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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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)(?:^crt|\G(?!\A))(?:(?!^$)\D)*\K[.:\d]+`) var str = `crt - 00:00:00 up 200 days, 23:35, 0 users, load average: 0.04, 0.05, 0.02 Tasks: 300 total, 2 running, 298 sleeping, 0 stopped, 0 zombie Cpu(s): 12.0%us, 2.5%sy, 0.0%ni, 89.2%id, 0.0%hi, 0.1%si, 0.0%st Mem: 123456K total, 1234567k used, 989991k free, 11156793k buffers Swap: 456K total, 30897564k used, 785431k free, 23445897k cached PID User Pr NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 24 455 36 63 700 800 900 456 87 35 46 2 root 80 0 0 0 0 0 0 0 0 0 0 0 0 0 0 thread crt - 00:00:04 up 200 days, 23:39, 0 users, load average: 0.04, 0.05, 0.02 Tasks: 300 total, 2 running, 298 sleeping, 0 stopped, 0 zombie Cpu(s): 12.0%us, 2.5%sy, 0.0%ni, 89.2%id, 0.0%hi, 0.1%si, 0.0%st Mem: 123456K total, 1234567k used, 989991k free, 11156793k buffers Swap: 456K total, 30897564k used, 785431k free, 23445897k cached` 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/