fullinfo()\fR, to obtain the length of the -compiled pattern: - - int rc; - unsigned long int length; - rc = pcre_fullinfo( - re, /* result of pcre_compile() */ - pe, /* result of pcre_study(), or NULL */ - PCRE_INFO_SIZE, /* what is required */ - &length); /* where to put the data */ - -The possible values for the third argument are defined in \fBpcre.h\fR, and are -as follows: - - PCRE_INFO_OPTIONS - -Return a copy of the options with which the pattern was compiled. The fourth -argument should point to an \fBunsigned long int\fR variable. These option bits -are those specified in the call to \fBpcre_compile()\fR, modified by any -top-level option settings within the pattern itself, and with the PCRE_ANCHORED -bit forcibly set if the form of the pattern implies that it can match only at -the start of a subject string. - - PCRE_INFO_SIZE - -Return the size of the compiled pattern, that is, the value that was passed as -the argument to \fBpcre_malloc()\fR when PCRE was getting memory in which to -place the compiled data. The fourth argument should point to a \fBsize_t\fR -variable. - - PCRE_INFO_CAPTURECOUNT - -Return the number of capturing subpatterns in the pattern. The fourth argument -should point to an \fbint\fR variable. - - PCRE_INFO_BACKREFMAX - -Return the number of the highest back reference in the pattern. The fourth -argument should point to an \fBint\fR variable. Zero is returned if there are -no back references. - - PCRE_INFO_FIRSTCHAR - -Return information about the first character of any matched string, for a -non-anchored pattern. If there is a fixed first character, e.g. from a pattern -such as (cat|cow|coyote), it is returned in the integer pointed to by -\fIwhere\fR. Otherwise, if either - -(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch -starts with "^", or - -(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set -(if it were set, the pattern would be anchored), - --1 is returned, indicating that the pattern matches only at the start of a -subject string or after any "\\n" within the string. Otherwise -2 is returned. -For anchored patterns, -2 is returned. - - PCRE_INFO_FIRSTTABLE - -If the pattern was studied, and this resulted in the construction of a 256-bit -table indicating a fixed set of characters for the first character in any -matching string, a pointer to the table is returned. Otherwise NULL is -returned. The fourth argument should point to an \fBunsigned char *\fR -variable. - - PCRE_INFO_LASTLITERAL - -For a non-anchored pattern, return the value of the rightmost literal character -which must exist in any matched string, other than at its start. The fourth -argument should point to an \fBint\fR variable. If there is no such character, -or if the pattern is anchored, -1 is returned. For example, for the pattern -/a\\d+z\\d+/ the returned value is 'z'. - -The \fBpcre_info()\fR function is now obsolete because its interface is too -restrictive to return all the available data about a compiled pattern. New -programs should use \fBpcre_fullinfo()\fR instead. The yield of -\fBpcre_info()\fR is the number of capturing subpatterns, or one of the -following negative numbers: - - PCRE_ERROR_NULL the argument \fIcode\fR was NULL - PCRE_ERROR_BADMAGIC the "magic number" was not found - -If the \fIoptptr\fR argument is not NULL, a copy of the options with which the -pattern was compiled is placed in the integer it points to (see -PCRE_INFO_OPTIONS above). - -If the pattern is not anchored and the \fIfirstcharptr\fR argument is not NULL, -it is used to pass back information about the first character of any matched -string (see PCRE_INFO_FIRSTCHAR above). - - -.SH MATCHING A PATTERN -The function \fBpcre_exec()\fR is called to match a subject string against a -pre-compiled pattern, which is passed in the \fIcode\fR argument. If the -pattern has been studied, the result of the study should be passed in the -\fIextra\fR argument. Otherwise this must be NULL. - -Here is an example of a simple call to \fBpcre_exec()\fR: - - int rc; - int ovector[30]; - rc = pcre_exec( - re, /* result of pcre_compile() */ - NULL, /* we didn't study the pattern */ - "some string", /* the subject string */ - 11, /* the length of the subject string */ - 0, /* start at offset 0 in the subject */ - 0, /* default options */ - ovector, /* vector for substring information */ - 30); /* number of elements in the vector */ - -The PCRE_ANCHORED option can be passed in the \fIoptions\fR argument, whose -unused bits must be zero. However, if a pattern was compiled with -PCRE_ANCHORED, or turned out to be anchored by virtue of its contents, it -cannot be made unachored at matching time. - -There are also three further options that can be set only at matching time: - - PCRE_NOTBOL - -The first character of the string is not the beginning of a line, so the -circumflex metacharacter should not match before it. Setting this without -PCRE_MULTILINE (at compile time) causes circumflex never to match. - - PCRE_NOTEOL - -The end of the string is not the end of a line, so the dollar metacharacter -should not match it nor (except in multiline mode) a newline immediately before -it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never -to match. - - PCRE_NOTEMPTY - -An empty string is not considered to be a valid match if this option is set. If -there are alternatives in the pattern, they are tried. If all the alternatives -match the empty string, the entire match fails. For example, if the pattern - - a?b? - -is applied to a string not beginning with "a" or "b", it matches the empty -string at the start of the subject. With PCRE_NOTEMPTY set, this match is not -valid, so PCRE searches further into the string for occurrences of "a" or "b". - -Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case -of a pattern match of the empty string within its \fBsplit()\fR function, and -when using the /g modifier. It is possible to emulate Perl's behaviour after -matching a null string by first trying the match again at the same offset with -PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see -below) and trying an ordinary match again. - -The subject string is passed as a pointer in \fIsubject\fR, a length in -\fIlength\fR, and a starting offset in \fIstartoffset\fR. Unlike the pattern -string, the subject may contain binary zero characters. When the starting -offset is zero, the search for a match starts at the beginning of the subject, -and this is by far the most common case. - -A non-zero starting offset is useful when searching for another match in the -same subject by calling \fBpcre_exec()\fR again after a previous success. -Setting \fIstartoffset\fR differs from just passing over a shortened string and -setting PCRE_NOTBOL in the case of a pattern that begins with any kind of -lookbehind. For example, consider the pattern - - \\Biss\\B - -which finds occurrences of "iss" in the middle of words. (\\B matches only if -the current position in the subject is not a word boundary.) When applied to -the string "Mississipi" the first call to \fBpcre_exec()\fR finds the first -occurrence. If \fBpcre_exec()\fR is called again with just the remainder of the -subject, namely "issipi", it does not match, because \\B is always false at the -start of the subject, which is deemed to be a word boundary. However, if -\fBpcre_exec()\fR is passed the entire string again, but with \fIstartoffset\fR -set to 4, it finds the second occurrence of "iss" because it is able to look -behind the starting point to discover that it is preceded by a letter. - -If a non-zero starting offset is passed when the pattern is anchored, one -attempt to match at the given offset is tried. This can only succeed if the -pattern does not require the match to be at the start of the subject. - -In general, a pattern matches a certain portion of the subject, and in -addition, further substrings from the subject may be picked out by parts of the -pattern. Following the usage in Jeffrey Friedl's book, this is called -"capturing" in what follows, and the phrase "capturing subpattern" is used for -a fragment of a pattern that picks out a substring. PCRE supports several other -kinds of parenthesized subpattern that do not cause substrings to be captured. - -Captured substrings are returned to the caller via a vector of integer offsets -whose address is passed in \fIovector\fR. The number of elements in the vector -is passed in \fIovecsize\fR. The first two-thirds of the vector is used to pass -back captured substrings, each substring using a pair of integers. The -remaining third of the vector is used as workspace by \fBpcre_exec()\fR while -matching capturing subpatterns, and is not available for passing back -information. The length passed in \fIovecsize\fR should always be a multiple of -three. If it is not, it is rounded down. - -When a match has been successful, information about captured substrings is -returned in pairs of integers, starting at the beginning of \fIovector\fR, and -continuing up to two-thirds of its length at the most. The first element of a -pair is set to the offset of the first character in a substring, and the second -is set to the offset of the first character after the end of a substring. The -first pair, \fIovector[0]\fR and \fIovector[1]\fR, identify the portion of the -subject string matched by the entire pattern. The next pair is used for the -first capturing subpattern, and so on. The value returned by \fBpcre_exec()\fR -is the number of pairs that have been set. If there are no capturing -subpatterns, the return value from a successful match is 1, indicating that -just the first pair of offsets has been set. - -Some convenience functions are provided for extracting the captured substrings -as separate strings. These are described in the following section. - -It is possible for an capturing subpattern number \fIn+1\fR to match some -part of the subject when subpattern \fIn\fR has not been used at all. For -example, if the string "abc" is matched against the pattern (a|(z))(bc) -subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset -values corresponding to the unused subpattern are set to -1. - -If a capturing subpattern is matched repeatedly, it is the last portion of the -string that it matched that gets returned. - -If the vector is too small to hold all the captured substrings, it is used as -far as possible (up to two-thirds of its length), and the function returns a -value of zero. In particular, if the substring offsets are not of interest, -\fBpcre_exec()\fR may be called with \fIovector\fR passed as NULL and -\fIovecsize\fR as zero. However, if the pattern contains back references and -the \fIovector\fR isn't big enough to remember the related substrings, PCRE has -to get additional memory for use during matching. Thus it is usually advisable -to supply an \fIovector\fR. - -Note that \fBpcre_info()\fR can be used to find out how many capturing -subpatterns there are in a compiled pattern. The smallest size for -\fIovector\fR that will allow for \fIn\fR captured substrings in addition to -the offsets of the substring matched by the whole pattern is (\fIn\fR+1)*3. - -If \fBpcre_exec()\fR fails, it returns a negative number. The following are -defined in the header file: - - PCRE_ERROR_NOMATCH (-1) - -The subject string did not match the pattern. - - PCRE_ERROR_NULL (-2) - -Either \fIcode\fR or \fIsubject\fR was passed as NULL, or \fIovector\fR was -NULL and \fIovecsize\fR was not zero. - - PCRE_ERROR_BADOPTION (-3) - -An unrecognized bit was set in the \fIoptions\fR argument. - - PCRE_ERROR_BADMAGIC (-4) - -PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch -the case when it is passed a junk pointer. This is the error it gives when the -magic number isn't present. - - PCRE_ERROR_UNKNOWN_NODE (-5) - -While running the pattern match, an unknown item was encountered in the -compiled pattern. This error could be caused by a bug in PCRE or by overwriting -of the compiled pattern. - - PCRE_ERROR_NOMEMORY (-6) - -If a pattern contains back references, but the \fIovector\fR that is passed to -\fBpcre_exec()\fR is not big enough to remember the referenced substrings, PCRE -gets a block of memory at the start of matching to use for this purpose. If the -call via \fBpcre_malloc()\fR fails, this error is given. The memory is freed at -the end of matching. - - -.SH EXTRACTING CAPTURED SUBSTRINGS -Captured substrings can be accessed directly by using the offsets returned by -\fBpcre_exec()\fR in \fIovector\fR. For convenience, the functions -\fBpcre_copy_substring()\fR, \fBpcre_get_substring()\fR, and -\fBpcre_get_substring_list()\fR are provided for extracting captured substrings -as new, separate, zero-terminated strings. A substring that contains a binary -zero is correctly extracted and has a further zero added on the end, but the -result does not, of course, function as a C string. - -The first three arguments are the same for all three functions: \fIsubject\fR -is the subject string which has just been successfully matched, \fIovector\fR -is a pointer to the vector of integer offsets that was passed to -\fBpcre_exec()\fR, and \fIstringcount\fR is the number of substrings that -were captured by the match, including the substring that matched the entire -regular expression. This is the value returned by \fBpcre_exec\fR if it -is greater than zero. If \fBpcre_exec()\fR returned zero, indicating that it -ran out of space in \fIovector\fR, the value passed as \fIstringcount\fR should -be the size of the vector divided by three. - -The functions \fBpcre_copy_substring()\fR and \fBpcre_get_substring()\fR -extract a single substring, whose number is given as \fIstringnumber\fR. A -value of zero extracts the substring that matched the entire pattern, while -higher values extract the captured substrings. For \fBpcre_copy_substring()\fR, -the string is placed in \fIbuffer\fR, whose length is given by -\fIbuffersize\fR, while for \fBpcre_get_substring()\fR a new block of memory is -obtained via \fBpcre_malloc\fR, and its address is returned via -\fIstringptr\fR. The yield of the function is the length of the string, not -including the terminating zero, or one of - - PCRE_ERROR_NOMEMORY (-6) - -The buffer was too small for \fBpcre_copy_substring()\fR, or the attempt to get -memory failed for \fBpcre_get_substring()\fR. - - PCRE_ERROR_NOSUBSTRING (-7) - -There is no substring whose number is \fIstringnumber\fR. - -The \fBpcre_get_substring_list()\fR function extracts all available substrings -and builds a list of pointers to them. All this is done in a single block of -memory which is obtained via \fBpcre_malloc\fR. The address of the memory block -is returned via \fIlistptr\fR, which is also the start of the list of string -pointers. The end of the list is marked by a NULL pointer. The yield of the -function is zero if all went well, or - - PCRE_ERROR_NOMEMORY (-6) - -if the attempt to get the memory block failed. - -When any of these functions encounter a substring that is unset, which can -happen when capturing subpattern number \fIn+1\fR matches some part of the -subject, but subpattern \fIn\fR has not been used at all, they return an empty -string. This can be distinguished from a genuine zero-length substring by -inspecting the appropriate offset in \fIovector\fR, which is negative for unset -substrings. - -The two convenience functions \fBpcre_free_substring()\fR and -\fBpcre_free_substring_list()\fR can be used to free the memory returned by -a previous call of \fBpcre_get_substring()\fR or -\fBpcre_get_substring_list()\fR, respectively. They do nothing more than call -the function pointed to by \fBpcre_free\fR, which of course could be called -directly from a C program. However, PCRE is used in some situations where it is -linked via a special interface to another programming language which cannot use -\fBpcre_free\fR directly; it is for these cases that the functions are -provided. - - -.SH LIMITATIONS -There are some size limitations in PCRE but it is hoped that they will never in -practice be relevant. -The maximum length of a compiled pattern is 65539 (sic) bytes. -All values in repeating quantifiers must be less than 65536. -There maximum number of capturing subpatterns is 65535. -There is no limit to the number of non-capturing subpatterns, but the maximum -depth of nesting of all kinds of parenthesized subpattern, including capturing -subpatterns, assertions, and other types of subpattern, is 200. - -The maximum length of a subject string is the largest positive number that an -integer variable can hold. However, PCRE uses recursion to handle subpatterns -and indefinite repetition. This means that the available stack space may limit -the size of a subject string that can be processed by certain patterns. - - -.SH DIFFERENCES FROM PERL -The differences described here are with respect to Perl 5.005. - -1. By default, a whitespace character is any character that the C library -function \fBisspace()\fR recognizes, though it is possible to compile PCRE with -alternative character type tables. Normally \fBisspace()\fR matches space, -formfeed, newline, carriage return, horizontal tab, and vertical tab. Perl 5 -no longer includes vertical tab in its set of whitespace characters. The \\v -escape that was in the Perl documentation for a long time was never in fact -recognized. However, the character itself was treated as whitespace at least -up to 5.002. In 5.004 and 5.005 it does not match \\s. - -2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl permits -them, but they do not mean what you might think. For example, (?!a){3} does -not assert that the next three characters are not "a". It just asserts that the -next character is not "a" three times. - -3. Capturing subpatterns that occur inside negative lookahead assertions are -counted, but their entries in the offsets vector are never set. Perl sets its -numerical variables from any such patterns that are matched before the -assertion fails to match something (thereby succeeding), but only if the -negative lookahead assertion contains just one branch. - -4. Though binary zero characters are supported in the subject string, they are -not allowed in a pattern string because it is passed as a normal C string, -terminated by zero. The escape sequence "\\0" can be used in the pattern to -represent a binary zero. - -5. The following Perl escape sequences are not supported: \\l, \\u, \\L, \\U, -\\E, \\Q. In fact these are implemented by Perl's general string-handling and -are not part of its pattern matching engine. - -6. The Perl \\G assertion is not supported as it is not relevant to single -pattern matches. - -7. Fairly obviously, PCRE does not support the (?{code}) and (?p{code}) -constructions. However, there is some experimental support for recursive -patterns using the non-Perl item (?R). - -8. There are at the time of writing some oddities in Perl 5.005_02 concerned -with the settings of captured strings when part of a pattern is repeated. For -example, matching "aba" against the pattern /^(a(b)?)+$/ sets $2 to the value -"b", but matching "aabbaa" against /^(aa(bb)?)+$/ leaves $2 unset. However, if -the pattern is changed to /^(aa(b(b))?)+$/ then $2 (and $3) are set. - -In Perl 5.004 $2 is set in both cases, and that is also true of PCRE. If in the -future Perl changes to a consistent state that is different, PCRE may change to -follow. - -9. Another as yet unresolved discrepancy is that in Perl 5.005_02 the pattern -/^(a)?(?(1)a|b)+$/ matches the string "a", whereas in PCRE it does not. -However, in both Perl and PCRE /^(a)?a/ matched against "a" leaves $1 unset. - -10. PCRE provides some extensions to the Perl regular expression facilities: - -(a) Although lookbehind assertions must match fixed length strings, each -alternative branch of a lookbehind assertion can match a different length of -string. Perl 5.005 requires them all to have the same length. - -(b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ meta- -character matches only at the very end of the string. - -(c) If PCRE_EXTRA is set, a backslash followed by a letter with no special -meaning is faulted. - -(d) If PCRE_UNGREEDY is set, the greediness of the repetition quantifiers is -inverted, that is, by default they are not greedy, but if followed by a -question mark they are. - -(e) PCRE_ANCHORED can be used to force a pattern to be tried only at the start -of the subject. - -(f) The PCRE_NOTBOL, PCRE_NOTEOL, and PCRE_NOTEMPTY options for -\fBpcre_exec()\fR have no Perl equivalents. - -(g) The (?R) construct allows for recursive pattern matching (Perl 5.6 can do -this using the (?p{code}) construct, which PCRE cannot of course support.) - - -.SH REGULAR EXPRESSION DETAILS -The syntax and semantics of the regular expressions supported by PCRE are -described below. Regular expressions are also described in the Perl -documentation and in a number of other books, some of which have copious -examples. Jeffrey Friedl's "Mastering Regular Expressions", published by -O'Reilly (ISBN 1-56592-257), covers them in great detail. - -The description here is intended as reference documentation. The basic -operation of PCRE is on strings of bytes. However, there is the beginnings of -some support for UTF-8 character strings. To use this support you must -configure PCRE to include it, and then call \fBpcre_compile()\fR with the -PCRE_UTF8 option. How this affects the pattern matching is described in the -final section of this document. - -A regular expression is a pattern that is matched against a subject string from -left to right. Most characters stand for themselves in a pattern, and match the -corresponding characters in the subject. As a trivial example, the pattern - - The quick brown fox - -matches a portion of a subject string that is identical to itself. The power of -regular expressions comes from the ability to include alternatives and -repetitions in the pattern. These are encoded in the pattern by the use of -\fImeta-characters\fR, which do not stand for themselves but instead are -interpreted in some special way. - -There are two different sets of meta-characters: those that are recognized -anywhere in the pattern except within square brackets, and those that are -recognized in square brackets. Outside square brackets, the meta-characters are -as follows: - - \\ general escape character with several uses - ^ assert start of subject (or line, in multiline mode) - $ assert end of subject (or line, in multiline mode) - . match any character except newline (by default) - [ start character class definition - | start of alternative branch - ( start subpattern - ) end subpattern - ? extends the meaning of ( - also 0 or 1 quantifier - also quantifier minimizer - * 0 or more quantifier - + 1 or more quantifier - { start min/max quantifier - -Part of a pattern that is in square brackets is called a "character class". In -a character class the only meta-characters are: - - \\ general escape character - ^ negate the class, but only if the first character - - indicates character range - ] terminates the character class - -The following sections describe the use of each of the meta-characters. - - -.SH BACKSLASH -The backslash character has several uses. Firstly, if it is followed by a -non-alphameric character, it takes away any special meaning that character may -have. This use of backslash as an escape character applies both inside and -outside character classes. - -For example, if you want to match a "*" character, you write "\\*" in the -pattern. This applies whether or not the following character would otherwise be -interpreted as a meta-character, so it is always safe to precede a -non-alphameric with "\\" to specify that it stands for itself. In particular, -if you want to match a backslash, you write "\\\\". - -If a pattern is compiled with the PCRE_EXTENDED option, whitespace in the -pattern (other than in a character class) and characters between a "#" outside -a character class and the next newline character are ignored. An escaping -backslash can be used to include a whitespace or "#" character as part of the -pattern. - -A second use of backslash provides a way of encoding non-printing characters -in patterns in a visible manner. There is no restriction on the appearance of -non-printing characters, apart from the binary zero that terminates a pattern, -but when a pattern is being prepared by text editing, it is usually easier to -use one of the following escape sequences than the binary character it -represents: - - \\a alarm, that is, the BEL character (hex 07) - \\cx "control-x", where x is any character - \\e escape (hex 1B) - \\f formfeed (hex 0C) - \\n newline (hex 0A) - \\r carriage return (hex 0D) - \\t tab (hex 09) - \\xhh character with hex code hh - \\ddd character with octal code ddd, or backreference - -The precise effect of "\\cx" is as follows: if "x" is a lower case letter, it -is converted to upper case. Then bit 6 of the character (hex 40) is inverted. -Thus "\\cz" becomes hex 1A, but "\\c{" becomes hex 3B, while "\\c;" becomes hex -7B. - -After "\\x", up to two hexadecimal digits are read (letters can be in upper or -lower case). - -After "\\0" up to two further octal digits are read. In both cases, if there -are fewer than two digits, just those that are present are used. Thus the -sequence "\\0\\x\\07" specifies two binary zeros followed by a BEL character. -Make sure you supply two digits after the initial zero if the character that -follows is itself an octal digit. - -The handling of a backslash followed by a digit other than 0 is complicated. -Outside a character class, PCRE reads it and any following digits as a decimal -number. If the number is less than 10, or if there have been at least that many -previous capturing left parentheses in the expression, the entire sequence is -taken as a \fIback reference\fR. A description of how this works is given -later, following the discussion of parenthesized subpatterns. - -Inside a character class, or if the decimal number is greater than 9 and there -have not been that many capturing subpatterns, PCRE re-reads up to three octal -digits following the backslash, and generates a single byte from the least -significant 8 bits of the value. Any subsequent digits stand for themselves. -For example: - - \\040 is another way of writing a space - \\40 is the same, provided there are fewer than 40 - previous capturing subpatterns - \\7 is always a back reference - \\11 might be a back reference, or another way of - writing a tab - \\011 is always a tab - \\0113 is a tab followed by the character "3" - \\113 is the character with octal code 113 (since there - can be no more than 99 back references) - \\377 is a byte consisting entirely of 1 bits - \\81 is either a back reference, or a binary zero - followed by the two characters "8" and "1" - -Note that octal values of 100 or greater must not be introduced by a leading -zero, because no more than three octal digits are ever read. - -All the sequences that define a single byte value can be used both inside and -outside character classes. In addition, inside a character class, the sequence -"\\b" is interpreted as the backspace character (hex 08). Outside a character -class it has a different meaning (see below). - -The third use of backslash is for specifying generic character types: - - \\d any decimal digit - \\D any character that is not a decimal digit - \\s any whitespace character - \\S any character that is not a whitespace character - \\w any "word" character - \\W any "non-word" character - -Each pair of escape sequences partitions the complete set of characters into -two disjoint sets. Any given character matches one, and only one, of each pair. - -A "word" character is any letter or digit or the underscore character, that is, -any character which can be part of a Perl "word". The definition of letters and -digits is controlled by PCRE's character tables, and may vary if locale- -specific matching is taking place (see "Locale support" above). For example, in -the "fr" (French) locale, some character codes greater than 128 are used for -accented letters, and these are matched by \\w. - -These character type sequences can appear both inside and outside character -classes. They each match one character of the appropriate type. If the current -matching point is at the end of the subject string, all of them fail, since -there is no character to match. - -The fourth use of backslash is for certain simple assertions. An assertion -specifies a condition that has to be met at a particular point in a match, -without consuming any characters from the subject string. The use of -subpatterns for more complicated assertions is described below. The backslashed -assertions are - - \\b word boundary - \\B not a word boundary - \\A start of subject (independent of multiline mode) - \\Z end of subject or newline at end (independent of multiline mode) - \\z end of subject (independent of multiline mode) - -These assertions may not appear in character classes (but note that "\\b" has a -different meaning, namely the backspace character, inside a character class). - -A word boundary is a position in the subject string where the current character -and the previous character do not both match \\w or \\W (i.e. one matches -\\w and the other matches \\W), or the start or end of the string if the -first or last character matches \\w, respectively. - -The \\A, \\Z, and \\z assertions differ from the traditional circumflex and -dollar (described below) in that they only ever match at the very start and end -of the subject string, whatever options are set. They are not affected by the -PCRE_NOTBOL or PCRE_NOTEOL options. If the \fIstartoffset\fR argument of -\fBpcre_exec()\fR is non-zero, \\A can never match. The difference between \\Z -and \\z is that \\Z matches before a newline that is the last character of the -string as well as at the end of the string, whereas \\z matches only at the -end. - - -.SH CIRCUMFLEX AND DOLLAR -Outside a character class, in the default matching mode, the circumflex -character is an assertion which is true only if the current matching point is -at the start of the subject string. If the \fIstartoffset\fR argument of -\fBpcre_exec()\fR is non-zero, circumflex can never match. Inside a character -class, circumflex has an entirely different meaning (see below). - -Circumflex need not be the first character of the pattern if a number of -alternatives are involved, but it should be the first thing in each alternative -in which it appears if the pattern is ever to match that branch. If all -possible alternatives start with a circumflex, that is, if the pattern is -constrained to match only at the start of the subject, it is said to be an -"anchored" pattern. (There are also other constructs that can cause a pattern -to be anchored.) - -A dollar character is an assertion which is true only if the current matching -point is at the end of the subject string, or immediately before a newline -character that is the last character in the string (by default). Dollar need -not be the last character of the pattern if a number of alternatives are -involved, but it should be the last item in any branch in which it appears. -Dollar has no special meaning in a character class. - -The meaning of dollar can be changed so that it matches only at the very end of -the string, by setting the PCRE_DOLLAR_ENDONLY option at compile or matching -time. This does not affect the \\Z assertion. - -The meanings of the circumflex and dollar characters are changed if the -PCRE_MULTILINE option is set. When this is the case, they match immediately -after and immediately before an internal "\\n" character, respectively, in -addition to matching at the start and end of the subject string. For example, -the pattern /^abc$/ matches the subject string "def\\nabc" in multiline mode, -but not otherwise. Consequently, patterns that are anchored in single line mode -because all branches start with "^" are not anchored in multiline mode, and a -match for circumflex is possible when the \fIstartoffset\fR argument of -\fBpcre_exec()\fR is non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if -PCRE_MULTILINE is set. - -Note that the sequences \\A, \\Z, and \\z can be used to match the start and -end of the subject in both modes, and if all branches of a pattern start with -\\A it is always anchored, whether PCRE_MULTILINE is set or not. - - -.SH FULL STOP (PERIOD, DOT) -Outside a character class, a dot in the pattern matches any one character in -the subject, including a non-printing character, but not (by default) newline. -If the PCRE_DOTALL option is set, dots match newlines as well. The handling of -dot is entirely independent of the handling of circumflex and dollar, the only -relationship being that they both involve newline characters. Dot has no -special meaning in a character class. - - -.SH SQUARE BRACKETS -An opening square bracket introduces a character class, terminated by a closing -square bracket. A closing square bracket on its own is not special. If a -closing square bracket is required as a member of the class, it should be the -first data character in the class (after an initial circumflex, if present) or -escaped with a backslash. - -A character class matches a single character in the subject; the character must -be in the set of characters defined by the class, unless the first character in -the class is a circumflex, in which case the subject character must not be in -the set defined by the class. If a circumflex is actually required as a member -of the class, ensure it is not the first character, or escape it with a -backslash. - -For example, the character class [aeiou] matches any lower case vowel, while -[^aeiou] matches any character that is not a lower case vowel. Note that a -circumflex is just a convenient notation for specifying the characters which -are in the class by enumerating those that are not. It is not an assertion: it -still consumes a character from the subject string, and fails if the current -pointer is at the end of the string. - -When caseless matching is set, any letters in a class represent both their -upper case and lower case versions, so for example, a caseless [aeiou] matches -"A" as well as "a", and a caseless [^aeiou] does not match "A", whereas a -caseful version would. - -The newline character is never treated in any special way in character classes, -whatever the setting of the PCRE_DOTALL or PCRE_MULTILINE options is. A class -such as [^a] will always match a newline. - -The minus (hyphen) character can be used to specify a range of characters in a -character class. For example, [d-m] matches any letter between d and m, -inclusive. If a minus character is required in a class, it must be escaped with -a backslash or appear in a position where it cannot be interpreted as -indicating a range, typically as the first or last character in the class. - -It is not possible to have the literal character "]" as the end character of a -range. A pattern such as [W-]46] is interpreted as a class of two characters -("W" and "-") followed by a literal string "46]", so it would match "W46]" or -"-46]". However, if the "]" is escaped with a backslash it is interpreted as -the end of range, so [W-\\]46] is interpreted as a single class containing a -range followed by two separate characters. The octal or hexadecimal -representation of "]" can also be used to end a range. - -Ranges operate in ASCII collating sequence. They can also be used for -characters specified numerically, for example [\\000-\\037]. If a range that -includes letters is used when caseless matching is set, it matches the letters -in either case. For example, [W-c] is equivalent to [][\\^_`wxyzabc], matched -caselessly, and if character tables for the "fr" locale are in use, -[\\xc8-\\xcb] matches accented E characters in both cases. - -The character types \\d, \\D, \\s, \\S, \\w, and \\W may also appear in a -character class, and add the characters that they match to the class. For -example, [\\dABCDEF] matches any hexadecimal digit. A circumflex can -conveniently be used with the upper case character types to specify a more -restricted set of characters than the matching lower case type. For example, -the class [^\\W_] matches any letter or digit, but not underscore. - -All non-alphameric characters other than \\, -, ^ (at the start) and the -terminating ] are non-special in character classes, but it does no harm if they -are escaped. - - -.SH POSIX CHARACTER CLASSES -Perl 5.6 (not yet released at the time of writing) is going to support the -POSIX notation for character classes, which uses names enclosed by [: and :] -within the enclosing square brackets. PCRE supports this notation. For example, - - [01[:alpha:]%] - -matches "0", "1", any alphabetic character, or "%". The supported class names -are - - alnum letters and digits - alpha letters - ascii character codes 0 - 127 - cntrl control characters - digit decimal digits (same as \\d) - graph printing characters, excluding space - lower lower case letters - print printing characters, including space - punct printing characters, excluding letters and digits - space white space (same as \\s) - upper upper case letters - word "word" characters (same as \\w) - xdigit hexadecimal digits - -The names "ascii" and "word" are Perl extensions. Another Perl extension is -negation, which is indicated by a ^ character after the colon. For example, - - [12[:^digit:]] - -matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the POSIX -syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not -supported, and an error is given if they are encountered. - - -.SH VERTICAL BAR -Vertical bar characters are used to separate alternative patterns. For example, -the pattern - - gilbert|sullivan - -matches either "gilbert" or "sullivan". Any number of alternatives may appear, -and an empty alternative is permitted (matching the empty string). -The matching process tries each alternative in turn, from left to right, -and the first one that succeeds is used. If the alternatives are within a -subpattern (defined below), "succeeds" means matching the rest of the main -pattern as well as the alternative in the subpattern. - - -.SH INTERNAL OPTION SETTING -The settings of PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and PCRE_EXTENDED -can be changed from within the pattern by a sequence of Perl option letters -enclosed between "(?" and ")". The option letters are - - i for PCRE_CASELESS - m for PCRE_MULTILINE - s for PCRE_DOTALL - x for PCRE_EXTENDED - -For example, (?im) sets caseless, multiline matching. It is also possible to -unset these options by preceding the letter with a hyphen, and a combined -setting and unsetting such as (?im-sx), which sets PCRE_CASELESS and -PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED, is also -permitted. If a letter appears both before and after the hyphen, the option is -unset. - -The scope of these option changes depends on where in the pattern the setting -occurs. For settings that are outside any subpattern (defined below), the -effect is the same as if the options were set or unset at the start of -matching. The following patterns all behave in exactly the same way: - - (?i)abc - a(?i)bc - ab(?i)c - abc(?i) - -which in turn is the same as compiling the pattern abc with PCRE_CASELESS set. -In other words, such "top level" settings apply to the whole pattern (unless -there are other changes inside subpatterns). If there is more than one setting -of the same option at top level, the rightmost setting is used. - -If an option change occurs inside a subpattern, the effect is different. This -is a change of behaviour in Perl 5.005. An option change inside a subpattern -affects only that part of the subpattern that follows it, so - - (a(?i)b)c - -matches abc and aBc and no other strings (assuming PCRE_CASELESS is not used). -By this means, options can be made to have different settings in different -parts of the pattern. Any changes made in one alternative do carry on -into subsequent branches within the same subpattern. For example, - - (a(?i)b|c) - -matches "ab", "aB", "c", and "C", even though when matching "C" the first -branch is abandoned before the option setting. This is because the effects of -option settings happen at compile time. There would be some very weird -behaviour otherwise. - -The PCRE-specific options PCRE_UNGREEDY and PCRE_EXTRA can be changed in the -same way as the Perl-compatible options by using the characters U and X -respectively. The (?X) flag setting is special in that it must always occur -earlier in the pattern than any of the additional features it turns on, even -when it is at top level. It is best put at the start. - - -.SH SUBPATTERNS -Subpatterns are delimited by parentheses (round brackets), which can be nested. -Marking part of a pattern as a subpattern does two things: - -1. It localizes a set of alternatives. For example, the pattern - - cat(aract|erpillar|) - -matches one of the words "cat", "cataract", or "caterpillar". Without the -parentheses, it would match "cataract", "erpillar" or the empty string. - -2. It sets up the subpattern as a capturing subpattern (as defined above). -When the whole pattern matches, that portion of the subject string that matched -the subpattern is passed back to the caller via the \fIovector\fR argument of -\fBpcre_exec()\fR. Opening parentheses are counted from left to right (starting -from 1) to obtain the numbers of the capturing subpatterns. - -For example, if the string "the red king" is matched against the pattern - - the ((red|white) (king|queen)) - -the captured substrings are "red king", "red", and "king", and are numbered 1, -2, and 3, respectively. - -The fact that plain parentheses fulfil two functions is not always helpful. -There are often times when a grouping subpattern is required without a -capturing requirement. If an opening parenthesis is followed by "?:", the -subpattern does not do any capturing, and is not counted when computing the -number of any subsequent capturing subpatterns. For example, if the string "the -white queen" is matched against the pattern - - the ((?:red|white) (king|queen)) - -the captured substrings are "white queen" and "queen", and are numbered 1 and -2. The maximum number of captured substrings is 99, and the maximum number of -all subpatterns, both capturing and non-capturing, is 200. - -As a convenient shorthand, if any option settings are required at the start of -a non-capturing subpattern, the option letters may appear between the "?" and -the ":". Thus the two patterns - - (?i:saturday|sunday) - (?:(?i)saturday|sunday) - -match exactly the same set of strings. Because alternative branches are tried -from left to right, and options are not reset until the end of the subpattern -is reached, an option setting in one branch does affect subsequent branches, so -the above patterns match "SUNDAY" as well as "Saturday". - - -.SH REPETITION -Repetition is specified by quantifiers, which can follow any of the following -items: - - a single character, possibly escaped - the . metacharacter - a character class - a back reference (see next section) - a parenthesized subpattern (unless it is an assertion - see below) - -The general repetition quantifier specifies a minimum and maximum number of -permitted matches, by giving the two numbers in curly brackets (braces), -separated by a comma. The numbers must be less than 65536, and the first must -be less than or equal to the second. For example: - - z{2,4} - -matches "zz", "zzz", or "zzzz". A closing brace on its own is not a special -character. If the second number is omitted, but the comma is present, there is -no upper limit; if the second number and the comma are both omitted, the -quantifier specifies an exact number of required matches. Thus - - [aeiou]{3,} - -matches at least 3 successive vowels, but may match many more, while - - \\d{8} - -matches exactly 8 digits. An opening curly bracket that appears in a position -where a quantifier is not allowed, or one that does not match the syntax of a -quantifier, is taken as a literal character. For example, {,6} is not a -quantifier, but a literal string of four characters. - -The quantifier {0} is permitted, causing the expression to behave as if the -previous item and the quantifier were not present. - -For convenience (and historical compatibility) the three most common -quantifiers have single-character abbreviations: - - * is equivalent to {0,} - + is equivalent to {1,} - ? is equivalent to {0,1} - -It is possible to construct infinite loops by following a subpattern that can -match no characters with a quantifier that has no upper limit, for example: - - (a?)* - -Earlier versions of Perl and PCRE used to give an error at compile time for -such patterns. However, because there are cases where this can be useful, such -patterns are now accepted, but if any repetition of the subpattern does in fact -match no characters, the loop is forcibly broken. - -By default, the quantifiers are "greedy", that is, they match as much as -possible (up to the maximum number of permitted times), without causing the -rest of the pattern to fail. The classic example of where this gives problems -is in trying to match comments in C programs. These appear between the -sequences /* and */ and within the sequence, individual * and / characters may -appear. An attempt to match C comments by applying the pattern - - /\\*.*\\*/ - -to the string - - /* first command */ not comment /* second comment */ - -fails, because it matches the entire string owing to the greediness of the .* -item. - -However, if a quantifier is followed by a question mark, it ceases to be -greedy, and instead matches the minimum number of times possible, so the -pattern - - /\\*.*?\\*/ - -does the right thing with the C comments. The meaning of the various -quantifiers is not otherwise changed, just the preferred number of matches. -Do not confuse this use of question mark with its use as a quantifier in its -own right. Because it has two uses, it can sometimes appear doubled, as in - - \\d??\\d - -which matches one digit by preference, but can match two if that is the only -way the rest of the pattern matches. - -If the PCRE_UNGREEDY option is set (an option which is not available in Perl), -the quantifiers are not greedy by default, but individual ones can be made -greedy by following them with a question mark. In other words, it inverts the -default behaviour. - -When a parenthesized subpattern is quantified with a minimum repeat count that -is greater than 1 or with a limited maximum, more store is required for the -compiled pattern, in proportion to the size of the minimum or maximum. - -If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equivalent -to Perl's /s) is set, thus allowing the . to match newlines, the pattern is -implicitly anchored, because whatever follows will be tried against every -character position in the subject string, so there is no point in retrying the -overall match at any position after the first. PCRE treats such a pattern as -though it were preceded by \\A. In cases where it is known that the subject -string contains no newlines, it is worth setting PCRE_DOTALL when the pattern -begins with .* in order to obtain this optimization, or alternatively using ^ -to indicate anchoring explicitly. - -When a capturing subpattern is repeated, the value captured is the substring -that matched the final iteration. For example, after - - (tweedle[dume]{3}\\s*)+ - -has matched "tweedledum tweedledee" the value of the captured substring is -"tweedledee". However, if there are nested capturing subpatterns, the -corresponding captured values may have been set in previous iterations. For -example, after - - /(a|(b))+/ - -matches "aba" the value of the second captured substring is "b". - - -.SH BACK REFERENCES -Outside a character class, a backslash followed by a digit greater than 0 (and -possibly further digits) is a back reference to a capturing subpattern earlier -(i.e. to its left) in the pattern, provided there have been that many previous -capturing left parentheses. - -However, if the decimal number following the backslash is less than 10, it is -always taken as a back reference, and causes an error only if there are not -that many capturing left parentheses in the entire pattern. In other words, the -parentheses that are referenced need not be to the left of the reference for -numbers less than 10. See the section entitled "Backslash" above for further -details of the handling of digits following a backslash. - -A back reference matches whatever actually matched the capturing subpattern in -the current subject string, rather than anything matching the subpattern -itself. So the pattern - - (sens|respons)e and \\1ibility - -matches "sense and sensibility" and "response and responsibility", but not -"sense and responsibility". If caseful matching is in force at the time of the -back reference, the case of letters is relevant. For example, - - ((?i)rah)\\s+\\1 - -matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original -capturing subpattern is matched caselessly. - -There may be more than one back reference to the same subpattern. If a -subpattern has not actually been used in a particular match, any back -references to it always fail. For example, the pattern - - (a|(bc))\\2 - -always fails if it starts to match "a" rather than "bc". Because there may be -up to 99 back references, all digits following the backslash are taken -as part of a potential back reference number. If the pattern continues with a -digit character, some delimiter must be used to terminate the back reference. -If the PCRE_EXTENDED option is set, this can be whitespace. Otherwise an empty -comment can be used. - -A back reference that occurs inside the parentheses to which it refers fails -when the subpattern is first used, so, for example, (a\\1) never matches. -However, such references can be useful inside repeated subpatterns. For -example, the pattern - - (a|b\\1)+ - -matches any number of "a"s and also "aba", "ababbaa" etc. At each iteration of -the subpattern, the back reference matches the character string corresponding -to the previous iteration. In order for this to work, the pattern must be such -that the first iteration does not need to match the back reference. This can be -done using alternation, as in the example above, or by a quantifier with a -minimum of zero. - - -.SH ASSERTIONS -An assertion is a test on the characters following or preceding the current -matching point that does not actually consume any characters. The simple -assertions coded as \\b, \\B, \\A, \\Z, \\z, ^ and $ are described above. More -complicated assertions are coded as subpatterns. There are two kinds: those -that look ahead of the current position in the subject string, and those that -look behind it. - -An assertion subpattern is matched in the normal way, except that it does not -cause the current matching position to be changed. Lookahead assertions start -with (?= for positive assertions and (?! for negative assertions. For example, - - \\w+(?=;) - -matches a word followed by a semicolon, but does not include the semicolon in -the match, and - - foo(?!bar) - -matches any occurrence of "foo" that is not followed by "bar". Note that the -apparently similar pattern - - (?!foo)bar - -does not find an occurrence of "bar" that is preceded by something other than -"foo"; it finds any occurrence of "bar" whatsoever, because the assertion -(?!foo) is always true when the next three characters are "bar". A -lookbehind assertion is needed to achieve this effect. - -Lookbehind assertions start with (?<= for positive assertions and (?<! for -negative assertions. For example, - - (?<!foo)bar - -does find an occurrence of "bar" that is not preceded by "foo". The contents of -a lookbehind assertion are restricted such that all the strings it matches must -have a fixed length. However, if there are several alternatives, they do not -all have to have the same fixed length. Thus - - (?<=bullock|donkey) - -is permitted, but - - (?<!dogs?|cats?) - -causes an error at compile time. Branches that match different length strings -are permitted only at the top level of a lookbehind assertion. This is an -extension compared with Perl 5.005, which requires all branches to match the -same length of string. An assertion such as - - (?<=ab(c|de)) - -is not permitted, because its single top-level branch can match two different -lengths, but it is acceptable if rewritten to use two top-level branches: - - (?<=abc|abde) - -The implementation of lookbehind assertions is, for each alternative, to -temporarily move the current position back by the fixed width and then try to -match. If there are insufficient characters before the current position, the -match is deemed to fail. Lookbehinds in conjunction with once-only subpatterns -can be particularly useful for matching at the ends of strings; an example is -given at the end of the section on once-only subpatterns. - -Several assertions (of any sort) may occur in succession. For example, - - (?<=\\d{3})(?<!999)foo - -matches "foo" preceded by three digits that are not "999". Notice that each of -the assertions is applied independently at the same point in the subject -string. First there is a check that the previous three characters are all -digits, and then there is a check that the same three characters are not "999". -This pattern does \fInot\fR match "foo" preceded by six characters, the first -of which are digits and the last three of which are not "999". For example, it -doesn't match "123abcfoo". A pattern to do that is - - (?<=\\d{3}...)(?<!999)foo - -This time the first assertion looks at the preceding six characters, checking -that the first three are digits, and then the second assertion checks that the -preceding three characters are not "999". - -Assertions can be nested in any combination. For example, - - (?<=(?<!foo)bar)baz - -matches an occurrence of "baz" that is preceded by "bar" which in turn is not -preceded by "foo", while - - (?<=\\d{3}(?!999)...)foo - -is another pattern which matches "foo" preceded by three digits and any three -characters that are not "999". - -Assertion subpatterns are not capturing subpatterns, and may not be repeated, -because it makes no sense to assert the same thing several times. If any kind -of assertion contains capturing subpatterns within it, these are counted for -the purposes of numbering the capturing subpatterns in the whole pattern. -However, substring capturing is carried out only for positive assertions, -because it does not make sense for negative assertions. - -Assertions count towards the maximum of 200 parenthesized subpatterns. - - -.SH ONCE-ONLY SUBPATTERNS -With both maximizing and minimizing repetition, failure of what follows -normally causes the repeated item to be re-evaluated to see if a different -number of repeats allows the rest of the pattern to match. Sometimes it is -useful to prevent this, either to change the nature of the match, or to cause -it fail earlier than it otherwise might, when the author of the pattern knows -there is no point in carrying on. - -Consider, for example, the pattern \\d+foo when applied to the subject line - - 123456bar - -After matching all 6 digits and then failing to match "foo", the normal -action of the matcher is to try again with only 5 digits matching the \\d+ -item, and then with 4, and so on, before ultimately failing. Once-only -subpatterns provide the means for specifying that once a portion of the pattern -has matched, it is not to be re-evaluated in this way, so the matcher would -give up immediately on failing to match "foo" the first time. The notation is -another kind of special parenthesis, starting with (?> as in this example: - - (?>\\d+)bar - -This kind of parenthesis "locks up" the part of the pattern it contains once -it has matched, and a failure further into the pattern is prevented from -backtracking into it. Backtracking past it to previous items, however, works as -normal. - -An alternative description is that a subpattern of this type matches the string -of characters that an identical standalone pattern would match, if anchored at -the current point in the subject string. - -Once-only subpatterns are not capturing subpatterns. Simple cases such as the -above example can be thought of as a maximizing repeat that must swallow -everything it can. So, while both \\d+ and \\d+? are prepared to adjust the -number of digits they match in order to make the rest of the pattern match, -(?>\\d+) can only match an entire sequence of digits. - -This construction can of course contain arbitrarily complicated subpatterns, -and it can be nested. - -Once-only subpatterns can be used in conjunction with lookbehind assertions to -specify efficient matching at the end of the subject string. Consider a simple -pattern such as - - abcd$ - -when applied to a long string which does not match. Because matching proceeds -from left to right, PCRE will look for each "a" in the subject and then see if -what follows matches the rest of the pattern. If the pattern is specified as - - ^.*abcd$ - -the initial .* matches the entire string at first, but when this fails (because -there is no following "a"), it backtracks to match all but the last character, -then all but the last two characters, and so on. Once again the search for "a" -covers the entire string, from right to left, so we are no better off. However, -if the pattern is written as - - ^(?>.*)(?<=abcd) - -there can be no backtracking for the .* item; it can match only the entire -string. The subsequent lookbehind assertion does a single test on the last four -characters. If it fails, the match fails immediately. For long strings, this -approach makes a significant difference to the processing time. - -When a pattern contains an unlimited repeat inside a subpattern that can itself -be repeated an unlimited number of times, the use of a once-only subpattern is -the only way to avoid some failing matches taking a very long time indeed. -The pattern - - (\\D+|<\\d+>)*[!?] - -matches an unlimited number of substrings that either consist of non-digits, or -digits enclosed in <>, followed by either ! or ?. When it matches, it runs -quickly. However, if it is applied to - - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa - -it takes a long time before reporting failure. This is because the string can -be divided between the two repeats in a large number of ways, and all have to -be tried. (The example used [!?] rather than a single character at the end, -because both PCRE and Perl have an optimization that allows for fast failure -when a single character is used. They remember the last single character that -is required for a match, and fail early if it is not present in the string.) -If the pattern is changed to - - ((?>\\D+)|<\\d+>)*[!?] - -sequences of non-digits cannot be broken, and failure happens quickly. - - -.SH CONDITIONAL SUBPATTERNS -It is possible to cause the matching process to obey a subpattern -conditionally or to choose between two alternative subpatterns, depending on -the result of an assertion, or whether a previous capturing subpattern matched -or not. The two possible forms of conditional subpattern are - - (?(condition)yes-pattern) - (?(condition)yes-pattern|no-pattern) - -If the condition is satisfied, the yes-pattern is used; otherwise the -no-pattern (if present) is used. If there are more than two alternatives in the -subpattern, a compile-time error occurs. - -There are two kinds of condition. If the text between the parentheses consists -of a sequence of digits, the condition is satisfied if the capturing subpattern -of that number has previously matched. The number must be greater than zero. -Consider the following pattern, which contains non-significant white space to -make it more readable (assume the PCRE_EXTENDED option) and to divide it into -three parts for ease of discussion: - - ( \\( )? [^()]+ (?(1) \\) ) - -The first part matches an optional opening parenthesis, and if that -character is present, sets it as the first captured substring. The second part -matches one or more characters that are not parentheses. The third part is a -conditional subpattern that tests whether the first set of parentheses matched -or not. If they did, that is, if subject started with an opening parenthesis, -the condition is true, and so the yes-pattern is executed and a closing -parenthesis is required. Otherwise, since no-pattern is not present, the -subpattern matches nothing. In other words, this pattern matches a sequence of -non-parentheses, optionally enclosed in parentheses. - -If the condition is not a sequence of digits, it must be an assertion. This may -be a positive or negative lookahead or lookbehind assertion. Consider this -pattern, again containing non-significant white space, and with the two -alternatives on the second line: - - (?(?=[^a-z]*[a-z]) - \\d{2}-[a-z]{3}-\\d{2} | \\d{2}-\\d{2}-\\d{2} ) - -The condition is a positive lookahead assertion that matches an optional -sequence of non-letters followed by a letter. In other words, it tests for the -presence of at least one letter in the subject. If a letter is found, the -subject is matched against the first alternative; otherwise it is matched -against the second. This pattern matches strings in one of the two forms -dd-aaa-dd or dd-dd-dd, where aaa are letters and dd are digits. - - -.SH COMMENTS -The sequence (?# marks the start of a comment which continues up to the next -closing parenthesis. Nested parentheses are not permitted. The characters -that make up a comment play no part in the pattern matching at all. - -If the PCRE_EXTENDED option is set, an unescaped # character outside a -character class introduces a comment that continues up to the next newline -character in the pattern. - - -.SH RECURSIVE PATTERNS -Consider the problem of matching a string in parentheses, allowing for -unlimited nested parentheses. Without the use of recursion, the best that can -be done is to use a pattern that matches up to some fixed depth of nesting. It -is not possible to handle an arbitrary nesting depth. Perl 5.6 has provided an -experimental facility that allows regular expressions to recurse (amongst other -things). It does this by interpolating Perl code in the expression at run time, -and the code can refer to the expression itself. A Perl pattern to solve the -parentheses problem can be created like this: - - $re = qr{\\( (?: (?>[^()]+) | (?p{$re}) )* \\)}x; - -The (?p{...}) item interpolates Perl code at run time, and in this case refers -recursively to the pattern in which it appears. Obviously, PCRE cannot support -the interpolation of Perl code. Instead, the special item (?R) is provided for -the specific case of recursion. This PCRE pattern solves the parentheses -problem (assume the PCRE_EXTENDED option is set so that white space is -ignored): - - \\( ( (?>[^()]+) | (?R) )* \\) - -First it matches an opening parenthesis. Then it matches any number of -substrings which can either be a sequence of non-parentheses, or a recursive -match of the pattern itself (i.e. a correctly parenthesized substring). Finally -there is a closing parenthesis. - -This particular example pattern contains nested unlimited repeats, and so the -use of a once-only subpattern for matching strings of non-parentheses is -important when applying the pattern to strings that do not match. For example, -when it is applied to - - (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() - -it yields "no match" quickly. However, if a once-only subpattern is not used, -the match runs for a very long time indeed because there are so many different -ways the + and * repeats can carve up the subject, and all have to be tested -before failure can be reported. - -The values set for any capturing subpatterns are those from the outermost level -of the recursion at which the subpattern value is set. If the pattern above is -matched against - - (ab(cd)ef) - -the value for the capturing parentheses is "ef", which is the last value taken -on at the top level. If additional parentheses are added, giving - - \\( ( ( (?>[^()]+) | (?R) )* ) \\) - ^ ^ - ^ ^ -the string they capture is "ab(cd)ef", the contents of the top level -parentheses. If there are more than 15 capturing parentheses in a pattern, PCRE -has to obtain extra memory to store data during a recursion, which it does by -using \fBpcre_malloc\fR, freeing it via \fBpcre_free\fR afterwards. If no -memory can be obtained, it saves data for the first 15 capturing parentheses -only, as there is no way to give an out-of-memory error from within a -recursion. - - -.SH PERFORMANCE -Certain items that may appear in patterns are more efficient than others. It is -more efficient to use a character class like [aeiou] than a set of alternatives -such as (a|e|i|o|u). In general, the simplest construction that provides the -required behaviour is usually the most efficient. Jeffrey Friedl's book -contains a lot of discussion about optimizing regular expressions for efficient -performance. - -When a pattern begins with .* and the PCRE_DOTALL option is set, the pattern is -implicitly anchored by PCRE, since it can match only at the start of a subject -string. However, if PCRE_DOTALL is not set, PCRE cannot make this optimization, -because the . metacharacter does not then match a newline, and if the subject -string contains newlines, the pattern may match from the character immediately -following one of them instead of from the very start. For example, the pattern - - (.*) second - -matches the subject "first\\nand second" (where \\n stands for a newline -character) with the first captured substring being "and". In order to do this, -PCRE has to retry the match starting after every newline in the subject. - -If you are using such a pattern with subject strings that do not contain -newlines, the best performance is obtained by setting PCRE_DOTALL, or starting -the pattern with ^.* to indicate explicit anchoring. That saves PCRE from -having to scan along the subject looking for a newline to restart at. - -Beware of patterns that contain nested indefinite repeats. These can take a -long time to run when applied to a string that does not match. Consider the -pattern fragment - - (a+)* - -This can match "aaaa" in 33 different ways, and this number increases very -rapidly as the string gets longer. (The * repeat can match 0, 1, 2, 3, or 4 -times, and for each of those cases other than 0, the + repeats can match -different numbers of times.) When the remainder of the pattern is such that the -entire match is going to fail, PCRE has in principle to try every possible -variation, and this can take an extremely long time. - -An optimization catches some of the more simple cases such as - - (a+)*b - -where a literal character follows. Before embarking on the standard matching -procedure, PCRE checks that there is a "b" later in the subject string, and if -there is not, it fails the match immediately. However, when there is no -following literal this optimization cannot be used. You can see the difference -by comparing the behaviour of - - (a+)*\\d - -with the pattern above. The former gives a failure almost instantly when -applied to a whole line of "a" characters, whereas the latter takes an -appreciable time with strings longer than about 20 characters. - - -.SH UTF-8 SUPPORT -Starting at release 3.3, PCRE has some support for character strings encoded -in the UTF-8 format. This is incomplete, and is regarded as experimental. In -order to use it, you must configure PCRE to include UTF-8 support in the code, -and, in addition, you must call \fBpcre_compile()\fR with the PCRE_UTF8 option -flag. When you do this, both the pattern and any subject strings that are -matched against it are treated as UTF-8 strings instead of just strings of -bytes, but only in the cases that are mentioned below. - -If you compile PCRE with UTF-8 support, but do not use it at run time, the -library will be a bit bigger, but the additional run time overhead is limited -to testing the PCRE_UTF8 flag in several places, so should not be very large. - -PCRE assumes that the strings it is given contain valid UTF-8 codes. It does -not diagnose invalid UTF-8 strings. If you pass invalid UTF-8 strings to PCRE, -the results are undefined. - -Running with PCRE_UTF8 set causes these changes in the way PCRE works: - -1. In a pattern, the escape sequence \\x{...}, where the contents of the braces -is a string of hexadecimal digits, is interpreted as a UTF-8 character whose -code number is the given hexadecimal number, for example: \\x{1234}. This -inserts from one to six literal bytes into the pattern, using the UTF-8 -encoding. If a non-hexadecimal digit appears between the braces, the item is -not recognized. - -2. The original hexadecimal escape sequence, \\xhh, generates a two-byte UTF-8 -character if its value is greater than 127. - -3. Repeat quantifiers are NOT correctly handled if they follow a multibyte -character. For example, \\x{100}* and \\xc3+ do not work. If you want to -repeat such characters, you must enclose them in non-capturing parentheses, -for example (?:\\x{100}), at present. - -4. The dot metacharacter matches one UTF-8 character instead of a single byte. - -5. Unlike literal UTF-8 characters, the dot metacharacter followed by a -repeat quantifier does operate correctly on UTF-8 characters instead of -single bytes. - -4. Although the \\x{...} escape is permitted in a character class, characters -whose values are greater than 255 cannot be included in a class. - -5. A class is matched against a UTF-8 character instead of just a single byte, -but it can match only characters whose values are less than 256. Characters -with greater values always fail to match a class. - -6. Repeated classes work correctly on multiple characters. - -7. Classes containing just a single character whose value is greater than 127 -(but less than 256), for example, [\\x80] or [^\\x{93}], do not work because -these are optimized into single byte matches. In the first case, of course, -the class brackets are just redundant. - -8. Lookbehind assertions move backwards in the subject by a fixed number of -characters instead of a fixed number of bytes. Simple cases have been tested -to work correctly, but there may be hidden gotchas herein. - -9. The character types such as \\d and \\w do not work correctly with UTF-8 -characters. They continue to test a single byte. - -10. Anything not explicitly mentioned here continues to work in bytes rather -than in characters. - -The following UTF-8 features of Perl 5.6 are not implemented: - -1. The escape sequence \\C to match a single byte. - -2. The use of Unicode tables and properties and escapes \\p, \\P, and \\X. - - -.SH SAMPLE PROGRAM -The code below is a simple, complete demonstration program, to get you started -with using PCRE. This code is also supplied in the file \fIpcredemo.c\fR in the -PCRE distribution. - -The program compiles the regular expression that is its first argument, and -matches it against the subject string in its second argument. No options are -set, and default character tables are used. If matching succeeds, the program -outputs the portion of the subject that matched, together with the contents of -any captured substrings. - -On a Unix system that has PCRE installed in \fI/usr/local\fR, you can compile -the demonstration program using a command like this: - - gcc -o pcredemo pcredemo.c -I/usr/local/include -L/usr/local/lib -lpcre - -Then you can run simple tests like this: - - ./pcredemo 'cat|dog' 'the cat sat on the mat' - -Note that there is a much more comprehensive test program, called -\fBpcretest\fR, which supports many more facilities for testing regular -expressions. The \fBpcredemo\fR program is provided as a simple coding example. - -On some operating systems (e.g. Solaris) you may get an error like this when -you try to run \fBpcredemo\fR: - - ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or directory - -This is caused by the way shared library support works on those systems. You -need to add - - -R/usr/local/lib - -to the compile command to get round this problem. Here's the code: - - #include <stdio.h> - #include <string.h> - #include <pcre.h> - - #define OVECCOUNT 30 /* should be a multiple of 3 */ - - int main(int argc, char **argv) - { - pcre *re; - const char *error; - int erroffset; - int ovector[OVECCOUNT]; - int rc, i; - - if (argc != 3) - { - printf("Two arguments required: a regex and a " - "subject string\\n"); - return 1; - } - - /* Compile the regular expression in the first argument */ - - re = pcre_compile( - argv[1], /* the pattern */ - 0, /* default options */ - &error, /* for error message */ - &erroffset, /* for error offset */ - NULL); /* use default character tables */ - - /* Compilation failed: print the error message and exit */ - - if (re == NULL) - { - printf("PCRE compilation failed at offset %d: %s\\n", - erroffset, error); - return 1; - } - - /* Compilation succeeded: match the subject in the second - argument */ - - rc = pcre_exec( - re, /* the compiled pattern */ - NULL, /* we didn't study the pattern */ - argv[2], /* the subject string */ - (int)strlen(argv[2]), /* the length of the subject */ - 0, /* start at offset 0 in the subject */ - 0, /* default options */ - ovector, /* vector for substring information */ - OVECCOUNT); /* number of elements in the vector */ - - /* Matching failed: handle error cases */ - - if (rc < 0) - { - switch(rc) - { - case PCRE_ERROR_NOMATCH: printf("No match\\n"); break; - /* - Handle other special cases if you like - */ - default: printf("Matching error %d\\n", rc); break; - } - return 1; - } - - /* Match succeded */ - - printf("Match succeeded\\n"); - - /* The output vector wasn't big enough */ - - if (rc == 0) - { - rc = OVECCOUNT/3; - printf("ovector only has room for %d captured " - substrings\\n", rc - 1); - } - - /* Show substrings stored in the output vector */ - - for (i = 0; i < rc; i++) - { - char *substring_start = argv[2] + ovector[2*i]; - int substring_length = ovector[2*i+1] - ovector[2*i]; - printf("%2d: %.*s\\n", i, substring_length, - substring_start); - } - - return 0; - } - - -.SH AUTHOR -Philip Hazel <ph10@cam.ac.uk> -.br -University Computing Service, -.br -New Museums Site, -.br -Cambridge CB2 3QG, England. -.br -Phone: +44 1223 334714 - -Last updated: 15 August 2001 -.br -Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.html b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.html deleted file mode 100644 index 3e9eb36b..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.html +++ /dev/null @@ -1,2669 +0,0 @@ -<HTML> -<HEAD> -<TITLE>pcre specification</TITLE> -</HEAD> -<body bgcolor="#FFFFFF" text="#00005A"> -<H1>pcre specification</H1> -This HTML document has been generated automatically from the original man page. -If there is any nonsense in it, please consult the man page in case the -conversion went wrong. -<UL> -<LI><A NAME="TOC1" HREF="#SEC1">NAME</A> -<LI><A NAME="TOC2" HREF="#SEC2">SYNOPSIS</A> -<LI><A NAME="TOC3" HREF="#SEC3">DESCRIPTION</A> -<LI><A NAME="TOC4" HREF="#SEC4">MULTI-THREADING</A> -<LI><A NAME="TOC5" HREF="#SEC5">COMPILING A PATTERN</A> -<LI><A NAME="TOC6" HREF="#SEC6">STUDYING A PATTERN</A> -<LI><A NAME="TOC7" HREF="#SEC7">LOCALE SUPPORT</A> -<LI><A NAME="TOC8" HREF="#SEC8">INFORMATION ABOUT A PATTERN</A> -<LI><A NAME="TOC9" HREF="#SEC9">MATCHING A PATTERN</A> -<LI><A NAME="TOC10" HREF="#SEC10">EXTRACTING CAPTURED SUBSTRINGS</A> -<LI><A NAME="TOC11" HREF="#SEC11">LIMITATIONS</A> -<LI><A NAME="TOC12" HREF="#SEC12">DIFFERENCES FROM PERL</A> -<LI><A NAME="TOC13" HREF="#SEC13">REGULAR EXPRESSION DETAILS</A> -<LI><A NAME="TOC14" HREF="#SEC14">BACKSLASH</A> -<LI><A NAME="TOC15" HREF="#SEC15">CIRCUMFLEX AND DOLLAR</A> -<LI><A NAME="TOC16" HREF="#SEC16">FULL STOP (PERIOD, DOT)</A> -<LI><A NAME="TOC17" HREF="#SEC17">SQUARE BRACKETS</A> -<LI><A NAME="TOC18" HREF="#SEC18">POSIX CHARACTER CLASSES</A> -<LI><A NAME="TOC19" HREF="#SEC19">VERTICAL BAR</A> -<LI><A NAME="TOC20" HREF="#SEC20">INTERNAL OPTION SETTING</A> -<LI><A NAME="TOC21" HREF="#SEC21">SUBPATTERNS</A> -<LI><A NAME="TOC22" HREF="#SEC22">REPETITION</A> -<LI><A NAME="TOC23" HREF="#SEC23">BACK REFERENCES</A> -<LI><A NAME="TOC24" HREF="#SEC24">ASSERTIONS</A> -<LI><A NAME="TOC25" HREF="#SEC25">ONCE-ONLY SUBPATTERNS</A> -<LI><A NAME="TOC26" HREF="#SEC26">CONDITIONAL SUBPATTERNS</A> -<LI><A NAME="TOC27" HREF="#SEC27">COMMENTS</A> -<LI><A NAME="TOC28" HREF="#SEC28">RECURSIVE PATTERNS</A> -<LI><A NAME="TOC29" HREF="#SEC29">PERFORMANCE</A> -<LI><A NAME="TOC30" HREF="#SEC30">UTF-8 SUPPORT</A> -<LI><A NAME="TOC31" HREF="#SEC31">SAMPLE PROGRAM</A> -<LI><A NAME="TOC32" HREF="#SEC32">AUTHOR</A> -</UL> -<LI><A NAME="SEC1" HREF="#TOC1">NAME</A> -<P> -pcre - Perl-compatible regular expressions. -</P> -<LI><A NAME="SEC2" HREF="#TOC1">SYNOPSIS</A> -<P> -<B>#include <pcre.h></B> -</P> -<P> -<B>pcre *pcre_compile(const char *<I>pattern</I>, int <I>options</I>,</B> -<B>const char **<I>errptr</I>, int *<I>erroffset</I>,</B> -<B>const unsigned char *<I>tableptr</I>);</B> -</P> -<P> -<B>pcre_extra *pcre_study(const pcre *<I>code</I>, int <I>options</I>,</B> -<B>const char **<I>errptr</I>);</B> -</P> -<P> -<B>int pcre_exec(const pcre *<I>code</I>, const pcre_extra *<I>extra</I>,</B> -<B>const char *<I>subject</I>, int <I>length</I>, int <I>startoffset</I>,</B> -<B>int <I>options</I>, int *<I>ovector</I>, int <I>ovecsize</I>);</B> -</P> -<P> -<B>int pcre_copy_substring(const char *<I>subject</I>, int *<I>ovector</I>,</B> -<B>int <I>stringcount</I>, int <I>stringnumber</I>, char *<I>buffer</I>,</B> -<B>int <I>buffersize</I>);</B> -</P> -<P> -<B>int pcre_get_substring(const char *<I>subject</I>, int *<I>ovector</I>,</B> -<B>int <I>stringcount</I>, int <I>stringnumber</I>,</B> -<B>const char **<I>stringptr</I>);</B> -</P> -<P> -<B>int pcre_get_substring_list(const char *<I>subject</I>,</B> -<B>int *<I>ovector</I>, int <I>stringcount</I>, const char ***<I>listptr</I>);</B> -</P> -<P> -<B>void pcre_free_substring(const char *<I>stringptr</I>);</B> -</P> -<P> -<B>void pcre_free_substring_list(const char **<I>stringptr</I>);</B> -</P> -<P> -<B>const unsigned char *pcre_maketables(void);</B> -</P> -<P> -<B>int pcre_fullinfo(const pcre *<I>code</I>, const pcre_extra *<I>extra</I>,</B> -<B>int <I>what</I>, void *<I>where</I>);</B> -</P> -<P> -<B>int pcre_info(const pcre *<I>code</I>, int *<I>optptr</I>, int</B> -<B>*<I>firstcharptr</I>);</B> -</P> -<P> -<B>char *pcre_version(void);</B> -</P> -<P> -<B>void *(*pcre_malloc)(size_t);</B> -</P> -<P> -<B>void (*pcre_free)(void *);</B> -</P> -<LI><A NAME="SEC3" HREF="#TOC1">DESCRIPTION</A> -<P> -The PCRE library is a set of functions that implement regular expression -pattern matching using the same syntax and semantics as Perl 5, with just a few -differences (see below). The current implementation corresponds to Perl 5.005, -with some additional features from later versions. This includes some -experimental, incomplete support for UTF-8 encoded strings. Details of exactly -what is and what is not supported are given below. -</P> -<P> -PCRE has its own native API, which is described in this document. There is also -a set of wrapper functions that correspond to the POSIX regular expression API. -These are described in the <B>pcreposix</B> documentation. -</P> -<P> -The native API function prototypes are defined in the header file <B>pcre.h</B>, -and on Unix systems the library itself is called <B>libpcre.a</B>, so can be -accessed by adding <B>-lpcre</B> to the command for linking an application which -calls it. The header file defines the macros PCRE_MAJOR and PCRE_MINOR to -contain the major and minor release numbers for the library. Applications can -use these to include support for different releases. -</P> -<P> -The functions <B>pcre_compile()</B>, <B>pcre_study()</B>, and <B>pcre_exec()</B> -are used for compiling and matching regular expressions. A sample program that -demonstrates the simplest way of using them is given in the file -<I>pcredemo.c</I>. The last section of this man page describes how to run it. -</P> -<P> -The functions <B>pcre_copy_substring()</B>, <B>pcre_get_substring()</B>, and -<B>pcre_get_substring_list()</B> are convenience functions for extracting -captured substrings from a matched subject string; <B>pcre_free_substring()</B> -and <B>pcre_free_substring_list()</B> are also provided, to free the memory used -for extracted strings. -</P> -<P> -The function <B>pcre_maketables()</B> is used (optionally) to build a set of -character tables in the current locale for passing to <B>pcre_compile()</B>. -</P> -<P> -The function <B>pcre_fullinfo()</B> is used to find out information about a -compiled pattern; <B>pcre_info()</B> is an obsolete version which returns only -some of the available information, but is retained for backwards compatibility. -The function <B>pcre_version()</B> returns a pointer to a string containing the -version of PCRE and its date of release. -</P> -<P> -The global variables <B>pcre_malloc</B> and <B>pcre_free</B> initially contain -the entry points of the standard <B>malloc()</B> and <B>free()</B> functions -respectively. PCRE calls the memory management functions via these variables, -so a calling program can replace them if it wishes to intercept the calls. This -should be done before calling any PCRE functions. -</P> -<LI><A NAME="SEC4" HREF="#TOC1">MULTI-THREADING</A> -<P> -The PCRE functions can be used in multi-threading applications, with the -proviso that the memory management functions pointed to by <B>pcre_malloc</B> -and <B>pcre_free</B> are shared by all threads. -</P> -<P> -The compiled form of a regular expression is not altered during matching, so -the same compiled pattern can safely be used by several threads at once. -</P> -<LI><A NAME="SEC5" HREF="#TOC1">COMPILING A PATTERN</A> -<P> -The function <B>pcre_compile()</B> is called to compile a pattern into an -internal form. The pattern is a C string terminated by a binary zero, and -is passed in the argument <I>pattern</I>. A pointer to a single block of memory -that is obtained via <B>pcre_malloc</B> is returned. This contains the compiled -code and related data. The <B>pcre</B> type is defined for the returned block; -this is a typedef for a structure whose contents are not externally defined. It -is up to the caller to free the memory when it is no longer required. -</P> -<P> -Although the compiled code of a PCRE regex is relocatable, that is, it does not -depend on memory location, the complete <B>pcre</B> data block is not -fully relocatable, because it contains a copy of the <I>tableptr</I> argument, -which is an address (see below). -</P> -<P> -The size of a compiled pattern is roughly proportional to the length of the -pattern string, except that each character class (other than those containing -just a single character, negated or not) requires 33 bytes, and repeat -quantifiers with a minimum greater than one or a bounded maximum cause the -relevant portions of the compiled pattern to be replicated. -</P> -<P> -The <I>options</I> argument contains independent bits that affect the -compilation. It should be zero if no options are required. Some of the options, -in particular, those that are compatible with Perl, can also be set and unset -from within the pattern (see the detailed description of regular expressions -below). For these options, the contents of the <I>options</I> argument specifies -their initial settings at the start of compilation and execution. The -PCRE_ANCHORED option can be set at the time of matching as well as at compile -time. -</P> -<P> -If <I>errptr</I> is NULL, <B>pcre_compile()</B> returns NULL immediately. -Otherwise, if compilation of a pattern fails, <B>pcre_compile()</B> returns -NULL, and sets the variable pointed to by <I>errptr</I> to point to a textual -error message. The offset from the start of the pattern to the character where -the error was discovered is placed in the variable pointed to by -<I>erroffset</I>, which must not be NULL. If it is, an immediate error is given. -</P> -<P> -If the final argument, <I>tableptr</I>, is NULL, PCRE uses a default set of -character tables which are built when it is compiled, using the default C -locale. Otherwise, <I>tableptr</I> must be the result of a call to -<B>pcre_maketables()</B>. See the section on locale support below. -</P> -<P> -This code fragment shows a typical straightforward call to <B>pcre_compile()</B>: -</P> -<P> -<PRE> - pcre *re; - const char *error; - int erroffset; - re = pcre_compile( - "^A.*Z", /* the pattern */ - 0, /* default options */ - &error, /* for error message */ - &erroffset, /* for error offset */ - NULL); /* use default character tables */ -</PRE> -</P> -<P> -The following option bits are defined in the header file: -</P> -<P> -<PRE> - PCRE_ANCHORED -</PRE> -</P> -<P> -If this bit is set, the pattern is forced to be "anchored", that is, it is -constrained to match only at the start of the string which is being searched -(the "subject string"). This effect can also be achieved by appropriate -constructs in the pattern itself, which is the only way to do it in Perl. -</P> -<P> -<PRE> - PCRE_CASELESS -</PRE> -</P> -<P> -If this bit is set, letters in the pattern match both upper and lower case -letters. It is equivalent to Perl's /i option. -</P> -<P> -<PRE> - PCRE_DOLLAR_ENDONLY -</PRE> -</P> -<P> -If this bit is set, a dollar metacharacter in the pattern matches only at the -end of the subject string. Without this option, a dollar also matches -immediately before the final character if it is a newline (but not before any -other newlines). The PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is -set. There is no equivalent to this option in Perl. -</P> -<P> -<PRE> - PCRE_DOTALL -</PRE> -</P> -<P> -If this bit is set, a dot metacharater in the pattern matches all characters, -including newlines. Without it, newlines are excluded. This option is -equivalent to Perl's /s option. A negative class such as [^a] always matches a -newline character, independent of the setting of this option. -</P> -<P> -<PRE> - PCRE_EXTENDED -</PRE> -</P> -<P> -If this bit is set, whitespace data characters in the pattern are totally -ignored except when escaped or inside a character class, and characters between -an unescaped # outside a character class and the next newline character, -inclusive, are also ignored. This is equivalent to Perl's /x option, and makes -it possible to include comments inside complicated patterns. Note, however, -that this applies only to data characters. Whitespace characters may never -appear within special character sequences in a pattern, for example within the -sequence (?( which introduces a conditional subpattern. -</P> -<P> -<PRE> - PCRE_EXTRA -</PRE> -</P> -<P> -This option was invented in order to turn on additional functionality of PCRE -that is incompatible with Perl, but it is currently of very little use. When -set, any backslash in a pattern that is followed by a letter that has no -special meaning causes an error, thus reserving these combinations for future -expansion. By default, as in Perl, a backslash followed by a letter with no -special meaning is treated as a literal. There are at present no other features -controlled by this option. It can also be set by a (?X) option setting within a -pattern. -</P> -<P> -<PRE> - PCRE_MULTILINE -</PRE> -</P> -<P> -By default, PCRE treats the subject string as consisting of a single "line" of -characters (even if it actually contains several newlines). The "start of line" -metacharacter (^) matches only at the start of the string, while the "end of -line" metacharacter ($) matches only at the end of the string, or before a -terminating newline (unless PCRE_DOLLAR_ENDONLY is set). This is the same as -Perl. -</P> -<P> -When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs -match immediately following or immediately before any newline in the subject -string, respectively, as well as at the very start and end. This is equivalent -to Perl's /m option. If there are no "\n" characters in a subject string, or -no occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no -effect. -</P> -<P> -<PRE> - PCRE_UNGREEDY -</PRE> -</P> -<P> -This option inverts the "greediness" of the quantifiers so that they are not -greedy by default, but become greedy if followed by "?". It is not compatible -with Perl. It can also be set by a (?U) option setting within the pattern. -</P> -<P> -<PRE> - PCRE_UTF8 -</PRE> -</P> -<P> -This option causes PCRE to regard both the pattern and the subject as strings -of UTF-8 characters instead of just byte strings. However, it is available only -if PCRE has been built to include UTF-8 support. If not, the use of this option -provokes an error. Support for UTF-8 is new, experimental, and incomplete. -Details of exactly what it entails are given below. -</P> -<LI><A NAME="SEC6" HREF="#TOC1">STUDYING A PATTERN</A> -<P> -When a pattern is going to be used several times, it is worth spending more -time analyzing it in order to speed up the time taken for matching. The -function <B>pcre_study()</B> takes a pointer to a compiled pattern as its first -argument, and returns a pointer to a <B>pcre_extra</B> block (another typedef -for a structure with hidden contents) containing additional information about -the pattern; this can be passed to <B>pcre_exec()</B>. If no additional -information is available, NULL is returned. -</P> -<P> -The second argument contains option bits. At present, no options are defined -for <B>pcre_study()</B>, and this argument should always be zero. -</P> -<P> -The third argument for <B>pcre_study()</B> is a pointer to an error message. If -studying succeeds (even if no data is returned), the variable it points to is -set to NULL. Otherwise it points to a textual error message. -</P> -<P> -This is a typical call to <B>pcre_study</B>(): -</P> -<P> -<PRE> - pcre_extra *pe; - pe = pcre_study( - re, /* result of pcre_compile() */ - 0, /* no options exist */ - &error); /* set to NULL or points to a message */ -</PRE> -</P> -<P> -At present, studying a pattern is useful only for non-anchored patterns that do -not have a single fixed starting character. A bitmap of possible starting -characters is created. -</P> -<LI><A NAME="SEC7" HREF="#TOC1">LOCALE SUPPORT</A> -<P> -PCRE handles caseless matching, and determines whether characters are letters, -digits, or whatever, by reference to a set of tables. The library contains a -default set of tables which is created in the default C locale when PCRE is -compiled. This is used when the final argument of <B>pcre_compile()</B> is NULL, -and is sufficient for many applications. -</P> -<P> -An alternative set of tables can, however, be supplied. Such tables are built -by calling the <B>pcre_maketables()</B> function, which has no arguments, in the -relevant locale. The result can then be passed to <B>pcre_compile()</B> as often -as necessary. For example, to build and use tables that are appropriate for the -French locale (where accented characters with codes greater than 128 are -treated as letters), the following code could be used: -</P> -<P> -<PRE> - setlocale(LC_CTYPE, "fr"); - tables = pcre_maketables(); - re = pcre_compile(..., tables); -</PRE> -</P> -<P> -The tables are built in memory that is obtained via <B>pcre_malloc</B>. The -pointer that is passed to <B>pcre_compile</B> is saved with the compiled -pattern, and the same tables are used via this pointer by <B>pcre_study()</B> -and <B>pcre_exec()</B>. Thus for any single pattern, compilation, studying and -matching all happen in the same locale, but different patterns can be compiled -in different locales. It is the caller's responsibility to ensure that the -memory containing the tables remains available for as long as it is needed. -</P> -<LI><A NAME="SEC8" HREF="#TOC1">INFORMATION ABOUT A PATTERN</A> -<P> -The <B>pcre_fullinfo()</B> function returns information about a compiled -pattern. It replaces the obsolete <B>pcre_info()</B> function, which is -nevertheless retained for backwards compability (and is documented below). -</P> -<P> -The first argument for <B>pcre_fullinfo()</B> is a pointer to the compiled -pattern. The second argument is the result of <B>pcre_study()</B>, or NULL if -the pattern was not studied. The third argument specifies which piece of -information is required, while the fourth argument is a pointer to a variable -to receive the data. The yield of the function is zero for success, or one of -the following negative numbers: -</P> -<P> -<PRE> - PCRE_ERROR_NULL the argument <I>code</I> was NULL - the argument <I>where</I> was NULL - PCRE_ERROR_BADMAGIC the "magic number" was not found - PCRE_ERROR_BADOPTION the value of <I>what</I> was invalid -</PRE> -</P> -<P> -Here is a typical call of <B>pcre_fullinfo()</B>, to obtain the length of the -compiled pattern: -</P> -<P> -<PRE> - int rc; - unsigned long int length; - rc = pcre_fullinfo( - re, /* result of pcre_compile() */ - pe, /* result of pcre_study(), or NULL */ - PCRE_INFO_SIZE, /* what is required */ - &length); /* where to put the data */ -</PRE> -</P> -<P> -The possible values for the third argument are defined in <B>pcre.h</B>, and are -as follows: -</P> -<P> -<PRE> - PCRE_INFO_OPTIONS -</PRE> -</P> -<P> -Return a copy of the options with which the pattern was compiled. The fourth -argument should point to an <B>unsigned long int</B> variable. These option bits -are those specified in the call to <B>pcre_compile()</B>, modified by any -top-level option settings within the pattern itself, and with the PCRE_ANCHORED -bit forcibly set if the form of the pattern implies that it can match only at -the start of a subject string. -</P> -<P> -<PRE> - PCRE_INFO_SIZE -</PRE> -</P> -<P> -Return the size of the compiled pattern, that is, the value that was passed as -the argument to <B>pcre_malloc()</B> when PCRE was getting memory in which to -place the compiled data. The fourth argument should point to a <B>size_t</B> -variable. -</P> -<P> -<PRE> - PCRE_INFO_CAPTURECOUNT -</PRE> -</P> -<P> -Return the number of capturing subpatterns in the pattern. The fourth argument -should point to an \fbint\fR variable. -</P> -<P> -<PRE> - PCRE_INFO_BACKREFMAX -</PRE> -</P> -<P> -Return the number of the highest back reference in the pattern. The fourth -argument should point to an <B>int</B> variable. Zero is returned if there are -no back references. -</P> -<P> -<PRE> - PCRE_INFO_FIRSTCHAR -</PRE> -</P> -<P> -Return information about the first character of any matched string, for a -non-anchored pattern. If there is a fixed first character, e.g. from a pattern -such as (cat|cow|coyote), it is returned in the integer pointed to by -<I>where</I>. Otherwise, if either -</P> -<P> -(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch -starts with "^", or -</P> -<P> -(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set -(if it were set, the pattern would be anchored), -</P> -<P> --1 is returned, indicating that the pattern matches only at the start of a -subject string or after any "\n" within the string. Otherwise -2 is returned. -For anchored patterns, -2 is returned. -</P> -<P> -<PRE> - PCRE_INFO_FIRSTTABLE -</PRE> -</P> -<P> -If the pattern was studied, and this resulted in the construction of a 256-bit -table indicating a fixed set of characters for the first character in any -matching string, a pointer to the table is returned. Otherwise NULL is -returned. The fourth argument should point to an <B>unsigned char *</B> -variable. -</P> -<P> -<PRE> - PCRE_INFO_LASTLITERAL -</PRE> -</P> -<P> -For a non-anchored pattern, return the value of the rightmost literal character -which must exist in any matched string, other than at its start. The fourth -argument should point to an <B>int</B> variable. If there is no such character, -or if the pattern is anchored, -1 is returned. For example, for the pattern -/a\d+z\d+/ the returned value is 'z'. -</P> -<P> -The <B>pcre_info()</B> function is now obsolete because its interface is too -restrictive to return all the available data about a compiled pattern. New -programs should use <B>pcre_fullinfo()</B> instead. The yield of -<B>pcre_info()</B> is the number of capturing subpatterns, or one of the -following negative numbers: -</P> -<P> -<PRE> - PCRE_ERROR_NULL the argument <I>code</I> was NULL - PCRE_ERROR_BADMAGIC the "magic number" was not found -</PRE> -</P> -<P> -If the <I>optptr</I> argument is not NULL, a copy of the options with which the -pattern was compiled is placed in the integer it points to (see -PCRE_INFO_OPTIONS above). -</P> -<P> -If the pattern is not anchored and the <I>firstcharptr</I> argument is not NULL, -it is used to pass back information about the first character of any matched -string (see PCRE_INFO_FIRSTCHAR above). -</P> -<LI><A NAME="SEC9" HREF="#TOC1">MATCHING A PATTERN</A> -<P> -The function <B>pcre_exec()</B> is called to match a subject string against a -pre-compiled pattern, which is passed in the <I>code</I> argument. If the -pattern has been studied, the result of the study should be passed in the -<I>extra</I> argument. Otherwise this must be NULL. -</P> -<P> -Here is an example of a simple call to <B>pcre_exec()</B>: -</P> -<P> -<PRE> - int rc; - int ovector[30]; - rc = pcre_exec( - re, /* result of pcre_compile() */ - NULL, /* we didn't study the pattern */ - "some string", /* the subject string */ - 11, /* the length of the subject string */ - 0, /* start at offset 0 in the subject */ - 0, /* default options */ - ovector, /* vector for substring information */ - 30); /* number of elements in the vector */ -</PRE> -</P> -<P> -The PCRE_ANCHORED option can be passed in the <I>options</I> argument, whose -unused bits must be zero. However, if a pattern was compiled with -PCRE_ANCHORED, or turned out to be anchored by virtue of its contents, it -cannot be made unachored at matching time. -</P> -<P> -There are also three further options that can be set only at matching time: -</P> -<P> -<PRE> - PCRE_NOTBOL -</PRE> -</P> -<P> -The first character of the string is not the beginning of a line, so the -circumflex metacharacter should not match before it. Setting this without -PCRE_MULTILINE (at compile time) causes circumflex never to match. -</P> -<P> -<PRE> - PCRE_NOTEOL -</PRE> -</P> -<P> -The end of the string is not the end of a line, so the dollar metacharacter -should not match it nor (except in multiline mode) a newline immediately before -it. Setting this without PCRE_MULTILINE (at compile time) causes dollar never -to match. -</P> -<P> -<PRE> - PCRE_NOTEMPTY -</PRE> -</P> -<P> -An empty string is not considered to be a valid match if this option is set. If -there are alternatives in the pattern, they are tried. If all the alternatives -match the empty string, the entire match fails. For example, if the pattern -</P> -<P> -<PRE> - a?b? -</PRE> -</P> -<P> -is applied to a string not beginning with "a" or "b", it matches the empty -string at the start of the subject. With PCRE_NOTEMPTY set, this match is not -valid, so PCRE searches further into the string for occurrences of "a" or "b". -</P> -<P> -Perl has no direct equivalent of PCRE_NOTEMPTY, but it does make a special case -of a pattern match of the empty string within its <B>split()</B> function, and -when using the /g modifier. It is possible to emulate Perl's behaviour after -matching a null string by first trying the match again at the same offset with -PCRE_NOTEMPTY set, and then if that fails by advancing the starting offset (see -below) and trying an ordinary match again. -</P> -<P> -The subject string is passed as a pointer in <I>subject</I>, a length in -<I>length</I>, and a starting offset in <I>startoffset</I>. Unlike the pattern -string, the subject may contain binary zero characters. When the starting -offset is zero, the search for a match starts at the beginning of the subject, -and this is by far the most common case. -</P> -<P> -A non-zero starting offset is useful when searching for another match in the -same subject by calling <B>pcre_exec()</B> again after a previous success. -Setting <I>startoffset</I> differs from just passing over a shortened string and -setting PCRE_NOTBOL in the case of a pattern that begins with any kind of -lookbehind. For example, consider the pattern -</P> -<P> -<PRE> - \Biss\B -</PRE> -</P> -<P> -which finds occurrences of "iss" in the middle of words. (\B matches only if -the current position in the subject is not a word boundary.) When applied to -the string "Mississipi" the first call to <B>pcre_exec()</B> finds the first -occurrence. If <B>pcre_exec()</B> is called again with just the remainder of the -subject, namely "issipi", it does not match, because \B is always false at the -start of the subject, which is deemed to be a word boundary. However, if -<B>pcre_exec()</B> is passed the entire string again, but with <I>startoffset</I> -set to 4, it finds the second occurrence of "iss" because it is able to look -behind the starting point to discover that it is preceded by a letter. -</P> -<P> -If a non-zero starting offset is passed when the pattern is anchored, one -attempt to match at the given offset is tried. This can only succeed if the -pattern does not require the match to be at the start of the subject. -</P> -<P> -In general, a pattern matches a certain portion of the subject, and in -addition, further substrings from the subject may be picked out by parts of the -pattern. Following the usage in Jeffrey Friedl's book, this is called -"capturing" in what follows, and the phrase "capturing subpattern" is used for -a fragment of a pattern that picks out a substring. PCRE supports several other -kinds of parenthesized subpattern that do not cause substrings to be captured. -</P> -<P> -Captured substrings are returned to the caller via a vector of integer offsets -whose address is passed in <I>ovector</I>. The number of elements in the vector -is passed in <I>ovecsize</I>. The first two-thirds of the vector is used to pass -back captured substrings, each substring using a pair of integers. The -remaining third of the vector is used as workspace by <B>pcre_exec()</B> while -matching capturing subpatterns, and is not available for passing back -information. The length passed in <I>ovecsize</I> should always be a multiple of -three. If it is not, it is rounded down. -</P> -<P> -When a match has been successful, information about captured substrings is -returned in pairs of integers, starting at the beginning of <I>ovector</I>, and -continuing up to two-thirds of its length at the most. The first element of a -pair is set to the offset of the first character in a substring, and the second -is set to the offset of the first character after the end of a substring. The -first pair, <I>ovector[0]</I> and <I>ovector[1]</I>, identify the portion of the -subject string matched by the entire pattern. The next pair is used for the -first capturing subpattern, and so on. The value returned by <B>pcre_exec()</B> -is the number of pairs that have been set. If there are no capturing -subpatterns, the return value from a successful match is 1, indicating that -just the first pair of offsets has been set. -</P> -<P> -Some convenience functions are provided for extracting the captured substrings -as separate strings. These are described in the following section. -</P> -<P> -It is possible for an capturing subpattern number <I>n+1</I> to match some -part of the subject when subpattern <I>n</I> has not been used at all. For -example, if the string "abc" is matched against the pattern (a|(z))(bc) -subpatterns 1 and 3 are matched, but 2 is not. When this happens, both offset -values corresponding to the unused subpattern are set to -1. -</P> -<P> -If a capturing subpattern is matched repeatedly, it is the last portion of the -string that it matched that gets returned. -</P> -<P> -If the vector is too small to hold all the captured substrings, it is used as -far as possible (up to two-thirds of its length), and the function returns a -value of zero. In particular, if the substring offsets are not of interest, -<B>pcre_exec()</B> may be called with <I>ovector</I> passed as NULL and -<I>ovecsize</I> as zero. However, if the pattern contains back references and -the <I>ovector</I> isn't big enough to remember the related substrings, PCRE has -to get additional memory for use during matching. Thus it is usually advisable -to supply an <I>ovector</I>. -</P> -<P> -Note that <B>pcre_info()</B> can be used to find out how many capturing -subpatterns there are in a compiled pattern. The smallest size for -<I>ovector</I> that will allow for <I>n</I> captured substrings in addition to -the offsets of the substring matched by the whole pattern is (<I>n</I>+1)*3. -</P> -<P> -If <B>pcre_exec()</B> fails, it returns a negative number. The following are -defined in the header file: -</P> -<P> -<PRE> - PCRE_ERROR_NOMATCH (-1) -</PRE> -</P> -<P> -The subject string did not match the pattern. -</P> -<P> -<PRE> - PCRE_ERROR_NULL (-2) -</PRE> -</P> -<P> -Either <I>code</I> or <I>subject</I> was passed as NULL, or <I>ovector</I> was -NULL and <I>ovecsize</I> was not zero. -</P> -<P> -<PRE> - PCRE_ERROR_BADOPTION (-3) -</PRE> -</P> -<P> -An unrecognized bit was set in the <I>options</I> argument. -</P> -<P> -<PRE> - PCRE_ERROR_BADMAGIC (-4) -</PRE> -</P> -<P> -PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch -the case when it is passed a junk pointer. This is the error it gives when the -magic number isn't present. -</P> -<P> -<PRE> - PCRE_ERROR_UNKNOWN_NODE (-5) -</PRE> -</P> -<P> -While running the pattern match, an unknown item was encountered in the -compiled pattern. This error could be caused by a bug in PCRE or by overwriting -of the compiled pattern. -</P> -<P> -<PRE> - PCRE_ERROR_NOMEMORY (-6) -</PRE> -</P> -<P> -If a pattern contains back references, but the <I>ovector</I> that is passed to -<B>pcre_exec()</B> is not big enough to remember the referenced substrings, PCRE -gets a block of memory at the start of matching to use for this purpose. If the -call via <B>pcre_malloc()</B> fails, this error is given. The memory is freed at -the end of matching. -</P> -<LI><A NAME="SEC10" HREF="#TOC1">EXTRACTING CAPTURED SUBSTRINGS</A> -<P> -Captured substrings can be accessed directly by using the offsets returned by -<B>pcre_exec()</B> in <I>ovector</I>. For convenience, the functions -<B>pcre_copy_substring()</B>, <B>pcre_get_substring()</B>, and -<B>pcre_get_substring_list()</B> are provided for extracting captured substrings -as new, separate, zero-terminated strings. A substring that contains a binary -zero is correctly extracted and has a further zero added on the end, but the -result does not, of course, function as a C string. -</P> -<P> -The first three arguments are the same for all three functions: <I>subject</I> -is the subject string which has just been successfully matched, <I>ovector</I> -is a pointer to the vector of integer offsets that was passed to -<B>pcre_exec()</B>, and <I>stringcount</I> is the number of substrings that -were captured by the match, including the substring that matched the entire -regular expression. This is the value returned by <B>pcre_exec</B> if it -is greater than zero. If <B>pcre_exec()</B> returned zero, indicating that it -ran out of space in <I>ovector</I>, the value passed as <I>stringcount</I> should -be the size of the vector divided by three. -</P> -<P> -The functions <B>pcre_copy_substring()</B> and <B>pcre_get_substring()</B> -extract a single substring, whose number is given as <I>stringnumber</I>. A -value of zero extracts the substring that matched the entire pattern, while -higher values extract the captured substrings. For <B>pcre_copy_substring()</B>, -the string is placed in <I>buffer</I>, whose length is given by -<I>buffersize</I>, while for <B>pcre_get_substring()</B> a new block of memory is -obtained via <B>pcre_malloc</B>, and its address is returned via -<I>stringptr</I>. The yield of the function is the length of the string, not -including the terminating zero, or one of -</P> -<P> -<PRE> - PCRE_ERROR_NOMEMORY (-6) -</PRE> -</P> -<P> -The buffer was too small for <B>pcre_copy_substring()</B>, or the attempt to get -memory failed for <B>pcre_get_substring()</B>. -</P> -<P> -<PRE> - PCRE_ERROR_NOSUBSTRING (-7) -</PRE> -</P> -<P> -There is no substring whose number is <I>stringnumber</I>. -</P> -<P> -The <B>pcre_get_substring_list()</B> function extracts all available substrings -and builds a list of pointers to them. All this is done in a single block of -memory which is obtained via <B>pcre_malloc</B>. The address of the memory block -is returned via <I>listptr</I>, which is also the start of the list of string -pointers. The end of the list is marked by a NULL pointer. The yield of the -function is zero if all went well, or -</P> -<P> -<PRE> - PCRE_ERROR_NOMEMORY (-6) -</PRE> -</P> -<P> -if the attempt to get the memory block failed. -</P> -<P> -When any of these functions encounter a substring that is unset, which can -happen when capturing subpattern number <I>n+1</I> matches some part of the -subject, but subpattern <I>n</I> has not been used at all, they return an empty -string. This can be distinguished from a genuine zero-length substring by -inspecting the appropriate offset in <I>ovector</I>, which is negative for unset -substrings. -</P> -<P> -The two convenience functions <B>pcre_free_substring()</B> and -<B>pcre_free_substring_list()</B> can be used to free the memory returned by -a previous call of <B>pcre_get_substring()</B> or -<B>pcre_get_substring_list()</B>, respectively. They do nothing more than call -the function pointed to by <B>pcre_free</B>, which of course could be called -directly from a C program. However, PCRE is used in some situations where it is -linked via a special interface to another programming language which cannot use -<B>pcre_free</B> directly; it is for these cases that the functions are -provided. -</P> -<LI><A NAME="SEC11" HREF="#TOC1">LIMITATIONS</A> -<P> -There are some size limitations in PCRE but it is hoped that they will never in -practice be relevant. -The maximum length of a compiled pattern is 65539 (sic) bytes. -All values in repeating quantifiers must be less than 65536. -There maximum number of capturing subpatterns is 65535. -There is no limit to the number of non-capturing subpatterns, but the maximum -depth of nesting of all kinds of parenthesized subpattern, including capturing -subpatterns, assertions, and other types of subpattern, is 200. -</P> -<P> -The maximum length of a subject string is the largest positive number that an -integer variable can hold. However, PCRE uses recursion to handle subpatterns -and indefinite repetition. This means that the available stack space may limit -the size of a subject string that can be processed by certain patterns. -</P> -<LI><A NAME="SEC12" HREF="#TOC1">DIFFERENCES FROM PERL</A> -<P> -The differences described here are with respect to Perl 5.005. -</P> -<P> -1. By default, a whitespace character is any character that the C library -function <B>isspace()</B> recognizes, though it is possible to compile PCRE with -alternative character type tables. Normally <B>isspace()</B> matches space, -formfeed, newline, carriage return, horizontal tab, and vertical tab. Perl 5 -no longer includes vertical tab in its set of whitespace characters. The \v -escape that was in the Perl documentation for a long time was never in fact -recognized. However, the character itself was treated as whitespace at least -up to 5.002. In 5.004 and 5.005 it does not match \s. -</P> -<P> -2. PCRE does not allow repeat quantifiers on lookahead assertions. Perl permits -them, but they do not mean what you might think. For example, (?!a){3} does -not assert that the next three characters are not "a". It just asserts that the -next character is not "a" three times. -</P> -<P> -3. Capturing subpatterns that occur inside negative lookahead assertions are -counted, but their entries in the offsets vector are never set. Perl sets its -numerical variables from any such patterns that are matched before the -assertion fails to match something (thereby succeeding), but only if the -negative lookahead assertion contains just one branch. -</P> -<P> -4. Though binary zero characters are supported in the subject string, they are -not allowed in a pattern string because it is passed as a normal C string, -terminated by zero. The escape sequence "\0" can be used in the pattern to -represent a binary zero. -</P> -<P> -5. The following Perl escape sequences are not supported: \l, \u, \L, \U, -\E, \Q. In fact these are implemented by Perl's general string-handling and -are not part of its pattern matching engine. -</P> -<P> -6. The Perl \G assertion is not supported as it is not relevant to single -pattern matches. -</P> -<P> -7. Fairly obviously, PCRE does not support the (?{code}) and (?p{code}) -constructions. However, there is some experimental support for recursive -patterns using the non-Perl item (?R). -</P> -<P> -8. There are at the time of writing some oddities in Perl 5.005_02 concerned -with the settings of captured strings when part of a pattern is repeated. For -example, matching "aba" against the pattern /^(a(b)?)+$/ sets $2 to the value -"b", but matching "aabbaa" against /^(aa(bb)?)+$/ leaves $2 unset. However, if -the pattern is changed to /^(aa(b(b))?)+$/ then $2 (and $3) are set. -</P> -<P> -In Perl 5.004 $2 is set in both cases, and that is also true of PCRE. If in the -future Perl changes to a consistent state that is different, PCRE may change to -follow. -</P> -<P> -9. Another as yet unresolved discrepancy is that in Perl 5.005_02 the pattern -/^(a)?(?(1)a|b)+$/ matches the string "a", whereas in PCRE it does not. -However, in both Perl and PCRE /^(a)?a/ matched against "a" leaves $1 unset. -</P> -<P> -10. PCRE provides some extensions to the Perl regular expression facilities: -</P> -<P> -(a) Although lookbehind assertions must match fixed length strings, each -alternative branch of a lookbehind assertion can match a different length of -string. Perl 5.005 requires them all to have the same length. -</P> -<P> -(b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not set, the $ meta- -character matches only at the very end of the string. -</P> -<P> -(c) If PCRE_EXTRA is set, a backslash followed by a letter with no special -meaning is faulted. -</P> -<P> -(d) If PCRE_UNGREEDY is set, the greediness of the repetition quantifiers is -inverted, that is, by default they are not greedy, but if followed by a -question mark they are. -</P> -<P> -(e) PCRE_ANCHORED can be used to force a pattern to be tried only at the start -of the subject. -</P> -<P> -(f) The PCRE_NOTBOL, PCRE_NOTEOL, and PCRE_NOTEMPTY options for -<B>pcre_exec()</B> have no Perl equivalents. -</P> -<P> -(g) The (?R) construct allows for recursive pattern matching (Perl 5.6 can do -this using the (?p{code}) construct, which PCRE cannot of course support.) -</P> -<LI><A NAME="SEC13" HREF="#TOC1">REGULAR EXPRESSION DETAILS</A> -<P> -The syntax and semantics of the regular expressions supported by PCRE are -described below. Regular expressions are also described in the Perl -documentation and in a number of other books, some of which have copious -examples. Jeffrey Friedl's "Mastering Regular Expressions", published by -O'Reilly (ISBN 1-56592-257), covers them in great detail. -</P> -<P> -The description here is intended as reference documentation. The basic -operation of PCRE is on strings of bytes. However, there is the beginnings of -some support for UTF-8 character strings. To use this support you must -configure PCRE to include it, and then call <B>pcre_compile()</B> with the -PCRE_UTF8 option. How this affects the pattern matching is described in the -final section of this document. -</P> -<P> -A regular expression is a pattern that is matched against a subject string from -left to right. Most characters stand for themselves in a pattern, and match the -corresponding characters in the subject. As a trivial example, the pattern -</P> -<P> -<PRE> - The quick brown fox -</PRE> -</P> -<P> -matches a portion of a subject string that is identical to itself. The power of -regular expressions comes from the ability to include alternatives and -repetitions in the pattern. These are encoded in the pattern by the use of -<I>meta-characters</I>, which do not stand for themselves but instead are -interpreted in some special way. -</P> -<P> -There are two different sets of meta-characters: those that are recognized -anywhere in the pattern except within square brackets, and those that are -recognized in square brackets. Outside square brackets, the meta-characters are -as follows: -</P> -<P> -<PRE> - \ general escape character with several uses - ^ assert start of subject (or line, in multiline mode) - $ assert end of subject (or line, in multiline mode) - . match any character except newline (by default) - [ start character class definition - | start of alternative branch - ( start subpattern - ) end subpattern - ? extends the meaning of ( - also 0 or 1 quantifier - also quantifier minimizer - * 0 or more quantifier - + 1 or more quantifier - { start min/max quantifier -</PRE> -</P> -<P> -Part of a pattern that is in square brackets is called a "character class". In -a character class the only meta-characters are: -</P> -<P> -<PRE> - \ general escape character - ^ negate the class, but only if the first character - - indicates character range - ] terminates the character class -</PRE> -</P> -<P> -The following sections describe the use of each of the meta-characters. -</P> -<LI><A NAME="SEC14" HREF="#TOC1">BACKSLASH</A> -<P> -The backslash character has several uses. Firstly, if it is followed by a -non-alphameric character, it takes away any special meaning that character may -have. This use of backslash as an escape character applies both inside and -outside character classes. -</P> -<P> -For example, if you want to match a "*" character, you write "\*" in the -pattern. This applies whether or not the following character would otherwise be -interpreted as a meta-character, so it is always safe to precede a -non-alphameric with "\" to specify that it stands for itself. In particular, -if you want to match a backslash, you write "\\". -</P> -<P> -If a pattern is compiled with the PCRE_EXTENDED option, whitespace in the -pattern (other than in a character class) and characters between a "#" outside -a character class and the next newline character are ignored. An escaping -backslash can be used to include a whitespace or "#" character as part of the -pattern. -</P> -<P> -A second use of backslash provides a way of encoding non-printing characters -in patterns in a visible manner. There is no restriction on the appearance of -non-printing characters, apart from the binary zero that terminates a pattern, -but when a pattern is being prepared by text editing, it is usually easier to -use one of the following escape sequences than the binary character it -represents: -</P> -<P> -<PRE> - \a alarm, that is, the BEL character (hex 07) - \cx "control-x", where x is any character - \e escape (hex 1B) - \f formfeed (hex 0C) - \n newline (hex 0A) - \r carriage return (hex 0D) - \t tab (hex 09) - \xhh character with hex code hh - \ddd character with octal code ddd, or backreference -</PRE> -</P> -<P> -The precise effect of "\cx" is as follows: if "x" is a lower case letter, it -is converted to upper case. Then bit 6 of the character (hex 40) is inverted. -Thus "\cz" becomes hex 1A, but "\c{" becomes hex 3B, while "\c;" becomes hex -7B. -</P> -<P> -After "\x", up to two hexadecimal digits are read (letters can be in upper or -lower case). -</P> -<P> -After "\0" up to two further octal digits are read. In both cases, if there -are fewer than two digits, just those that are present are used. Thus the -sequence "\0\x\07" specifies two binary zeros followed by a BEL character. -Make sure you supply two digits after the initial zero if the character that -follows is itself an octal digit. -</P> -<P> -The handling of a backslash followed by a digit other than 0 is complicated. -Outside a character class, PCRE reads it and any following digits as a decimal -number. If the number is less than 10, or if there have been at least that many -previous capturing left parentheses in the expression, the entire sequence is -taken as a <I>back reference</I>. A description of how this works is given -later, following the discussion of parenthesized subpatterns. -</P> -<P> -Inside a character class, or if the decimal number is greater than 9 and there -have not been that many capturing subpatterns, PCRE re-reads up to three octal -digits following the backslash, and generates a single byte from the least -significant 8 bits of the value. Any subsequent digits stand for themselves. -For example: -</P> -<P> -<PRE> - \040 is another way of writing a space - \40 is the same, provided there are fewer than 40 - previous capturing subpatterns - \7 is always a back reference - \11 might be a back reference, or another way of - writing a tab - \011 is always a tab - \0113 is a tab followed by the character "3" - \113 is the character with octal code 113 (since there - can be no more than 99 back references) - \377 is a byte consisting entirely of 1 bits - \81 is either a back reference, or a binary zero - followed by the two characters "8" and "1" -</PRE> -</P> -<P> -Note that octal values of 100 or greater must not be introduced by a leading -zero, because no more than three octal digits are ever read. -</P> -<P> -All the sequences that define a single byte value can be used both inside and -outside character classes. In addition, inside a character class, the sequence -"\b" is interpreted as the backspace character (hex 08). Outside a character -class it has a different meaning (see below). -</P> -<P> -The third use of backslash is for specifying generic character types: -</P> -<P> -<PRE> - \d any decimal digit - \D any character that is not a decimal digit - \s any whitespace character - \S any character that is not a whitespace character - \w any "word" character - \W any "non-word" character -</PRE> -</P> -<P> -Each pair of escape sequences partitions the complete set of characters into -two disjoint sets. Any given character matches one, and only one, of each pair. -</P> -<P> -A "word" character is any letter or digit or the underscore character, that is, -any character which can be part of a Perl "word". The definition of letters and -digits is controlled by PCRE's character tables, and may vary if locale- -specific matching is taking place (see "Locale support" above). For example, in -the "fr" (French) locale, some character codes greater than 128 are used for -accented letters, and these are matched by \w. -</P> -<P> -These character type sequences can appear both inside and outside character -classes. They each match one character of the appropriate type. If the current -matching point is at the end of the subject string, all of them fail, since -there is no character to match. -</P> -<P> -The fourth use of backslash is for certain simple assertions. An assertion -specifies a condition that has to be met at a particular point in a match, -without consuming any characters from the subject string. The use of -subpatterns for more complicated assertions is described below. The backslashed -assertions are -</P> -<P> -<PRE> - \b word boundary - \B not a word boundary - \A start of subject (independent of multiline mode) - \Z end of subject or newline at end (independent of multiline mode) - \z end of subject (independent of multiline mode) -</PRE> -</P> -<P> -These assertions may not appear in character classes (but note that "\b" has a -different meaning, namely the backspace character, inside a character class). -</P> -<P> -A word boundary is a position in the subject string where the current character -and the previous character do not both match \w or \W (i.e. one matches -\w and the other matches \W), or the start or end of the string if the -first or last character matches \w, respectively. -</P> -<P> -The \A, \Z, and \z assertions differ from the traditional circumflex and -dollar (described below) in that they only ever match at the very start and end -of the subject string, whatever options are set. They are not affected by the -PCRE_NOTBOL or PCRE_NOTEOL options. If the <I>startoffset</I> argument of -<B>pcre_exec()</B> is non-zero, \A can never match. The difference between \Z -and \z is that \Z matches before a newline that is the last character of the -string as well as at the end of the string, whereas \z matches only at the -end. -</P> -<LI><A NAME="SEC15" HREF="#TOC1">CIRCUMFLEX AND DOLLAR</A> -<P> -Outside a character class, in the default matching mode, the circumflex -character is an assertion which is true only if the current matching point is -at the start of the subject string. If the <I>startoffset</I> argument of -<B>pcre_exec()</B> is non-zero, circumflex can never match. Inside a character -class, circumflex has an entirely different meaning (see below). -</P> -<P> -Circumflex need not be the first character of the pattern if a number of -alternatives are involved, but it should be the first thing in each alternative -in which it appears if the pattern is ever to match that branch. If all -possible alternatives start with a circumflex, that is, if the pattern is -constrained to match only at the start of the subject, it is said to be an -"anchored" pattern. (There are also other constructs that can cause a pattern -to be anchored.) -</P> -<P> -A dollar character is an assertion which is true only if the current matching -point is at the end of the subject string, or immediately before a newline -character that is the last character in the string (by default). Dollar need -not be the last character of the pattern if a number of alternatives are -involved, but it should be the last item in any branch in which it appears. -Dollar has no special meaning in a character class. -</P> -<P> -The meaning of dollar can be changed so that it matches only at the very end of -the string, by setting the PCRE_DOLLAR_ENDONLY option at compile or matching -time. This does not affect the \Z assertion. -</P> -<P> -The meanings of the circumflex and dollar characters are changed if the -PCRE_MULTILINE option is set. When this is the case, they match immediately -after and immediately before an internal "\n" character, respectively, in -addition to matching at the start and end of the subject string. For example, -the pattern /^abc$/ matches the subject string "def\nabc" in multiline mode, -but not otherwise. Consequently, patterns that are anchored in single line mode -because all branches start with "^" are not anchored in multiline mode, and a -match for circumflex is possible when the <I>startoffset</I> argument of -<B>pcre_exec()</B> is non-zero. The PCRE_DOLLAR_ENDONLY option is ignored if -PCRE_MULTILINE is set. -</P> -<P> -Note that the sequences \A, \Z, and \z can be used to match the start and -end of the subject in both modes, and if all branches of a pattern start with -\A it is always anchored, whether PCRE_MULTILINE is set or not. -</P> -<LI><A NAME="SEC16" HREF="#TOC1">FULL STOP (PERIOD, DOT)</A> -<P> -Outside a character class, a dot in the pattern matches any one character in -the subject, including a non-printing character, but not (by default) newline. -If the PCRE_DOTALL option is set, dots match newlines as well. The handling of -dot is entirely independent of the handling of circumflex and dollar, the only -relationship being that they both involve newline characters. Dot has no -special meaning in a character class. -</P> -<LI><A NAME="SEC17" HREF="#TOC1">SQUARE BRACKETS</A> -<P> -An opening square bracket introduces a character class, terminated by a closing -square bracket. A closing square bracket on its own is not special. If a -closing square bracket is required as a member of the class, it should be the -first data character in the class (after an initial circumflex, if present) or -escaped with a backslash. -</P> -<P> -A character class matches a single character in the subject; the character must -be in the set of characters defined by the class, unless the first character in -the class is a circumflex, in which case the subject character must not be in -the set defined by the class. If a circumflex is actually required as a member -of the class, ensure it is not the first character, or escape it with a -backslash. -</P> -<P> -For example, the character class [aeiou] matches any lower case vowel, while -[^aeiou] matches any character that is not a lower case vowel. Note that a -circumflex is just a convenient notation for specifying the characters which -are in the class by enumerating those that are not. It is not an assertion: it -still consumes a character from the subject string, and fails if the current -pointer is at the end of the string. -</P> -<P> -When caseless matching is set, any letters in a class represent both their -upper case and lower case versions, so for example, a caseless [aeiou] matches -"A" as well as "a", and a caseless [^aeiou] does not match "A", whereas a -caseful version would. -</P> -<P> -The newline character is never treated in any special way in character classes, -whatever the setting of the PCRE_DOTALL or PCRE_MULTILINE options is. A class -such as [^a] will always match a newline. -</P> -<P> -The minus (hyphen) character can be used to specify a range of characters in a -character class. For example, [d-m] matches any letter between d and m, -inclusive. If a minus character is required in a class, it must be escaped with -a backslash or appear in a position where it cannot be interpreted as -indicating a range, typically as the first or last character in the class. -</P> -<P> -It is not possible to have the literal character "]" as the end character of a -range. A pattern such as [W-]46] is interpreted as a class of two characters -("W" and "-") followed by a literal string "46]", so it would match "W46]" or -"-46]". However, if the "]" is escaped with a backslash it is interpreted as -the end of range, so [W-\]46] is interpreted as a single class containing a -range followed by two separate characters. The octal or hexadecimal -representation of "]" can also be used to end a range. -</P> -<P> -Ranges operate in ASCII collating sequence. They can also be used for -characters specified numerically, for example [\000-\037]. If a range that -includes letters is used when caseless matching is set, it matches the letters -in either case. For example, [W-c] is equivalent to [][\^_`wxyzabc], matched -caselessly, and if character tables for the "fr" locale are in use, -[\xc8-\xcb] matches accented E characters in both cases. -</P> -<P> -The character types \d, \D, \s, \S, \w, and \W may also appear in a -character class, and add the characters that they match to the class. For -example, [\dABCDEF] matches any hexadecimal digit. A circumflex can -conveniently be used with the upper case character types to specify a more -restricted set of characters than the matching lower case type. For example, -the class [^\W_] matches any letter or digit, but not underscore. -</P> -<P> -All non-alphameric characters other than \, -, ^ (at the start) and the -terminating ] are non-special in character classes, but it does no harm if they -are escaped. -</P> -<LI><A NAME="SEC18" HREF="#TOC1">POSIX CHARACTER CLASSES</A> -<P> -Perl 5.6 (not yet released at the time of writing) is going to support the -POSIX notation for character classes, which uses names enclosed by [: and :] -within the enclosing square brackets. PCRE supports this notation. For example, -</P> -<P> -<PRE> - [01[:alpha:]%] -</PRE> -</P> -<P> -matches "0", "1", any alphabetic character, or "%". The supported class names -are -</P> -<P> -<PRE> - alnum letters and digits - alpha letters - ascii character codes 0 - 127 - cntrl control characters - digit decimal digits (same as \d) - graph printing characters, excluding space - lower lower case letters - print printing characters, including space - punct printing characters, excluding letters and digits - space white space (same as \s) - upper upper case letters - word "word" characters (same as \w) - xdigit hexadecimal digits -</PRE> -</P> -<P> -The names "ascii" and "word" are Perl extensions. Another Perl extension is -negation, which is indicated by a ^ character after the colon. For example, -</P> -<P> -<PRE> - [12[:^digit:]] -</PRE> -</P> -<P> -matches "1", "2", or any non-digit. PCRE (and Perl) also recognize the POSIX -syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not -supported, and an error is given if they are encountered. -</P> -<LI><A NAME="SEC19" HREF="#TOC1">VERTICAL BAR</A> -<P> -Vertical bar characters are used to separate alternative patterns. For example, -the pattern -</P> -<P> -<PRE> - gilbert|sullivan -</PRE> -</P> -<P> -matches either "gilbert" or "sullivan". Any number of alternatives may appear, -and an empty alternative is permitted (matching the empty string). -The matching process tries each alternative in turn, from left to right, -and the first one that succeeds is used. If the alternatives are within a -subpattern (defined below), "succeeds" means matching the rest of the main -pattern as well as the alternative in the subpattern. -</P> -<LI><A NAME="SEC20" HREF="#TOC1">INTERNAL OPTION SETTING</A> -<P> -The settings of PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, and PCRE_EXTENDED -can be changed from within the pattern by a sequence of Perl option letters -enclosed between "(?" and ")". The option letters are -</P> -<P> -<PRE> - i for PCRE_CASELESS - m for PCRE_MULTILINE - s for PCRE_DOTALL - x for PCRE_EXTENDED -</PRE> -</P> -<P> -For example, (?im) sets caseless, multiline matching. It is also possible to -unset these options by preceding the letter with a hyphen, and a combined -setting and unsetting such as (?im-sx), which sets PCRE_CASELESS and -PCRE_MULTILINE while unsetting PCRE_DOTALL and PCRE_EXTENDED, is also -permitted. If a letter appears both before and after the hyphen, the option is -unset. -</P> -<P> -The scope of these option changes depends on where in the pattern the setting -occurs. For settings that are outside any subpattern (defined below), the -effect is the same as if the options were set or unset at the start of -matching. The following patterns all behave in exactly the same way: -</P> -<P> -<PRE> - (?i)abc - a(?i)bc - ab(?i)c - abc(?i) -</PRE> -</P> -<P> -which in turn is the same as compiling the pattern abc with PCRE_CASELESS set. -In other words, such "top level" settings apply to the whole pattern (unless -there are other changes inside subpatterns). If there is more than one setting -of the same option at top level, the rightmost setting is used. -</P> -<P> -If an option change occurs inside a subpattern, the effect is different. This -is a change of behaviour in Perl 5.005. An option change inside a subpattern -affects only that part of the subpattern that follows it, so -</P> -<P> -<PRE> - (a(?i)b)c -</PRE> -</P> -<P> -matches abc and aBc and no other strings (assuming PCRE_CASELESS is not used). -By this means, options can be made to have different settings in different -parts of the pattern. Any changes made in one alternative do carry on -into subsequent branches within the same subpattern. For example, -</P> -<P> -<PRE> - (a(?i)b|c) -</PRE> -</P> -<P> -matches "ab", "aB", "c", and "C", even though when matching "C" the first -branch is abandoned before the option setting. This is because the effects of -option settings happen at compile time. There would be some very weird -behaviour otherwise. -</P> -<P> -The PCRE-specific options PCRE_UNGREEDY and PCRE_EXTRA can be changed in the -same way as the Perl-compatible options by using the characters U and X -respectively. The (?X) flag setting is special in that it must always occur -earlier in the pattern than any of the additional features it turns on, even -when it is at top level. It is best put at the start. -</P> -<LI><A NAME="SEC21" HREF="#TOC1">SUBPATTERNS</A> -<P> -Subpatterns are delimited by parentheses (round brackets), which can be nested. -Marking part of a pattern as a subpattern does two things: -</P> -<P> -1. It localizes a set of alternatives. For example, the pattern -</P> -<P> -<PRE> - cat(aract|erpillar|) -</PRE> -</P> -<P> -matches one of the words "cat", "cataract", or "caterpillar". Without the -parentheses, it would match "cataract", "erpillar" or the empty string. -</P> -<P> -2. It sets up the subpattern as a capturing subpattern (as defined above). -When the whole pattern matches, that portion of the subject string that matched -the subpattern is passed back to the caller via the <I>ovector</I> argument of -<B>pcre_exec()</B>. Opening parentheses are counted from left to right (starting -from 1) to obtain the numbers of the capturing subpatterns. -</P> -<P> -For example, if the string "the red king" is matched against the pattern -</P> -<P> -<PRE> - the ((red|white) (king|queen)) -</PRE> -</P> -<P> -the captured substrings are "red king", "red", and "king", and are numbered 1, -2, and 3, respectively. -</P> -<P> -The fact that plain parentheses fulfil two functions is not always helpful. -There are often times when a grouping subpattern is required without a -capturing requirement. If an opening parenthesis is followed by "?:", the -subpattern does not do any capturing, and is not counted when computing the -number of any subsequent capturing subpatterns. For example, if the string "the -white queen" is matched against the pattern -</P> -<P> -<PRE> - the ((?:red|white) (king|queen)) -</PRE> -</P> -<P> -the captured substrings are "white queen" and "queen", and are numbered 1 and -2. The maximum number of captured substrings is 99, and the maximum number of -all subpatterns, both capturing and non-capturing, is 200. -</P> -<P> -As a convenient shorthand, if any option settings are required at the start of -a non-capturing subpattern, the option letters may appear between the "?" and -the ":". Thus the two patterns -</P> -<P> -<PRE> - (?i:saturday|sunday) - (?:(?i)saturday|sunday) -</PRE> -</P> -<P> -match exactly the same set of strings. Because alternative branches are tried -from left to right, and options are not reset until the end of the subpattern -is reached, an option setting in one branch does affect subsequent branches, so -the above patterns match "SUNDAY" as well as "Saturday". -</P> -<LI><A NAME="SEC22" HREF="#TOC1">REPETITION</A> -<P> -Repetition is specified by quantifiers, which can follow any of the following -items: -</P> -<P> -<PRE> - a single character, possibly escaped - the . metacharacter - a character class - a back reference (see next section) - a parenthesized subpattern (unless it is an assertion - see below) -</PRE> -</P> -<P> -The general repetition quantifier specifies a minimum and maximum number of -permitted matches, by giving the two numbers in curly brackets (braces), -separated by a comma. The numbers must be less than 65536, and the first must -be less than or equal to the second. For example: -</P> -<P> -<PRE> - z{2,4} -</PRE> -</P> -<P> -matches "zz", "zzz", or "zzzz". A closing brace on its own is not a special -character. If the second number is omitted, but the comma is present, there is -no upper limit; if the second number and the comma are both omitted, the -quantifier specifies an exact number of required matches. Thus -</P> -<P> -<PRE> - [aeiou]{3,} -</PRE> -</P> -<P> -matches at least 3 successive vowels, but may match many more, while -</P> -<P> -<PRE> - \d{8} -</PRE> -</P> -<P> -matches exactly 8 digits. An opening curly bracket that appears in a position -where a quantifier is not allowed, or one that does not match the syntax of a -quantifier, is taken as a literal character. For example, {,6} is not a -quantifier, but a literal string of four characters. -</P> -<P> -The quantifier {0} is permitted, causing the expression to behave as if the -previous item and the quantifier were not present. -</P> -<P> -For convenience (and historical compatibility) the three most common -quantifiers have single-character abbreviations: -</P> -<P> -<PRE> - * is equivalent to {0,} - + is equivalent to {1,} - ? is equivalent to {0,1} -</PRE> -</P> -<P> -It is possible to construct infinite loops by following a subpattern that can -match no characters with a quantifier that has no upper limit, for example: -</P> -<P> -<PRE> - (a?)* -</PRE> -</P> -<P> -Earlier versions of Perl and PCRE used to give an error at compile time for -such patterns. However, because there are cases where this can be useful, such -patterns are now accepted, but if any repetition of the subpattern does in fact -match no characters, the loop is forcibly broken. -</P> -<P> -By default, the quantifiers are "greedy", that is, they match as much as -possible (up to the maximum number of permitted times), without causing the -rest of the pattern to fail. The classic example of where this gives problems -is in trying to match comments in C programs. These appear between the -sequences /* and */ and within the sequence, individual * and / characters may -appear. An attempt to match C comments by applying the pattern -</P> -<P> -<PRE> - /\*.*\*/ -</PRE> -</P> -<P> -to the string -</P> -<P> -<PRE> - /* first command */ not comment /* second comment */ -</PRE> -</P> -<P> -fails, because it matches the entire string owing to the greediness of the .* -item. -</P> -<P> -However, if a quantifier is followed by a question mark, it ceases to be -greedy, and instead matches the minimum number of times possible, so the -pattern -</P> -<P> -<PRE> - /\*.*?\*/ -</PRE> -</P> -<P> -does the right thing with the C comments. The meaning of the various -quantifiers is not otherwise changed, just the preferred number of matches. -Do not confuse this use of question mark with its use as a quantifier in its -own right. Because it has two uses, it can sometimes appear doubled, as in -</P> -<P> -<PRE> - \d??\d -</PRE> -</P> -<P> -which matches one digit by preference, but can match two if that is the only -way the rest of the pattern matches. -</P> -<P> -If the PCRE_UNGREEDY option is set (an option which is not available in Perl), -the quantifiers are not greedy by default, but individual ones can be made -greedy by following them with a question mark. In other words, it inverts the -default behaviour. -</P> -<P> -When a parenthesized subpattern is quantified with a minimum repeat count that -is greater than 1 or with a limited maximum, more store is required for the -compiled pattern, in proportion to the size of the minimum or maximum. -</P> -<P> -If a pattern starts with .* or .{0,} and the PCRE_DOTALL option (equivalent -to Perl's /s) is set, thus allowing the . to match newlines, the pattern is -implicitly anchored, because whatever follows will be tried against every -character position in the subject string, so there is no point in retrying the -overall match at any position after the first. PCRE treats such a pattern as -though it were preceded by \A. In cases where it is known that the subject -string contains no newlines, it is worth setting PCRE_DOTALL when the pattern -begins with .* in order to obtain this optimization, or alternatively using ^ -to indicate anchoring explicitly. -</P> -<P> -When a capturing subpattern is repeated, the value captured is the substring -that matched the final iteration. For example, after -</P> -<P> -<PRE> - (tweedle[dume]{3}\s*)+ -</PRE> -</P> -<P> -has matched "tweedledum tweedledee" the value of the captured substring is -"tweedledee". However, if there are nested capturing subpatterns, the -corresponding captured values may have been set in previous iterations. For -example, after -</P> -<P> -<PRE> - /(a|(b))+/ -</PRE> -</P> -<P> -matches "aba" the value of the second captured substring is "b". -</P> -<LI><A NAME="SEC23" HREF="#TOC1">BACK REFERENCES</A> -<P> -Outside a character class, a backslash followed by a digit greater than 0 (and -possibly further digits) is a back reference to a capturing subpattern earlier -(i.e. to its left) in the pattern, provided there have been that many previous -capturing left parentheses. -</P> -<P> -However, if the decimal number following the backslash is less than 10, it is -always taken as a back reference, and causes an error only if there are not -that many capturing left parentheses in the entire pattern. In other words, the -parentheses that are referenced need not be to the left of the reference for -numbers less than 10. See the section entitled "Backslash" above for further -details of the handling of digits following a backslash. -</P> -<P> -A back reference matches whatever actually matched the capturing subpattern in -the current subject string, rather than anything matching the subpattern -itself. So the pattern -</P> -<P> -<PRE> - (sens|respons)e and \1ibility -</PRE> -</P> -<P> -matches "sense and sensibility" and "response and responsibility", but not -"sense and responsibility". If caseful matching is in force at the time of the -back reference, the case of letters is relevant. For example, -</P> -<P> -<PRE> - ((?i)rah)\s+\1 -</PRE> -</P> -<P> -matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original -capturing subpattern is matched caselessly. -</P> -<P> -There may be more than one back reference to the same subpattern. If a -subpattern has not actually been used in a particular match, any back -references to it always fail. For example, the pattern -</P> -<P> -<PRE> - (a|(bc))\2 -</PRE> -</P> -<P> -always fails if it starts to match "a" rather than "bc". Because there may be -up to 99 back references, all digits following the backslash are taken -as part of a potential back reference number. If the pattern continues with a -digit character, some delimiter must be used to terminate the back reference. -If the PCRE_EXTENDED option is set, this can be whitespace. Otherwise an empty -comment can be used. -</P> -<P> -A back reference that occurs inside the parentheses to which it refers fails -when the subpattern is first used, so, for example, (a\1) never matches. -However, such references can be useful inside repeated subpatterns. For -example, the pattern -</P> -<P> -<PRE> - (a|b\1)+ -</PRE> -</P> -<P> -matches any number of "a"s and also "aba", "ababbaa" etc. At each iteration of -the subpattern, the back reference matches the character string corresponding -to the previous iteration. In order for this to work, the pattern must be such -that the first iteration does not need to match the back reference. This can be -done using alternation, as in the example above, or by a quantifier with a -minimum of zero. -</P> -<LI><A NAME="SEC24" HREF="#TOC1">ASSERTIONS</A> -<P> -An assertion is a test on the characters following or preceding the current -matching point that does not actually consume any characters. The simple -assertions coded as \b, \B, \A, \Z, \z, ^ and $ are described above. More -complicated assertions are coded as subpatterns. There are two kinds: those -that look ahead of the current position in the subject string, and those that -look behind it. -</P> -<P> -An assertion subpattern is matched in the normal way, except that it does not -cause the current matching position to be changed. Lookahead assertions start -with (?= for positive assertions and (?! for negative assertions. For example, -</P> -<P> -<PRE> - \w+(?=;) -</PRE> -</P> -<P> -matches a word followed by a semicolon, but does not include the semicolon in -the match, and -</P> -<P> -<PRE> - foo(?!bar) -</PRE> -</P> -<P> -matches any occurrence of "foo" that is not followed by "bar". Note that the -apparently similar pattern -</P> -<P> -<PRE> - (?!foo)bar -</PRE> -</P> -<P> -does not find an occurrence of "bar" that is preceded by something other than -"foo"; it finds any occurrence of "bar" whatsoever, because the assertion -(?!foo) is always true when the next three characters are "bar". A -lookbehind assertion is needed to achieve this effect. -</P> -<P> -Lookbehind assertions start with (?<= for positive assertions and (?<! for -negative assertions. For example, -</P> -<P> -<PRE> - (?<!foo)bar -</PRE> -</P> -<P> -does find an occurrence of "bar" that is not preceded by "foo". The contents of -a lookbehind assertion are restricted such that all the strings it matches must -have a fixed length. However, if there are several alternatives, they do not -all have to have the same fixed length. Thus -</P> -<P> -<PRE> - (?<=bullock|donkey) -</PRE> -</P> -<P> -is permitted, but -</P> -<P> -<PRE> - (?<!dogs?|cats?) -</PRE> -</P> -<P> -causes an error at compile time. Branches that match different length strings -are permitted only at the top level of a lookbehind assertion. This is an -extension compared with Perl 5.005, which requires all branches to match the -same length of string. An assertion such as -</P> -<P> -<PRE> - (?<=ab(c|de)) -</PRE> -</P> -<P> -is not permitted, because its single top-level branch can match two different -lengths, but it is acceptable if rewritten to use two top-level branches: -</P> -<P> -<PRE> - (?<=abc|abde) -</PRE> -</P> -<P> -The implementation of lookbehind assertions is, for each alternative, to -temporarily move the current position back by the fixed width and then try to -match. If there are insufficient characters before the current position, the -match is deemed to fail. Lookbehinds in conjunction with once-only subpatterns -can be particularly useful for matching at the ends of strings; an example is -given at the end of the section on once-only subpatterns. -</P> -<P> -Several assertions (of any sort) may occur in succession. For example, -</P> -<P> -<PRE> - (?<=\d{3})(?<!999)foo -</PRE> -</P> -<P> -matches "foo" preceded by three digits that are not "999". Notice that each of -the assertions is applied independently at the same point in the subject -string. First there is a check that the previous three characters are all -digits, and then there is a check that the same three characters are not "999". -This pattern does <I>not</I> match "foo" preceded by six characters, the first -of which are digits and the last three of which are not "999". For example, it -doesn't match "123abcfoo". A pattern to do that is -</P> -<P> -<PRE> - (?<=\d{3}...)(?<!999)foo -</PRE> -</P> -<P> -This time the first assertion looks at the preceding six characters, checking -that the first three are digits, and then the second assertion checks that the -preceding three characters are not "999". -</P> -<P> -Assertions can be nested in any combination. For example, -</P> -<P> -<PRE> - (?<=(?<!foo)bar)baz -</PRE> -</P> -<P> -matches an occurrence of "baz" that is preceded by "bar" which in turn is not -preceded by "foo", while -</P> -<P> -<PRE> - (?<=\d{3}(?!999)...)foo -</PRE> -</P> -<P> -is another pattern which matches "foo" preceded by three digits and any three -characters that are not "999". -</P> -<P> -Assertion subpatterns are not capturing subpatterns, and may not be repeated, -because it makes no sense to assert the same thing several times. If any kind -of assertion contains capturing subpatterns within it, these are counted for -the purposes of numbering the capturing subpatterns in the whole pattern. -However, substring capturing is carried out only for positive assertions, -because it does not make sense for negative assertions. -</P> -<P> -Assertions count towards the maximum of 200 parenthesized subpatterns. -</P> -<LI><A NAME="SEC25" HREF="#TOC1">ONCE-ONLY SUBPATTERNS</A> -<P> -With both maximizing and minimizing repetition, failure of what follows -normally causes the repeated item to be re-evaluated to see if a different -number of repeats allows the rest of the pattern to match. Sometimes it is -useful to prevent this, either to change the nature of the match, or to cause -it fail earlier than it otherwise might, when the author of the pattern knows -there is no point in carrying on. -</P> -<P> -Consider, for example, the pattern \d+foo when applied to the subject line -</P> -<P> -<PRE> - 123456bar -</PRE> -</P> -<P> -After matching all 6 digits and then failing to match "foo", the normal -action of the matcher is to try again with only 5 digits matching the \d+ -item, and then with 4, and so on, before ultimately failing. Once-only -subpatterns provide the means for specifying that once a portion of the pattern -has matched, it is not to be re-evaluated in this way, so the matcher would -give up immediately on failing to match "foo" the first time. The notation is -another kind of special parenthesis, starting with (?> as in this example: -</P> -<P> -<PRE> - (?>\d+)bar -</PRE> -</P> -<P> -This kind of parenthesis "locks up" the part of the pattern it contains once -it has matched, and a failure further into the pattern is prevented from -backtracking into it. Backtracking past it to previous items, however, works as -normal. -</P> -<P> -An alternative description is that a subpattern of this type matches the string -of characters that an identical standalone pattern would match, if anchored at -the current point in the subject string. -</P> -<P> -Once-only subpatterns are not capturing subpatterns. Simple cases such as the -above example can be thought of as a maximizing repeat that must swallow -everything it can. So, while both \d+ and \d+? are prepared to adjust the -number of digits they match in order to make the rest of the pattern match, -(?>\d+) can only match an entire sequence of digits. -</P> -<P> -This construction can of course contain arbitrarily complicated subpatterns, -and it can be nested. -</P> -<P> -Once-only subpatterns can be used in conjunction with lookbehind assertions to -specify efficient matching at the end of the subject string. Consider a simple -pattern such as -</P> -<P> -<PRE> - abcd$ -</PRE> -</P> -<P> -when applied to a long string which does not match. Because matching proceeds -from left to right, PCRE will look for each "a" in the subject and then see if -what follows matches the rest of the pattern. If the pattern is specified as -</P> -<P> -<PRE> - ^.*abcd$ -</PRE> -</P> -<P> -the initial .* matches the entire string at first, but when this fails (because -there is no following "a"), it backtracks to match all but the last character, -then all but the last two characters, and so on. Once again the search for "a" -covers the entire string, from right to left, so we are no better off. However, -if the pattern is written as -</P> -<P> -<PRE> - ^(?>.*)(?<=abcd) -</PRE> -</P> -<P> -there can be no backtracking for the .* item; it can match only the entire -string. The subsequent lookbehind assertion does a single test on the last four -characters. If it fails, the match fails immediately. For long strings, this -approach makes a significant difference to the processing time. -</P> -<P> -When a pattern contains an unlimited repeat inside a subpattern that can itself -be repeated an unlimited number of times, the use of a once-only subpattern is -the only way to avoid some failing matches taking a very long time indeed. -The pattern -</P> -<P> -<PRE> - (\D+|<\d+>)*[!?] -</PRE> -</P> -<P> -matches an unlimited number of substrings that either consist of non-digits, or -digits enclosed in <>, followed by either ! or ?. When it matches, it runs -quickly. However, if it is applied to -</P> -<P> -<PRE> - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa -</PRE> -</P> -<P> -it takes a long time before reporting failure. This is because the string can -be divided between the two repeats in a large number of ways, and all have to -be tried. (The example used [!?] rather than a single character at the end, -because both PCRE and Perl have an optimization that allows for fast failure -when a single character is used. They remember the last single character that -is required for a match, and fail early if it is not present in the string.) -If the pattern is changed to -</P> -<P> -<PRE> - ((?>\D+)|<\d+>)*[!?] -</PRE> -</P> -<P> -sequences of non-digits cannot be broken, and failure happens quickly. -</P> -<LI><A NAME="SEC26" HREF="#TOC1">CONDITIONAL SUBPATTERNS</A> -<P> -It is possible to cause the matching process to obey a subpattern -conditionally or to choose between two alternative subpatterns, depending on -the result of an assertion, or whether a previous capturing subpattern matched -or not. The two possible forms of conditional subpattern are -</P> -<P> -<PRE> - (?(condition)yes-pattern) - (?(condition)yes-pattern|no-pattern) -</PRE> -</P> -<P> -If the condition is satisfied, the yes-pattern is used; otherwise the -no-pattern (if present) is used. If there are more than two alternatives in the -subpattern, a compile-time error occurs. -</P> -<P> -There are two kinds of condition. If the text between the parentheses consists -of a sequence of digits, the condition is satisfied if the capturing subpattern -of that number has previously matched. The number must be greater than zero. -Consider the following pattern, which contains non-significant white space to -make it more readable (assume the PCRE_EXTENDED option) and to divide it into -three parts for ease of discussion: -</P> -<P> -<PRE> - ( \( )? [^()]+ (?(1) \) ) -</PRE> -</P> -<P> -The first part matches an optional opening parenthesis, and if that -character is present, sets it as the first captured substring. The second part -matches one or more characters that are not parentheses. The third part is a -conditional subpattern that tests whether the first set of parentheses matched -or not. If they did, that is, if subject started with an opening parenthesis, -the condition is true, and so the yes-pattern is executed and a closing -parenthesis is required. Otherwise, since no-pattern is not present, the -subpattern matches nothing. In other words, this pattern matches a sequence of -non-parentheses, optionally enclosed in parentheses. -</P> -<P> -If the condition is not a sequence of digits, it must be an assertion. This may -be a positive or negative lookahead or lookbehind assertion. Consider this -pattern, again containing non-significant white space, and with the two -alternatives on the second line: -</P> -<P> -<PRE> - (?(?=[^a-z]*[a-z]) - \d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) -</PRE> -</P> -<P> -The condition is a positive lookahead assertion that matches an optional -sequence of non-letters followed by a letter. In other words, it tests for the -presence of at least one letter in the subject. If a letter is found, the -subject is matched against the first alternative; otherwise it is matched -against the second. This pattern matches strings in one of the two forms -dd-aaa-dd or dd-dd-dd, where aaa are letters and dd are digits. -</P> -<LI><A NAME="SEC27" HREF="#TOC1">COMMENTS</A> -<P> -The sequence (?# marks the start of a comment which continues up to the next -closing parenthesis. Nested parentheses are not permitted. The characters -that make up a comment play no part in the pattern matching at all. -</P> -<P> -If the PCRE_EXTENDED option is set, an unescaped # character outside a -character class introduces a comment that continues up to the next newline -character in the pattern. -</P> -<LI><A NAME="SEC28" HREF="#TOC1">RECURSIVE PATTERNS</A> -<P> -Consider the problem of matching a string in parentheses, allowing for -unlimited nested parentheses. Without the use of recursion, the best that can -be done is to use a pattern that matches up to some fixed depth of nesting. It -is not possible to handle an arbitrary nesting depth. Perl 5.6 has provided an -experimental facility that allows regular expressions to recurse (amongst other -things). It does this by interpolating Perl code in the expression at run time, -and the code can refer to the expression itself. A Perl pattern to solve the -parentheses problem can be created like this: -</P> -<P> -<PRE> - $re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x; -</PRE> -</P> -<P> -The (?p{...}) item interpolates Perl code at run time, and in this case refers -recursively to the pattern in which it appears. Obviously, PCRE cannot support -the interpolation of Perl code. Instead, the special item (?R) is provided for -the specific case of recursion. This PCRE pattern solves the parentheses -problem (assume the PCRE_EXTENDED option is set so that white space is -ignored): -</P> -<P> -<PRE> - \( ( (?>[^()]+) | (?R) )* \) -</PRE> -</P> -<P> -First it matches an opening parenthesis. Then it matches any number of -substrings which can either be a sequence of non-parentheses, or a recursive -match of the pattern itself (i.e. a correctly parenthesized substring). Finally -there is a closing parenthesis. -</P> -<P> -This particular example pattern contains nested unlimited repeats, and so the -use of a once-only subpattern for matching strings of non-parentheses is -important when applying the pattern to strings that do not match. For example, -when it is applied to -</P> -<P> -<PRE> - (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() -</PRE> -</P> -<P> -it yields "no match" quickly. However, if a once-only subpattern is not used, -the match runs for a very long time indeed because there are so many different -ways the + and * repeats can carve up the subject, and all have to be tested -before failure can be reported. -</P> -<P> -The values set for any capturing subpatterns are those from the outermost level -of the recursion at which the subpattern value is set. If the pattern above is -matched against -</P> -<P> -<PRE> - (ab(cd)ef) -</PRE> -</P> -<P> -the value for the capturing parentheses is "ef", which is the last value taken -on at the top level. If additional parentheses are added, giving -</P> -<P> -<PRE> - \( ( ( (?>[^()]+) | (?R) )* ) \) - ^ ^ - ^ ^ -</PRE> -the string they capture is "ab(cd)ef", the contents of the top level -parentheses. If there are more than 15 capturing parentheses in a pattern, PCRE -has to obtain extra memory to store data during a recursion, which it does by -using <B>pcre_malloc</B>, freeing it via <B>pcre_free</B> afterwards. If no -memory can be obtained, it saves data for the first 15 capturing parentheses -only, as there is no way to give an out-of-memory error from within a -recursion. -</P> -<LI><A NAME="SEC29" HREF="#TOC1">PERFORMANCE</A> -<P> -Certain items that may appear in patterns are more efficient than others. It is -more efficient to use a character class like [aeiou] than a set of alternatives -such as (a|e|i|o|u). In general, the simplest construction that provides the -required behaviour is usually the most efficient. Jeffrey Friedl's book -contains a lot of discussion about optimizing regular expressions for efficient -performance. -</P> -<P> -When a pattern begins with .* and the PCRE_DOTALL option is set, the pattern is -implicitly anchored by PCRE, since it can match only at the start of a subject -string. However, if PCRE_DOTALL is not set, PCRE cannot make this optimization, -because the . metacharacter does not then match a newline, and if the subject -string contains newlines, the pattern may match from the character immediately -following one of them instead of from the very start. For example, the pattern -</P> -<P> -<PRE> - (.*) second -</PRE> -</P> -<P> -matches the subject "first\nand second" (where \n stands for a newline -character) with the first captured substring being "and". In order to do this, -PCRE has to retry the match starting after every newline in the subject. -</P> -<P> -If you are using such a pattern with subject strings that do not contain -newlines, the best performance is obtained by setting PCRE_DOTALL, or starting -the pattern with ^.* to indicate explicit anchoring. That saves PCRE from -having to scan along the subject looking for a newline to restart at. -</P> -<P> -Beware of patterns that contain nested indefinite repeats. These can take a -long time to run when applied to a string that does not match. Consider the -pattern fragment -</P> -<P> -<PRE> - (a+)* -</PRE> -</P> -<P> -This can match "aaaa" in 33 different ways, and this number increases very -rapidly as the string gets longer. (The * repeat can match 0, 1, 2, 3, or 4 -times, and for each of those cases other than 0, the + repeats can match -different numbers of times.) When the remainder of the pattern is such that the -entire match is going to fail, PCRE has in principle to try every possible -variation, and this can take an extremely long time. -</P> -<P> -An optimization catches some of the more simple cases such as -</P> -<P> -<PRE> - (a+)*b -</PRE> -</P> -<P> -where a literal character follows. Before embarking on the standard matching -procedure, PCRE checks that there is a "b" later in the subject string, and if -there is not, it fails the match immediately. However, when there is no -following literal this optimization cannot be used. You can see the difference -by comparing the behaviour of -</P> -<P> -<PRE> - (a+)*\d -</PRE> -</P> -<P> -with the pattern above. The former gives a failure almost instantly when -applied to a whole line of "a" characters, whereas the latter takes an -appreciable time with strings longer than about 20 characters. -</P> -<LI><A NAME="SEC30" HREF="#TOC1">UTF-8 SUPPORT</A> -<P> -Starting at release 3.3, PCRE has some support for character strings encoded -in the UTF-8 format. This is incomplete, and is regarded as experimental. In -order to use it, you must configure PCRE to include UTF-8 support in the code, -and, in addition, you must call <B>pcre_compile()</B> with the PCRE_UTF8 option -flag. When you do this, both the pattern and any subject strings that are -matched against it are treated as UTF-8 strings instead of just strings of -bytes, but only in the cases that are mentioned below. -</P> -<P> -If you compile PCRE with UTF-8 support, but do not use it at run time, the -library will be a bit bigger, but the additional run time overhead is limited -to testing the PCRE_UTF8 flag in several places, so should not be very large. -</P> -<P> -PCRE assumes that the strings it is given contain valid UTF-8 codes. It does -not diagnose invalid UTF-8 strings. If you pass invalid UTF-8 strings to PCRE, -the results are undefined. -</P> -<P> -Running with PCRE_UTF8 set causes these changes in the way PCRE works: -</P> -<P> -1. In a pattern, the escape sequence \x{...}, where the contents of the braces -is a string of hexadecimal digits, is interpreted as a UTF-8 character whose -code number is the given hexadecimal number, for example: \x{1234}. This -inserts from one to six literal bytes into the pattern, using the UTF-8 -encoding. If a non-hexadecimal digit appears between the braces, the item is -not recognized. -</P> -<P> -2. The original hexadecimal escape sequence, \xhh, generates a two-byte UTF-8 -character if its value is greater than 127. -</P> -<P> -3. Repeat quantifiers are NOT correctly handled if they follow a multibyte -character. For example, \x{100}* and \xc3+ do not work. If you want to -repeat such characters, you must enclose them in non-capturing parentheses, -for example (?:\x{100}), at present. -</P> -<P> -4. The dot metacharacter matches one UTF-8 character instead of a single byte. -</P> -<P> -5. Unlike literal UTF-8 characters, the dot metacharacter followed by a -repeat quantifier does operate correctly on UTF-8 characters instead of -single bytes. -</P> -<P> -4. Although the \x{...} escape is permitted in a character class, characters -whose values are greater than 255 cannot be included in a class. -</P> -<P> -5. A class is matched against a UTF-8 character instead of just a single byte, -but it can match only characters whose values are less than 256. Characters -with greater values always fail to match a class. -</P> -<P> -6. Repeated classes work correctly on multiple characters. -</P> -<P> -7. Classes containing just a single character whose value is greater than 127 -(but less than 256), for example, [\x80] or [^\x{93}], do not work because -these are optimized into single byte matches. In the first case, of course, -the class brackets are just redundant. -</P> -<P> -8. Lookbehind assertions move backwards in the subject by a fixed number of -characters instead of a fixed number of bytes. Simple cases have been tested -to work correctly, but there may be hidden gotchas herein. -</P> -<P> -9. The character types such as \d and \w do not work correctly with UTF-8 -characters. They continue to test a single byte. -</P> -<P> -10. Anything not explicitly mentioned here continues to work in bytes rather -than in characters. -</P> -<P> -The following UTF-8 features of Perl 5.6 are not implemented: -</P> -<P> -1. The escape sequence \C to match a single byte. -</P> -<P> -2. The use of Unicode tables and properties and escapes \p, \P, and \X. -</P> -<LI><A NAME="SEC31" HREF="#TOC1">SAMPLE PROGRAM</A> -<P> -The code below is a simple, complete demonstration program, to get you started -with using PCRE. This code is also supplied in the file <I>pcredemo.c</I> in the -PCRE distribution. -</P> -<P> -The program compiles the regular expression that is its first argument, and -matches it against the subject string in its second argument. No options are -set, and default character tables are used. If matching succeeds, the program -outputs the portion of the subject that matched, together with the contents of -any captured substrings. -</P> -<P> -On a Unix system that has PCRE installed in <I>/usr/local</I>, you can compile -the demonstration program using a command like this: -</P> -<P> -<PRE> - gcc -o pcredemo pcredemo.c -I/usr/local/include -L/usr/local/lib -lpcre -</PRE> -</P> -<P> -Then you can run simple tests like this: -</P> -<P> -<PRE> - ./pcredemo 'cat|dog' 'the cat sat on the mat' -</PRE> -</P> -<P> -Note that there is a much more comprehensive test program, called -<B>pcretest</B>, which supports many more facilities for testing regular -expressions. The <B>pcredemo</B> program is provided as a simple coding example. -</P> -<P> -On some operating systems (e.g. Solaris) you may get an error like this when -you try to run <B>pcredemo</B>: -</P> -<P> -<PRE> - ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or directory -</PRE> -</P> -<P> -This is caused by the way shared library support works on those systems. You -need to add -</P> -<P> -<PRE> - -R/usr/local/lib -</PRE> -</P> -<P> -to the compile command to get round this problem. Here's the code: -</P> -<P> -<PRE> - #include <stdio.h> - #include <string.h> - #include <pcre.h> -</PRE> -</P> -<P> -<PRE> - #define OVECCOUNT 30 /* should be a multiple of 3 */ -</PRE> -</P> -<P> -<PRE> - int main(int argc, char **argv) - { - pcre *re; - const char *error; - int erroffset; - int ovector[OVECCOUNT]; - int rc, i; -</PRE> -</P> -<P> -<PRE> - if (argc != 3) - { - printf("Two arguments required: a regex and a " - "subject string\n"); - return 1; - } -</PRE> -</P> -<P> -<PRE> - /* Compile the regular expression in the first argument */ -</PRE> -</P> -<P> -<PRE> - re = pcre_compile( - argv[1], /* the pattern */ - 0, /* default options */ - &error, /* for error message */ - &erroffset, /* for error offset */ - NULL); /* use default character tables */ -</PRE> -</P> -<P> -<PRE> - /* Compilation failed: print the error message and exit */ -</PRE> -</P> -<P> -<PRE> - if (re == NULL) - { - printf("PCRE compilation failed at offset %d: %s\n", - erroffset, error); - return 1; - } -</PRE> -</P> -<P> -<PRE> - /* Compilation succeeded: match the subject in the second - argument */ -</PRE> -</P> -<P> -<PRE> - rc = pcre_exec( - re, /* the compiled pattern */ - NULL, /* we didn't study the pattern */ - argv[2], /* the subject string */ - (int)strlen(argv[2]), /* the length of the subject */ - 0, /* start at offset 0 in the subject */ - 0, /* default options */ - ovector, /* vector for substring information */ - OVECCOUNT); /* number of elements in the vector */ -</PRE> -</P> -<P> -<PRE> - /* Matching failed: handle error cases */ -</PRE> -</P> -<P> -<PRE> - if (rc < 0) - { - switch(rc) - { - case PCRE_ERROR_NOMATCH: printf("No match\n"); break; - /* - Handle other special cases if you like - */ - default: printf("Matching error %d\n", rc); break; - } - return 1; - } -</PRE> -</P> -<P> -<PRE> - /* Match succeded */ -</PRE> -</P> -<P> -<PRE> - printf("Match succeeded\n"); -</PRE> -</P> -<P> -<PRE> - /* The output vector wasn't big enough */ -</PRE> -</P> -<P> -<PRE> - if (rc == 0) - { - rc = OVECCOUNT/3; - printf("ovector only has room for %d captured " - substrings\n", rc - 1); - } -</PRE> -</P> -<P> -<PRE> - /* Show substrings stored in the output vector */ -</PRE> -</P> -<P> -<PRE> - for (i = 0; i < rc; i++) - { - char *substring_start = argv[2] + ovector[2*i]; - int substring_length = ovector[2*i+1] - ovector[2*i]; - printf("%2d: %.*s\n", i, substring_length, - substring_start); - } -</PRE> -</P> -<P> -<PRE> - return 0; - } -</PRE> -</P> -<LI><A NAME="SEC32" HREF="#TOC1">AUTHOR</A> -<P> -Philip Hazel <ph10@cam.ac.uk> -<BR> -University Computing Service, -<BR> -New Museums Site, -<BR> -Cambridge CB2 3QG, England. -<BR> -Phone: +44 1223 334714 -</P> -<P> -Last updated: 15 August 2001 -<BR> -Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.txt b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.txt deleted file mode 100644 index 95f148f3..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcre.txt +++ /dev/null @@ -1,2315 +0,0 @@ -NAME - pcre - Perl-compatible regular expressions. - - - -SYNOPSIS - #include <pcre.h> - - pcre *pcre_compile(const char *pattern, int options, - const char **errptr, int *erroffset, - const unsigned char *tableptr); - - pcre_extra *pcre_study(const pcre *code, int options, - const char **errptr); - - int pcre_exec(const pcre *code, const pcre_extra *extra, - const char *subject, int length, int startoffset, - int options, int *ovector, int ovecsize); - - int pcre_copy_substring(const char *subject, int *ovector, - int stringcount, int stringnumber, char *buffer, - int buffersize); - - int pcre_get_substring(const char *subject, int *ovector, - int stringcount, int stringnumber, - const char **stringptr); - - int pcre_get_substring_list(const char *subject, - int *ovector, int stringcount, const char ***listptr); - - void pcre_free_substring(const char *stringptr); - - void pcre_free_substring_list(const char **stringptr); - - const unsigned char *pcre_maketables(void); - - int pcre_fullinfo(const pcre *code, const pcre_extra *extra, - int what, void *where); - - int pcre_info(const pcre *code, int *optptr, *firstcharptr); - - char *pcre_version(void); - - void *(*pcre_malloc)(size_t); - - void (*pcre_free)(void *); - - - - -DESCRIPTION - The PCRE library is a set of functions that implement regu- - lar expression pattern matching using the same syntax and - semantics as Perl 5, with just a few differences (see - - below). The current implementation corresponds to Perl - 5.005, with some additional features from later versions. - This includes some experimental, incomplete support for - UTF-8 encoded strings. Details of exactly what is and what - is not supported are given below. - - PCRE has its own native API, which is described in this - document. There is also a set of wrapper functions that - correspond to the POSIX regular expression API. These are - described in the pcreposix documentation. - - The native API function prototypes are defined in the header - file pcre.h, and on Unix systems the library itself is - called libpcre.a, so can be accessed by adding -lpcre to the - command for linking an application which calls it. The - header file defines the macros PCRE_MAJOR and PCRE_MINOR to - contain the major and minor release numbers for the library. - Applications can use these to include support for different - releases. - - The functions pcre_compile(), pcre_study(), and pcre_exec() - are used for compiling and matching regular expressions. A - sample program that demonstrates the simplest way of using - them is given in the file pcredemo.c. The last section of - this man page describes how to run it. - - The functions pcre_copy_substring(), pcre_get_substring(), - and pcre_get_substring_list() are convenience functions for - extracting captured substrings from a matched subject - string; pcre_free_substring() and pcre_free_substring_list() - are also provided, to free the memory used for extracted - strings. - - The function pcre_maketables() is used (optionally) to build - a set of character tables in the current locale for passing - to pcre_compile(). - - The function pcre_fullinfo() is used to find out information - about a compiled pattern; pcre_info() is an obsolete version - which returns only some of the available information, but is - retained for backwards compatibility. The function - pcre_version() returns a pointer to a string containing the - version of PCRE and its date of release. - - The global variables pcre_malloc and pcre_free initially - contain the entry points of the standard malloc() and free() - functions respectively. PCRE calls the memory management - functions via these variables, so a calling program can - replace them if it wishes to intercept the calls. This - should be done before calling any PCRE functions. - - - -MULTI-THREADING - The PCRE functions can be used in multi-threading applica- - tions, with the proviso that the memory management functions - pointed to by pcre_malloc and pcre_free are shared by all - threads. - - The compiled form of a regular expression is not altered - during matching, so the same compiled pattern can safely be - used by several threads at once. - - - -COMPILING A PATTERN - The function pcre_compile() is called to compile a pattern - into an internal form. The pattern is a C string terminated - by a binary zero, and is passed in the argument pattern. A - pointer to a single block of memory that is obtained via - pcre_malloc is returned. This contains the compiled code and - related data. The pcre type is defined for the returned - block; this is a typedef for a structure whose contents are - not externally defined. It is up to the caller to free the - memory when it is no longer required. - - Although the compiled code of a PCRE regex is relocatable, - that is, it does not depend on memory location, the complete - pcre data block is not fully relocatable, because it con- - tains a copy of the tableptr argument, which is an address - (see below). - - The size of a compiled pattern is roughly proportional to - the length of the pattern string, except that each character - class (other than those containing just a single character, - negated or not) requires 33 bytes, and repeat quantifiers - with a minimum greater than one or a bounded maximum cause - the relevant portions of the compiled pattern to be repli- - cated. - - The options argument contains independent bits that affect - the compilation. It should be zero if no options are - required. Some of the options, in particular, those that are - compatible with Perl, can also be set and unset from within - the pattern (see the detailed description of regular expres- - sions below). For these options, the contents of the options - argument specifies their initial settings at the start of - compilation and execution. The PCRE_ANCHORED option can be - set at the time of matching as well as at compile time. - - If errptr is NULL, pcre_compile() returns NULL immediately. - Otherwise, if compilation of a pattern fails, pcre_compile() - returns NULL, and sets the variable pointed to by errptr to - point to a textual error message. The offset from the start - of the pattern to the character where the error was - discovered is placed in the variable pointed to by - erroffset, which must not be NULL. If it is, an immediate - error is given. - - If the final argument, tableptr, is NULL, PCRE uses a - default set of character tables which are built when it is - compiled, using the default C locale. Otherwise, tableptr - must be the result of a call to pcre_maketables(). See the - section on locale support below. - - This code fragment shows a typical straightforward call to - pcre_compile(): - - pcre *re; - const char *error; - int erroffset; - re = pcre_compile( - "^A.*Z", /* the pattern */ - 0, /* default options */ - &error, /* for error message */ - &erroffset, /* for error offset */ - NULL); /* use default character tables */ - - The following option bits are defined in the header file: - - PCRE_ANCHORED - - If this bit is set, the pattern is forced to be "anchored", - that is, it is constrained to match only at the start of the - string which is being searched (the "subject string"). This - effect can also be achieved by appropriate constructs in the - pattern itself, which is the only way to do it in Perl. - - PCRE_CASELESS - - If this bit is set, letters in the pattern match both upper - and lower case letters. It is equivalent to Perl's /i - option. - - PCRE_DOLLAR_ENDONLY - - If this bit is set, a dollar metacharacter in the pattern - matches only at the end of the subject string. Without this - option, a dollar also matches immediately before the final - character if it is a newline (but not before any other new- - lines). The PCRE_DOLLAR_ENDONLY option is ignored if - PCRE_MULTILINE is set. There is no equivalent to this option - in Perl. - - PCRE_DOTALL - - If this bit is set, a dot metacharater in the pattern - matches all characters, including newlines. Without it, new- - lines are excluded. This option is equivalent to Perl's /s - option. A negative class such as [^a] always matches a new- - line character, independent of the setting of this option. - - PCRE_EXTENDED - - If this bit is set, whitespace data characters in the pat- - tern are totally ignored except when escaped or inside a - character class, and characters between an unescaped # out- - side a character class and the next newline character, - inclusive, are also ignored. This is equivalent to Perl's /x - option, and makes it possible to include comments inside - complicated patterns. Note, however, that this applies only - to data characters. Whitespace characters may never appear - within special character sequences in a pattern, for example - within the sequence (?( which introduces a conditional sub- - pattern. - - PCRE_EXTRA - - This option was invented in order to turn on additional - functionality of PCRE that is incompatible with Perl, but it - is currently of very little use. When set, any backslash in - a pattern that is followed by a letter that has no special - meaning causes an error, thus reserving these combinations - for future expansion. By default, as in Perl, a backslash - followed by a letter with no special meaning is treated as a - literal. There are at present no other features controlled - by this option. It can also be set by a (?X) option setting - within a pattern. - - PCRE_MULTILINE - - By default, PCRE treats the subject string as consisting of - a single "line" of characters (even if it actually contains - several newlines). The "start of line" metacharacter (^) - matches only at the start of the string, while the "end of - line" metacharacter ($) matches only at the end of the - string, or before a terminating newline (unless - PCRE_DOLLAR_ENDONLY is set). This is the same as Perl. - - When PCRE_MULTILINE it is set, the "start of line" and "end - of line" constructs match immediately following or immedi- - ately before any newline in the subject string, respec- - tively, as well as at the very start and end. This is - equivalent to Perl's /m option. If there are no "\n" charac- - ters in a subject string, or no occurrences of ^ or $ in a - pattern, setting PCRE_MULTILINE has no effect. - - PCRE_UNGREEDY - - This option inverts the "greediness" of the quantifiers so - that they are not greedy by default, but become greedy if - followed by "?". It is not compatible with Perl. It can also - be set by a (?U) option setting within the pattern. - - PCRE_UTF8 - - This option causes PCRE to regard both the pattern and the - subject as strings of UTF-8 characters instead of just byte - strings. However, it is available only if PCRE has been - built to include UTF-8 support. If not, the use of this - option provokes an error. Support for UTF-8 is new, experi- - mental, and incomplete. Details of exactly what it entails - are given below. - - - -STUDYING A PATTERN - When a pattern is going to be used several times, it is - worth spending more time analyzing it in order to speed up - the time taken for matching. The function pcre_study() takes - a pointer to a compiled pattern as its first argument, and - returns a pointer to a pcre_extra block (another typedef for - a structure with hidden contents) containing additional - information about the pattern; this can be passed to - pcre_exec(). If no additional information is available, NULL - is returned. - - The second argument contains option bits. At present, no - options are defined for pcre_study(), and this argument - should always be zero. - - The third argument for pcre_study() is a pointer to an error - message. If studying succeeds (even if no data is returned), - the variable it points to is set to NULL. Otherwise it - points to a textual error message. - - This is a typical call to pcre_study(): - - pcre_extra *pe; - pe = pcre_study( - re, /* result of pcre_compile() */ - 0, /* no options exist */ - &error); /* set to NULL or points to a message */ - - At present, studying a pattern is useful only for non- - anchored patterns that do not have a single fixed starting - character. A bitmap of possible starting characters is - created. - - - -LOCALE SUPPORT - PCRE handles caseless matching, and determines whether char- - acters are letters, digits, or whatever, by reference to a - set of tables. The library contains a default set of tables - which is created in the default C locale when PCRE is com- - piled. This is used when the final argument of - pcre_compile() is NULL, and is sufficient for many applica- - tions. - - An alternative set of tables can, however, be supplied. Such - tables are built by calling the pcre_maketables() function, - which has no arguments, in the relevant locale. The result - can then be passed to pcre_compile() as often as necessary. - For example, to build and use tables that are appropriate - for the French locale (where accented characters with codes - greater than 128 are treated as letters), the following code - could be used: - - setlocale(LC_CTYPE, "fr"); - tables = pcre_maketables(); - re = pcre_compile(..., tables); - - The tables are built in memory that is obtained via - pcre_malloc. The pointer that is passed to pcre_compile is - saved with the compiled pattern, and the same tables are - used via this pointer by pcre_study() and pcre_exec(). Thus - for any single pattern, compilation, studying and matching - all happen in the same locale, but different patterns can be - compiled in different locales. It is the caller's responsi- - bility to ensure that the memory containing the tables - remains available for as long as it is needed. - - - -INFORMATION ABOUT A PATTERN - The pcre_fullinfo() function returns information about a - compiled pattern. It replaces the obsolete pcre_info() func- - tion, which is nevertheless retained for backwards compabil- - ity (and is documented below). - - The first argument for pcre_fullinfo() is a pointer to the - compiled pattern. The second argument is the result of - pcre_study(), or NULL if the pattern was not studied. The - third argument specifies which piece of information is - required, while the fourth argument is a pointer to a vari- - able to receive the data. The yield of the function is zero - for success, or one of the following negative numbers: - - PCRE_ERROR_NULL the argument code was NULL - the argument where was NULL - PCRE_ERROR_BADMAGIC the "magic number" was not found - PCRE_ERROR_BADOPTION the value of what was invalid - - Here is a typical call of pcre_fullinfo(), to obtain the - length of the compiled pattern: - - int rc; - unsigned long int length; - rc = pcre_fullinfo( - re, /* result of pcre_compile() */ - pe, /* result of pcre_study(), or NULL */ - PCRE_INFO_SIZE, /* what is required */ - &length); /* where to put the data */ - - The possible values for the third argument are defined in - pcre.h, and are as follows: - - PCRE_INFO_OPTIONS - - Return a copy of the options with which the pattern was com- - piled. The fourth argument should point to an unsigned long - int variable. These option bits are those specified in the - call to pcre_compile(), modified by any top-level option - settings within the pattern itself, and with the - PCRE_ANCHORED bit forcibly set if the form of the pattern - implies that it can match only at the start of a subject - string. - - PCRE_INFO_SIZE - - Return the size of the compiled pattern, that is, the value - that was passed as the argument to pcre_malloc() when PCRE - was getting memory in which to place the compiled data. The - fourth argument should point to a size_t variable. - - PCRE_INFO_CAPTURECOUNT - - Return the number of capturing subpatterns in the pattern. - The fourth argument should point to an int variable. - - PCRE_INFO_BACKREFMAX - - Return the number of the highest back reference in the pat- - tern. The fourth argument should point to an int variable. - Zero is returned if there are no back references. - - PCRE_INFO_FIRSTCHAR - - Return information about the first character of any matched - string, for a non-anchored pattern. If there is a fixed - first character, e.g. from a pattern such as - (cat|cow|coyote), it is returned in the integer pointed to - by where. Otherwise, if either - - (a) the pattern was compiled with the PCRE_MULTILINE option, - and every branch starts with "^", or - - (b) every branch of the pattern starts with ".*" and - PCRE_DOTALL is not set (if it were set, the pattern would be - anchored), - - -1 is returned, indicating that the pattern matches only at - the start of a subject string or after any "\n" within the - string. Otherwise -2 is returned. For anchored patterns, -2 - is returned. - - PCRE_INFO_FIRSTTABLE - - If the pattern was studied, and this resulted in the con- - struction of a 256-bit table indicating a fixed set of char- - acters for the first character in any matching string, a - pointer to the table is returned. Otherwise NULL is - returned. The fourth argument should point to an unsigned - char * variable. - - PCRE_INFO_LASTLITERAL - - For a non-anchored pattern, return the value of the right- - most literal character which must exist in any matched - string, other than at its start. The fourth argument should - point to an int variable. If there is no such character, or - if the pattern is anchored, -1 is returned. For example, for - the pattern /a\d+z\d+/ the returned value is 'z'. - - The pcre_info() function is now obsolete because its inter- - face is too restrictive to return all the available data - about a compiled pattern. New programs should use - pcre_fullinfo() instead. The yield of pcre_info() is the - number of capturing subpatterns, or one of the following - negative numbers: - - PCRE_ERROR_NULL the argument code was NULL - PCRE_ERROR_BADMAGIC the "magic number" was not found - - If the optptr argument is not NULL, a copy of the options - with which the pattern was compiled is placed in the integer - it points to (see PCRE_INFO_OPTIONS above). - - If the pattern is not anchored and the firstcharptr argument - is not NULL, it is used to pass back information about the - first character of any matched string (see - PCRE_INFO_FIRSTCHAR above). - - - -MATCHING A PATTERN - The function pcre_exec() is called to match a subject string - - - - - -SunOS 5.8 Last change: 9 - - - - against a pre-compiled pattern, which is passed in the code - argument. If the pattern has been studied, the result of the - study should be passed in the extra argument. Otherwise this - must be NULL. - - Here is an example of a simple call to pcre_exec(): - - int rc; - int ovector[30]; - rc = pcre_exec( - re, /* result of pcre_compile() */ - NULL, /* we didn't study the pattern */ - "some string", /* the subject string */ - 11, /* the length of the subject string */ - 0, /* start at offset 0 in the subject */ - 0, /* default options */ - ovector, /* vector for substring information */ - 30); /* number of elements in the vector */ - - The PCRE_ANCHORED option can be passed in the options argu- - ment, whose unused bits must be zero. However, if a pattern - was compiled with PCRE_ANCHORED, or turned out to be - anchored by virtue of its contents, it cannot be made - unachored at matching time. - - There are also three further options that can be set only at - matching time: - - PCRE_NOTBOL - - The first character of the string is not the beginning of a - line, so the circumflex metacharacter should not match - before it. Setting this without PCRE_MULTILINE (at compile - time) causes circumflex never to match. - - PCRE_NOTEOL - - The end of the string is not the end of a line, so the dol- - lar metacharacter should not match it nor (except in multi- - line mode) a newline immediately before it. Setting this - without PCRE_MULTILINE (at compile time) causes dollar never - to match. - - PCRE_NOTEMPTY - - An empty string is not considered to be a valid match if - this option is set. If there are alternatives in the pat- - tern, they are tried. If all the alternatives match the - empty string, the entire match fails. For example, if the - pattern - - a?b? - - is applied to a string not beginning with "a" or "b", it - matches the empty string at the start of the subject. With - PCRE_NOTEMPTY set, this match is not valid, so PCRE searches - further into the string for occurrences of "a" or "b". - - Perl has no direct equivalent of PCRE_NOTEMPTY, but it does - make a special case of a pattern match of the empty string - within its split() function, and when using the /g modifier. - It is possible to emulate Perl's behaviour after matching a - null string by first trying the match again at the same - offset with PCRE_NOTEMPTY set, and then if that fails by - advancing the starting offset (see below) and trying an - ordinary match again. - - The subject string is passed as a pointer in subject, a - length in length, and a starting offset in startoffset. - Unlike the pattern string, the subject may contain binary - zero characters. When the starting offset is zero, the - search for a match starts at the beginning of the subject, - and this is by far the most common case. - - A non-zero starting offset is useful when searching for - another match in the same subject by calling pcre_exec() - again after a previous success. Setting startoffset differs - from just passing over a shortened string and setting - PCRE_NOTBOL in the case of a pattern that begins with any - kind of lookbehind. For example, consider the pattern - - \Biss\B - - which finds occurrences of "iss" in the middle of words. (\B - matches only if the current position in the subject is not a - word boundary.) When applied to the string "Mississipi" the - first call to pcre_exec() finds the first occurrence. If - pcre_exec() is called again with just the remainder of the - subject, namely "issipi", it does not match, because \B is - always false at the start of the subject, which is deemed to - be a word boundary. However, if pcre_exec() is passed the - entire string again, but with startoffset set to 4, it finds - the second occurrence of "iss" because it is able to look - behind the starting point to discover that it is preceded by - a letter. - - If a non-zero starting offset is passed when the pattern is - anchored, one attempt to match at the given offset is tried. - This can only succeed if the pattern does not require the - match to be at the start of the subject. - - In general, a pattern matches a certain portion of the sub- - ject, and in addition, further substrings from the subject - may be picked out by parts of the pattern. Following the - usage in Jeffrey Friedl's book, this is called "capturing" - in what follows, and the phrase "capturing subpattern" is - used for a fragment of a pattern that picks out a substring. - PCRE supports several other kinds of parenthesized subpat- - tern that do not cause substrings to be captured. - - Captured substrings are returned to the caller via a vector - of integer offsets whose address is passed in ovector. The - number of elements in the vector is passed in ovecsize. The - first two-thirds of the vector is used to pass back captured - substrings, each substring using a pair of integers. The - remaining third of the vector is used as workspace by - pcre_exec() while matching capturing subpatterns, and is not - available for passing back information. The length passed in - ovecsize should always be a multiple of three. If it is not, - it is rounded down. - - When a match has been successful, information about captured - substrings is returned in pairs of integers, starting at the - beginning of ovector, and continuing up to two-thirds of its - length at the most. The first element of a pair is set to - the offset of the first character in a substring, and the - second is set to the offset of the first character after the - end of a substring. The first pair, ovector[0] and ovec- - tor[1], identify the portion of the subject string matched - by the entire pattern. The next pair is used for the first - capturing subpattern, and so on. The value returned by - pcre_exec() is the number of pairs that have been set. If - there are no capturing subpatterns, the return value from a - successful match is 1, indicating that just the first pair - of offsets has been set. - - Some convenience functions are provided for extracting the - captured substrings as separate strings. These are described - in the following section. - - It is possible for an capturing subpattern number n+1 to - match some part of the subject when subpattern n has not - been used at all. For example, if the string "abc" is - matched against the pattern (a|(z))(bc) subpatterns 1 and 3 - are matched, but 2 is not. When this happens, both offset - values corresponding to the unused subpattern are set to -1. - - If a capturing subpattern is matched repeatedly, it is the - last portion of the string that it matched that gets - returned. - - If the vector is too small to hold all the captured sub- - strings, it is used as far as possible (up to two-thirds of - its length), and the function returns a value of zero. In - particular, if the substring offsets are not of interest, - pcre_exec() may be called with ovector passed as NULL and - ovecsize as zero. However, if the pattern contains back - references and the ovector isn't big enough to remember the - related substrings, PCRE has to get additional memory for - use during matching. Thus it is usually advisable to supply - an ovector. - - Note that pcre_info() can be used to find out how many cap- - turing subpatterns there are in a compiled pattern. The - smallest size for ovector that will allow for n captured - substrings in addition to the offsets of the substring - matched by the whole pattern is (n+1)*3. - - If pcre_exec() fails, it returns a negative number. The fol- - lowing are defined in the header file: - - PCRE_ERROR_NOMATCH (-1) - - The subject string did not match the pattern. - - PCRE_ERROR_NULL (-2) - - Either code or subject was passed as NULL, or ovector was - NULL and ovecsize was not zero. - - PCRE_ERROR_BADOPTION (-3) - - An unrecognized bit was set in the options argument. - - PCRE_ERROR_BADMAGIC (-4) - - PCRE stores a 4-byte "magic number" at the start of the com- - piled code, to catch the case when it is passed a junk - pointer. This is the error it gives when the magic number - isn't present. - - PCRE_ERROR_UNKNOWN_NODE (-5) - - While running the pattern match, an unknown item was encoun- - tered in the compiled pattern. This error could be caused by - a bug in PCRE or by overwriting of the compiled pattern. - - PCRE_ERROR_NOMEMORY (-6) - - If a pattern contains back references, but the ovector that - is passed to pcre_exec() is not big enough to remember the - referenced substrings, PCRE gets a block of memory at the - start of matching to use for this purpose. If the call via - pcre_malloc() fails, this error is given. The memory is - freed at the end of matching. - - - - -EXTRACTING CAPTURED SUBSTRINGS - Captured substrings can be accessed directly by using the - offsets returned by pcre_exec() in ovector. For convenience, - the functions pcre_copy_substring(), pcre_get_substring(), - and pcre_get_substring_list() are provided for extracting - captured substrings as new, separate, zero-terminated - strings. A substring that contains a binary zero is - correctly extracted and has a further zero added on the end, - but the result does not, of course, function as a C string. - - The first three arguments are the same for all three func- - tions: subject is the subject string which has just been - successfully matched, ovector is a pointer to the vector of - integer offsets that was passed to pcre_exec(), and - stringcount is the number of substrings that were captured - by the match, including the substring that matched the - entire regular expression. This is the value returned by - pcre_exec if it is greater than zero. If pcre_exec() - returned zero, indicating that it ran out of space in ovec- - tor, the value passed as stringcount should be the size of - the vector divided by three. - - The functions pcre_copy_substring() and pcre_get_substring() - extract a single substring, whose number is given as string- - number. A value of zero extracts the substring that matched - the entire pattern, while higher values extract the captured - substrings. For pcre_copy_substring(), the string is placed - in buffer, whose length is given by buffersize, while for - pcre_get_substring() a new block of memory is obtained via - pcre_malloc, and its address is returned via stringptr. The - yield of the function is the length of the string, not - including the terminating zero, or one of - - PCRE_ERROR_NOMEMORY (-6) - - The buffer was too small for pcre_copy_substring(), or the - attempt to get memory failed for pcre_get_substring(). - - PCRE_ERROR_NOSUBSTRING (-7) - - There is no substring whose number is stringnumber. - - The pcre_get_substring_list() function extracts all avail- - able substrings and builds a list of pointers to them. All - this is done in a single block of memory which is obtained - via pcre_malloc. The address of the memory block is returned - via listptr, which is also the start of the list of string - pointers. The end of the list is marked by a NULL pointer. - The yield of the function is zero if all went well, or - - PCRE_ERROR_NOMEMORY (-6) - - if the attempt to get the memory block failed. - - When any of these functions encounter a substring that is - unset, which can happen when capturing subpattern number n+1 - matches some part of the subject, but subpattern n has not - been used at all, they return an empty string. This can be - distinguished from a genuine zero-length substring by - inspecting the appropriate offset in ovector, which is nega- - tive for unset substrings. - - The two convenience functions pcre_free_substring() and - pcre_free_substring_list() can be used to free the memory - returned by a previous call of pcre_get_substring() or - pcre_get_substring_list(), respectively. They do nothing - more than call the function pointed to by pcre_free, which - of course could be called directly from a C program. How- - ever, PCRE is used in some situations where it is linked via - a special interface to another programming language which - cannot use pcre_free directly; it is for these cases that - the functions are provided. - - - -LIMITATIONS - There are some size limitations in PCRE but it is hoped that - they will never in practice be relevant. The maximum length - of a compiled pattern is 65539 (sic) bytes. All values in - repeating quantifiers must be less than 65536. There max- - imum number of capturing subpatterns is 65535. There is no - limit to the number of non-capturing subpatterns, but the - maximum depth of nesting of all kinds of parenthesized sub- - pattern, including capturing subpatterns, assertions, and - other types of subpattern, is 200. - - The maximum length of a subject string is the largest posi- - tive number that an integer variable can hold. However, PCRE - uses recursion to handle subpatterns and indefinite repeti- - tion. This means that the available stack space may limit - the size of a subject string that can be processed by cer- - tain patterns. - - - -DIFFERENCES FROM PERL - The differences described here are with respect to Perl - 5.005. - - 1. By default, a whitespace character is any character that - the C library function isspace() recognizes, though it is - possible to compile PCRE with alternative character type - tables. Normally isspace() matches space, formfeed, newline, - carriage return, horizontal tab, and vertical tab. Perl 5 no - longer includes vertical tab in its set of whitespace char- - acters. The \v escape that was in the Perl documentation for - a long time was never in fact recognized. However, the char- - acter itself was treated as whitespace at least up to 5.002. - In 5.004 and 5.005 it does not match \s. - - 2. PCRE does not allow repeat quantifiers on lookahead - assertions. Perl permits them, but they do not mean what you - might think. For example, (?!a){3} does not assert that the - next three characters are not "a". It just asserts that the - next character is not "a" three times. - - 3. Capturing subpatterns that occur inside negative looka- - head assertions are counted, but their entries in the - offsets vector are never set. Perl sets its numerical vari- - ables from any such patterns that are matched before the - assertion fails to match something (thereby succeeding), but - only if the negative lookahead assertion contains just one - branch. - - 4. Though binary zero characters are supported in the sub- - ject string, they are not allowed in a pattern string - because it is passed as a normal C string, terminated by - zero. The escape sequence "\0" can be used in the pattern to - represent a binary zero. - - 5. The following Perl escape sequences are not supported: - \l, \u, \L, \U, \E, \Q. In fact these are implemented by - Perl's general string-handling and are not part of its pat- - tern matching engine. - - 6. The Perl \G assertion is not supported as it is not - relevant to single pattern matches. - - 7. Fairly obviously, PCRE does not support the (?{code}) and - (?p{code}) constructions. However, there is some experimen- - tal support for recursive patterns using the non-Perl item - (?R). - - 8. There are at the time of writing some oddities in Perl - 5.005_02 concerned with the settings of captured strings - when part of a pattern is repeated. For example, matching - "aba" against the pattern /^(a(b)?)+$/ sets $2 to the value - "b", but matching "aabbaa" against /^(aa(bb)?)+$/ leaves $2 - unset. However, if the pattern is changed to - /^(aa(b(b))?)+$/ then $2 (and $3) are set. - - In Perl 5.004 $2 is set in both cases, and that is also true - of PCRE. If in the future Perl changes to a consistent state - that is different, PCRE may change to follow. - - 9. Another as yet unresolved discrepancy is that in Perl - 5.005_02 the pattern /^(a)?(?(1)a|b)+$/ matches the string - "a", whereas in PCRE it does not. However, in both Perl and - PCRE /^(a)?a/ matched against "a" leaves $1 unset. - - 10. PCRE provides some extensions to the Perl regular - expression facilities: - - (a) Although lookbehind assertions must match fixed length - strings, each alternative branch of a lookbehind assertion - can match a different length of string. Perl 5.005 requires - them all to have the same length. - - (b) If PCRE_DOLLAR_ENDONLY is set and PCRE_MULTILINE is not - set, the $ meta- character matches only at the very end of - the string. - - (c) If PCRE_EXTRA is set, a backslash followed by a letter - with no special meaning is faulted. - - (d) If PCRE_UNGREEDY is set, the greediness of the repeti- - tion quantifiers is inverted, that is, by default they are - not greedy, but if followed by a question mark they are. - - (e) PCRE_ANCHORED can be used to force a pattern to be tried - only at the start of the subject. - - (f) The PCRE_NOTBOL, PCRE_NOTEOL, and PCRE_NOTEMPTY options - for pcre_exec() have no Perl equivalents. - - (g) The (?R) construct allows for recursive pattern matching - (Perl 5.6 can do this using the (?p{code}) construct, which - PCRE cannot of course support.) - - - -REGULAR EXPRESSION DETAILS - The syntax and semantics of the regular expressions sup- - ported by PCRE are described below. Regular expressions are - also described in the Perl documentation and in a number of - other books, some of which have copious examples. Jeffrey - Friedl's "Mastering Regular Expressions", published by - O'Reilly (ISBN 1-56592-257), covers them in great detail. - - The description here is intended as reference documentation. - The basic operation of PCRE is on strings of bytes. However, - there is the beginnings of some support for UTF-8 character - strings. To use this support you must configure PCRE to - include it, and then call pcre_compile() with the PCRE_UTF8 - option. How this affects the pattern matching is described - in the final section of this document. - - A regular expression is a pattern that is matched against a - subject string from left to right. Most characters stand for - themselves in a pattern, and match the corresponding charac- - ters in the subject. As a trivial example, the pattern - - The quick brown fox - - matches a portion of a subject string that is identical to - itself. The power of regular expressions comes from the - ability to include alternatives and repetitions in the pat- - tern. These are encoded in the pattern by the use of meta- - characters, which do not stand for themselves but instead - are interpreted in some special way. - - There are two different sets of meta-characters: those that - are recognized anywhere in the pattern except within square - brackets, and those that are recognized in square brackets. - Outside square brackets, the meta-characters are as follows: - - \ general escape character with several uses - ^ assert start of subject (or line, in multiline - mode) - $ assert end of subject (or line, in multiline mode) - . match any character except newline (by default) - [ start character class definition - | start of alternative branch - ( start subpattern - ) end subpattern - ? extends the meaning of ( - also 0 or 1 quantifier - also quantifier minimizer - * 0 or more quantifier - + 1 or more quantifier - { start min/max quantifier - - Part of a pattern that is in square brackets is called a - "character class". In a character class the only meta- - characters are: - - \ general escape character - ^ negate the class, but only if the first character - - indicates character range - ] terminates the character class - - The following sections describe the use of each of the - meta-characters. - - - -BACKSLASH - The backslash character has several uses. Firstly, if it is - followed by a non-alphameric character, it takes away any - special meaning that character may have. This use of - - backslash as an escape character applies both inside and - outside character classes. - - For example, if you want to match a "*" character, you write - "\*" in the pattern. This applies whether or not the follow- - ing character would otherwise be interpreted as a meta- - character, so it is always safe to precede a non-alphameric - with "\" to specify that it stands for itself. In particu- - lar, if you want to match a backslash, you write "\\". - - If a pattern is compiled with the PCRE_EXTENDED option, whi- - tespace in the pattern (other than in a character class) and - characters between a "#" outside a character class and the - next newline character are ignored. An escaping backslash - can be used to include a whitespace or "#" character as part - of the pattern. - - A second use of backslash provides a way of encoding non- - printing characters in patterns in a visible manner. There - is no restriction on the appearance of non-printing charac- - ters, apart from the binary zero that terminates a pattern, - but when a pattern is being prepared by text editing, it is - usually easier to use one of the following escape sequences - than the binary character it represents: - - \a alarm, that is, the BEL character (hex 07) - \cx "control-x", where x is any character - \e escape (hex 1B) - \f formfeed (hex 0C) - \n newline (hex 0A) - \r carriage return (hex 0D) - \t tab (hex 09) - \xhh character with hex code hh - \ddd character with octal code ddd, or backreference - - The precise effect of "\cx" is as follows: if "x" is a lower - case letter, it is converted to upper case. Then bit 6 of - the character (hex 40) is inverted. Thus "\cz" becomes hex - 1A, but "\c{" becomes hex 3B, while "\c;" becomes hex 7B. - - After "\x", up to two hexadecimal digits are read (letters - can be in upper or lower case). - - After "\0" up to two further octal digits are read. In both - cases, if there are fewer than two digits, just those that - are present are used. Thus the sequence "\0\x\07" specifies - two binary zeros followed by a BEL character. Make sure you - supply two digits after the initial zero if the character - that follows is itself an octal digit. - - The handling of a backslash followed by a digit other than 0 - is complicated. Outside a character class, PCRE reads it - and any following digits as a decimal number. If the number - is less than 10, or if there have been at least that many - previous capturing left parentheses in the expression, the - entire sequence is taken as a back reference. A description - of how this works is given later, following the discussion - of parenthesized subpatterns. - - Inside a character class, or if the decimal number is - greater than 9 and there have not been that many capturing - subpatterns, PCRE re-reads up to three octal digits follow- - ing the backslash, and generates a single byte from the - least significant 8 bits of the value. Any subsequent digits - stand for themselves. For example: - - \040 is another way of writing a space - \40 is the same, provided there are fewer than 40 - previous capturing subpatterns - \7 is always a back reference - \11 might be a back reference, or another way of - writing a tab - \011 is always a tab - \0113 is a tab followed by the character "3" - \113 is the character with octal code 113 (since there - can be no more than 99 back references) - \377 is a byte consisting entirely of 1 bits - \81 is either a back reference, or a binary zero - followed by the two characters "8" and "1" - - Note that octal values of 100 or greater must not be intro- - duced by a leading zero, because no more than three octal - digits are ever read. - - All the sequences that define a single byte value can be - used both inside and outside character classes. In addition, - inside a character class, the sequence "\b" is interpreted - as the backspace character (hex 08). Outside a character - class it has a different meaning (see below). - - The third use of backslash is for specifying generic charac- - ter types: - - \d any decimal digit - \D any character that is not a decimal digit - \s any whitespace character - \S any character that is not a whitespace character - \w any "word" character - \W any "non-word" character - - Each pair of escape sequences partitions the complete set of - characters into two disjoint sets. Any given character - matches one, and only one, of each pair. - - A "word" character is any letter or digit or the underscore - character, that is, any character which can be part of a - Perl "word". The definition of letters and digits is con- - trolled by PCRE's character tables, and may vary if locale- - specific matching is taking place (see "Locale support" - above). For example, in the "fr" (French) locale, some char- - acter codes greater than 128 are used for accented letters, - and these are matched by \w. - - These character type sequences can appear both inside and - outside character classes. They each match one character of - the appropriate type. If the current matching point is at - the end of the subject string, all of them fail, since there - is no character to match. - - The fourth use of backslash is for certain simple asser- - tions. An assertion specifies a condition that has to be met - at a particular point in a match, without consuming any - characters from the subject string. The use of subpatterns - for more complicated assertions is described below. The - backslashed assertions are - - \b word boundary - \B not a word boundary - \A start of subject (independent of multiline mode) - \Z end of subject or newline at end (independent of - multiline mode) - \z end of subject (independent of multiline mode) - - These assertions may not appear in character classes (but - note that "\b" has a different meaning, namely the backspace - character, inside a character class). - - A word boundary is a position in the subject string where - the current character and the previous character do not both - match \w or \W (i.e. one matches \w and the other matches - \W), or the start or end of the string if the first or last - character matches \w, respectively. - - The \A, \Z, and \z assertions differ from the traditional - circumflex and dollar (described below) in that they only - ever match at the very start and end of the subject string, - whatever options are set. They are not affected by the - PCRE_NOTBOL or PCRE_NOTEOL options. If the startoffset argu- - ment of pcre_exec() is non-zero, \A can never match. The - difference between \Z and \z is that \Z matches before a - newline that is the last character of the string as well as - at the end of the string, whereas \z matches only at the - end. - - - -CIRCUMFLEX AND DOLLAR - Outside a character class, in the default matching mode, the - circumflex character is an assertion which is true only if - the current matching point is at the start of the subject - string. If the startoffset argument of pcre_exec() is non- - zero, circumflex can never match. Inside a character class, - circumflex has an entirely different meaning (see below). - - Circumflex need not be the first character of the pattern if - a number of alternatives are involved, but it should be the - first thing in each alternative in which it appears if the - pattern is ever to match that branch. If all possible alter- - natives start with a circumflex, that is, if the pattern is - constrained to match only at the start of the subject, it is - said to be an "anchored" pattern. (There are also other con- - structs that can cause a pattern to be anchored.) - - A dollar character is an assertion which is true only if the - current matching point is at the end of the subject string, - or immediately before a newline character that is the last - character in the string (by default). Dollar need not be the - last character of the pattern if a number of alternatives - are involved, but it should be the last item in any branch - in which it appears. Dollar has no special meaning in a - character class. - - The meaning of dollar can be changed so that it matches only - at the very end of the string, by setting the - PCRE_DOLLAR_ENDONLY option at compile or matching time. This - does not affect the \Z assertion. - - The meanings of the circumflex and dollar characters are - changed if the PCRE_MULTILINE option is set. When this is - the case, they match immediately after and immediately - before an internal "\n" character, respectively, in addition - to matching at the start and end of the subject string. For - example, the pattern /^abc$/ matches the subject string - "def\nabc" in multiline mode, but not otherwise. Conse- - quently, patterns that are anchored in single line mode - because all branches start with "^" are not anchored in mul- - tiline mode, and a match for circumflex is possible when the - startoffset argument of pcre_exec() is non-zero. The - PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is - set. - - Note that the sequences \A, \Z, and \z can be used to match - the start and end of the subject in both modes, and if all - branches of a pattern start with \A it is always anchored, - whether PCRE_MULTILINE is set or not. - - - -FULL STOP (PERIOD, DOT) - Outside a character class, a dot in the pattern matches any - one character in the subject, including a non-printing char- - acter, but not (by default) newline. If the PCRE_DOTALL - option is set, dots match newlines as well. The handling of - dot is entirely independent of the handling of circumflex - and dollar, the only relationship being that they both - involve newline characters. Dot has no special meaning in a - character class. - - - -SQUARE BRACKETS - An opening square bracket introduces a character class, ter- - minated by a closing square bracket. A closing square - bracket on its own is not special. If a closing square - bracket is required as a member of the class, it should be - the first data character in the class (after an initial cir- - cumflex, if present) or escaped with a backslash. - - A character class matches a single character in the subject; - the character must be in the set of characters defined by - the class, unless the first character in the class is a cir- - cumflex, in which case the subject character must not be in - the set defined by the class. If a circumflex is actually - required as a member of the class, ensure it is not the - first character, or escape it with a backslash. - - For example, the character class [aeiou] matches any lower - case vowel, while [^aeiou] matches any character that is not - a lower case vowel. Note that a circumflex is just a con- - venient notation for specifying the characters which are in - the class by enumerating those that are not. It is not an - assertion: it still consumes a character from the subject - string, and fails if the current pointer is at the end of - the string. - - When caseless matching is set, any letters in a class - represent both their upper case and lower case versions, so - for example, a caseless [aeiou] matches "A" as well as "a", - and a caseless [^aeiou] does not match "A", whereas a case- - ful version would. - - The newline character is never treated in any special way in - character classes, whatever the setting of the PCRE_DOTALL - or PCRE_MULTILINE options is. A class such as [^a] will - always match a newline. - - The minus (hyphen) character can be used to specify a range - of characters in a character class. For example, [d-m] - matches any letter between d and m, inclusive. If a minus - character is required in a class, it must be escaped with a - backslash or appear in a position where it cannot be inter- - preted as indicating a range, typically as the first or last - character in the class. - - It is not possible to have the literal character "]" as the - end character of a range. A pattern such as [W-]46] is - interpreted as a class of two characters ("W" and "-") fol- - lowed by a literal string "46]", so it would match "W46]" or - "-46]". However, if the "]" is escaped with a backslash it - is interpreted as the end of range, so [W-\]46] is inter- - preted as a single class containing a range followed by two - separate characters. The octal or hexadecimal representation - of "]" can also be used to end a range. - - Ranges operate in ASCII collating sequence. They can also be - used for characters specified numerically, for example - [\000-\037]. If a range that includes letters is used when - caseless matching is set, it matches the letters in either - case. For example, [W-c] is equivalent to [][\^_`wxyzabc], - matched caselessly, and if character tables for the "fr" - locale are in use, [\xc8-\xcb] matches accented E characters - in both cases. - - The character types \d, \D, \s, \S, \w, and \W may also - appear in a character class, and add the characters that - they match to the class. For example, [\dABCDEF] matches any - hexadecimal digit. A circumflex can conveniently be used - with the upper case character types to specify a more res- - tricted set of characters than the matching lower case type. - For example, the class [^\W_] matches any letter or digit, - but not underscore. - - All non-alphameric characters other than \, -, ^ (at the - start) and the terminating ] are non-special in character - classes, but it does no harm if they are escaped. - - - -POSIX CHARACTER CLASSES - Perl 5.6 (not yet released at the time of writing) is going - to support the POSIX notation for character classes, which - uses names enclosed by [: and :] within the enclosing - square brackets. PCRE supports this notation. For example, - - [01[:alpha:]%] - - matches "0", "1", any alphabetic character, or "%". The sup- - ported class names are - - alnum letters and digits - alpha letters - ascii character codes 0 - 127 - cntrl control characters - digit decimal digits (same as \d) - graph printing characters, excluding space - lower lower case letters - print printing characters, including space - punct printing characters, excluding letters and digits - space white space (same as \s) - upper upper case letters - word "word" characters (same as \w) - xdigit hexadecimal digits - - The names "ascii" and "word" are Perl extensions. Another - Perl extension is negation, which is indicated by a ^ char- - acter after the colon. For example, - - [12[:^digit:]] - - matches "1", "2", or any non-digit. PCRE (and Perl) also - recognize the POSIX syntax [.ch.] and [=ch=] where "ch" is a - "collating element", but these are not supported, and an - error is given if they are encountered. - - - -VERTICAL BAR - Vertical bar characters are used to separate alternative - patterns. For example, the pattern - - gilbert|sullivan - - matches either "gilbert" or "sullivan". Any number of alter- - natives may appear, and an empty alternative is permitted - (matching the empty string). The matching process tries - each alternative in turn, from left to right, and the first - one that succeeds is used. If the alternatives are within a - subpattern (defined below), "succeeds" means matching the - rest of the main pattern as well as the alternative in the - subpattern. - - - -INTERNAL OPTION SETTING - The settings of PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, - and PCRE_EXTENDED can be changed from within the pattern by - a sequence of Perl option letters enclosed between "(?" and - ")". The option letters are - - i for PCRE_CASELESS - m for PCRE_MULTILINE - s for PCRE_DOTALL - x for PCRE_EXTENDED - - For example, (?im) sets caseless, multiline matching. It is - also possible to unset these options by preceding the letter - with a hyphen, and a combined setting and unsetting such as - (?im-sx), which sets PCRE_CASELESS and PCRE_MULTILINE while - unsetting PCRE_DOTALL and PCRE_EXTENDED, is also permitted. - If a letter appears both before and after the hyphen, the - option is unset. - - The scope of these option changes depends on where in the - pattern the setting occurs. For settings that are outside - any subpattern (defined below), the effect is the same as if - the options were set or unset at the start of matching. The - following patterns all behave in exactly the same way: - - (?i)abc - a(?i)bc - ab(?i)c - abc(?i) - - which in turn is the same as compiling the pattern abc with - PCRE_CASELESS set. In other words, such "top level" set- - tings apply to the whole pattern (unless there are other - changes inside subpatterns). If there is more than one set- - ting of the same option at top level, the rightmost setting - is used. - - If an option change occurs inside a subpattern, the effect - is different. This is a change of behaviour in Perl 5.005. - An option change inside a subpattern affects only that part - of the subpattern that follows it, so - - (a(?i)b)c - - matches abc and aBc and no other strings (assuming - PCRE_CASELESS is not used). By this means, options can be - made to have different settings in different parts of the - pattern. Any changes made in one alternative do carry on - into subsequent branches within the same subpattern. For - example, - - (a(?i)b|c) - - matches "ab", "aB", "c", and "C", even though when matching - "C" the first branch is abandoned before the option setting. - This is because the effects of option settings happen at - compile time. There would be some very weird behaviour oth- - erwise. - - The PCRE-specific options PCRE_UNGREEDY and PCRE_EXTRA can - be changed in the same way as the Perl-compatible options by - using the characters U and X respectively. The (?X) flag - setting is special in that it must always occur earlier in - the pattern than any of the additional features it turns on, - even when it is at top level. It is best put at the start. - - - -SUBPATTERNS - Subpatterns are delimited by parentheses (round brackets), - which can be nested. Marking part of a pattern as a subpat- - tern does two things: - - 1. It localizes a set of alternatives. For example, the pat- - tern - - cat(aract|erpillar|) - - matches one of the words "cat", "cataract", or "caterpil- - lar". Without the parentheses, it would match "cataract", - "erpillar" or the empty string. - - 2. It sets up the subpattern as a capturing subpattern (as - defined above). When the whole pattern matches, that por- - tion of the subject string that matched the subpattern is - passed back to the caller via the ovector argument of - pcre_exec(). Opening parentheses are counted from left to - right (starting from 1) to obtain the numbers of the captur- - ing subpatterns. - - For example, if the string "the red king" is matched against - the pattern - - the ((red|white) (king|queen)) - - the captured substrings are "red king", "red", and "king", - and are numbered 1, 2, and 3, respectively. - - The fact that plain parentheses fulfil two functions is not - always helpful. There are often times when a grouping sub- - pattern is required without a capturing requirement. If an - opening parenthesis is followed by "?:", the subpattern does - not do any capturing, and is not counted when computing the - number of any subsequent capturing subpatterns. For example, - if the string "the white queen" is matched against the pat- - tern - - the ((?:red|white) (king|queen)) - - the captured substrings are "white queen" and "queen", and - are numbered 1 and 2. The maximum number of captured sub- - strings is 99, and the maximum number of all subpatterns, - both capturing and non-capturing, is 200. - - As a convenient shorthand, if any option settings are - required at the start of a non-capturing subpattern, the - option letters may appear between the "?" and the ":". Thus - the two patterns - - (?i:saturday|sunday) - (?:(?i)saturday|sunday) - - match exactly the same set of strings. Because alternative - branches are tried from left to right, and options are not - reset until the end of the subpattern is reached, an option - setting in one branch does affect subsequent branches, so - the above patterns match "SUNDAY" as well as "Saturday". - - - -REPETITION - Repetition is specified by quantifiers, which can follow any - of the following items: - - a single character, possibly escaped - the . metacharacter - a character class - a back reference (see next section) - a parenthesized subpattern (unless it is an assertion - - see below) - - The general repetition quantifier specifies a minimum and - maximum number of permitted matches, by giving the two - numbers in curly brackets (braces), separated by a comma. - The numbers must be less than 65536, and the first must be - less than or equal to the second. For example: - - z{2,4} - - matches "zz", "zzz", or "zzzz". A closing brace on its own - is not a special character. If the second number is omitted, - but the comma is present, there is no upper limit; if the - second number and the comma are both omitted, the quantifier - specifies an exact number of required matches. Thus - - [aeiou]{3,} - - matches at least 3 successive vowels, but may match many - more, while - - \d{8} - - matches exactly 8 digits. An opening curly bracket that - appears in a position where a quantifier is not allowed, or - one that does not match the syntax of a quantifier, is taken - as a literal character. For example, {,6} is not a quantif- - ier, but a literal string of four characters. - The quantifier {0} is permitted, causing the expression to - behave as if the previous item and the quantifier were not - present. - - For convenience (and historical compatibility) the three - most common quantifiers have single-character abbreviations: - - * is equivalent to {0,} - + is equivalent to {1,} - ? is equivalent to {0,1} - - It is possible to construct infinite loops by following a - subpattern that can match no characters with a quantifier - that has no upper limit, for example: - - (a?)* - - Earlier versions of Perl and PCRE used to give an error at - compile time for such patterns. However, because there are - cases where this can be useful, such patterns are now - accepted, but if any repetition of the subpattern does in - fact match no characters, the loop is forcibly broken. - - By default, the quantifiers are "greedy", that is, they - match as much as possible (up to the maximum number of per- - mitted times), without causing the rest of the pattern to - fail. The classic example of where this gives problems is in - trying to match comments in C programs. These appear between - the sequences /* and */ and within the sequence, individual - * and / characters may appear. An attempt to match C com- - ments by applying the pattern - - /\*.*\*/ - - to the string - - /* first command */ not comment /* second comment */ - - fails, because it matches the entire string owing to the - greediness of the .* item. - - However, if a quantifier is followed by a question mark, it - ceases to be greedy, and instead matches the minimum number - of times possible, so the pattern - - /\*.*?\*/ - - does the right thing with the C comments. The meaning of the - various quantifiers is not otherwise changed, just the pre- - ferred number of matches. Do not confuse this use of ques- - tion mark with its use as a quantifier in its own right. - Because it has two uses, it can sometimes appear doubled, as - in - - \d??\d - - which matches one digit by preference, but can match two if - that is the only way the rest of the pattern matches. - - If the PCRE_UNGREEDY option is set (an option which is not - available in Perl), the quantifiers are not greedy by - default, but individual ones can be made greedy by following - them with a question mark. In other words, it inverts the - default behaviour. - - When a parenthesized subpattern is quantified with a minimum - repeat count that is greater than 1 or with a limited max- - imum, more store is required for the compiled pattern, in - proportion to the size of the minimum or maximum. - - If a pattern starts with .* or .{0,} and the PCRE_DOTALL - option (equivalent to Perl's /s) is set, thus allowing the . - to match newlines, the pattern is implicitly anchored, - because whatever follows will be tried against every charac- - ter position in the subject string, so there is no point in - retrying the overall match at any position after the first. - PCRE treats such a pattern as though it were preceded by \A. - In cases where it is known that the subject string contains - no newlines, it is worth setting PCRE_DOTALL when the pat- - tern begins with .* in order to obtain this optimization, or - alternatively using ^ to indicate anchoring explicitly. - - When a capturing subpattern is repeated, the value captured - is the substring that matched the final iteration. For exam- - ple, after - - (tweedle[dume]{3}\s*)+ - - has matched "tweedledum tweedledee" the value of the cap- - tured substring is "tweedledee". However, if there are - nested capturing subpatterns, the corresponding captured - values may have been set in previous iterations. For exam- - ple, after - - /(a|(b))+/ - - matches "aba" the value of the second captured substring is - "b". - - - -BACK REFERENCES - Outside a character class, a backslash followed by a digit - greater than 0 (and possibly further digits) is a back - - - - -SunOS 5.8 Last change: 30 - - - - reference to a capturing subpattern earlier (i.e. to its - left) in the pattern, provided there have been that many - previous capturing left parentheses. - - However, if the decimal number following the backslash is - less than 10, it is always taken as a back reference, and - causes an error only if there are not that many capturing - left parentheses in the entire pattern. In other words, the - parentheses that are referenced need not be to the left of - the reference for numbers less than 10. See the section - entitled "Backslash" above for further details of the han- - dling of digits following a backslash. - - A back reference matches whatever actually matched the cap- - turing subpattern in the current subject string, rather than - anything matching the subpattern itself. So the pattern - - (sens|respons)e and \1ibility - - matches "sense and sensibility" and "response and responsi- - bility", but not "sense and responsibility". If caseful - matching is in force at the time of the back reference, the - case of letters is relevant. For example, - - ((?i)rah)\s+\1 - - matches "rah rah" and "RAH RAH", but not "RAH rah", even - though the original capturing subpattern is matched case- - lessly. - - There may be more than one back reference to the same sub- - pattern. If a subpattern has not actually been used in a - particular match, any back references to it always fail. For - example, the pattern - - (a|(bc))\2 - - always fails if it starts to match "a" rather than "bc". - Because there may be up to 99 back references, all digits - following the backslash are taken as part of a potential - back reference number. If the pattern continues with a digit - character, some delimiter must be used to terminate the back - reference. If the PCRE_EXTENDED option is set, this can be - whitespace. Otherwise an empty comment can be used. - - A back reference that occurs inside the parentheses to which - it refers fails when the subpattern is first used, so, for - example, (a\1) never matches. However, such references can - be useful inside repeated subpatterns. For example, the pat- - tern - - (a|b\1)+ - - matches any number of "a"s and also "aba", "ababbaa" etc. At - each iteration of the subpattern, the back reference matches - the character string corresponding to the previous itera- - tion. In order for this to work, the pattern must be such - that the first iteration does not need to match the back - reference. This can be done using alternation, as in the - example above, or by a quantifier with a minimum of zero. - - - -ASSERTIONS - An assertion is a test on the characters following or - preceding the current matching point that does not actually - consume any characters. The simple assertions coded as \b, - \B, \A, \Z, \z, ^ and $ are described above. More compli- - cated assertions are coded as subpatterns. There are two - kinds: those that look ahead of the current position in the - subject string, and those that look behind it. - - An assertion subpattern is matched in the normal way, except - that it does not cause the current matching position to be - changed. Lookahead assertions start with (?= for positive - assertions and (?! for negative assertions. For example, - - \w+(?=;) - - matches a word followed by a semicolon, but does not include - the semicolon in the match, and - - foo(?!bar) - - matches any occurrence of "foo" that is not followed by - "bar". Note that the apparently similar pattern - - (?!foo)bar - - does not find an occurrence of "bar" that is preceded by - something other than "foo"; it finds any occurrence of "bar" - whatsoever, because the assertion (?!foo) is always true - when the next three characters are "bar". A lookbehind - assertion is needed to achieve this effect. - - Lookbehind assertions start with (?<= for positive asser- - tions and (?<! for negative assertions. For example, - - (?<!foo)bar - - does find an occurrence of "bar" that is not preceded by - "foo". The contents of a lookbehind assertion are restricted - such that all the strings it matches must have a fixed - length. However, if there are several alternatives, they do - not all have to have the same fixed length. Thus - - (?<=bullock|donkey) - - is permitted, but - - (?<!dogs?|cats?) - - causes an error at compile time. Branches that match dif- - ferent length strings are permitted only at the top level of - a lookbehind assertion. This is an extension compared with - Perl 5.005, which requires all branches to match the same - length of string. An assertion such as - - (?<=ab(c|de)) - - is not permitted, because its single top-level branch can - match two different lengths, but it is acceptable if rewrit- - ten to use two top-level branches: - - (?<=abc|abde) - - The implementation of lookbehind assertions is, for each - alternative, to temporarily move the current position back - by the fixed width and then try to match. If there are - insufficient characters before the current position, the - match is deemed to fail. Lookbehinds in conjunction with - once-only subpatterns can be particularly useful for match- - ing at the ends of strings; an example is given at the end - of the section on once-only subpatterns. - - Several assertions (of any sort) may occur in succession. - For example, - - (?<=\d{3})(?<!999)foo - - matches "foo" preceded by three digits that are not "999". - Notice that each of the assertions is applied independently - at the same point in the subject string. First there is a - check that the previous three characters are all digits, and - then there is a check that the same three characters are not - "999". This pattern does not match "foo" preceded by six - characters, the first of which are digits and the last three - of which are not "999". For example, it doesn't match - "123abcfoo". A pattern to do that is - - (?<=\d{3}...)(?<!999)foo - - This time the first assertion looks at the preceding six - characters, checking that the first three are digits, and - then the second assertion checks that the preceding three - characters are not "999". - - Assertions can be nested in any combination. For example, - - (?<=(?<!foo)bar)baz - - matches an occurrence of "baz" that is preceded by "bar" - which in turn is not preceded by "foo", while - - (?<=\d{3}(?!999)...)foo - - is another pattern which matches "foo" preceded by three - digits and any three characters that are not "999". - - Assertion subpatterns are not capturing subpatterns, and may - not be repeated, because it makes no sense to assert the - same thing several times. If any kind of assertion contains - capturing subpatterns within it, these are counted for the - purposes of numbering the capturing subpatterns in the whole - pattern. However, substring capturing is carried out only - for positive assertions, because it does not make sense for - negative assertions. - - Assertions count towards the maximum of 200 parenthesized - subpatterns. - - - -ONCE-ONLY SUBPATTERNS - With both maximizing and minimizing repetition, failure of - what follows normally causes the repeated item to be re- - evaluated to see if a different number of repeats allows the - rest of the pattern to match. Sometimes it is useful to - prevent this, either to change the nature of the match, or - to cause it fail earlier than it otherwise might, when the - author of the pattern knows there is no point in carrying - on. - - Consider, for example, the pattern \d+foo when applied to - the subject line - - 123456bar - - After matching all 6 digits and then failing to match "foo", - the normal action of the matcher is to try again with only 5 - digits matching the \d+ item, and then with 4, and so on, - before ultimately failing. Once-only subpatterns provide the - means for specifying that once a portion of the pattern has - matched, it is not to be re-evaluated in this way, so the - matcher would give up immediately on failing to match "foo" - the first time. The notation is another kind of special - parenthesis, starting with (?> as in this example: - - (?>\d+)bar - - This kind of parenthesis "locks up" the part of the pattern - it contains once it has matched, and a failure further into - the pattern is prevented from backtracking into it. Back- - tracking past it to previous items, however, works as nor- - mal. - - An alternative description is that a subpattern of this type - matches the string of characters that an identical stan- - dalone pattern would match, if anchored at the current point - in the subject string. - - Once-only subpatterns are not capturing subpatterns. Simple - cases such as the above example can be thought of as a max- - imizing repeat that must swallow everything it can. So, - while both \d+ and \d+? are prepared to adjust the number of - digits they match in order to make the rest of the pattern - match, (?>\d+) can only match an entire sequence of digits. - - This construction can of course contain arbitrarily compli- - cated subpatterns, and it can be nested. - - Once-only subpatterns can be used in conjunction with look- - behind assertions to specify efficient matching at the end - of the subject string. Consider a simple pattern such as - - abcd$ - - when applied to a long string which does not match. Because - matching proceeds from left to right, PCRE will look for - each "a" in the subject and then see if what follows matches - the rest of the pattern. If the pattern is specified as - - ^.*abcd$ - - the initial .* matches the entire string at first, but when - this fails (because there is no following "a"), it back- - tracks to match all but the last character, then all but the - last two characters, and so on. Once again the search for - "a" covers the entire string, from right to left, so we are - no better off. However, if the pattern is written as - - ^(?>.*)(?<=abcd) - - there can be no backtracking for the .* item; it can match - only the entire string. The subsequent lookbehind assertion - does a single test on the last four characters. If it fails, - the match fails immediately. For long strings, this approach - makes a significant difference to the processing time. - - When a pattern contains an unlimited repeat inside a subpat- - tern that can itself be repeated an unlimited number of - times, the use of a once-only subpattern is the only way to - avoid some failing matches taking a very long time indeed. - The pattern - - (\D+|<\d+>)*[!?] - - matches an unlimited number of substrings that either con- - sist of non-digits, or digits enclosed in <>, followed by - either ! or ?. When it matches, it runs quickly. However, if - it is applied to - - aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa - - it takes a long time before reporting failure. This is - because the string can be divided between the two repeats in - a large number of ways, and all have to be tried. (The exam- - ple used [!?] rather than a single character at the end, - because both PCRE and Perl have an optimization that allows - for fast failure when a single character is used. They - remember the last single character that is required for a - match, and fail early if it is not present in the string.) - If the pattern is changed to - - ((?>\D+)|<\d+>)*[!?] - - sequences of non-digits cannot be broken, and failure hap- - pens quickly. - - - -CONDITIONAL SUBPATTERNS - It is possible to cause the matching process to obey a sub- - pattern conditionally or to choose between two alternative - subpatterns, depending on the result of an assertion, or - whether a previous capturing subpattern matched or not. The - two possible forms of conditional subpattern are - - (?(condition)yes-pattern) - (?(condition)yes-pattern|no-pattern) - - If the condition is satisfied, the yes-pattern is used; oth- - erwise the no-pattern (if present) is used. If there are - more than two alternatives in the subpattern, a compile-time - error occurs. - - There are two kinds of condition. If the text between the - parentheses consists of a sequence of digits, the condition - is satisfied if the capturing subpattern of that number has - previously matched. The number must be greater than zero. - Consider the following pattern, which contains non- - significant white space to make it more readable (assume the - PCRE_EXTENDED option) and to divide it into three parts for - ease of discussion: - - ( \( )? [^()]+ (?(1) \) ) - - The first part matches an optional opening parenthesis, and - if that character is present, sets it as the first captured - substring. The second part matches one or more characters - that are not parentheses. The third part is a conditional - subpattern that tests whether the first set of parentheses - matched or not. If they did, that is, if subject started - with an opening parenthesis, the condition is true, and so - the yes-pattern is executed and a closing parenthesis is - required. Otherwise, since no-pattern is not present, the - subpattern matches nothing. In other words, this pattern - matches a sequence of non-parentheses, optionally enclosed - in parentheses. - - If the condition is not a sequence of digits, it must be an - assertion. This may be a positive or negative lookahead or - lookbehind assertion. Consider this pattern, again contain- - ing non-significant white space, and with the two alterna- - tives on the second line: - - (?(?=[^a-z]*[a-z]) - \d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) - - The condition is a positive lookahead assertion that matches - an optional sequence of non-letters followed by a letter. In - other words, it tests for the presence of at least one - letter in the subject. If a letter is found, the subject is - matched against the first alternative; otherwise it is - matched against the second. This pattern matches strings in - one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are - letters and dd are digits. - - - -COMMENTS - The sequence (?# marks the start of a comment which contin- - ues up to the next closing parenthesis. Nested parentheses - are not permitted. The characters that make up a comment - play no part in the pattern matching at all. - - If the PCRE_EXTENDED option is set, an unescaped # character - outside a character class introduces a comment that contin- - ues up to the next newline character in the pattern. - - - -RECURSIVE PATTERNS - Consider the problem of matching a string in parentheses, - allowing for unlimited nested parentheses. Without the use - of recursion, the best that can be done is to use a pattern - that matches up to some fixed depth of nesting. It is not - possible to handle an arbitrary nesting depth. Perl 5.6 has - provided an experimental facility that allows regular - expressions to recurse (amongst other things). It does this - by interpolating Perl code in the expression at run time, - and the code can refer to the expression itself. A Perl pat- - tern to solve the parentheses problem can be created like - this: - - $re = qr{\( (?: (?>[^()]+) | (?p{$re}) )* \)}x; - - The (?p{...}) item interpolates Perl code at run time, and - in this case refers recursively to the pattern in which it - appears. Obviously, PCRE cannot support the interpolation of - Perl code. Instead, the special item (?R) is provided for - the specific case of recursion. This PCRE pattern solves the - parentheses problem (assume the PCRE_EXTENDED option is set - so that white space is ignored): - - \( ( (?>[^()]+) | (?R) )* \) - - First it matches an opening parenthesis. Then it matches any - number of substrings which can either be a sequence of non- - parentheses, or a recursive match of the pattern itself - (i.e. a correctly parenthesized substring). Finally there is - a closing parenthesis. - - This particular example pattern contains nested unlimited - repeats, and so the use of a once-only subpattern for match- - ing strings of non-parentheses is important when applying - the pattern to strings that do not match. For example, when - it is applied to - - (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() - - it yields "no match" quickly. However, if a once-only sub- - pattern is not used, the match runs for a very long time - indeed because there are so many different ways the + and * - repeats can carve up the subject, and all have to be tested - before failure can be reported. - - The values set for any capturing subpatterns are those from - the outermost level of the recursion at which the subpattern - value is set. If the pattern above is matched against - - (ab(cd)ef) - - the value for the capturing parentheses is "ef", which is - the last value taken on at the top level. If additional - parentheses are added, giving - - \( ( ( (?>[^()]+) | (?R) )* ) \) - ^ ^ - ^ ^ the string they capture is - "ab(cd)ef", the contents of the top level parentheses. If - there are more than 15 capturing parentheses in a pattern, - PCRE has to obtain extra memory to store data during a - recursion, which it does by using pcre_malloc, freeing it - via pcre_free afterwards. If no memory can be obtained, it - saves data for the first 15 capturing parentheses only, as - there is no way to give an out-of-memory error from within a - recursion. - - - -PERFORMANCE - Certain items that may appear in patterns are more efficient - than others. It is more efficient to use a character class - like [aeiou] than a set of alternatives such as (a|e|i|o|u). - In general, the simplest construction that provides the - required behaviour is usually the most efficient. Jeffrey - Friedl's book contains a lot of discussion about optimizing - regular expressions for efficient performance. - - When a pattern begins with .* and the PCRE_DOTALL option is - set, the pattern is implicitly anchored by PCRE, since it - can match only at the start of a subject string. However, if - PCRE_DOTALL is not set, PCRE cannot make this optimization, - because the . metacharacter does not then match a newline, - and if the subject string contains newlines, the pattern may - match from the character immediately following one of them - instead of from the very start. For example, the pattern - - (.*) second - - matches the subject "first\nand second" (where \n stands for - a newline character) with the first captured substring being - "and". In order to do this, PCRE has to retry the match - starting after every newline in the subject. - - If you are using such a pattern with subject strings that do - not contain newlines, the best performance is obtained by - setting PCRE_DOTALL, or starting the pattern with ^.* to - indicate explicit anchoring. That saves PCRE from having to - scan along the subject looking for a newline to restart at. - - Beware of patterns that contain nested indefinite repeats. - These can take a long time to run when applied to a string - that does not match. Consider the pattern fragment - - (a+)* - - This can match "aaaa" in 33 different ways, and this number - increases very rapidly as the string gets longer. (The * - repeat can match 0, 1, 2, 3, or 4 times, and for each of - those cases other than 0, the + repeats can match different - numbers of times.) When the remainder of the pattern is such - that the entire match is going to fail, PCRE has in princi- - ple to try every possible variation, and this can take an - extremely long time. - - An optimization catches some of the more simple cases such - as - - (a+)*b - - where a literal character follows. Before embarking on the - standard matching procedure, PCRE checks that there is a "b" - later in the subject string, and if there is not, it fails - the match immediately. However, when there is no following - literal this optimization cannot be used. You can see the - difference by comparing the behaviour of - - (a+)*\d - - with the pattern above. The former gives a failure almost - instantly when applied to a whole line of "a" characters, - whereas the latter takes an appreciable time with strings - longer than about 20 characters. - - - -UTF-8 SUPPORT - Starting at release 3.3, PCRE has some support for character - strings encoded in the UTF-8 format. This is incomplete, and - is regarded as experimental. In order to use it, you must - configure PCRE to include UTF-8 support in the code, and, in - addition, you must call pcre_compile() with the PCRE_UTF8 - option flag. When you do this, both the pattern and any sub- - ject strings that are matched against it are treated as - UTF-8 strings instead of just strings of bytes, but only in - the cases that are mentioned below. - - If you compile PCRE with UTF-8 support, but do not use it at - run time, the library will be a bit bigger, but the addi- - tional run time overhead is limited to testing the PCRE_UTF8 - flag in several places, so should not be very large. - - PCRE assumes that the strings it is given contain valid - UTF-8 codes. It does not diagnose invalid UTF-8 strings. If - you pass invalid UTF-8 strings to PCRE, the results are - undefined. - - Running with PCRE_UTF8 set causes these changes in the way - PCRE works: - - 1. In a pattern, the escape sequence \x{...}, where the - contents of the braces is a string of hexadecimal digits, is - interpreted as a UTF-8 character whose code number is the - given hexadecimal number, for example: \x{1234}. This - inserts from one to six literal bytes into the pattern, - using the UTF-8 encoding. If a non-hexadecimal digit appears - between the braces, the item is not recognized. - - 2. The original hexadecimal escape sequence, \xhh, generates - a two-byte UTF-8 character if its value is greater than 127. - - 3. Repeat quantifiers are NOT correctly handled if they fol- - low a multibyte character. For example, \x{100}* and \xc3+ - do not work. If you want to repeat such characters, you must - enclose them in non-capturing parentheses, for example - (?:\x{100}), at present. - - 4. The dot metacharacter matches one UTF-8 character instead - of a single byte. - - 5. Unlike literal UTF-8 characters, the dot metacharacter - followed by a repeat quantifier does operate correctly on - UTF-8 characters instead of single bytes. - - 4. Although the \x{...} escape is permitted in a character - class, characters whose values are greater than 255 cannot - be included in a class. - - 5. A class is matched against a UTF-8 character instead of - just a single byte, but it can match only characters whose - values are less than 256. Characters with greater values - always fail to match a class. - - 6. Repeated classes work correctly on multiple characters. - - 7. Classes containing just a single character whose value is - greater than 127 (but less than 256), for example, [\x80] or - [^\x{93}], do not work because these are optimized into sin- - gle byte matches. In the first case, of course, the class - brackets are just redundant. - - 8. Lookbehind assertions move backwards in the subject by a - fixed number of characters instead of a fixed number of - bytes. Simple cases have been tested to work correctly, but - there may be hidden gotchas herein. - - 9. The character types such as \d and \w do not work - correctly with UTF-8 characters. They continue to test a - single byte. - - 10. Anything not explicitly mentioned here continues to work - in bytes rather than in characters. - - The following UTF-8 features of Perl 5.6 are not imple- - mented: - - 1. The escape sequence \C to match a single byte. - - 2. The use of Unicode tables and properties and escapes \p, - \P, and \X. - - - -SAMPLE PROGRAM - The code below is a simple, complete demonstration program, - to get you started with using PCRE. This code is also sup- - plied in the file pcredemo.c in the PCRE distribution. - - The program compiles the regular expression that is its - first argument, and matches it against the subject string in - its second argument. No options are set, and default charac- - ter tables are used. If matching succeeds, the program out- - puts the portion of the subject that matched, together with - the contents of any captured substrings. - - On a Unix system that has PCRE installed in /usr/local, you - can compile the demonstration program using a command like - this: - - gcc -o pcredemo pcredemo.c -I/usr/local/include - -L/usr/local/lib -lpcre - - Then you can run simple tests like this: - - ./pcredemo 'cat|dog' 'the cat sat on the mat' - - Note that there is a much more comprehensive test program, - called pcretest, which supports many more facilities for - testing regular expressions. The pcredemo program is pro- - vided as a simple coding example. - - On some operating systems (e.g. Solaris) you may get an - error like this when you try to run pcredemo: - - ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such - file or directory - - This is caused by the way shared library support works on - those systems. You need to add - - -R/usr/local/lib - - to the compile command to get round this problem. Here's the - code: - - #include <stdio.h> - #include <string.h> - #include <pcre.h> - - #define OVECCOUNT 30 /* should be a multiple of 3 */ - - int main(int argc, char **argv) - { - pcre *re; - const char *error; - int erroffset; - int ovector[OVECCOUNT]; - int rc, i; - - if (argc != 3) - { - printf("Two arguments required: a regex and a " - "subject string\n"); - return 1; - } - - /* Compile the regular expression in the first argument */ - - re = pcre_compile( - argv[1], /* the pattern */ - 0, /* default options */ - &error, /* for error message */ - &erroffset, /* for error offset */ - NULL); /* use default character tables */ - - /* Compilation failed: print the error message and exit */ - - if (re == NULL) - { - printf("PCRE compilation failed at offset %d: %s\n", - erroffset, error); - return 1; - } - - /* Compilation succeeded: match the subject in the second - argument */ - - rc = pcre_exec( - re, /* the compiled pattern */ - NULL, /* we didn't study the pattern */ - argv[2], /* the subject string */ - (int)strlen(argv[2]), /* the length of the subject */ - 0, /* start at offset 0 in the subject */ - 0, /* default options */ - ovector, /* vector for substring information */ - OVECCOUNT); /* number of elements in the vector */ - - /* Matching failed: handle error cases */ - - if (rc < 0) - { - switch(rc) - { - case PCRE_ERROR_NOMATCH: printf("No match\n"); break; - /* - Handle other special cases if you like - */ - default: printf("Matching error %d\n", rc); break; - } - return 1; - } - - /* Match succeded */ - - printf("Match succeeded\n"); - - /* The output vector wasn't big enough */ - - if (rc == 0) - { - rc = OVECCOUNT/3; - printf("ovector only has room for %d captured " - substrings\n", rc - 1); - } - - /* Show substrings stored in the output vector */ - - for (i = 0; i < rc; i++) - { - char *substring_start = argv[2] + ovector[2*i]; - int substring_length = ovector[2*i+1] - ovector[2*i]; - printf("%2d: %.*s\n", i, substring_length, - substring_start); - } - - return 0; - } - - - -AUTHOR - Philip Hazel <ph10@cam.ac.uk> - University Computing Service, - New Museums Site, - Cambridge CB2 3QG, England. - Phone: +44 1223 334714 - - Last updated: 15 August 2001 - Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.1 b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.1 deleted file mode 100644 index 5d3151e8..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.1 +++ /dev/null @@ -1,88 +0,0 @@ -.TH PCREGREP 1 -.SH NAME -pcregrep - a grep with Perl-compatible regular expressions. -.SH SYNOPSIS -.B pcregrep [-Vcfhilnrsvx] pattern [file] ... - - -.SH DESCRIPTION -\fBpcregrep\fR searches files for character patterns, in the same way as other -grep commands do, but it uses the PCRE regular expression library to support -patterns that are compatible with the regular expressions of Perl 5. See -\fBpcre(3)\fR for a full description of syntax and semantics. - -If no files are specified, \fBpcregrep\fR reads the standard input. By default, -each line that matches the pattern is copied to the standard output, and if -there is more than one file, the file name is printed before each line of -output. However, there are options that can change how \fBpcregrep\fR behaves. - -Lines are limited to BUFSIZ characters. BUFSIZ is defined in \fB<stdio.h>\fR. -The newline character is removed from the end of each line before it is matched -against the pattern. - - -.SH OPTIONS -.TP 10 -\fB-V\fR -Write the version number of the PCRE library being used to the standard error -stream. -.TP -\fB-c\fR -Do not print individual lines; instead just print a count of the number of -lines that would otherwise have been printed. If several files are given, a -count is printed for each of them. -.TP -\fB-f\fIfilename\fR -Read patterns from the file, one per line, and match all patterns against each -line. There is a maximum of 100 patterns. Trailing white space is removed, and -blank lines are ignored. An empty file contains no patterns and therefore -matches nothing. -.TP -\fB-h\fR -Suppress printing of filenames when searching multiple files. -.TP -\fB-i\fR -Ignore upper/lower case distinctions during comparisons. -.TP -\fB-l\fR -Instead of printing lines from the files, just print the names of the files -containing lines that would have been printed. Each file name is printed -once, on a separate line. -.TP -\fB-n\fR -Precede each line by its line number in the file. -.TP -\fB-r\fR -If any file is a directory, recursively scan the files it contains. Without -\fB-r\fR a directory is scanned as a normal file. -.TP -\fB-s\fR -Work silently, that is, display nothing except error messages. -The exit status indicates whether any matches were found. -.TP -\fB-v\fR -Invert the sense of the match, so that lines which do \fInot\fR match the -pattern are now the ones that are found. -.TP -\fB-x\fR -Force the pattern to be anchored (it must start matching at the beginning of -the line) and in addition, require it to match the entire line. This is -equivalent to having ^ and $ characters at the start and end of each -alternative branch in the regular expression. - - -.SH SEE ALSO -\fBpcre(3)\fR, Perl 5 documentation - - -.SH DIAGNOSTICS -Exit status is 0 if any matches were found, 1 if no matches were found, and 2 -for syntax errors or inacessible files (even if matches were found). - - -.SH AUTHOR -Philip Hazel <ph10@cam.ac.uk> - -Last updated: 15 August 2001 -.br -Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.html b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.html deleted file mode 100644 index 7bc210c6..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.html +++ /dev/null @@ -1,120 +0,0 @@ -<HTML> -<HEAD> -<TITLE>pcregrep specification</TITLE> -</HEAD> -<body bgcolor="#FFFFFF" text="#00005A"> -<H1>pcregrep specification</H1> -This HTML document has been generated automatically from the original man page. -If there is any nonsense in it, please consult the man page in case the -conversion went wrong. -<UL> -<LI><A NAME="TOC1" HREF="#SEC1">NAME</A> -<LI><A NAME="TOC2" HREF="#SEC2">SYNOPSIS</A> -<LI><A NAME="TOC3" HREF="#SEC3">DESCRIPTION</A> -<LI><A NAME="TOC4" HREF="#SEC4">OPTIONS</A> -<LI><A NAME="TOC5" HREF="#SEC5">SEE ALSO</A> -<LI><A NAME="TOC6" HREF="#SEC6">DIAGNOSTICS</A> -<LI><A NAME="TOC7" HREF="#SEC7">AUTHOR</A> -</UL> -<LI><A NAME="SEC1" HREF="#TOC1">NAME</A> -<P> -pcregrep - a grep with Perl-compatible regular expressions. -</P> -<LI><A NAME="SEC2" HREF="#TOC1">SYNOPSIS</A> -<P> -<B>pcregrep [-Vcfhilnrsvx] pattern [file] ...</B> -</P> -<LI><A NAME="SEC3" HREF="#TOC1">DESCRIPTION</A> -<P> -<B>pcregrep</B> searches files for character patterns, in the same way as other -grep commands do, but it uses the PCRE regular expression library to support -patterns that are compatible with the regular expressions of Perl 5. See -<B>pcre(3)</B> for a full description of syntax and semantics. -</P> -<P> -If no files are specified, <B>pcregrep</B> reads the standard input. By default, -each line that matches the pattern is copied to the standard output, and if -there is more than one file, the file name is printed before each line of -output. However, there are options that can change how <B>pcregrep</B> behaves. -</P> -<P> -Lines are limited to BUFSIZ characters. BUFSIZ is defined in <B><stdio.h></B>. -The newline character is removed from the end of each line before it is matched -against the pattern. -</P> -<LI><A NAME="SEC4" HREF="#TOC1">OPTIONS</A> -<P> -<B>-V</B> -Write the version number of the PCRE library being used to the standard error -stream. -</P> -<P> -<B>-c</B> -Do not print individual lines; instead just print a count of the number of -lines that would otherwise have been printed. If several files are given, a -count is printed for each of them. -</P> -<P> -\fB-f<I>filename</I> -Read patterns from the file, one per line, and match all patterns against each -line. There is a maximum of 100 patterns. Trailing white space is removed, and -blank lines are ignored. An empty file contains no patterns and therefore -matches nothing. -</P> -<P> -<B>-h</B> -Suppress printing of filenames when searching multiple files. -</P> -<P> -<B>-i</B> -Ignore upper/lower case distinctions during comparisons. -</P> -<P> -<B>-l</B> -Instead of printing lines from the files, just print the names of the files -containing lines that would have been printed. Each file name is printed -once, on a separate line. -</P> -<P> -<B>-n</B> -Precede each line by its line number in the file. -</P> -<P> -<B>-r</B> -If any file is a directory, recursively scan the files it contains. Without -<B>-r</B> a directory is scanned as a normal file. -</P> -<P> -<B>-s</B> -Work silently, that is, display nothing except error messages. -The exit status indicates whether any matches were found. -</P> -<P> -<B>-v</B> -Invert the sense of the match, so that lines which do <I>not</I> match the -pattern are now the ones that are found. -</P> -<P> -<B>-x</B> -Force the pattern to be anchored (it must start matching at the beginning of -the line) and in addition, require it to match the entire line. This is -equivalent to having ^ and $ characters at the start and end of each -alternative branch in the regular expression. -</P> -<LI><A NAME="SEC5" HREF="#TOC1">SEE ALSO</A> -<P> -<B>pcre(3)</B>, Perl 5 documentation -</P> -<LI><A NAME="SEC6" HREF="#TOC1">DIAGNOSTICS</A> -<P> -Exit status is 0 if any matches were found, 1 if no matches were found, and 2 -for syntax errors or inacessible files (even if matches were found). -</P> -<LI><A NAME="SEC7" HREF="#TOC1">AUTHOR</A> -<P> -Philip Hazel <ph10@cam.ac.uk> -</P> -<P> -Last updated: 15 August 2001 -<BR> -Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.txt b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.txt deleted file mode 100644 index 16002284..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcregrep.txt +++ /dev/null @@ -1,101 +0,0 @@ -NAME - pcregrep - a grep with Perl-compatible regular expressions. - - - -SYNOPSIS - pcregrep [-Vcfhilnrsvx] pattern [file] ... - - - -DESCRIPTION - pcregrep searches files for character patterns, in the same - way as other grep commands do, but it uses the PCRE regular - expression library to support patterns that are compatible - with the regular expressions of Perl 5. See pcre(3) for a - full description of syntax and semantics. - - If no files are specified, pcregrep reads the standard - input. By default, each line that matches the pattern is - copied to the standard output, and if there is more than one - file, the file name is printed before each line of output. - However, there are options that can change how pcregrep - behaves. - - Lines are limited to BUFSIZ characters. BUFSIZ is defined in - <stdio.h>. The newline character is removed from the end of - each line before it is matched against the pattern. - - - -OPTIONS - -V Write the version number of the PCRE library being - used to the standard error stream. - - -c Do not print individual lines; instead just print - a count of the number of lines that would other- - wise have been printed. If several files are - given, a count is printed for each of them. - - -ffilename - Read patterns from the file, one per line, and - match all patterns against each line. There is a - maximum of 100 patterns. Trailing white space is - removed, and blank lines are ignored. An empty - file contains no patterns and therefore matches - nothing. - - -h Suppress printing of filenames when searching mul- - tiple files. - - -i Ignore upper/lower case distinctions during com- - parisons. - - -l Instead of printing lines from the files, just - - print the names of the files containing lines that - would have been printed. Each file name is printed - once, on a separate line. - - -n Precede each line by its line number in the file. - - -r If any file is a directory, recursively scan the - files it contains. Without -r a directory is - scanned as a normal file. - - -s Work silently, that is, display nothing except - error messages. The exit status indicates whether - any matches were found. - - -v Invert the sense of the match, so that lines which - do not match the pattern are now the ones that are - found. - - -x Force the pattern to be anchored (it must start - matching at the beginning of the line) and in - addition, require it to match the entire line. - This is equivalent to having ^ and $ characters at - the start and end of each alternative branch in - the regular expression. - - - -SEE ALSO - pcre(3), Perl 5 documentation - - - - - -DIAGNOSTICS - Exit status is 0 if any matches were found, 1 if no matches - were found, and 2 for syntax errors or inacessible files - (even if matches were found). - - - -AUTHOR - Philip Hazel <ph10@cam.ac.uk> - - Last updated: 15 August 2001 - Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.3 b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.3 deleted file mode 100644 index 41716ead..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.3 +++ /dev/null @@ -1,149 +0,0 @@ -.TH PCRE 3 -.SH NAME -pcreposix - POSIX API for Perl-compatible regular expressions. -.SH SYNOPSIS -.B #include <pcreposix.h> -.PP -.SM -.br -.B int regcomp(regex_t *\fIpreg\fR, const char *\fIpattern\fR, -.ti +5n -.B int \fIcflags\fR); -.PP -.br -.B int regexec(regex_t *\fIpreg\fR, const char *\fIstring\fR, -.ti +5n -.B size_t \fInmatch\fR, regmatch_t \fIpmatch\fR[], int \fIeflags\fR); -.PP -.br -.B size_t regerror(int \fIerrcode\fR, const regex_t *\fIpreg\fR, -.ti +5n -.B char *\fIerrbuf\fR, size_t \fIerrbuf_size\fR); -.PP -.br -.B void regfree(regex_t *\fIpreg\fR); - - -.SH DESCRIPTION -This set of functions provides a POSIX-style API to the PCRE regular expression -package. See the \fBpcre\fR documentation for a description of the native API, -which contains additional functionality. - -The functions described here are just wrapper functions that ultimately call -the native API. Their prototypes are defined in the \fBpcreposix.h\fR header -file, and on Unix systems the library itself is called \fBpcreposix.a\fR, so -can be accessed by adding \fB-lpcreposix\fR to the command for linking an -application which uses them. Because the POSIX functions call the native ones, -it is also necessary to add \fR-lpcre\fR. - -I have implemented only those option bits that can be reasonably mapped to PCRE -native options. In addition, the options REG_EXTENDED and REG_NOSUB are defined -with the value zero. They have no effect, but since programs that are written -to the POSIX interface often use them, this makes it easier to slot in PCRE as -a replacement library. Other POSIX options are not even defined. - -When PCRE is called via these functions, it is only the API that is POSIX-like -in style. The syntax and semantics of the regular expressions themselves are -still those of Perl, subject to the setting of various PCRE options, as -described below. - -The header for these functions is supplied as \fBpcreposix.h\fR to avoid any -potential clash with other POSIX libraries. It can, of course, be renamed or -aliased as \fBregex.h\fR, which is the "correct" name. It provides two -structure types, \fIregex_t\fR for compiled internal forms, and -\fIregmatch_t\fR for returning captured substrings. It also defines some -constants whose names start with "REG_"; these are used for setting options and -identifying error codes. - - -.SH COMPILING A PATTERN - -The function \fBregcomp()\fR is called to compile a pattern into an -internal form. The pattern is a C string terminated by a binary zero, and -is passed in the argument \fIpattern\fR. The \fIpreg\fR argument is a pointer -to a regex_t structure which is used as a base for storing information about -the compiled expression. - -The argument \fIcflags\fR is either zero, or contains one or more of the bits -defined by the following macros: - - REG_ICASE - -The PCRE_CASELESS option is set when the expression is passed for compilation -to the native function. - - REG_NEWLINE - -The PCRE_MULTILINE option is set when the expression is passed for compilation -to the native function. - -In the absence of these flags, no options are passed to the native function. -This means the the regex is compiled with PCRE default semantics. In -particular, the way it handles newline characters in the subject string is the -Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only -\fIsome\fR of the effects specified for REG_NEWLINE. It does not affect the way -newlines are matched by . (they aren't) or a negative class such as [^a] (they -are). - -The yield of \fBregcomp()\fR is zero on success, and non-zero otherwise. The -\fIpreg\fR structure is filled in on success, and one member of the structure -is publicized: \fIre_nsub\fR contains the number of capturing subpatterns in -the regular expression. Various error codes are defined in the header file. - - -.SH MATCHING A PATTERN -The function \fBregexec()\fR is called to match a pre-compiled pattern -\fIpreg\fR against a given \fIstring\fR, which is terminated by a zero byte, -subject to the options in \fIeflags\fR. These can be: - - REG_NOTBOL - -The PCRE_NOTBOL option is set when calling the underlying PCRE matching -function. - - REG_NOTEOL - -The PCRE_NOTEOL option is set when calling the underlying PCRE matching -function. - -The portion of the string that was matched, and also any captured substrings, -are returned via the \fIpmatch\fR argument, which points to an array of -\fInmatch\fR structures of type \fIregmatch_t\fR, containing the members -\fIrm_so\fR and \fIrm_eo\fR. These contain the offset to the first character of -each substring and the offset to the first character after the end of each -substring, respectively. The 0th element of the vector relates to the entire -portion of \fIstring\fR that was matched; subsequent elements relate to the -capturing subpatterns of the regular expression. Unused entries in the array -have both structure members set to -1. - -A successful match yields a zero return; various error codes are defined in the -header file, of which REG_NOMATCH is the "expected" failure code. - - -.SH ERROR MESSAGES -The \fBregerror()\fR function maps a non-zero errorcode from either -\fBregcomp\fR or \fBregexec\fR to a printable message. If \fIpreg\fR is not -NULL, the error should have arisen from the use of that structure. A message -terminated by a binary zero is placed in \fIerrbuf\fR. The length of the -message, including the zero, is limited to \fIerrbuf_size\fR. The yield of the -function is the size of buffer needed to hold the whole message. - - -.SH STORAGE -Compiling a regular expression causes memory to be allocated and associated -with the \fIpreg\fR structure. The function \fBregfree()\fR frees all such -memory, after which \fIpreg\fR may no longer be used as a compiled expression. - - -.SH AUTHOR -Philip Hazel <ph10@cam.ac.uk> -.br -University Computing Service, -.br -New Museums Site, -.br -Cambridge CB2 3QG, England. -.br -Phone: +44 1223 334714 - -Copyright (c) 1997-2000 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.html b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.html deleted file mode 100644 index 9c894784..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.html +++ /dev/null @@ -1,191 +0,0 @@ -<HTML> -<HEAD> -<TITLE>pcreposix specification</TITLE> -</HEAD> -<body bgcolor="#FFFFFF" text="#00005A"> -<H1>pcreposix specification</H1> -This HTML document has been generated automatically from the original man page. -If there is any nonsense in it, please consult the man page in case the -conversion went wrong. -<UL> -<LI><A NAME="TOC1" HREF="#SEC1">NAME</A> -<LI><A NAME="TOC2" HREF="#SEC2">SYNOPSIS</A> -<LI><A NAME="TOC3" HREF="#SEC3">DESCRIPTION</A> -<LI><A NAME="TOC4" HREF="#SEC4">COMPILING A PATTERN</A> -<LI><A NAME="TOC5" HREF="#SEC5">MATCHING A PATTERN</A> -<LI><A NAME="TOC6" HREF="#SEC6">ERROR MESSAGES</A> -<LI><A NAME="TOC7" HREF="#SEC7">STORAGE</A> -<LI><A NAME="TOC8" HREF="#SEC8">AUTHOR</A> -</UL> -<LI><A NAME="SEC1" HREF="#TOC1">NAME</A> -<P> -pcreposix - POSIX API for Perl-compatible regular expressions. -</P> -<LI><A NAME="SEC2" HREF="#TOC1">SYNOPSIS</A> -<P> -<B>#include <pcreposix.h></B> -</P> -<P> -<B>int regcomp(regex_t *<I>preg</I>, const char *<I>pattern</I>,</B> -<B>int <I>cflags</I>);</B> -</P> -<P> -<B>int regexec(regex_t *<I>preg</I>, const char *<I>string</I>,</B> -<B>size_t <I>nmatch</I>, regmatch_t <I>pmatch</I>[], int <I>eflags</I>);</B> -</P> -<P> -<B>size_t regerror(int <I>errcode</I>, const regex_t *<I>preg</I>,</B> -<B>char *<I>errbuf</I>, size_t <I>errbuf_size</I>);</B> -</P> -<P> -<B>void regfree(regex_t *<I>preg</I>);</B> -</P> -<LI><A NAME="SEC3" HREF="#TOC1">DESCRIPTION</A> -<P> -This set of functions provides a POSIX-style API to the PCRE regular expression -package. See the <B>pcre</B> documentation for a description of the native API, -which contains additional functionality. -</P> -<P> -The functions described here are just wrapper functions that ultimately call -the native API. Their prototypes are defined in the <B>pcreposix.h</B> header -file, and on Unix systems the library itself is called <B>pcreposix.a</B>, so -can be accessed by adding <B>-lpcreposix</B> to the command for linking an -application which uses them. Because the POSIX functions call the native ones, -it is also necessary to add \fR-lpcre\fR. -</P> -<P> -I have implemented only those option bits that can be reasonably mapped to PCRE -native options. In addition, the options REG_EXTENDED and REG_NOSUB are defined -with the value zero. They have no effect, but since programs that are written -to the POSIX interface often use them, this makes it easier to slot in PCRE as -a replacement library. Other POSIX options are not even defined. -</P> -<P> -When PCRE is called via these functions, it is only the API that is POSIX-like -in style. The syntax and semantics of the regular expressions themselves are -still those of Perl, subject to the setting of various PCRE options, as -described below. -</P> -<P> -The header for these functions is supplied as <B>pcreposix.h</B> to avoid any -potential clash with other POSIX libraries. It can, of course, be renamed or -aliased as <B>regex.h</B>, which is the "correct" name. It provides two -structure types, <I>regex_t</I> for compiled internal forms, and -<I>regmatch_t</I> for returning captured substrings. It also defines some -constants whose names start with "REG_"; these are used for setting options and -identifying error codes. -</P> -<LI><A NAME="SEC4" HREF="#TOC1">COMPILING A PATTERN</A> -<P> -The function <B>regcomp()</B> is called to compile a pattern into an -internal form. The pattern is a C string terminated by a binary zero, and -is passed in the argument <I>pattern</I>. The <I>preg</I> argument is a pointer -to a regex_t structure which is used as a base for storing information about -the compiled expression. -</P> -<P> -The argument <I>cflags</I> is either zero, or contains one or more of the bits -defined by the following macros: -</P> -<P> -<PRE> - REG_ICASE -</PRE> -</P> -<P> -The PCRE_CASELESS option is set when the expression is passed for compilation -to the native function. -</P> -<P> -<PRE> - REG_NEWLINE -</PRE> -</P> -<P> -The PCRE_MULTILINE option is set when the expression is passed for compilation -to the native function. -</P> -<P> -In the absence of these flags, no options are passed to the native function. -This means the the regex is compiled with PCRE default semantics. In -particular, the way it handles newline characters in the subject string is the -Perl way, not the POSIX way. Note that setting PCRE_MULTILINE has only -<I>some</I> of the effects specified for REG_NEWLINE. It does not affect the way -newlines are matched by . (they aren't) or a negative class such as [^a] (they -are). -</P> -<P> -The yield of <B>regcomp()</B> is zero on success, and non-zero otherwise. The -<I>preg</I> structure is filled in on success, and one member of the structure -is publicized: <I>re_nsub</I> contains the number of capturing subpatterns in -the regular expression. Various error codes are defined in the header file. -</P> -<LI><A NAME="SEC5" HREF="#TOC1">MATCHING A PATTERN</A> -<P> -The function <B>regexec()</B> is called to match a pre-compiled pattern -<I>preg</I> against a given <I>string</I>, which is terminated by a zero byte, -subject to the options in <I>eflags</I>. These can be: -</P> -<P> -<PRE> - REG_NOTBOL -</PRE> -</P> -<P> -The PCRE_NOTBOL option is set when calling the underlying PCRE matching -function. -</P> -<P> -<PRE> - REG_NOTEOL -</PRE> -</P> -<P> -The PCRE_NOTEOL option is set when calling the underlying PCRE matching -function. -</P> -<P> -The portion of the string that was matched, and also any captured substrings, -are returned via the <I>pmatch</I> argument, which points to an array of -<I>nmatch</I> structures of type <I>regmatch_t</I>, containing the members -<I>rm_so</I> and <I>rm_eo</I>. These contain the offset to the first character of -each substring and the offset to the first character after the end of each -substring, respectively. The 0th element of the vector relates to the entire -portion of <I>string</I> that was matched; subsequent elements relate to the -capturing subpatterns of the regular expression. Unused entries in the array -have both structure members set to -1. -</P> -<P> -A successful match yields a zero return; various error codes are defined in the -header file, of which REG_NOMATCH is the "expected" failure code. -</P> -<LI><A NAME="SEC6" HREF="#TOC1">ERROR MESSAGES</A> -<P> -The <B>regerror()</B> function maps a non-zero errorcode from either -<B>regcomp</B> or <B>regexec</B> to a printable message. If <I>preg</I> is not -NULL, the error should have arisen from the use of that structure. A message -terminated by a binary zero is placed in <I>errbuf</I>. The length of the -message, including the zero, is limited to <I>errbuf_size</I>. The yield of the -function is the size of buffer needed to hold the whole message. -</P> -<LI><A NAME="SEC7" HREF="#TOC1">STORAGE</A> -<P> -Compiling a regular expression causes memory to be allocated and associated -with the <I>preg</I> structure. The function <B>regfree()</B> frees all such -memory, after which <I>preg</I> may no longer be used as a compiled expression. -</P> -<LI><A NAME="SEC8" HREF="#TOC1">AUTHOR</A> -<P> -Philip Hazel <ph10@cam.ac.uk> -<BR> -University Computing Service, -<BR> -New Museums Site, -<BR> -Cambridge CB2 3QG, England. -<BR> -Phone: +44 1223 334714 -</P> -<P> -Copyright (c) 1997-2000 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.txt b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.txt deleted file mode 100644 index 2d76f7cd..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcreposix.txt +++ /dev/null @@ -1,159 +0,0 @@ -NAME - pcreposix - POSIX API for Perl-compatible regular expres- - sions. - - - -SYNOPSIS - #include <pcreposix.h> - - int regcomp(regex_t *preg, const char *pattern, - int cflags); - - int regexec(regex_t *preg, const char *string, - size_t nmatch, regmatch_t pmatch[], int eflags); - - size_t regerror(int errcode, const regex_t *preg, - char *errbuf, size_t errbuf_size); - - void regfree(regex_t *preg); - - - -DESCRIPTION - This set of functions provides a POSIX-style API to the PCRE - regular expression package. See the pcre documentation for a - description of the native API, which contains additional - functionality. - - The functions described here are just wrapper functions that - ultimately call the native API. Their prototypes are defined - in the pcreposix.h header file, and on Unix systems the - library itself is called pcreposix.a, so can be accessed by - adding -lpcreposix to the command for linking an application - which uses them. Because the POSIX functions call the native - ones, it is also necessary to add -lpcre. - - I have implemented only those option bits that can be rea- - sonably mapped to PCRE native options. In addition, the - options REG_EXTENDED and REG_NOSUB are defined with the - value zero. They have no effect, but since programs that are - written to the POSIX interface often use them, this makes it - easier to slot in PCRE as a replacement library. Other POSIX - options are not even defined. - - When PCRE is called via these functions, it is only the API - that is POSIX-like in style. The syntax and semantics of the - regular expressions themselves are still those of Perl, sub- - ject to the setting of various PCRE options, as described - below. - - The header for these functions is supplied as pcreposix.h to - avoid any potential clash with other POSIX libraries. It - can, of course, be renamed or aliased as regex.h, which is - the "correct" name. It provides two structure types, regex_t - for compiled internal forms, and regmatch_t for returning - captured substrings. It also defines some constants whose - names start with "REG_"; these are used for setting options - and identifying error codes. - - - -COMPILING A PATTERN - The function regcomp() is called to compile a pattern into - an internal form. The pattern is a C string terminated by a - binary zero, and is passed in the argument pattern. The preg - argument is a pointer to a regex_t structure which is used - as a base for storing information about the compiled expres- - sion. - - The argument cflags is either zero, or contains one or more - of the bits defined by the following macros: - - REG_ICASE - - The PCRE_CASELESS option is set when the expression is - passed for compilation to the native function. - - REG_NEWLINE - - The PCRE_MULTILINE option is set when the expression is - passed for compilation to the native function. - - In the absence of these flags, no options are passed to the - native function. This means the the regex is compiled with - PCRE default semantics. In particular, the way it handles - newline characters in the subject string is the Perl way, - not the POSIX way. Note that setting PCRE_MULTILINE has only - some of the effects specified for REG_NEWLINE. It does not - affect the way newlines are matched by . (they aren't) or a - negative class such as [^a] (they are). - - The yield of regcomp() is zero on success, and non-zero oth- - erwise. The preg structure is filled in on success, and one - member of the structure is publicized: re_nsub contains the - number of capturing subpatterns in the regular expression. - Various error codes are defined in the header file. - - - -MATCHING A PATTERN - The function regexec() is called to match a pre-compiled - pattern preg against a given string, which is terminated by - a zero byte, subject to the options in eflags. These can be: - - REG_NOTBOL - - The PCRE_NOTBOL option is set when calling the underlying - PCRE matching function. - - REG_NOTEOL - - The PCRE_NOTEOL option is set when calling the underlying - PCRE matching function. - - The portion of the string that was matched, and also any - captured substrings, are returned via the pmatch argument, - which points to an array of nmatch structures of type - regmatch_t, containing the members rm_so and rm_eo. These - contain the offset to the first character of each substring - and the offset to the first character after the end of each - substring, respectively. The 0th element of the vector - relates to the entire portion of string that was matched; - subsequent elements relate to the capturing subpatterns of - the regular expression. Unused entries in the array have - both structure members set to -1. - - A successful match yields a zero return; various error codes - are defined in the header file, of which REG_NOMATCH is the - "expected" failure code. - - - -ERROR MESSAGES - The regerror() function maps a non-zero errorcode from - either regcomp or regexec to a printable message. If preg is - not NULL, the error should have arisen from the use of that - structure. A message terminated by a binary zero is placed - in errbuf. The length of the message, including the zero, is - limited to errbuf_size. The yield of the function is the - size of buffer needed to hold the whole message. - - - -STORAGE - Compiling a regular expression causes memory to be allocated - and associated with the preg structure. The function reg- - free() frees all such memory, after which preg may no longer - be used as a compiled expression. - - - -AUTHOR - Philip Hazel <ph10@cam.ac.uk> - University Computing Service, - New Museums Site, - Cambridge CB2 3QG, England. - Phone: +44 1223 334714 - - Copyright (c) 1997-2000 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.1 b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.1 deleted file mode 100644 index b2e25560..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.1 +++ /dev/null @@ -1,282 +0,0 @@ -.TH PCRETEST 1 -.SH NAME -pcretest - a program for testing Perl-compatible regular expressions. -.SH SYNOPSIS -.B pcretest "[-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination]" - -\fBpcretest\fR was written as a test program for the PCRE regular expression -library itself, but it can also be used for experimenting with regular -expressions. This man page describes the features of the test program; for -details of the regular expressions themselves, see the \fBpcre\fR man page. - -.SH OPTIONS -.TP 10 -\fB-d\fR -Behave as if each regex had the \fB/D\fR modifier (see below); the internal -form is output after compilation. -.TP 10 -\fB-i\fR -Behave as if each regex had the \fB/I\fR modifier; information about the -compiled pattern is given after compilation. -.TP 10 -\fB-m\fR -Output the size of each compiled pattern after it has been compiled. This is -equivalent to adding /M to each regular expression. For compatibility with -earlier versions of pcretest, \fB-s\fR is a synonym for \fB-m\fR. -.TP 10 -\fB-o\fR \fIosize\fR -Set the number of elements in the output vector that is used when calling PCRE -to be \fIosize\fR. The default value is 45, which is enough for 14 capturing -subexpressions. The vector size can be changed for individual matching calls by -including \\O in the data line (see below). -.TP 10 -\fB-p\fR -Behave as if each regex has \fB/P\fR modifier; the POSIX wrapper API is used -to call PCRE. None of the other options has any effect when \fB-p\fR is set. -.TP 10 -\fB-t\fR -Run each compile, study, and match 20000 times with a timer, and output -resulting time per compile or match (in milliseconds). Do not set \fB-t\fR with -\fB-m\fR, because you will then get the size output 20000 times and the timing -will be distorted. - - -.SH DESCRIPTION - -If \fBpcretest\fR is given two filename arguments, it reads from the first and -writes to the second. If it is given only one filename argument, it reads from -that file and writes to stdout. Otherwise, it reads from stdin and writes to -stdout, and prompts for each line of input, using "re>" to prompt for regular -expressions, and "data>" to prompt for data lines. - -The program handles any number of sets of input on a single input file. Each -set starts with a regular expression, and continues with any number of data -lines to be matched against the pattern. An empty line signals the end of the -data lines, at which point a new regular expression is read. The regular -expressions are given enclosed in any non-alphameric delimiters other than -backslash, for example - - /(a|bc)x+yz/ - -White space before the initial delimiter is ignored. A regular expression may -be continued over several input lines, in which case the newline characters are -included within it. It is possible to include the delimiter within the pattern -by escaping it, for example - - /abc\\/def/ - -If you do so, the escape and the delimiter form part of the pattern, but since -delimiters are always non-alphameric, this does not affect its interpretation. -If the terminating delimiter is immediately followed by a backslash, for -example, - - /abc/\\ - -then a backslash is added to the end of the pattern. This is done to provide a -way of testing the error condition that arises if a pattern finishes with a -backslash, because - - /abc\\/ - -is interpreted as the first line of a pattern that starts with "abc/", causing -pcretest to read the next line as a continuation of the regular expression. - - -.SH PATTERN MODIFIERS - -The pattern may be followed by \fBi\fR, \fBm\fR, \fBs\fR, or \fBx\fR to set the -PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, -respectively. For example: - - /caseless/i - -These modifier letters have the same effect as they do in Perl. There are -others which set PCRE options that do not correspond to anything in Perl: -\fB/A\fR, \fB/E\fR, and \fB/X\fR set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and -PCRE_EXTRA respectively. - -Searching for all possible matches within each subject string can be requested -by the \fB/g\fR or \fB/G\fR modifier. After finding a match, PCRE is called -again to search the remainder of the subject string. The difference between -\fB/g\fR and \fB/G\fR is that the former uses the \fIstartoffset\fR argument to -\fBpcre_exec()\fR to start searching at a new point within the entire string -(which is in effect what Perl does), whereas the latter passes over a shortened -substring. This makes a difference to the matching process if the pattern -begins with a lookbehind assertion (including \\b or \\B). - -If any call to \fBpcre_exec()\fR in a \fB/g\fR or \fB/G\fR sequence matches an -empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED -flags set in order to search for another, non-empty, match at the same point. -If this second match fails, the start offset is advanced by one, and the normal -match is retried. This imitates the way Perl handles such cases when using the -\fB/g\fR modifier or the \fBsplit()\fR function. - -There are a number of other modifiers for controlling the way \fBpcretest\fR -operates. - -The \fB/+\fR modifier requests that as well as outputting the substring that -matched the entire pattern, pcretest should in addition output the remainder of -the subject string. This is useful for tests where the subject contains -multiple copies of the same substring. - -The \fB/L\fR modifier must be followed directly by the name of a locale, for -example, - - /pattern/Lfr - -For this reason, it must be the last modifier letter. The given locale is set, -\fBpcre_maketables()\fR is called to build a set of character tables for the -locale, and this is then passed to \fBpcre_compile()\fR when compiling the -regular expression. Without an \fB/L\fR modifier, NULL is passed as the tables -pointer; that is, \fB/L\fR applies only to the expression on which it appears. - -The \fB/I\fR modifier requests that \fBpcretest\fR output information about the -compiled expression (whether it is anchored, has a fixed first character, and -so on). It does this by calling \fBpcre_fullinfo()\fR after compiling an -expression, and outputting the information it gets back. If the pattern is -studied, the results of that are also output. - -The \fB/D\fR modifier is a PCRE debugging feature, which also assumes \fB/I\fR. -It causes the internal form of compiled regular expressions to be output after -compilation. - -The \fB/S\fR modifier causes \fBpcre_study()\fR to be called after the -expression has been compiled, and the results used when the expression is -matched. - -The \fB/M\fR modifier causes the size of memory block used to hold the compiled -pattern to be output. - -The \fB/P\fR modifier causes \fBpcretest\fR to call PCRE via the POSIX wrapper -API rather than its native API. When this is done, all other modifiers except -\fB/i\fR, \fB/m\fR, and \fB/+\fR are ignored. REG_ICASE is set if \fB/i\fR is -present, and REG_NEWLINE is set if \fB/m\fR is present. The wrapper functions -force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set. - -The \fB/8\fR modifier causes \fBpcretest\fR to call PCRE with the PCRE_UTF8 -option set. This turns on the (currently incomplete) support for UTF-8 -character handling in PCRE, provided that it was compiled with this support -enabled. This modifier also causes any non-printing characters in output -strings to be printed using the \\x{hh...} notation if they are valid UTF-8 -sequences. - - -.SH DATA LINES - -Before each data line is passed to \fBpcre_exec()\fR, leading and trailing -whitespace is removed, and it is then scanned for \\ escapes. The following are -recognized: - - \\a alarm (= BEL) - \\b backspace - \\e escape - \\f formfeed - \\n newline - \\r carriage return - \\t tab - \\v vertical tab - \\nnn octal character (up to 3 octal digits) - \\xhh hexadecimal character (up to 2 hex digits) - \\x{hh...} hexadecimal UTF-8 character - - \\A pass the PCRE_ANCHORED option to \fBpcre_exec()\fR - \\B pass the PCRE_NOTBOL option to \fBpcre_exec()\fR - \\Cdd call pcre_copy_substring() for substring dd - after a successful match (any decimal number - less than 32) - \\Gdd call pcre_get_substring() for substring dd - after a successful match (any decimal number - less than 32) - \\L call pcre_get_substringlist() after a - successful match - \\N pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fR - \\Odd set the size of the output vector passed to - \fBpcre_exec()\fR to dd (any number of decimal - digits) - \\Z pass the PCRE_NOTEOL option to \fBpcre_exec()\fR - -When \\O is used, it may be higher or lower than the size set by the \fB-O\fR -option (or defaulted to 45); \\O applies only to the call of \fBpcre_exec()\fR -for the line in which it appears. - -A backslash followed by anything else just escapes the anything else. If the -very last character is a backslash, it is ignored. This gives a way of passing -an empty line as data, since a real empty line terminates the data input. - -If \fB/P\fR was present on the regex, causing the POSIX wrapper API to be used, -only \fB\B\fR, and \fB\Z\fR have any effect, causing REG_NOTBOL and REG_NOTEOL -to be passed to \fBregexec()\fR respectively. - -The use of \\x{hh...} to represent UTF-8 characters is not dependent on the use -of the \fB/8\fR modifier on the pattern. It is recognized always. There may be -any number of hexadecimal digits inside the braces. The result is from one to -six bytes, encoded according to the UTF-8 rules. - - -.SH OUTPUT FROM PCRETEST - -When a match succeeds, pcretest outputs the list of captured substrings that -\fBpcre_exec()\fR returns, starting with number 0 for the string that matched -the whole pattern. Here is an example of an interactive pcretest run. - - $ pcretest - PCRE version 2.06 08-Jun-1999 - - re> /^abc(\\d+)/ - data> abc123 - 0: abc123 - 1: 123 - data> xyz - No match - -If the strings contain any non-printing characters, they are output as \\0x -escapes, or as \\x{...} escapes if the \fB/8\fR modifier was present on the -pattern. If the pattern has the \fB/+\fR modifier, then the output for -substring 0 is followed by the the rest of the subject string, identified by -"0+" like this: - - re> /cat/+ - data> cataract - 0: cat - 0+ aract - -If the pattern has the \fB/g\fR or \fB/G\fR modifier, the results of successive -matching attempts are output in sequence, like this: - - re> /\\Bi(\\w\\w)/g - data> Mississippi - 0: iss - 1: ss - 0: iss - 1: ss - 0: ipp - 1: pp - -"No match" is output only if the first match attempt fails. - -If any of the sequences \fB\\C\fR, \fB\\G\fR, or \fB\\L\fR are present in a -data line that is successfully matched, the substrings extracted by the -convenience functions are output with C, G, or L after the string number -instead of a colon. This is in addition to the normal full list. The string -length (that is, the return from the extraction function) is given in -parentheses after each string for \fB\\C\fR and \fB\\G\fR. - -Note that while patterns can be continued over several lines (a plain ">" -prompt is used for continuations), data lines may not. However newlines can be -included in data by means of the \\n escape. - - -.SH AUTHOR -Philip Hazel <ph10@cam.ac.uk> -.br -University Computing Service, -.br -New Museums Site, -.br -Cambridge CB2 3QG, England. -.br -Phone: +44 1223 334714 - -Last updated: 15 August 2001 -.br -Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.html b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.html deleted file mode 100644 index 918e6dec..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.html +++ /dev/null @@ -1,369 +0,0 @@ -<HTML> -<HEAD> -<TITLE>pcretest specification</TITLE> -</HEAD> -<body bgcolor="#FFFFFF" text="#00005A"> -<H1>pcretest specification</H1> -This HTML document has been generated automatically from the original man page. -If there is any nonsense in it, please consult the man page in case the -conversion went wrong. -<UL> -<LI><A NAME="TOC1" HREF="#SEC1">NAME</A> -<LI><A NAME="TOC2" HREF="#SEC2">SYNOPSIS</A> -<LI><A NAME="TOC3" HREF="#SEC3">OPTIONS</A> -<LI><A NAME="TOC4" HREF="#SEC4">DESCRIPTION</A> -<LI><A NAME="TOC5" HREF="#SEC5">PATTERN MODIFIERS</A> -<LI><A NAME="TOC6" HREF="#SEC6">DATA LINES</A> -<LI><A NAME="TOC7" HREF="#SEC7">OUTPUT FROM PCRETEST</A> -<LI><A NAME="TOC8" HREF="#SEC8">AUTHOR</A> -</UL> -<LI><A NAME="SEC1" HREF="#TOC1">NAME</A> -<P> -pcretest - a program for testing Perl-compatible regular expressions. -</P> -<LI><A NAME="SEC2" HREF="#TOC1">SYNOPSIS</A> -<P> -<B>pcretest [-d] [-i] [-m] [-o osize] [-p] [-t] [source] [destination]</B> -</P> -<P> -<B>pcretest</B> was written as a test program for the PCRE regular expression -library itself, but it can also be used for experimenting with regular -expressions. This man page describes the features of the test program; for -details of the regular expressions themselves, see the <B>pcre</B> man page. -</P> -<LI><A NAME="SEC3" HREF="#TOC1">OPTIONS</A> -<P> -<B>-d</B> -Behave as if each regex had the <B>/D</B> modifier (see below); the internal -form is output after compilation. -</P> -<P> -<B>-i</B> -Behave as if each regex had the <B>/I</B> modifier; information about the -compiled pattern is given after compilation. -</P> -<P> -<B>-m</B> -Output the size of each compiled pattern after it has been compiled. This is -equivalent to adding /M to each regular expression. For compatibility with -earlier versions of pcretest, <B>-s</B> is a synonym for <B>-m</B>. -</P> -<P> -<B>-o</B> <I>osize</I> -Set the number of elements in the output vector that is used when calling PCRE -to be <I>osize</I>. The default value is 45, which is enough for 14 capturing -subexpressions. The vector size can be changed for individual matching calls by -including \O in the data line (see below). -</P> -<P> -<B>-p</B> -Behave as if each regex has <B>/P</B> modifier; the POSIX wrapper API is used -to call PCRE. None of the other options has any effect when <B>-p</B> is set. -</P> -<P> -<B>-t</B> -Run each compile, study, and match 20000 times with a timer, and output -resulting time per compile or match (in milliseconds). Do not set <B>-t</B> with -<B>-m</B>, because you will then get the size output 20000 times and the timing -will be distorted. -</P> -<LI><A NAME="SEC4" HREF="#TOC1">DESCRIPTION</A> -<P> -If <B>pcretest</B> is given two filename arguments, it reads from the first and -writes to the second. If it is given only one filename argument, it reads from -that file and writes to stdout. Otherwise, it reads from stdin and writes to -stdout, and prompts for each line of input, using "re>" to prompt for regular -expressions, and "data>" to prompt for data lines. -</P> -<P> -The program handles any number of sets of input on a single input file. Each -set starts with a regular expression, and continues with any number of data -lines to be matched against the pattern. An empty line signals the end of the -data lines, at which point a new regular expression is read. The regular -expressions are given enclosed in any non-alphameric delimiters other than -backslash, for example -</P> -<P> -<PRE> - /(a|bc)x+yz/ -</PRE> -</P> -<P> -White space before the initial delimiter is ignored. A regular expression may -be continued over several input lines, in which case the newline characters are -included within it. It is possible to include the delimiter within the pattern -by escaping it, for example -</P> -<P> -<PRE> - /abc\/def/ -</PRE> -</P> -<P> -If you do so, the escape and the delimiter form part of the pattern, but since -delimiters are always non-alphameric, this does not affect its interpretation. -If the terminating delimiter is immediately followed by a backslash, for -example, -</P> -<P> -<PRE> - /abc/\ -</PRE> -</P> -<P> -then a backslash is added to the end of the pattern. This is done to provide a -way of testing the error condition that arises if a pattern finishes with a -backslash, because -</P> -<P> -<PRE> - /abc\/ -</PRE> -</P> -<P> -is interpreted as the first line of a pattern that starts with "abc/", causing -pcretest to read the next line as a continuation of the regular expression. -</P> -<LI><A NAME="SEC5" HREF="#TOC1">PATTERN MODIFIERS</A> -<P> -The pattern may be followed by <B>i</B>, <B>m</B>, <B>s</B>, or <B>x</B> to set the -PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, -respectively. For example: -</P> -<P> -<PRE> - /caseless/i -</PRE> -</P> -<P> -These modifier letters have the same effect as they do in Perl. There are -others which set PCRE options that do not correspond to anything in Perl: -<B>/A</B>, <B>/E</B>, and <B>/X</B> set PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and -PCRE_EXTRA respectively. -</P> -<P> -Searching for all possible matches within each subject string can be requested -by the <B>/g</B> or <B>/G</B> modifier. After finding a match, PCRE is called -again to search the remainder of the subject string. The difference between -<B>/g</B> and <B>/G</B> is that the former uses the <I>startoffset</I> argument to -<B>pcre_exec()</B> to start searching at a new point within the entire string -(which is in effect what Perl does), whereas the latter passes over a shortened -substring. This makes a difference to the matching process if the pattern -begins with a lookbehind assertion (including \b or \B). -</P> -<P> -If any call to <B>pcre_exec()</B> in a <B>/g</B> or <B>/G</B> sequence matches an -empty string, the next call is done with the PCRE_NOTEMPTY and PCRE_ANCHORED -flags set in order to search for another, non-empty, match at the same point. -If this second match fails, the start offset is advanced by one, and the normal -match is retried. This imitates the way Perl handles such cases when using the -<B>/g</B> modifier or the <B>split()</B> function. -</P> -<P> -There are a number of other modifiers for controlling the way <B>pcretest</B> -operates. -</P> -<P> -The <B>/+</B> modifier requests that as well as outputting the substring that -matched the entire pattern, pcretest should in addition output the remainder of -the subject string. This is useful for tests where the subject contains -multiple copies of the same substring. -</P> -<P> -The <B>/L</B> modifier must be followed directly by the name of a locale, for -example, -</P> -<P> -<PRE> - /pattern/Lfr -</PRE> -</P> -<P> -For this reason, it must be the last modifier letter. The given locale is set, -<B>pcre_maketables()</B> is called to build a set of character tables for the -locale, and this is then passed to <B>pcre_compile()</B> when compiling the -regular expression. Without an <B>/L</B> modifier, NULL is passed as the tables -pointer; that is, <B>/L</B> applies only to the expression on which it appears. -</P> -<P> -The <B>/I</B> modifier requests that <B>pcretest</B> output information about the -compiled expression (whether it is anchored, has a fixed first character, and -so on). It does this by calling <B>pcre_fullinfo()</B> after compiling an -expression, and outputting the information it gets back. If the pattern is -studied, the results of that are also output. -</P> -<P> -The <B>/D</B> modifier is a PCRE debugging feature, which also assumes <B>/I</B>. -It causes the internal form of compiled regular expressions to be output after -compilation. -</P> -<P> -The <B>/S</B> modifier causes <B>pcre_study()</B> to be called after the -expression has been compiled, and the results used when the expression is -matched. -</P> -<P> -The <B>/M</B> modifier causes the size of memory block used to hold the compiled -pattern to be output. -</P> -<P> -The <B>/P</B> modifier causes <B>pcretest</B> to call PCRE via the POSIX wrapper -API rather than its native API. When this is done, all other modifiers except -<B>/i</B>, <B>/m</B>, and <B>/+</B> are ignored. REG_ICASE is set if <B>/i</B> is -present, and REG_NEWLINE is set if <B>/m</B> is present. The wrapper functions -force PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless REG_NEWLINE is set. -</P> -<P> -The <B>/8</B> modifier causes <B>pcretest</B> to call PCRE with the PCRE_UTF8 -option set. This turns on the (currently incomplete) support for UTF-8 -character handling in PCRE, provided that it was compiled with this support -enabled. This modifier also causes any non-printing characters in output -strings to be printed using the \x{hh...} notation if they are valid UTF-8 -sequences. -</P> -<LI><A NAME="SEC6" HREF="#TOC1">DATA LINES</A> -<P> -Before each data line is passed to <B>pcre_exec()</B>, leading and trailing -whitespace is removed, and it is then scanned for \ escapes. The following are -recognized: -</P> -<P> -<PRE> - \a alarm (= BEL) - \b backspace - \e escape - \f formfeed - \n newline - \r carriage return - \t tab - \v vertical tab - \nnn octal character (up to 3 octal digits) - \xhh hexadecimal character (up to 2 hex digits) - \x{hh...} hexadecimal UTF-8 character -</PRE> -</P> -<P> -<PRE> - \A pass the PCRE_ANCHORED option to <B>pcre_exec()</B> - \B pass the PCRE_NOTBOL option to <B>pcre_exec()</B> - \Cdd call pcre_copy_substring() for substring dd - after a successful match (any decimal number - less than 32) - \Gdd call pcre_get_substring() for substring dd - after a successful match (any decimal number - less than 32) - \L call pcre_get_substringlist() after a - successful match - \N pass the PCRE_NOTEMPTY option to <B>pcre_exec()</B> - \Odd set the size of the output vector passed to - <B>pcre_exec()</B> to dd (any number of decimal - digits) - \Z pass the PCRE_NOTEOL option to <B>pcre_exec()</B> -</PRE> -</P> -<P> -When \O is used, it may be higher or lower than the size set by the <B>-O</B> -option (or defaulted to 45); \O applies only to the call of <B>pcre_exec()</B> -for the line in which it appears. -</P> -<P> -A backslash followed by anything else just escapes the anything else. If the -very last character is a backslash, it is ignored. This gives a way of passing -an empty line as data, since a real empty line terminates the data input. -</P> -<P> -If <B>/P</B> was present on the regex, causing the POSIX wrapper API to be used, -only <B>\B</B>, and <B>\Z</B> have any effect, causing REG_NOTBOL and REG_NOTEOL -to be passed to <B>regexec()</B> respectively. -</P> -<P> -The use of \x{hh...} to represent UTF-8 characters is not dependent on the use -of the <B>/8</B> modifier on the pattern. It is recognized always. There may be -any number of hexadecimal digits inside the braces. The result is from one to -six bytes, encoded according to the UTF-8 rules. -</P> -<LI><A NAME="SEC7" HREF="#TOC1">OUTPUT FROM PCRETEST</A> -<P> -When a match succeeds, pcretest outputs the list of captured substrings that -<B>pcre_exec()</B> returns, starting with number 0 for the string that matched -the whole pattern. Here is an example of an interactive pcretest run. -</P> -<P> -<PRE> - $ pcretest - PCRE version 2.06 08-Jun-1999 -</PRE> -</P> -<P> -<PRE> - re> /^abc(\d+)/ - data> abc123 - 0: abc123 - 1: 123 - data> xyz - No match -</PRE> -</P> -<P> -If the strings contain any non-printing characters, they are output as \0x -escapes, or as \x{...} escapes if the <B>/8</B> modifier was present on the -pattern. If the pattern has the <B>/+</B> modifier, then the output for -substring 0 is followed by the the rest of the subject string, identified by -"0+" like this: -</P> -<P> -<PRE> - re> /cat/+ - data> cataract - 0: cat - 0+ aract -</PRE> -</P> -<P> -If the pattern has the <B>/g</B> or <B>/G</B> modifier, the results of successive -matching attempts are output in sequence, like this: -</P> -<P> -<PRE> - re> /\Bi(\w\w)/g - data> Mississippi - 0: iss - 1: ss - 0: iss - 1: ss - 0: ipp - 1: pp -</PRE> -</P> -<P> -"No match" is output only if the first match attempt fails. -</P> -<P> -If any of the sequences <B>\C</B>, <B>\G</B>, or <B>\L</B> are present in a -data line that is successfully matched, the substrings extracted by the -convenience functions are output with C, G, or L after the string number -instead of a colon. This is in addition to the normal full list. The string -length (that is, the return from the extraction function) is given in -parentheses after each string for <B>\C</B> and <B>\G</B>. -</P> -<P> -Note that while patterns can be continued over several lines (a plain ">" -prompt is used for continuations), data lines may not. However newlines can be -included in data by means of the \n escape. -</P> -<LI><A NAME="SEC8" HREF="#TOC1">AUTHOR</A> -<P> -Philip Hazel <ph10@cam.ac.uk> -<BR> -University Computing Service, -<BR> -New Museums Site, -<BR> -Cambridge CB2 3QG, England. -<BR> -Phone: +44 1223 334714 -</P> -<P> -Last updated: 15 August 2001 -<BR> -Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.txt b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.txt deleted file mode 100644 index 0e13b6c6..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pcretest.txt +++ /dev/null @@ -1,319 +0,0 @@ -NAME - pcretest - a program for testing Perl-compatible regular - expressions. - - - -SYNOPSIS - pcretest [-d] [-i] [-m] [-o osize] [-p] [-t] [source] [des- - tination] - - pcretest was written as a test program for the PCRE regular - expression library itself, but it can also be used for - experimenting with regular expressions. This man page - describes the features of the test program; for details of - the regular expressions themselves, see the pcre man page. - - - -OPTIONS - -d Behave as if each regex had the /D modifier (see - below); the internal form is output after compila- - tion. - - -i Behave as if each regex had the /I modifier; - information about the compiled pattern is given - after compilation. - - -m Output the size of each compiled pattern after it - has been compiled. This is equivalent to adding /M - to each regular expression. For compatibility with - earlier versions of pcretest, -s is a synonym for - -m. - - -o osize Set the number of elements in the output vector - that is used when calling PCRE to be osize. The - default value is 45, which is enough for 14 cap- - turing subexpressions. The vector size can be - changed for individual matching calls by including - \O in the data line (see below). - - -p Behave as if each regex has /P modifier; the POSIX - wrapper API is used to call PCRE. None of the - other options has any effect when -p is set. - - -t Run each compile, study, and match 20000 times - with a timer, and output resulting time per com- - pile or match (in milliseconds). Do not set -t - with -m, because you will then get the size output - 20000 times and the timing will be distorted. - - - -DESCRIPTION - If pcretest is given two filename arguments, it reads from - the first and writes to the second. If it is given only one - - - - -SunOS 5.8 Last change: 1 - - - - filename argument, it reads from that file and writes to - stdout. Otherwise, it reads from stdin and writes to stdout, - and prompts for each line of input, using "re>" to prompt - for regular expressions, and "data>" to prompt for data - lines. - - The program handles any number of sets of input on a single - input file. Each set starts with a regular expression, and - continues with any number of data lines to be matched - against the pattern. An empty line signals the end of the - data lines, at which point a new regular expression is read. - The regular expressions are given enclosed in any non- - alphameric delimiters other than backslash, for example - - /(a|bc)x+yz/ - - White space before the initial delimiter is ignored. A regu- - lar expression may be continued over several input lines, in - which case the newline characters are included within it. It - is possible to include the delimiter within the pattern by - escaping it, for example - - /abc\/def/ - - If you do so, the escape and the delimiter form part of the - pattern, but since delimiters are always non-alphameric, - this does not affect its interpretation. If the terminating - delimiter is immediately followed by a backslash, for exam- - ple, - - /abc/\ - - then a backslash is added to the end of the pattern. This is - done to provide a way of testing the error condition that - arises if a pattern finishes with a backslash, because - - /abc\/ - - is interpreted as the first line of a pattern that starts - with "abc/", causing pcretest to read the next line as a - continuation of the regular expression. - - - -PATTERN MODIFIERS - The pattern may be followed by i, m, s, or x to set the - PCRE_CASELESS, PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED - options, respectively. For example: - - /caseless/i - - These modifier letters have the same effect as they do in - Perl. There are others which set PCRE options that do not - correspond to anything in Perl: /A, /E, and /X set - PCRE_ANCHORED, PCRE_DOLLAR_ENDONLY, and PCRE_EXTRA respec- - tively. - - Searching for all possible matches within each subject - string can be requested by the /g or /G modifier. After - finding a match, PCRE is called again to search the - remainder of the subject string. The difference between /g - and /G is that the former uses the startoffset argument to - pcre_exec() to start searching at a new point within the - entire string (which is in effect what Perl does), whereas - the latter passes over a shortened substring. This makes a - difference to the matching process if the pattern begins - with a lookbehind assertion (including \b or \B). - - If any call to pcre_exec() in a /g or /G sequence matches an - empty string, the next call is done with the PCRE_NOTEMPTY - and PCRE_ANCHORED flags set in order to search for another, - non-empty, match at the same point. If this second match - fails, the start offset is advanced by one, and the normal - match is retried. This imitates the way Perl handles such - cases when using the /g modifier or the split() function. - - There are a number of other modifiers for controlling the - way pcretest operates. - - The /+ modifier requests that as well as outputting the sub- - string that matched the entire pattern, pcretest should in - addition output the remainder of the subject string. This is - useful for tests where the subject contains multiple copies - of the same substring. - - The /L modifier must be followed directly by the name of a - locale, for example, - - /pattern/Lfr - - For this reason, it must be the last modifier letter. The - given locale is set, pcre_maketables() is called to build a - set of character tables for the locale, and this is then - passed to pcre_compile() when compiling the regular expres- - sion. Without an /L modifier, NULL is passed as the tables - pointer; that is, /L applies only to the expression on which - it appears. - - The /I modifier requests that pcretest output information - about the compiled expression (whether it is anchored, has a - fixed first character, and so on). It does this by calling - pcre_fullinfo() after compiling an expression, and output- - ting the information it gets back. If the pattern is stu- - died, the results of that are also output. - The /D modifier is a PCRE debugging feature, which also - assumes /I. It causes the internal form of compiled regular - expressions to be output after compilation. - - The /S modifier causes pcre_study() to be called after the - expression has been compiled, and the results used when the - expression is matched. - - The /M modifier causes the size of memory block used to hold - the compiled pattern to be output. - - The /P modifier causes pcretest to call PCRE via the POSIX - wrapper API rather than its native API. When this is done, - all other modifiers except /i, /m, and /+ are ignored. - REG_ICASE is set if /i is present, and REG_NEWLINE is set if - /m is present. The wrapper functions force - PCRE_DOLLAR_ENDONLY always, and PCRE_DOTALL unless - REG_NEWLINE is set. - - The /8 modifier causes pcretest to call PCRE with the - PCRE_UTF8 option set. This turns on the (currently incom- - plete) support for UTF-8 character handling in PCRE, pro- - vided that it was compiled with this support enabled. This - modifier also causes any non-printing characters in output - strings to be printed using the \x{hh...} notation if they - are valid UTF-8 sequences. - - - -DATA LINES - Before each data line is passed to pcre_exec(), leading and - trailing whitespace is removed, and it is then scanned for \ - escapes. The following are recognized: - - \a alarm (= BEL) - \b backspace - \e escape - \f formfeed - \n newline - \r carriage return - \t tab - \v vertical tab - \nnn octal character (up to 3 octal digits) - \xhh hexadecimal character (up to 2 hex digits) - \x{hh...} hexadecimal UTF-8 character - - \A pass the PCRE_ANCHORED option to pcre_exec() - \B pass the PCRE_NOTBOL option to pcre_exec() - \Cdd call pcre_copy_substring() for substring dd - after a successful match (any decimal number - less than 32) - \Gdd call pcre_get_substring() for substring dd - - after a successful match (any decimal number - less than 32) - \L call pcre_get_substringlist() after a - successful match - \N pass the PCRE_NOTEMPTY option to pcre_exec() - \Odd set the size of the output vector passed to - pcre_exec() to dd (any number of decimal - digits) - \Z pass the PCRE_NOTEOL option to pcre_exec() - - When \O is used, it may be higher or lower than the size set - by the -O option (or defaulted to 45); \O applies only to - the call of pcre_exec() for the line in which it appears. - - A backslash followed by anything else just escapes the any- - thing else. If the very last character is a backslash, it is - ignored. This gives a way of passing an empty line as data, - since a real empty line terminates the data input. - - If /P was present on the regex, causing the POSIX wrapper - API to be used, only B, and Z have any effect, causing - REG_NOTBOL and REG_NOTEOL to be passed to regexec() respec- - tively. - - The use of \x{hh...} to represent UTF-8 characters is not - dependent on the use of the /8 modifier on the pattern. It - is recognized always. There may be any number of hexadecimal - digits inside the braces. The result is from one to six - bytes, encoded according to the UTF-8 rules. - - - -OUTPUT FROM PCRETEST - When a match succeeds, pcretest outputs the list of captured - substrings that pcre_exec() returns, starting with number 0 - for the string that matched the whole pattern. Here is an - example of an interactive pcretest run. - - $ pcretest - PCRE version 2.06 08-Jun-1999 - - re> /^abc(\d+)/ - data> abc123 - 0: abc123 - 1: 123 - data> xyz - No match - - If the strings contain any non-printing characters, they are - output as \0x escapes, or as \x{...} escapes if the /8 - modifier was present on the pattern. If the pattern has the - /+ modifier, then the output for substring 0 is followed by - the the rest of the subject string, identified by "0+" like - this: - - re> /cat/+ - data> cataract - 0: cat - 0+ aract - - If the pattern has the /g or /G modifier, the results of - successive matching attempts are output in sequence, like - this: - - re> /\Bi(\w\w)/g - data> Mississippi - 0: iss - 1: ss - 0: iss - 1: ss - 0: ipp - 1: pp - - "No match" is output only if the first match attempt fails. - - If any of the sequences \C, \G, or \L are present in a data - line that is successfully matched, the substrings extracted - by the convenience functions are output with C, G, or L - after the string number instead of a colon. This is in addi- - tion to the normal full list. The string length (that is, - the return from the extraction function) is given in - parentheses after each string for \C and \G. - - Note that while patterns can be continued over several lines - (a plain ">" prompt is used for continuations), data lines - may not. However newlines can be included in data by means - of the \n escape. - - - -AUTHOR - Philip Hazel <ph10@cam.ac.uk> - University Computing Service, - New Museums Site, - Cambridge CB2 3QG, England. - Phone: +44 1223 334714 - - Last updated: 15 August 2001 - Copyright (c) 1997-2001 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/perltest.txt b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/perltest.txt deleted file mode 100644 index 5a404016..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/perltest.txt +++ /dev/null @@ -1,29 +0,0 @@ -The perltest program --------------------- - -The perltest program tests Perl's regular expressions; it has the same -specification as pcretest, and so can be given identical input, except that -input patterns can be followed only by Perl's lower case modifiers and /+ (as -used by pcretest), which is recognized and handled by the program. - -The data lines are processed as Perl double-quoted strings, so if they contain -" \ $ or @ characters, these have to be escaped. For this reason, all such -characters in testinput1 and testinput3 are escaped so that they can be used -for perltest as well as for pcretest, and the special upper case modifiers such -as /A that pcretest recognizes are not used in these files. The output should -be identical, apart from the initial identifying banner. - -For testing UTF-8 features, an alternative form of perltest, called perltest8, -is supplied. This requires Perl 5.6 or higher. It recognizes the special -modifier /8 that pcretest uses to invoke UTF-8 functionality. The testinput5 -file can be fed to perltest8. - -The testinput2 and testinput4 files are not suitable for feeding to perltest, -since they do make use of the special upper case modifiers and escapes that -pcretest uses to test some features of PCRE. The first of these files also -contains malformed regular expressions, in order to check that PCRE diagnoses -them correctly. Similarly, testinput6 tests UTF-8 features that do not relate -to Perl. - -Philip Hazel <ph10@cam.ac.uk> -August 2000 diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.1 b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.1 deleted file mode 100644 index d9e9b575..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.1 +++ /dev/null @@ -1,76 +0,0 @@ -.TH PGREP 1 -.SH NAME -pgrep - a grep with Perl-compatible regular expressions. -.SH SYNOPSIS -.B pgrep [-Vchilnsvx] pattern [file] ... - - -.SH DESCRIPTION -\fBpgrep\fR searches files for character patterns, in the same way as other -grep commands do, but it uses the PCRE regular expression library to support -patterns that are compatible with the regular expressions of Perl 5. See -\fBpcre(3)\fR for a full description of syntax and semantics. - -If no files are specified, \fBpgrep\fR reads the standard input. By default, -each line that matches the pattern is copied to the standard output, and if -there is more than one file, the file name is printed before each line of -output. However, there are options that can change how \fBpgrep\fR behaves. - -Lines are limited to BUFSIZ characters. BUFSIZ is defined in \fB<stdio.h>\fR. -The newline character is removed from the end of each line before it is matched -against the pattern. - - -.SH OPTIONS -.TP 10 -\fB-V\fR -Write the version number of the PCRE library being used to the standard error -stream. -.TP -\fB-c\fR -Do not print individual lines; instead just print a count of the number of -lines that would otherwise have been printed. If several files are given, a -count is printed for each of them. -.TP -\fB-h\fR -Suppress printing of filenames when searching multiple files. -.TP -\fB-i\fR -Ignore upper/lower case distinctions during comparisons. -.TP -\fB-l\fR -Instead of printing lines from the files, just print the names of the files -containing lines that would have been printed. Each file name is printed -once, on a separate line. -.TP -\fB-n\fR -Precede each line by its line number in the file. -.TP -\fB-s\fR -Work silently, that is, display nothing except error messages. -The exit status indicates whether any matches were found. -.TP -\fB-v\fR -Invert the sense of the match, so that lines which do \fInot\fR match the -pattern are now the ones that are found. -.TP -\fB-x\fR -Force the pattern to be anchored (it must start matching at the beginning of -the line) and in addition, require it to match the entire line. This is -equivalent to having ^ and $ characters at the start and end of each -alternative branch in the regular expression. - - -.SH SEE ALSO -\fBpcre(3)\fR, Perl 5 documentation - - -.SH DIAGNOSTICS -Exit status is 0 if any matches were found, 1 if no matches were found, and 2 -for syntax errors or inacessible files (even if matches were found). - - -.SH AUTHOR -Philip Hazel <ph10@cam.ac.uk> -.br -Copyright (c) 1997-1999 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.html b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.html deleted file mode 100644 index 54efed67..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.html +++ /dev/null @@ -1,105 +0,0 @@ -<HTML> -<HEAD> -<TITLE>pgrep specification</TITLE> -</HEAD> -<body bgcolor="#FFFFFF" text="#00005A"> -<H1>pgrep specification</H1> -This HTML document has been generated automatically from the original man page. -If there is any nonsense in it, please consult the man page in case the -conversion went wrong. -<UL> -<LI><A NAME="TOC1" HREF="#SEC1">NAME</A> -<LI><A NAME="TOC2" HREF="#SEC2">SYNOPSIS</A> -<LI><A NAME="TOC3" HREF="#SEC3">DESCRIPTION</A> -<LI><A NAME="TOC4" HREF="#SEC4">OPTIONS</A> -<LI><A NAME="TOC5" HREF="#SEC5">SEE ALSO</A> -<LI><A NAME="TOC6" HREF="#SEC6">DIAGNOSTICS</A> -<LI><A NAME="TOC7" HREF="#SEC7">AUTHOR</A> -</UL> -<LI><A NAME="SEC1" HREF="#TOC1">NAME</A> -<P> -pgrep - a grep with Perl-compatible regular expressions. -</P> -<LI><A NAME="SEC2" HREF="#TOC1">SYNOPSIS</A> -<P> -<B>pgrep [-Vchilnsvx] pattern [file] ...</B> -</P> -<LI><A NAME="SEC3" HREF="#TOC1">DESCRIPTION</A> -<P> -<B>pgrep</B> searches files for character patterns, in the same way as other -grep commands do, but it uses the PCRE regular expression library to support -patterns that are compatible with the regular expressions of Perl 5. See -<B>pcre(3)</B> for a full description of syntax and semantics. -</P> -<P> -If no files are specified, <B>pgrep</B> reads the standard input. By default, -each line that matches the pattern is copied to the standard output, and if -there is more than one file, the file name is printed before each line of -output. However, there are options that can change how <B>pgrep</B> behaves. -</P> -<P> -Lines are limited to BUFSIZ characters. BUFSIZ is defined in <B><stdio.h></B>. -The newline character is removed from the end of each line before it is matched -against the pattern. -</P> -<LI><A NAME="SEC4" HREF="#TOC1">OPTIONS</A> -<P> -<B>-V</B> -Write the version number of the PCRE library being used to the standard error -stream. -</P> -<P> -<B>-c</B> -Do not print individual lines; instead just print a count of the number of -lines that would otherwise have been printed. If several files are given, a -count is printed for each of them. -</P> -<P> -<B>-h</B> -Suppress printing of filenames when searching multiple files. -</P> -<P> -<B>-i</B> -Ignore upper/lower case distinctions during comparisons. -</P> -<P> -<B>-l</B> -Instead of printing lines from the files, just print the names of the files -containing lines that would have been printed. Each file name is printed -once, on a separate line. -</P> -<P> -<B>-n</B> -Precede each line by its line number in the file. -</P> -<P> -<B>-s</B> -Work silently, that is, display nothing except error messages. -The exit status indicates whether any matches were found. -</P> -<P> -<B>-v</B> -Invert the sense of the match, so that lines which do <I>not</I> match the -pattern are now the ones that are found. -</P> -<P> -<B>-x</B> -Force the pattern to be anchored (it must start matching at the beginning of -the line) and in addition, require it to match the entire line. This is -equivalent to having ^ and $ characters at the start and end of each -alternative branch in the regular expression. -</P> -<LI><A NAME="SEC5" HREF="#TOC1">SEE ALSO</A> -<P> -<B>pcre(3)</B>, Perl 5 documentation -</P> -<LI><A NAME="SEC6" HREF="#TOC1">DIAGNOSTICS</A> -<P> -Exit status is 0 if any matches were found, 1 if no matches were found, and 2 -for syntax errors or inacessible files (even if matches were found). -</P> -<LI><A NAME="SEC7" HREF="#TOC1">AUTHOR</A> -<P> -Philip Hazel <ph10@cam.ac.uk> -<BR> -Copyright (c) 1997-1999 University of Cambridge. diff --git a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.txt b/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.txt deleted file mode 100644 index bcd08c0a..00000000 --- a/rubbos/app/httpd-2.0.64/srclib/pcre/doc/pgrep.txt +++ /dev/null @@ -1,86 +0,0 @@ -NAME - pgrep - a grep with Perl-compatible regular expressions. - - - -SYNOPSIS - pgrep [-Vchilnsvx] pattern [file] ... - - - -DESCRIPTION - pgrep searches files for character patterns, in the same way - as other grep commands do, but it uses the PCRE regular - expression library to support patterns that are compatible - with the regular expressions of Perl 5. See pcre(3) for a - full description of syntax and semantics. - - If no files are specified, pgrep reads the standard input. - By default, each line that matches the pattern is copied to - the standard output, and if there is more than one file, the - file name is printed before each line of output. However, - there are options that can change how pgrep behaves. - - Lines are limited to BUFSIZ characters. BUFSIZ is defined in - <stdio.h>. The newline character is removed from the end of - each line before it is matched against the pattern. - - - -OPTIONS - -V Write the version number of the PCRE library being - used to the standard error stream. - - -c Do not print individual lines; instead just print - a count of the number of lines that would other- - wise have been printed. If several files are - given, a count is printed for each of them. - - -h Suppress printing of filenames when searching mul- - tiple files. - - -i Ignore upper/lower case distinctions during com- - parisons. - - -l Instead of printing lines from the files, just - print the names of the files containing lines that - would have been printed. Each file name is printed - once, on a separate line. - - -n Precede each line by its line number in the file. - - -s Work silently, that is, display nothing except - error messages. The exit status indicates whether - any matches were found. - - -v Invert the sense of the match, so that lines which - do not match the pattern are now the ones that are - found. - - -x Force the pattern to be anchored (it must start - matching at the beginning of the line) and in - addition, require it to match the entire line. - This is equivalent to having ^ and $ characters at - the start and end of each alternative branch in - the regular expression. - - - -SEE ALSO - pcre(3), Perl 5 documentation - - - - - -DIAGNOSTICS - Exit status is 0 if any matches were found, 1 if no matches - were found, and 2 for syntax errors or inacessible files - (even if matches were found). - - - -AUTHOR - Philip Hazel <ph10@cam.ac.uk> - Copyright (c) 1997-1999 University of Cambridge. - |