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RegularExpression

RegularExpression["regex"]
represents the generalized regular expression specified by the string "regex".
  • 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 c1-c2
[^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 0-9
\\Dnondigit
\\sspace, newline, tab or other whitespace character
\\Snonwhitespace 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 Mathematica patterns such as x:expr can be set up in regular expression strings using (regex).
  • Within a regular expression string, \\n represents the substring matched by the n^(th) parenthesized regular expression object (regex).
  • For the purpose of functions such as StringReplace and StringCases, any $n appearing in the right-hand 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.
EXAMPLESCLOSE ALL
Basic Examples   (2)
Find words involving the characters a, b, c, d, e:
Equivalent form using string patterns:
Decide whether the string consists of words and whitespace:
Equivalent form using string patterns:
Find words involving the characters a, b, c, d, e:
In[1]:=
Click for copyable input
Out[1]=
Equivalent form using string patterns:
In[2]:=
Click for copyable input
Out[2]=
 
Decide whether the string consists of words and whitespace:
In[1]:=
Click for copyable input
Out[1]=
Equivalent form using string patterns:
In[2]:=
Click for copyable input
Out[2]=
Scope   (21)
Extract any character except newline:
Either of the characters "a" and "b":
Any character between "a" and "e", including "a" and "e":
Any character except "a" and "1":
Any digit repeated one or more times:
The character "a" repeated 2 or 3 times:
Any digit:
Nondigit characters:
Space, newline, tab or other whitespace character:
Nonwhitespace characters:
Word characters:
Nonword characters:
Find all uppercase letters:
Split a string at the beginning of a new line:
Split a string at the end of a new line:
Insert a character at the boundary of each word:
Split a string at every character except at the boundary of a word:
StringExpression can contain RegularExpression objects:
Conditional patterns:
Use alternatives to match one or more line breaks:
Nongreedy matches are done by appending a question mark "?" to the quantifiers:
Generalizations & Extensions   (1)
The $1 refers to the letter matched by (.):
Numbered subpatterns:
Properties & Relations   (3)
Use StringMatchQ to determine string pattern matches:
Use StringCases to find matching substrings:
Use StringSplit to split a string into substrings using a delimiter pattern:
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