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

Substitution

Processing...

Code Generator

Language

Generated Code

import Foundation let pattern = #"^\s+$\n^([ \t]+)Summary.*(?:\n\1[ \t]*\S.*)+"# let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines) let testString = #""" COMMENT REVIEWED REFSEQ: This record has been curated by NCBI staff. The reference sequence was derived from AC105339.9 and FJ695193.1. This sequence is a reference standard in the RefSeqGene project. Summary: Adaptor protein complex 3 (AP-3 complex) is a heterotrimeric protein complex involved in the formation of clathrin-coated synaptic vesicles. The protein encoded by this gene represents the beta subunit of the neuron-specific AP-3 complex and was first identified as the target antigen in human paraneoplastic neurologic disorders. The encoded subunit binds clathrin and is phosphorylated by a casein kinase-like protein, which mediates synaptic vesicle coat assembly. Defects in this gene are a cause of early-onset epileptic encephalopathy. [provided by RefSeq, Feb 2017]. Another paragrph PRIMARY REFSEQ_SPAN PRIMARY_IDENTIFIER PRIMARY_SPAN COMP 1-35060 AC105339.9 88079-123138 35061-35259 FJ695193.1 1-199 c 35260-57628 AC105339.9 123337-145705 """# let stringRange = NSRange(location: 0, length: testString.utf16.count) let substitutionString = #""# let result = regex.stringByReplacingMatches(in: testString, range: stringRange, withTemplate: substitutionString) print(result)

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 Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression