Details

• 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 c_i [c₁-c₂]any character in the range c₁–c₂ [^c₁c₂…]any character except the c_i 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 \\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 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 right‐hand side of a rule RegularExpression["regex"]->rhs is taken to correspond to the substring matched by the n parenthesized regular expression object in regex. $0 represents the whole matched string.

Examples

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:

Scope  (21)

Basic Constructs  (17)

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:

Non-whitespace 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:

Compound Constructs  (4)

StringExpression can contain RegularExpression objects:

Conditional patterns:

Use alternatives to match one or more line breaks:

Non-greedy 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: