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
Processing...

Test String

Code Generator

Language

Generated Code

const regex = /^\[\S+\s+\S+\s+\S+\s+\S+\s+\S+\] \[(\w*:)?error\] (\[pid \d+(:tid \d+)?\] )?\[client (\S+)\] (\w+: )?ModSecurity:(( \[[^]]+\])*)? Access denied/; // Alternative syntax using RegExp constructor // const regex = new RegExp('^\\[\\S+\\s+\\S+\\s+\\S+\\s+\\S+\\s+\\S+\\] \\[(\\w*:)?error\\] (\\[pid \\d+(:tid \\d+)?\\] )?\\[client (\\S+)\\] (\\w+: )?ModSecurity:(( \\[[^]]+\\])*)? Access denied', '') const str = `[Sun Nov 08 14:58:57 2015] [error] [client 52.23.156.32] ModSecurity: [file "/etc/httpd/modsecurity.d/99_asl_zzzz_threat_intelligence.conf"] [line "73"] [id "355506"] [rev "1"] [msg "Atomicorp.com WAF Rules: Threat Intelligence Match for Known multi event attacker Source on Atomicorp Threat Intelligence RBL. See this URL for details http://www.atomicrbl.com/lookup"] [severity "ALERT"] Access denied with code 403 (phase 2). RBL lookup of 32.156.23.52.threat5.atomicrbl.com. succeeded at REMOTE_ADDR. [hostname "www.ourdomain.org"] [uri "/robots.txt"] [unique_id "Vj@3kaLy1rMAAAnKrs8AAAAY"]`; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; if ((m = regex.exec(str)) !== null) { // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

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 JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions