PCRE2SAMPLE(3) Introduction to Library Functions PCRE2SAMPLE(3)

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 re-create 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'

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.

AUTHOR

Philip Hazel
Retired from University Computing Service
Cambridge, England.

REVISION

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

PCRE2 10.45 14 November 2023 PCRE2SAMPLE(3)