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

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`(?m)(?P<timestamp>[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}.[0-9]{3}-[0-9]{4}) (?P<severity>[A-Z]) (?P<component>[A-Z]+) ?\[ ?(?P<context>[a-zA-Z0-9 ]+)] (?<message>[^\n]+)`) var str = `MongoDB 2014-11-03T18:28:32.450-0500 I NETWORK [initandlisten] waiting for connections on port 27017 2019-04-09T14:03:15.546-0400 I COMMAND [conn1] command test.items appName: "MongoDB Shell" command: aggregate { aggregate: "items", pipeline: [ { $match: { a: { $gte: 4.0 } } } ], cursor: {}, lsid: { id: UUID("042b423f-91bb-43bd-a378-4657ad4e0b35") }, $db: "test" } planSummary: COLLSCAN cursorid:7185821004643502676 keysExamined:0 docsExamined:25000 hasSortStage:1 numYields:289 nreturned:101 reslen:1305014 locks:{ Global: { acquireCount: { r: 387 } }, Database: { acquireCount: { r: 387 } }, Collection: { acquireCount: { r: 387 } } } storage:{ data: { bytesRead: 6808584, timeReadingMicros: 4336 } } protocol:op_msg 34439ms 2014-11-03T18:28:32.450-0500 ` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", i) } }

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/