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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 appropri