Regular Expressions Cheatsheet
This site is a reference for Regular Expressions (RegEx)
Regular Expressions are powerful sequences of characters that define search patterns. Regular Expressions are used in search engines, text processing tools like Sed and Awk, for lexical analysis and a lot more. The concept of Regular Expressions arose around the 1950s and later saw heavy use with the introduction of UNIX text processing tools in the 1980s.
Syntax and Flavors
There are serveral flavors (different syntax) of RegExp with the two most common being POSIX and PCRE (Perl Compatible Regular Expressions). The IEEE POSIX standard has three sets of compliance which are Basic Regular Expression (BRE), Extended Regular Expressions (ERE) and Simple Regular Expressions (SRE).