# pcre2sample

## NAME



           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
           the PCRE2 distribution, you can save this listing to recreate the
           contents of _pcre2demo.c_.
    
           The demonstration program compiles the regular expression that is
           its first argument, and matches it against the subject string in
           its second argument. No PCRE2 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.
    
           The code in **pcre2demo.c** is an 8-bit program that uses the PCRE2
           8-bit library. It handles strings and characters that are stored
           in 8-bit code units.  By default, one character corresponds to one
           code unit, but if the pattern starts with "(*UTF)", both it and
           the subject are treated as UTF-8 strings, where characters may
           occupy multiple code units.
    
           If PCRE2 is installed in the standard include and library
           directories for your operating system, you should be able to
           compile the demonstration program using a command like this:
    
             cc -o pcre2demo pcre2demo.c -lpcre2-8
    
           If PCRE2 is installed elsewhere, you may need to add additional
           options to the command line. For example, on a Unix-like system
           that has PCRE2 installed in _/usr/local_ , you can compile the
           demonstration program using a command like this:
    
             cc -o pcre2demo -I/usr/local/include pcre2demo.c \
                -L/usr/local/lib -lpcre2-8
    
           Once you have built the demonstration program, you can run simple
           tests like this:
    
             ./pcre2demo 'cat|dog' 'the cat sat on the mat'
             ./pcre2demo -g 'cat|dog' 'the dog sat on the cat'
             ./pcre2demo -i 'cat' 'the dog sat on the CAT'
    
           Note that there is a much more comprehensive test program, called
           **pcre2test** , which supports many more facilities for testing regular
           expressions using all three PCRE2 libraries (8-bit, 16-bit, and
           32-bit, though not all three need be installed). The **pcre2demo**
           program is provided as a relatively simple coding example.
    
           If you try to run **pcre2demo** when PCRE2 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: pcre2demo: fatal: libpcre2-8.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.
    


## REVISION



    
           Last updated: 14 November 2023
           Copyright (c) 1997-2016 University of Cambridge.
    


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