pcrelimits(3) [centos man page]

PCRELIMITS(3)						     Library Functions Manual						     PCRELIMITS(3)

NAME

       PCRE - Perl-compatible regular expressions

SIZE AND OTHER LIMITATIONS


       There are some size limitations in PCRE but it is hoped that they will never in practice be relevant.

       The maximum length of a compiled pattern is approximately 64K data units (bytes for the 8-bit library, 32-bit units for the 32-bit library,
       and 32-bit units for the 32-bit library) if PCRE is compiled with the default internal linkage size of 2 bytes. If you want to process reg-
       ular  expressions that are truly enormous, you can compile PCRE with an internal linkage size of 3 or 4 (when building the 16-bit or 32-bit
       library, 3 is rounded up to 4). See the README file in the source distribution and the pcrebuild documentation for details. In these  cases
       the limit is substantially larger.  However, the speed of execution is slower.

       All values in repeating quantifiers must be less than 65536.

       There is no limit to the number of parenthesized subpatterns, but there can be no more than 65535 capturing subpatterns.

       There  is  a  limit to the number of forward references to subsequent subpatterns of around 200,000. Repeated forward references with fixed
       upper limits, for example, (?2){0,100} when subpattern number 2 is to the right, are included in the count. There is no limit to the number
       of backward references.

       The maximum length of name for a named subpattern is 32 characters, and the maximum number of named subpatterns is 10000.

       The  maximum  length  of  a name in a (*MARK), (*PRUNE), (*SKIP), or (*THEN) verb is 255 for the 8-bit library and 65535 for the 16-bit and
       32-bit library.

       The maximum length of a subject string is the largest positive number that an integer variable can hold. However,  when	using  the  tradi-
       tional  matching  function, PCRE uses recursion to handle subpatterns and indefinite repetition.  This means that the available stack space
       may limit the size of a subject string that can be processed by certain patterns. For a discussion of stack issues, see the pcrestack docu-
       mentation.

AUTHOR


       Philip Hazel
       University Computing Service
       Cambridge CB2 3QH, England.

REVISION


       Last updated: 04 May 2012
       Copyright (c) 1997-2012 University of Cambridge.

PCRE 8.30							   24 June 2012 						     PCRELIMITS(3)

PCRESAMPLE(3)						     Library Functions Manual						     PCRESAMPLE(3)

NAME

       PCRE - Perl-compatible regular expressions

PCRE SAMPLE PROGRAM


       A  simple, complete demonstration program, to get you started with using PCRE, is supplied in the file pcredemo.c in the PCRE distribution.
       A listing of this program is given in the pcredemo documentation. If you do not have a copy of the PCRE distribution,  you  can	save  this
       listing to re-create pcredemo.c.

       The  demonstration  program,  which  uses  the original PCRE 8-bit library, compiles the regular expression that is its first argument, and
       matches it against the subject string in its second argument. No PCRE options are set, and default character tables are used.  If  matching
       succeeds, the program outputs the portion of the subject that matched, together with the contents of any captured substrings.

       If  the -g option is given on the command line, the program then goes on to check for further matches of the same regular expression in the
       same subject string. The logic is a little bit tricky because of the possibility of matching an empty string. Comments in the code  explain
       what is going on.

       If  PCRE  is  installed in the standard include and library directories for your operating system, you should be able to compile the demon-
       stration program using this command:

	 gcc -o pcredemo pcredemo.c -lpcre

       If PCRE is installed elsewhere, you may need to add additional options to the command line. For example, on a  Unix-like  system  that  has
       PCRE installed in /usr/local, you can compile the demonstration program using a command like this:

	 gcc -o pcredemo -I/usr/local/include pcredemo.c 
	     -L/usr/local/lib -lpcre

       In  a  Windows  environment,  if  you  want  to statically link the program against a non-dll pcre.a file, you must uncomment the line that
       defines PCRE_STATIC before including pcre.h, because otherwise the pcre_malloc()  and  pcre_free()  exported  functions	will  be  declared
       __declspec(dllimport), with unwanted results.

       Once you have compiled and linked the demonstration program, you can run simple tests like this:

	 ./pcredemo 'cat|dog' 'the cat sat on the mat'
	 ./pcredemo -g 'cat|dog' 'the dog sat on the cat'

       Note that there is a much more comprehensive test program, called pcretest, which supports many more facilities for testing regular expres-
       sions and both PCRE libraries. The pcredemo program is provided as a simple coding example.

       If you try to run pcredemo when PCRE is not installed in the standard library directory, you may get an error like this on  some  operating
       systems (e.g. Solaris):

	 ld.so.1: a.out: fatal: libpcre.so.0: open failed: No such file or directory

       This is caused by the way shared library support works on those systems. You need to add

	 -R/usr/local/lib

       (for example) to the compile command to get round this problem.

AUTHOR


       Philip Hazel
       University Computing Service
       Cambridge CB2 3QH, England.

REVISION


       Last updated: 10 January 2012
       Copyright (c) 1997-2012 University of Cambridge.

PCRE 8.30							  10 January 2012						     PCRESAMPLE(3)