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.TH PCRE 3 | .TH PCRE 3 "01 Oct 2013" "PCRE 8.33" |
.SH NAME |
.SH NAME |
PCRE - Perl-compatible regular expressions |
PCRE - Perl-compatible regular expressions |
.SH INTRODUCTION |
.SH INTRODUCTION |
Line 11 appeared in Perl are also available using the Python s
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Line 11 appeared in Perl are also available using the Python s
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support for one or two .NET and Oniguruma syntax items, and there is an option |
support for one or two .NET and Oniguruma syntax items, and there is an option |
for requesting some minor changes that give better JavaScript compatibility. |
for requesting some minor changes that give better JavaScript compatibility. |
.P |
.P |
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Starting with release 8.30, it is possible to compile two separate PCRE |
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libraries: the original, which supports 8-bit character strings (including |
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UTF-8 strings), and a second library that supports 16-bit character strings |
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(including UTF-16 strings). The build process allows either one or both to be |
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built. The majority of the work to make this possible was done by Zoltan |
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Herczeg. |
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.P |
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Starting with release 8.32 it is possible to compile a third separate PCRE |
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library that supports 32-bit character strings (including UTF-32 strings). The |
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build process allows any combination of the 8-, 16- and 32-bit libraries. The |
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work to make this possible was done by Christian Persch. |
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.P |
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The three libraries contain identical sets of functions, except that the names |
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in the 16-bit library start with \fBpcre16_\fP instead of \fBpcre_\fP, and the |
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names in the 32-bit library start with \fBpcre32_\fP instead of \fBpcre_\fP. To |
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avoid over-complication and reduce the documentation maintenance load, most of |
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the documentation describes the 8-bit library, with the differences for the |
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16-bit and 32-bit libraries described separately in the |
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.\" HREF |
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\fBpcre16\fP |
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and |
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.\" HREF |
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\fBpcre32\fP |
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.\" |
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pages. References to functions or structures of the form \fIpcre[16|32]_xxx\fP |
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should be read as meaning "\fIpcre_xxx\fP when using the 8-bit library, |
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\fIpcre16_xxx\fP when using the 16-bit library, or \fIpcre32_xxx\fP when using |
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the 32-bit library". |
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.P |
The current implementation of PCRE corresponds approximately with Perl 5.12, |
The current implementation of PCRE corresponds approximately with Perl 5.12, |
including support for UTF-8 encoded strings and Unicode general category | including support for UTF-8/16/32 encoded strings and Unicode general category |
properties. However, UTF-8 and Unicode support has to be explicitly enabled; it | properties. However, UTF-8/16/32 and Unicode support has to be explicitly |
is not the default. The Unicode tables correspond to Unicode release 6.0.0. | enabled; it is not the default. The Unicode tables correspond to Unicode |
| release 6.3.0. |
.P |
.P |
In addition to the Perl-compatible matching function, PCRE contains an |
In addition to the Perl-compatible matching function, PCRE contains an |
alternative function that matches the same compiled patterns in a different |
alternative function that matches the same compiled patterns in a different |
Line 27 page.
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Line 57 page.
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.P |
.P |
PCRE is written in C and released as a C library. A number of people have |
PCRE is written in C and released as a C library. A number of people have |
written wrappers and interfaces of various kinds. In particular, Google Inc. |
written wrappers and interfaces of various kinds. In particular, Google Inc. |
have provided a comprehensive C++ wrapper. This is now included as part of the | have provided a comprehensive C++ wrapper for the 8-bit library. This is now |
PCRE distribution. The | included as part of the PCRE distribution. The |
.\" HREF |
.\" HREF |
\fBpcrecpp\fP |
\fBpcrecpp\fP |
.\" |
.\" |
Line 38 in the \fIContrib\fP directory at the primary FTP site
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Line 68 in the \fIContrib\fP directory at the primary FTP site
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.\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre"> |
.\" HTML <a href="ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre"> |
.\" </a> |
.\" </a> |
ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre |
ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre |
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.\" |
.P |
.P |
Details of exactly which Perl regular expression features are and are not |
Details of exactly which Perl regular expression features are and are not |
supported by PCRE are given in separate documents. See the |
supported by PCRE are given in separate documents. See the |
Line 65 available. The features themselves are described in th
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Line 96 available. The features themselves are described in th
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\fBpcrebuild\fP |
\fBpcrebuild\fP |
.\" |
.\" |
page. Documentation about building PCRE for various operating systems can be |
page. Documentation about building PCRE for various operating systems can be |
found in the \fBREADME\fP and \fBNON-UNIX-USE\fP files in the source | found in the |
distribution. | .\" HTML <a href="README.txt"> |
| .\" </a> |
| \fBREADME\fP |
| .\" |
| and |
| .\" HTML <a href="NON-AUTOTOOLS-BUILD.txt"> |
| .\" </a> |
| \fBNON-AUTOTOOLS_BUILD\fP |
| .\" |
| files in the source distribution. |
.P |
.P |
The library contains a number of undocumented internal functions and data | The libraries contains a number of undocumented internal functions and data |
tables that are used by more than one of the exported external functions, but |
tables that are used by more than one of the exported external functions, but |
which are not intended for use by external callers. Their names all begin with |
which are not intended for use by external callers. Their names all begin with |
"_pcre_", which hopefully will not provoke any name clashes. In some | "_pcre_" or "_pcre16_" or "_pcre32_", which hopefully will not provoke any name |
environments, it is possible to control which external symbols are exported | clashes. In some environments, it is possible to control which external symbols |
when a shared library is built, and in these cases the undocumented symbols are | are exported when a shared library is built, and in these cases the |
not exported. | undocumented symbols are not exported. |
. |
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. |
. |
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.SH "SECURITY CONSIDERATIONS" |
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.rs |
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.sp |
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If you are using PCRE in a non-UTF application that permits users to supply |
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arbitrary patterns for compilation, you should be aware of a feature that |
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allows users to turn on UTF support from within a pattern, provided that PCRE |
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was built with UTF support. For example, an 8-bit pattern that begins with |
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"(*UTF8)" or "(*UTF)" turns on UTF-8 mode, which interprets patterns and |
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subjects as strings of UTF-8 characters instead of individual 8-bit characters. |
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This causes both the pattern and any data against which it is matched to be |
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checked for UTF-8 validity. If the data string is very long, such a check might |
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use sufficiently many resources as to cause your application to lose |
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performance. |
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.P |
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One way of guarding against this possibility is to use the |
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\fBpcre_fullinfo()\fP function to check the compiled pattern's options for UTF. |
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Alternatively, from release 8.33, you can set the PCRE_NEVER_UTF option at |
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compile time. This causes an compile time error if a pattern contains a |
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UTF-setting sequence. |
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.P |
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If your application is one that supports UTF, be aware that validity checking |
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can take time. If the same data string is to be matched many times, you can use |
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the PCRE_NO_UTF[8|16|32]_CHECK option for the second and subsequent matches to |
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save redundant checks. |
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.P |
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Another way that performance can be hit is by running a pattern that has a very |
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large search tree against a string that will never match. Nested unlimited |
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repeats in a pattern are a common example. PCRE provides some protection |
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against this: see the PCRE_EXTRA_MATCH_LIMIT feature in the |
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.\" HREF |
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\fBpcreapi\fP |
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.\" |
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page. |
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. |
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. |
.SH "USER DOCUMENTATION" |
.SH "USER DOCUMENTATION" |
.rs |
.rs |
.sp |
.sp |
Line 88 of searching. The sections are as follows:
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Line 163 of searching. The sections are as follows:
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.sp |
.sp |
pcre this document |
pcre this document |
pcre-config show PCRE installation configuration information |
pcre-config show PCRE installation configuration information |
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pcre16 details of the 16-bit library |
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pcre32 details of the 32-bit library |
pcreapi details of PCRE's native C API |
pcreapi details of PCRE's native C API |
pcrebuild options for building PCRE | pcrebuild building PCRE |
pcrecallout details of the callout feature |
pcrecallout details of the callout feature |
pcrecompat discussion of Perl compatibility |
pcrecompat discussion of Perl compatibility |
pcrecpp details of the C++ wrapper | pcrecpp details of the C++ wrapper for the 8-bit library |
pcredemo a demonstration C program that uses PCRE |
pcredemo a demonstration C program that uses PCRE |
pcregrep description of the \fBpcregrep\fP command | pcregrep description of the \fBpcregrep\fP command (8-bit only) |
pcrejit discussion of the just-in-time optimization support |
pcrejit discussion of the just-in-time optimization support |
pcrelimits details of size and other limits |
pcrelimits details of size and other limits |
pcrematching discussion of the two matching algorithms |
pcrematching discussion of the two matching algorithms |
Line 103 of searching. The sections are as follows:
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Line 180 of searching. The sections are as follows:
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pcrepattern syntax and semantics of supported |
pcrepattern syntax and semantics of supported |
regular expressions |
regular expressions |
pcreperform discussion of performance issues |
pcreperform discussion of performance issues |
pcreposix the POSIX-compatible C API | pcreposix the POSIX-compatible C API for the 8-bit library |
pcreprecompile details of saving and re-using precompiled patterns |
pcreprecompile details of saving and re-using precompiled patterns |
pcresample discussion of the pcredemo program |
pcresample discussion of the pcredemo program |
pcrestack discussion of stack usage |
pcrestack discussion of stack usage |
pcresyntax quick syntax reference |
pcresyntax quick syntax reference |
pcretest description of the \fBpcretest\fP testing command |
pcretest description of the \fBpcretest\fP testing command |
pcreunicode discussion of Unicode and UTF-8 support | pcreunicode discussion of Unicode and UTF-8/16/32 support |
.sp |
.sp |
In addition, in the "man" and HTML formats, there is a short page for each |
In addition, in the "man" and HTML formats, there is a short page for each |
C library function, listing its arguments and results. |
C library function, listing its arguments and results. |
Line 133 two digits 10, at the domain cam.ac.uk.
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Line 210 two digits 10, at the domain cam.ac.uk.
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.rs |
.rs |
.sp |
.sp |
.nf |
.nf |
Last updated: 24 August 2011 | Last updated: 13 May 2013 |
Copyright (c) 1997-2011 University of Cambridge. | Copyright (c) 1997-2013 University of Cambridge. |
.fi |
.fi |