Greg
A Go regular expression editor and tester

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Your regular expression
Greg is a Go-based regular expression editor. It's a handy way to test regular expressions as you write them. To start, enter a regular expression and a test string, or try an example.
Single characters
. any character, possibly including newline
[xyz] character class
[^xyz] negated character class
\d Perl character class
\D negated Perl character class
[:alpha:] ASCII character class
[:^alpha:] negated ASCII character class
\pN Unicode character class (one-letter name)
\p{Greek} Unicode character class
\PN negated Unicode character class (one-letter name)
P{Greek} negated Unicode character class
Composites
xy x followed by y
x|y x or y (prefer x)
Repetitions
x* zero or more x, prefer more
x+ one or more x, prefer more
x? zero or one x, prefer one
x{n,m} n or n+1 or ... or m x, prefer more
x{n,} n or more x, prefer more
x{n} exactly n x
x*? zero or more x, prefer fewer
x+? one or more x, prefer fewer
x?? zero or one x, prefer zero
x{n,m}? n or n+1 or ... or m x, prefer fewer
x{n,}? n or more x, prefer fewer
x{n}? exactly n x
Grouping
(re) numbered capturing group
(?P<name>re) named & numbered capturing group (submatch)
(?:re) non-capturing group (submatch)
(?flags) set flags within current group
(?flags:re) set flags during re; non-capturing
flag i case-insensitive (default false)
flag m multi-line mode: ^ and $ match begin/end line in addition to begin/end text (default false)
flag s let . match \n (default false)
flag U ungreedy: swap meaning of x* and x*?, x+ and x+?, etc (default false)
Empty strings
^ at beginning of text or line (flag m=true)
$ at end of text (like \z not \Z) or line (flag m=true)
\A at beginning of text
\b at ASCII word boundary (\w on one side and \W, \A, or \z on the other)
\B not an ASCII word boundary
\z at end of text
Escape sequences
\a bell (== \007)
\f form feed (== \014)
\t horizontal tab (== \011)
\n newline (== \012)
\r carriage return (== \015)
\v vertical tab character (== \013)
\* literal *, for any punctuation character *
\123 octal character code (up to three digits)
\x7F hex character code (exactly two digits)
\x{10FFFF} hex character code
\Q...\E literal text ... even if ... has punctuation
Character class elements
x single character
A-Z character range (inclusive)
\d Perl character class
[:foo:] ASCII character class foo
\p{Foo} Unicode character class Foo
\pF Unicode character class F (one-letter name)

Created by laumann. Heavily inspired by Rubular. The source code can be found on Github

Features to come

  • Permalink generation under options
  • Further regex options should be tick-off-able (aligned to the left of options dropdown). Options: POSIX