SysTutorials Posts

PCRE – Perl-compatible regular expressions #include < pcre.h> Pcre 32-Bit Api Basic Functions pcre32 *pcre32_compile(PCRE_SPTR32 pattern, int options, const char **errptr, int *erroffset, const unsigned char *tableptr); pcre32 *pcre32_compile2(PCRE_SPTR32 pattern, int options, int *errorcodeptr, const unsigned char *tableptr); pcre32_extra *pcre32_study(const pcre32 *code, int options, const char **errptr); void pcre32_free_study(pcre32_extra *extra); int pcre32_exec(const pcre32 *code, const…

PCRE – Perl-compatible regular expressions (revised API) Unicode And Utf Support PCRE2 is normally built with Unicode support, though if you do not need it, you can build it without, in which case the library will be smaller. With Unicode support, PCRE2 has knowledge of Unicode character properties and can process text strings in UTF-8,…

PCRE2 – Perl-compatible regular expressions (revised API) Pcre2 Regular Expression Syntax Summary The full syntax and semantics of the regular expressions that are supported by PCRE2 are described in the pcre2pattern documentation. This document contains a quick-reference summary of the syntax. Quoting   

PCRE2 – Perl-compatible regular expressions (revised API) Pcre2 Discussion Of Stack Usage When you call pcre2_match(), it makes use of an internal function called match(). This calls itself recursively at branch points in the pattern, in order to remember the state of the match so that it can back up and try a different alternative…

PCRE2 – Perl-compatible regular expressions (revised API) Saving And Re-Using Precompiled Pcre2 Patterns int32_t pcre2_serialize_decode(pcre2_code **codes, int32_t number_of_codes, const uint32_t *bytes, pcre2_general_context *gcontext); int32_t pcre2_serialize_encode(pcre2_code **codes, int32_t number_of_codes, uint32_t **serialized_bytes, PCRE2_SIZE *serialized_size, pcre2_general_context *gcontext); void pcre2_serialize_free(uint8_t *bytes); int32_t pcre2_serialize_get_number_of_codes(const uint8_t *bytes); If you are running an application that uses a large number of regular expression…

PCRE2 – Perl-compatible regular expressions (revised API) Pcre2 Sample Program A simple, complete demonstration program to get you started with using PCRE2 is supplied in the file pcre2demo.c in the src directory in the PCRE2 distribution. A listing of this program is given in the pcre2demo documentation. If you do not have a copy of…

PCRE2 – Perl-compatible regular expressions (revised API) Synopsis #include <pcre2posix.h> int pcre2_regcomp(regex_t *preg, const char *pattern, int cflags); int pcre2_regexec(const regex_t *preg, const char *string, size_t nmatch, regmatch_t pmatch[], int eflags); size_t pcre2_regerror(int errcode, const regex_t *preg, char *errbuf, size_t errbuf_size); void pcre2_regfree(regex_t *preg); Description This set of functions provides a POSIX-style API for the…

PCRE2 – Perl-compatible regular expressions (revised API) Pcre2 Performance Two aspects of performance are discussed below: memory usage and processing time. The way you express your pattern as a regular expression can affect both of them. Compiled Pattern Memory Usage Patterns are compiled by PCRE2 into a reasonably efficient interpretive code, so that most simple…

PCRE2 – Perl-compatible regular expressions (revised API) Pcre2 Regular Expression Details The syntax and semantics of the regular expressions that are supported by PCRE2 are described in detail below. There is a quick-reference syntax summary in the pcre2syntax page. PCRE2 tries to match Perl syntax and semantics as closely as it can. PCRE2 also supports…

PCRE2 – Perl-compatible regular expressions Partial Matching In Pcre2 In normal use of PCRE2, if there is a match up to the end of a subject string, but more characters are needed to match the entire pattern, PCRE2_ERROR_NOMATCH is returned, just like any other failing match. There are circumstances where it might be helpful to…

PCRE2 – Perl-compatible regular expressions (revised API) Pcre2 Matching Algorithms This document describes the two different algorithms that are available in PCRE2 for matching a compiled regular expression against a given subject string. The "standard" algorithm is the one provided by the pcre2_match() function. This works in the same as as Perl’s matching function, and…

PCRE2 – Perl-compatible regular expressions (revised API) Size And Other Limitations There are some size limitations in PCRE2 but it is hoped that they will never in practice be relevant. The maximum size of a compiled pattern is approximately 64 thousand code units for the 8-bit and 16-bit libraries if PCRE2 is compiled with the…

PCRE2 – Perl-compatible regular expressions (revised API) Pcre2 Just-In-Time Compiler Support Just-in-time compiling is a heavyweight optimization that can greatly speed up pattern matching. However, it comes at the cost of extra processing before the match is performed, so it is of most benefit when the same pattern is going to be matched many times….

PCRE2 – Perl-compatible regular expressions (revised API) Experimental Pattern Conversion Functions This document describes a set of functions that can be used to convert "foreign" patterns into PCRE2 regular expressions. This facility is currently experimental, and may be changed in future releases. Two kinds of pattern, globs and POSIX patterns, are supported. The Convert Context…

PCRE2 – Perl-compatible regular expressions (revised API) Differences Between Pcre2 And Perl This document describes the differences in the ways that PCRE2 and Perl handle regular expressions. The differences described here are with respect to Perl versions 5.26, but as both Perl and PCRE2 are continually changing, the information may sometimes be out of date….

PCRE2 – Perl-compatible regular expressions (revised API) Synopsis #include <pcre2.h> int (*pcre2_callout)(pcre2_callout_block *, void *); int pcre2_callout_enumerate(const pcre2_code *code, int (*callback)(pcre2_callout_enumerate_block *, void *), void *user_data); Description PCRE2 provides a feature called "callout", which is a means of temporarily passing control to the caller of PCRE2 in the middle of pattern matching. The caller of…

PCRE2 – Perl-compatible regular expressions (revised API) Building Pcre2 PCRE2 is distributed with a configure script that can be used to build the library in Unix-like environments using the applications known as Autotools. Also in the distribution are files to support building using CMake instead of configure. The text file README contains general information about…

PCRE2 – Perl-compatible regular expressions (revised API) #include < pcre2.h> PCRE2 is a new API for PCRE, starting at release 10.0. This document contains a description of all its native functions. See the pcre2 document for an overview of all the PCRE2 documentation. Pcre2 Native Api Basic Functions pcre2_code *pcre2_compile(PCRE2_SPTR pattern, PCRE2_SIZE length, uint32_t options,…

PCRE2 – Perl-compatible regular expressions (revised API) Synopsis #include <pcre2.h> int pcre2_substring_number_from_name(const pcre2_code *code, PCRE2_SPTR name); Description This convenience function finds the number of a named substring capturing parenthesis in a compiled pattern, provided that it is a unique name. The function arguments are:   code    Compiled regular expression   name    Name whose number is required The yield of…

PCRE2 – Perl-compatible regular expressions (revised API) Synopsis #include <pcre2.h> int pcre2_substring_nametable_scan(const pcre2_code *code, PCRE2_SPTR name, PCRE2_SPTR *first, PCRE2_SPTR *last); Description This convenience function finds, for a compiled pattern, the first and last entries for a given name in the table that translates capture group names into numbers. When the name is found in the…