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"
"
xs

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?s) ^(?P<timestamp>\d{4}/\d{2}/\d{2}\ \d{2}:\d{2}:\d{2}) \ \[(?P<severity>emerg|alert|crit|error|warn|notice|info)\] \ (?P<process_id>\d+) \#(?P<thread_id>\d+): \ \*(?P<connection_id>\d+) \ (?P<error>.+?) (?:\ while\ (?P<context>.+?))? ,\ client:\ (?P<client_ip>\d+\.\d+\.\d+\.\d+) ,\ server:\ (?P<server>.+?) (?:,\ request:\ \"(?P<request_method>[A-Z]+?) \ (?P<request_path>\/.+?) \ (?P<request_protocol>.+?)\")? (?:,\ upstream:\ \"(?P<upstream>.+?)\")? (?:,\ host:\ \"(?P<host>.+?)\")? (?:,\ referrer:\ \"(?P<referrer>.+?)\")? $`) var str = `2019/07/11 07:19:30 [error] 934#934: *18897816 open() "/local/nginx/static/ads.txt" failed (2: No such file or directory), client: 85.195.82.90, server: app.digitale-sammlungen.de, request: "GET /ads.txt HTTP/1.1", host: "app.digitale-sammlungen.de"` if len(re.FindStringIndex(str)) > 0 { fmt.Println(re.FindString(str),"found at index",re.FindStringIndex(str)[0]) } }

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/