Regular Expressions on a Mouse Mat * Regular Expression Training
POSIX details * Perl details * Java details

Regular expressions can be used in a wide variety of languages, but they're implemented slightly differently every time. There are two groupings - the regular expressions that use the POSIX standard, and the others that are Perl like - but that does NOT mean that a one Perl-like implementation will be identical to another Perl-like implementation. The most basic stuff always applies, but it's the extensions that differ.

Language	Implementation Type
grep	Very basic
egrep	Basic
awk	Similar to egrep
sed	Basic; differs from egrep and awk
perl	Perl like (as you would expect)
java	From Java 1.4; Perl like
Tcl	Basic up to Tcl 8.0 POSIX from Tcl 8.1
.NET	Perl like
MySQL	POSIX based
PHP	Two regex handlers One POSIX based, the other Perl based
Python	awk, grep egrep or emacs style
Ruby	Similar to Perl
Coldfusion	Uses POSIX character classes
vi and vim	egrep style
Hardware (Raqia / Safenet chip)	Perl based

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