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

/
/
g

Test String

Code Generator

Language

Generated Code

const regex = /(?:rd|ed|USER=|disconnected by|closed)\s?(?:for)?\s?(?:invalid\suser\s)?(?<user>\w+)/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?:rd|ed|USER=|disconnected by|closed)\\s?(?:for)?\\s?(?:invalid\\suser\\s)?(?<user>\\w+)', 'g') const str = `Sat Jun 03 2017 22:53:03 cisco_router1 sshd[4926]: Failed password for invalid user info from 2.229.4.58 port 4509 ssh2 Sat Jun 03 2017 22:55:37 cisco_router1 sshd[3720]: Failed password for peevish from 2.229.4.58 port 1299 ssh2 Sat Jun 03 2017 22:54:09 cisco_router1 sshd[15833]: pam_unix(sshd:session): session opened for user nsharpe by (uid=0) Tue Jul 04 2017 16:59:10 cisco_router1 sshd[64913]: pam_unix(sshd:session): session closed for user nsharpe by (uid=0) Tue Jul 04 2017 14:21:40 cisco_router1 su: pam_unix(su:session): session closed for user root Sat Jun 03 2017 22:55:13 cisco_router1 sshd[1952]: Accepted password for djohnson from 10.3.10.46 port 1182 ssh2 Sat Jun 03 2017 22:55:37 cisco_router1 sudo: myuan ; TTY=pts/0 ; PWD=/home/myuan ; USER=root ; COMMAND=/bin/su Tue Jul 04 2017 16:59:10 cisco_router1 sshd[59602]: Received disconnect from 10.2.10.163 11: disconnected by user Tue Jul 04 2017 16:59:10 cisco_router1 sshd[59602]: Received disconnect from 10.2.10.163 11: disconnected by user `; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // 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