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)(?<=url=tcp://)[1-9][0-9]?\.tcp\.(?:ap|au|eu|in|jp|sa|us)\.ngrok\.io:[1-9][0-9]{4}\b`) var str = `t=2023-07-05T16:17:15+0300 lvl=info msg="no configuration paths supplied" t=2023-07-05T16:17:15+0300 lvl=info msg="using configuration at default config path" path=C:\\Users\\***\\AppData\\Local/ngrok/ngrok.yml t=2023-07-05T16:17:15+0300 lvl=info msg="open config file" path=C:\\Users\\***\\AppData\\Local\\ngrok\\ngrok.yml err=nil t=2023-07-05T16:17:15+0300 lvl=info msg="starting web service" obj=web addr=127.0.0.1:4040 allow_hosts=[] t=2023-07-05T16:17:15+0300 lvl=info msg="tunnel session started" obj=tunnels.session t=2023-07-05T16:17:15+0300 lvl=info msg="client session established" obj=csess t=2023-07-05T16:17:15+0300 lvl=info msg="started tunnel" obj=tunnels name=command_line addr=//localhost:8865 url=tcp://4.tcp.eu.ngrok.io:10355 t=2023-07-05T16:17:16+0300 lvl=info msg="update available" obj=updater` 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/