Regular expressions in GNU grep (opens in a new tab)
Compare basic, extended, and Perl-compatible expressions and understand matching behavior.
GNU Project · gnu.org
GNU grep; BRE, ERE, and PCRE modes differ
POSIX & GNU
Patterns, engines & matching
Regex
Choose the right syntax for POSIX, GNU tools, and PCRE2.
5References
2Subtopics
POSIX regular expression specification (opens in a new tab)
The normative definitions of basic and extended regular expressions, including locale behavior.
The Open Group / IEEE · pubs.opengroup.org
POSIX.1-2024, Base Definitions chapter 9
POSIX & GNU
Regular expressions in awk (opens in a new tab)
Apply patterns in awk and understand operators, escapes, and dynamic regular expressions.
GNU Project · gnu.org
GNU awk; ERE with documented extensions
POSIX & GNU
PCRE2 pattern reference (opens in a new tab)
Explore captures, lookarounds, Unicode properties, backtracking, and advanced pattern semantics.
PCRE2 Project · pcre.org
Current PCRE2 documentation
PCRE2
PCRE2 syntax quick reference (opens in a new tab)
A compact syntax reference for metacharacters, character classes, groups, and assertions.
PCRE2 Project · pcre.org
Current PCRE2 documentation
PCRE2