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

r"
"
ug

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`\(groupid=\s+(?P<groupid>\d+)`) var str = `seq_read_4k: (groupid= 0 jobs= 1): err= 0: pid= 7396: Wed Sep 2 14:07:25 2015 read : io= 72013 MB bw= 614510 KB/s iops= 153627 runt= 120001msec -- seq_read_128k: (groupid= 1 jobs= 1): err= 0: pid= 7463: Wed Sep 2 14:07:25 2015 read : io= 74277 MB bw= 633821 KB/s iops= 4951 runt= 120001msec -- rand_read_4k: (groupid= 2 jobs= 1): err= 0: pid= 7480: Wed Sep 2 14:07:25 2015 read : io= 4102.4 MB bw= 35006 KB/s iops= 8751 runt= 120001msec -- rand_read_1M: (groupid= 3 jobs= 1): err= 0: pid= 7497: Wed Sep 2 14:07:25 2015 read : io= 44963 MB bw= 383678 KB/s iops= 374 runt= 120002msec ` 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/