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Building Blocks


  • \d a digit
  • \D a non-digit
  • \s a whitespace
  • \S a non-whitespace
  • \w a word
  • \W a non-word
  • \b a word boundary
  • . any character
  • \ Escape special char or start a sequence

Repeated Characters or Patterns


  • ? 0 or 1 time
  • + 0 or more times
  • * 1 or more times
  • {#} # of times
  • {#,} # or more times
  • {,#} 0 to # times
  • {#, #} # to # of times

Specific Possible Characters


  • [xyz] either x, y or z
  • [^xyz] Any character besides x, y, or z
  • [a-zA-Z] ranges of characters

Location of Characters


  • ^ beginning of line
  • $ end of line
  • \A beginning of string
  • \z end of string

Capturing


  • (...) capture the pattern enclosed
  • (...|...) capture either pattern enclosed