# Regular Expressions Syntax (Advanced)

Argus uses Perl-compatible regular expressions.(PCRE) library. The library is a set of functions that implement regular expression pattern matching using the same syntax and semantics as Perl 5, with just a few differences. The current implementation corresponds to Perl 5.005. The syntax and semantics of the regular expressions supported by PCRE are described in this chapter.

- Meta-Characters.
- Backslash.
- Circumflex and Dollar.
- Full Stop (Period, Dot).
- Square Brackets.
- Vertical Bar.
- Internal Option Setting.
- Subpatterns.
- Repetition.
- Back References.
- Assertions.
- Once-Only Subpatterns.
- Conditional Subpatterns.
- Comments.
- Performance.
- Limitiations.
- Differences From Perl.

PCRE Library and this chapter (Regular Expressions Syntax (Advanced)) are written by Philip Hazel <ph10@cam.ac.uk>, University of Cambridge Computing Service, Cambridge, England. Phone: +44 1223 334714. Copyright © 1997-1999 University of Cambridge

Regular expressions are also described in the Perl documentation and in a number of other books, some of which have copious examples. Jeffrey Friedl's "Mastering Regular Expressions", published by O'Reilly (ISBN 1-56592-257-3), covers them in great detail. The description here is intended as reference documentation.