Miscellaneous tools exist to ease this task. This post was inspired by redet’s comparison of regexp helper tools – it could be sufficient to read only that, if you’re going to try the mentioned tools yourself. Otherwise, read on.

Kodos is an easy-to-use (but powerful enough) Python tool to verify regular expressions against sample user-provided strings. Available for both Linux and Windows. Generates ready-to-use Python regexp code.

redet assumes some knowledge of REs. Unlike all the other helper tools, it has the widest code generation coverage – just go to “Tools->Save command information” to generate code (Python, Perl, C, grep – just to name a few of the 57 (!) languages/tools/editors supported). At the same time, redet does not depend on specific versions of all supported RE engines – instead, redet automatically tests for features in available versions.

visual-regexp is similar to kodos in features.

txt2regex is a regex wizard written in bash, capable of generating code for 24 languages/editors/programs (by default, these are enabled: perl, php, postgres, python, sed and vim). It is really simple and convenient, though some understanding of “groups” and “character ranges” is highly recommended.

KRegExpEditor was a part of kde3-utils, and seems to be missing from current KDE 4.3. It is similar to kodos and visual-regexp in its philosophy and features.

I would recommend using one of kodos/visual-regexp/kregexpeditor to quickly test or design your regular expression, then use redet to generate appropriate source code. As an alternative (and when working in a console), just use txt2regexp to generate the code you need.

Tools I haven’t tried include regex coach and regexpviewer.

Please also see this extensive list of regular expression and pattern-matching related software.