PCRE(3) Library Functions Manual PCRE(3)
PCRE - Perl-compatible regular expressions (original API)
This document relates to PCRE releases that use the original API, with library names libpcre, libpcre16, and libpcre32. January 2015 saw the first release of a new API, known as PCRE2, with release numbers starting at 10.00 and library names libpcre2-8, libpcre2-16, and libpcre2-32. The old libraries (now called PCRE1) are now at end of life, and 8.45 is the final release. New projects are advised to use the new PCRE2 libraries.
If you are using PCRE in a non-UTF application that permits users to supply arbitrary patterns for compilation, you should be aware of a feature that allows users to turn on UTF support from within a pattern, provided that PCRE was built with UTF support. For example, an 8-bit pattern that begins with "(*UTF8)" or "(*UTF)" turns on UTF-8 mode, which interprets patterns and subjects as strings of UTF-8 characters instead of individual 8-bit characters. This causes both the pattern and any data against which it is matched to be checked for UTF-8 validity. If the data string is very long, such a check might use sufficiently many resources as to cause your application to lose performance. One way of guarding against this possibility is to use the pcre_fullinfo() function to check the compiled pattern's options for UTF. Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF option at compile time. This causes a compile time error if a pattern contains a UTF-setting sequence. If your application is one that supports UTF, be aware that validity checking can take time. If the same data string is to be matched many times, you can use the PCRE_NO_UTF[8|16|32]_CHECK option for the second and subsequent matches to save redundant checks. Another way that performance can be hit is by running a pattern that has a very large search tree against a string that will never match. Nested unlimited repeats in a pattern are a common example. PCRE provides some protection against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the pcreapi page.
The user documentation for PCRE comprises a number of different sections. In the "man" format, each of these is a separate "man page". In the HTML format, each is a separate page, linked from the index page. In the plain text format, the descriptions of the pcregrep and pcretest programs are in files called pcregrep.txt and pcretest.txt, respectively. The remaining sections, except for the pcredemo section (which is a program listing), are concatenated in pcre.txt, for ease of searching. The sections are as follows: pcre this document pcre-config show PCRE installation configuration information pcre16 details of the 16-bit library pcre32 details of the 32-bit library pcreapi details of PCRE's native C API pcrebuild building PCRE pcrecallout details of the callout feature pcrecompat discussion of Perl compatibility pcrecpp details of the C++ wrapper for the 8-bit library pcredemo a demonstration C program that uses PCRE pcregrep description of the pcregrep command (8-bit only) pcrejit discussion of the just-in-time optimization support pcrelimits details of size and other limits pcrematching discussion of the two matching algorithms pcrepartial details of the partial matching facility pcrepattern syntax and semantics of supported regular expressions pcreperform discussion of performance issues pcreposix the POSIX-compatible C API for the 8-bit library pcreprecompile details of saving and re-using precompiled patterns pcresample discussion of the pcredemo program pcrestack discussion of stack usage pcresyntax quick syntax reference pcretest description of the pcretest testing command pcreunicode discussion of Unicode and UTF-8/16/32 support In the "man" and HTML formats, there is also a short page for each C library function, listing its arguments and results.
Philip Hazel University Computing Service Cambridge CB2 3QH, England. Putting an actual email address here seems to have been a spam magnet, so I've taken it away. If you want to email me, use my two initials, followed by the two digits 10, at the domain cam.ac.uk.
Last updated: 14 June 2021 Copyright (c) 1997-2021 University of Cambridge.
This page is part of the PCRE (Perl Compatible Regular Expressions) project. Information about the project can be found at ⟨http://www.pcre.org/⟩. If you have a bug report for this manual page, see ⟨http://bugs.exim.org/enter_bug.cgi?product=PCRE⟩. This page was obtained from the tarball pcre-8.45.tar.gz fetched from ⟨ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/⟩ on 2021-08-27. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to email@example.com PCRE 8.45 14 June 2021 PCRE(3)
Pages that refer to this page: grep(1), pcre-config(1), pcretest(1), pcrepattern(3), pcresyntax(3), sefcontext_compile(8)