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

/
/
gm

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)^(?<event>\d+-\d+-\d+\s+\d+:\d+:\d+,\d+\s(ERROR|SEVERE).*)`) var str = `2021-08-31 02:03:52,081 INFO [stdout] jkwqdwqjdk 2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83) 2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83) Abc fgh, app continuing 2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83) 2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83)kwqskqw 2021-08-31 02:03:52,081 INFO [stdout] (ServerService Thread Pool -- 83) 2021-08-31 02:03:52,081 INFO [org.kjskj.akjs] (ServerService Thread Pool -- 11) WFLYUT0021: Registered web context: '/dyn' for server 'default-server' 2021-08-31 02:03:52,081 ERROR [org.kjskj.akjs] "There is an error" 2021-08-31 02:03:52,081 SEVERE [org.kjskj.akjs] There is Severe 2021-08-31 02:03:55,166 INFO [org.jboss.as] (Controller Boot Thread) WAAAAAA0033: JBoss EAP 1.1.9.GA (abcfegc Core 2.0.10.Final-call-00000) started in 169999ms - Started 2222 of 2222 services (311 services are lazy, passive or on-demand) 2021-08-31 02:03:55,169 INFO [org.jboss.as] (aa nnnThread) WAAAAAA0033: Http interface listening on http://111.11.11.11:8080/aaa 2021-08-31 02:03:55,169 INFO [org.nnn.as] (ioio llkl Thread) WAAAAAA0033: console listening on http://111.11.11.11:8080/aaa` 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/