RegularExpression

RegularExpression["regex"]
represents the generalized regular expression specified by the string "regex".

DetailsDetails

  • RegularExpression can be used to represent classes of strings in functions like StringMatchQ, StringReplace, StringCases, and StringSplit.
  • RegularExpression supports standard regular expression syntax of the kind used in typical string manipulation languages.
  • The following basic elements can be used in regular expression strings:
  • cthe literal character c
    .any character except newline
    [c1c2]any of the characters ci
    [c1-c2]any character in the range c1c2
    [^c1c2]any character except the ci
    p*p repeated zero or more times
    p+p repeated one or more times
    p?zero or one occurrence of p
    p{m,n}p repeated between m and n times
    p*?,p+?,p??the shortest consistent strings that match
    (p1p2)strings matching the sequence p1, p2,
    p1|p2strings matching p1 or p2
  • The following represent classes of characters:
  • \\ddigit 09
    \\Dnondigit
    \\sspace, newline, tab, or other whitespace character
    \\Snon-whitespace character
    \\wword character (letter, digit, or _)
    \\Wnonword character
    [[:class:]]characters in a named class
    [^[:class:]]characters not in a named class
  • The following named classes can be used: alnum, alpha, ascii, blank, cntrl, digit, graph, lower, print, punct, space, upper, word, xdigit.
  • The following represent positions in strings:
  • ^the beginning of the string (or line)
    $the end of the string (or line)
    \\bword boundary
    \\Banywhere except a word boundary
  • The following set options for all regular expression elements that follow them:
  • (?i)treat uppercase and lowercase as equivalent (ignore case)
    (?m)make ^ and $ match start and end of lines (multiline mode)
    (?s)allow . to match newline
    (?-c)unset options
  • \\., \\[, etc. represent literal characters ., [, etc.
  • Analogs of named Wolfram Language patterns such as x:expr can be set up in regular expression strings using (regex).
  • Within a regular expression string, \\gn represents the substring matched by the n ^(th) parenthesized regular expression object (regex). The shorter \\n is often equivalent to \\gn.
  • For the purpose of functions such as StringReplace and StringCases, any $n appearing in the righthand side of a rule RegularExpression["regex"]->rhs is taken to correspond to the substring matched by the n ^(th) parenthesized regular expression object in regex. $0 represents the whole matched string.

ExamplesExamplesopen allclose all

Basic Examples  (2)Basic Examples  (2)

Find words involving the characters a, b, c, d, e:

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Equivalent form using string patterns:

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Decide whether the string consists of words and whitespace:

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Equivalent form using string patterns:

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Introduced in 2004
(5.1)