109 lines
3.4 KiB
HTML
109 lines
3.4 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of PCRELIMITS</TITLE>
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</HEAD><BODY>
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<H1>PCRELIMITS</H1>
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Section: C Library Functions (3)<BR>Updated: 05 November 2013<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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PCRE - Perl-compatible regular expressions
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<A NAME="lbAC"> </A>
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<H2>SIZE AND OTHER LIMITATIONS</H2>
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<P>
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There are some size limitations in PCRE but it is hoped that they will never in
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practice be relevant.
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<P>
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The maximum length of a compiled pattern is approximately 64K data units (bytes
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for the 8-bit library, 16-bit units for the 16-bit library, and 32-bit units for
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the 32-bit library) if PCRE is compiled with the default internal linkage size,
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which is 2 bytes for the 8-bit and 16-bit libraries, and 4 bytes for the 32-bit
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library. If you want to process regular expressions that are truly enormous,
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you can compile PCRE with an internal linkage size of 3 or 4 (when building the
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16-bit or 32-bit library, 3 is rounded up to 4). See the <B>README</B> file in
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the source distribution and the
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<B>pcrebuild</B>
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documentation for details. In these cases the limit is substantially larger.
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However, the speed of execution is slower.
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<P>
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All values in repeating quantifiers must be less than 65536.
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<P>
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There is no limit to the number of parenthesized subpatterns, but there can be
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no more than 65535 capturing subpatterns. There is, however, a limit to the
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depth of nesting of parenthesized subpatterns of all kinds. This is imposed in
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order to limit the amount of system stack used at compile time. The limit can
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be specified when PCRE is built; the default is 250.
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<P>
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There is a limit to the number of forward references to subsequent subpatterns
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of around 200,000. Repeated forward references with fixed upper limits, for
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example, (?2){0,100} when subpattern number 2 is to the right, are included in
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the count. There is no limit to the number of backward references.
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<P>
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The maximum length of name for a named subpattern is 32 characters, and the
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maximum number of named subpatterns is 10000.
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<P>
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The maximum length of a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb
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is 255 for the 8-bit library and 65535 for the 16-bit and 32-bit libraries.
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<P>
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The maximum length of a subject string is the largest positive number that an
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integer variable can hold. However, when using the traditional matching
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function, PCRE uses recursion to handle subpatterns and indefinite repetition.
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This means that the available stack space may limit the size of a subject
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string that can be processed by certain patterns. For a discussion of stack
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issues, see the
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<B>pcrestack</B>
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documentation.
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<A NAME="lbAD"> </A>
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<H2>AUTHOR</H2>
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<P>
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<PRE>
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Philip Hazel
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University Computing Service
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Cambridge CB2 3QH, England.
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</PRE>
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<A NAME="lbAE"> </A>
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<H2>REVISION</H2>
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<P>
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<PRE>
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Last updated: 05 November 2013
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Copyright (c) 1997-2013 University of Cambridge.
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</PRE>
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="1"><A HREF="#lbAB">NAME</A><DD>
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<DT id="2"><A HREF="#lbAC">SIZE AND OTHER LIMITATIONS</A><DD>
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<DT id="3"><A HREF="#lbAD">AUTHOR</A><DD>
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<DT id="4"><A HREF="#lbAE">REVISION</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:52 GMT, March 31, 2021
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</BODY>
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</HTML>
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