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Regular Expressions

Is a programming language used to search pattern inside a text



From RegExr

Character Meaning
Character classes
. any character except newline
\w\d\s word, digit, whitespace
\W\D\S not word, digit, whitespace
[abc] any of a, b, or c
[^abc] not a, b, or c
[a-g] character between a & g
^abc$ start / end of the string
\b\B word, not-word boundary
Escaped characters
\.\*\\ escaped special characters
\t\n\r tab, linefeed, carriage return
Groups & Lookaround
(abc) capture group
\1 backreference to group #1
(?:abc) non-capturing group
(?=abc) positive lookahead
(?!abc) negative lookahead
Quantifiers & Alternation
a*a+a? 0 or more, 1 or more, 0 or 1
a{5}a{2,} exactly five, two or more
a{1,3} between one & three
a+?a{2,}? match as few as possible
ab\|cd match ab or cd (without the \)
\n\n Empty line