Question

The \K escape sequence resets the beginning of the match to the current position in
the token list (this only affects what is reported as the full match).

What environments/languages/versions support \K (keep) in its regular expression engines and what libraries are needed (if any) to use this feature within patterns?

Answer 1

The \K escape sequence is supported by several engines, languages or tools, such as:

• boost (since ???)
• grep -P ——————–⇢ Uses PCRE
• Oniguruma (since 5.13.3)
• PCRE (since 7.2)
• Perl (since 5.10.0)
• PHP (since 5.2.4)
• Ruby (since 2.0.0 due to its use of the Onigmo engine (a fork of Oniguruma))
• Notepad++ (since 6.0)

…and (so far) not supported by:

• .NET
• awk
• bash
• ICU
• Java
• Javascript
• Objective-C
• POSIX
• Python
• Qt/QRegExp
• sed
• Tcl
• vim ——————–⇢ It doesn’t have \K, but its \zs is equivalent
• XML
• XPath