Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
g

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?:(?<=@import\s*(['"]|url\()\s*)((?:\S|\\\1)+)\s*(?:\1|\))\s*\)?\s?(.*?);)`) var str = `# Drupal core/tests/Drupal/Tests/Core/Asset/css_test_files/css_input_with_import.css @import "import1.css"; @import "import2.css"; @import url("http://example.com/style.css"); @import url("//example.com/style.css"); # Examples from https://developer.mozilla.org/en-US/docs/Web/CSS/%40import @import url("finep;rint.css") print; @import url("bluish.;css") projection, tv; @import 'cust;om.css'; @import url("chrome://communi;cator/skin/"); @import "common.css" screen, projection; @import url('landscape.css') screen and (orientation:landscape); # Examples using htmlentities @import 'https://fonts.googleapis.com/css?family=Sedgwick+Ave+Display&amp;subset=latin-ext'; @import "https://fonts.googleapis.com/css?family=Sedgwick+Ave+Display&amp;subset=latin-ext" ; @import url("https://fonts.googleapis.com/css?family=Sedgwick+Ave+Display&amp;subset=latin-ext"); @import url("https://fonts.googleapis.com/css?family=Sedgwick+Ave+Display&amp;subset=latin-ext") tv; @import url("https://fonts.googleapis.com/css?family=Sedgwick+Ave+Display&amp;subset=latin-ext") only screen and (max-width:639px) and (orientation: portrait); # Additional @import "cu'st;om.css"; @import "cu\"st;om.css"; @import "cu\22st;om.css"; @import 'cus\'t;om.css'; @import 'cus\27t;om.css' ; @import 'cus(t;om.css' ; @import 'cus)t;om.css'; @import 'cus(t);om.css'; @import url( " http://user:pass@example.com/c'u(s)t;o\"m.css " ) ; @import url( ' http://user:pass@example.com/c"u(s)t;o\'m.css ' ) ; @import url( http://user:pass@example.com/c\'u\(s\)t;om.css ) ; # Inline @import "cu'st;om.css"; @import "cu\"st;om.css"; .my-class { display: block; } @import "cu'st;om.css";@import url( " http://user:pass@example.com/c'u(s)t;o\"m.css " ) ;.some-class { color: rgba(0, 0, 0); }@import url( http://user:pass@example.com/c\'u\(s\)t;om.css ) ;.some-class { color: rgba(0, 0, 0); } ` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", i) } }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Golang, please visit: https://golang.org/pkg/regexp/