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

/
/
gm

Test String

Code Generator

Language

Generated Code

const regex = /^(?P<hostname>[\w-_]+)\s+(?P<localInterface>[A-Za-z]+\d+(?:\/\d+)*)\s+(?P<holdTime>\d+)\s+(?P<capabilities>[A-Z]+)\s+(?P<remoteInterface>[A-Za-z]+\d+(?:\/\d+)*) /gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?P<hostname>[\\w-_]+)\\s+(?P<localInterface>[A-Za-z]+\\d+(?:\\\/\\d+)*)\\s+(?P<holdTime>\\d+)\\s+(?P<capabilities>[A-Z]+)\\s+(?P<remoteInterface>[A-Za-z]+\\d+(?:\\\/\\d+)*) ', 'gm') const str = `sh cdp nei Capability Codes: R - Router, T - Trans-Bridge, B - Source-Route-Bridge S - Switch, H - Host, I - IGMP, r - Repeater, V - VoIP-Phone, D - Remotely-Managed-Device, s - Supports-STP-Dispute Device-ID Local Intrfce Hldtme Capability Platform Port ID CHOD-MGMT-STACK.mhmp mgmt0 129 S I WS-C2960X-48T Gig1/0/25 SPINE-401(FDO22041YMP) Eth1/49 153 R S s N9K-C9336PQ Eth1/36 SPINE-402(FDO22081W5Y) Eth1/50 176 R S s N9K-C9336PQ Eth1/36 IPN-2-CH(FDO221610MG) Eth1/51 125 R S s N9K-C93180YC- Eth1/51 IPN-2-CH(FDO221610MG) Eth1/52 125 R S s N9K-C93180YC- Eth1/52 IPN-1-KCP(FDO22152M53) Eth1/54 143 R S s N9K-C93180YC- Eth1/54 Total entries displayed: 6 IPN-1-CH# sh lldp nei Capability codes: (R) Router, (B) Bridge, (T) Telephone, (C) DOCSIS Cable Device (W) WLAN Access Point, (P) Repeater, (S) Station, (O) Other Device ID Local Intf Hold-time Capability Port ID SPINE-401 Eth1/49 120 BR Eth1/36 SPINE-402 Eth1/50 120 BR Eth1/36 IPN-2-CH Eth1/51 120 BR Ethernet1/51 IPN-2-CH Eth1/52 120 BR Ethernet1/52 IPN-1-KCP Eth1/54 120 BR Ethernet1/54 Total entries displayed: 5`; // 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