Is there a list of Regex implementations on the web, showing their differences / similarities?
For exaple, Emacs elisp Regex is different to JavaScript or Perl regex, not to mention all the different implementations used by different editor software,
e.g. VS2010 uses {}
instead of ()
to group expressions for back references.
Once upon a time I could rely on a Regex conversion list in O'Reilly's Regex Pocket Quick Reference, but something online would be so much easier, and complete.
By the way, I am aware of (of course) http://www.regular-expressions.info/ which is good, but no where near complete.
I'll compile a list from the answers posted here, and anything else I can find.
Variations
General Variations
The differences in implementations are usually the way special characters {}()[]^$
are handled (escaping rules etc.), and occasionally substituted; the handling/availability of POSIX character classes e.g. [:digit:]
, and the use of options, e.g. g
i
etc.
(a work in progress, if you know any caveats, differences for these implementations please add them as an answer)
- ActionScript – uses ECMA style
- Delphi (.Net) – Uses .Net style. Delphi Win32 has no native regex, but PCRE wrappers are available.
- Emacs/ELisp – has 2 different contexts, escaping uses
\\
in elisp, and\
inregexp-replace
. Special chars(){}[]
are escaped when using them for regex features, much likesed
. - Eclipse – Search uses Java style regex.
- GNU (Linux) – POSIX BRE / ERE
- Grep – POSIX BRE / ERE
- Groovy – Uses Java style.
- IntelliJ
- Java – Java style.
- JavaScript – uses ECMA style.
- NetBeans
- .NET – Uses the classes in System.Text.RegularExpressions
- Notepad++ – PCRE
- PCRE (C/C++) – Open source library, used by many third party languages and apps. (e.g. PHP, TCL, R etc.)
- Perl – Perl style
- PHP – POSIX ERE, PCRE, (PHP5's multibyte string module uses Oniguruma)
- POSIX – BRE (Basic Regex), ERE (Extended Regex)
- PowerShell – .Net style
- Python – Python style
- R – POSIX ERE/BRE, PCRE
- REALbasic – PCRE
- Ruby – Oniguruma
- Sed – special chars
(){}[]
are escaped when using them for regex features. - Tcl – Three flavors, Tcl ARE (advanced regex), POSIX ERE, POSIX BRE.
- TextMate – Oniguruma
- Tera Term – Oniguruma
- VBScript – ECMA
- Visual Basic 6 – ECMA (when using Microsoft VBScript Regular Expressions 5.5 COM object)
- Visual Studio – Grouping braces are
{}
(more details to follow.) - wxWidgets – Tcl ARE, POSIX BRE/ERE
- XML Schema – XML
- XQuery & XPath – Xpath
Best Answer
Take a look at the Regular Expression Flavor Comparison on Regular-Expressions.info. It contains at least the nowadays most important regular expression implementations and their characteristics.