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

%
%
mg

Test String

Code Generator

Language

Generated Code

const regex = new RegExp('^\\s*\\S*\\w*\\W*(?<severity>\\w)(?<time>\\d{4}\\s[^\\s]*)\\s+(?<pid>\\d+)\\s+(?<source>[^ \\]]+)\\](?<message>.*\\n)', 'mg') const str = `{"log":"I1121 14:37:42.883962 1 serve.go:85] Serving securely on 0.0.0.0:6443\\n","stream":"stderr","time":"2017-11-21T14:37:42.902231562Z"} {"log":"I1121 14:37:42.885062 1 apiservice_controller.go:112] Starting APIServiceRegistrationController\\n","stream":"stderr","time":"2017-11-21T14:37:42.902266652Z"} {"log":"I1121 14:37:42.885079 1 cache.go:32] Waiting for caches to sync for APIServiceRegistrationController controller\\n","stream":"stderr","time":"2017-11-21T14:37:42.902269685Z"} {"log":"I1121 14:37:42.886031 1 available_controller.go:192] Starting AvailableConditionController\\n","stream":"stderr","time":"2017-11-21T14:37:42.902271525Z"} {"log":"I1121 14:37:42.886043 1 cache.go:32] Waiting for caches to sync for AvailableConditionController controller\\n","stream":"stderr","time":"2017-11-21T14:37:42.902273437Z"} {"log":"E0213 13:30:06.573154 1 cleaner.go:100] Error while attempting to clean CSR "csr-4nzcx": unable to delete CSR \\\\\\"csr-4nzcx\\\\\\": certificatesigningrequests.certificates.k8s.io \\\\\\"csr-4nzcx\\\\\\" is forbidden: User \\\\\\"system:serviceaccount:kube-system:certificate-controller\\\\\\" cannot delete certificatesigningrequests.certificates.k8s.io at the cluster scope\\\\n\\",\\"stream\\":\\"stderr\\",\\"time\\":\\"2018-02-13T13:30:06.575560335Z\\"}" "log": "I0213 17:07:12.217422 1 trace.go:76] Trace[120533389]: \\"Create /api/v1/namespaces/default/events\\" (started: 2018-02-13 17:07:08.211886864 +0000 UTC m=+8.804410052) (total time: 4.005504088s):\\n", `; // 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