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RegularExpression
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RegularExpression

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represents the generalized regular expression specified by the string "regex".

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 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
    \\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 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.

Examples

open allclose all

Basic Examples  (2)Summary of the most common use cases

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

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-bvws1x
Out[1]=1

Equivalent form using string patterns:

In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-c2nvnd
Out[2]=2

Decide whether the string consists of words and whitespace:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-hwo0ol
Out[1]=1

Equivalent form using string patterns:

In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-l8cuqv
Out[2]=2

Scope  (22)Survey of the scope of standard use cases

Basic Constructs  (17)

Extract any character except newline:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-wau8e2
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-w4hydd
Out[2]=2

Either of the characters "a" and "b":

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-d7r9kh
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-i0jmqw
Out[2]=2

Any character between "a" and "e", including "a" and "e":

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-o7hd44
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-o92xxj
Out[2]=2

Any character except "a" and "1":

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-5l58p4
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-od63gz
Out[2]=2

Any digit repeated one or more times:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-jppyzw
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-1muhv3
Out[2]=2

The character "a" repeated 2 or 3 times:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-qsi4wp
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-qilu59
Out[2]=2

Any digit:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-o31a2j
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-o282an
Out[2]=2

Nondigit characters:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-wy0ncj
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-7nbenu
Out[2]=2

Space, newline, tab, or other whitespace character:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-rf38ll
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-r1rx6g

Non-whitespace characters:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-24y6b7
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-peqgki
Out[2]=2

Word characters:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-nz8lki
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-ry18u0
Out[2]=2

Nonword characters:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-4126rn
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-4a3hhu
Out[2]=2

Find all uppercase letters:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-9n93cz
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-gvrm1g
Out[2]=2

Split a string at the beginning of a new line:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-i3zsqg
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-c0ui0d

Split a string at the end of a new line:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-tzmzng
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-bbae3k

Insert a character at the boundary of each word:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-ofjaz0
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-0pzjgd
Out[2]=2

Split a string at every character except at the boundary of a word:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-k60uey
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-59e639
Out[2]=2

Compound Constructs  (5)

StringExpression can contain RegularExpression objects:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-meg9qn
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-cux7tm
Out[2]=2

Conditional patterns:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-lsolo
Out[1]=1
In[2]:=2
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https://wolfram.com/xid/0i1pspc3m-g4q96h
Out[2]=2

Use alternatives to match one or more line breaks:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-4q4jul
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0i1pspc3m-ccppng
Out[2]=2

Non-greedy matches are done by appending a question mark "?" to the quantifiers:

In[1]:=1
✖
https://wolfram.com/xid/0i1pspc3m-czq8it
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0i1pspc3m-iioam
Out[2]=2

The $1 refers to the letter matched by (.):

In[1]:=1
✖
https://wolfram.com/xid/0i1pspc3m-qbl9j2
Out[1]=1
In[2]:=2
✖
https://wolfram.com/xid/0i1pspc3m-e17tgo
Out[2]=2

Numbered subpatterns:

In[3]:=3
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https://wolfram.com/xid/0i1pspc3m-jv6h6x
Out[3]=3
In[4]:=4
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https://wolfram.com/xid/0i1pspc3m-xdpi2s
Out[4]=4

Properties & Relations  (3)Properties of the function, and connections to other functions

Use StringMatchQ to determine string pattern matches:

In[1]:=1
✖
https://wolfram.com/xid/0i1pspc3m-h2j60s
Out[1]=1

Use StringCases to find matching substrings:

In[1]:=1
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https://wolfram.com/xid/0i1pspc3m-ld9gz9
Out[1]=1

Use StringSplit to split a string into substrings using a delimiter pattern:

In[1]:=1
✖
https://wolfram.com/xid/0i1pspc3m-kqx6if
Out[1]=1
Wolfram Research (2004), RegularExpression, Wolfram Language function, https://reference.wolfram.com/language/ref/RegularExpression.html.
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Wolfram Research (2004), RegularExpression, Wolfram Language function, https://reference.wolfram.com/language/ref/RegularExpression.html.

Text

Wolfram Research (2004), RegularExpression, Wolfram Language function, https://reference.wolfram.com/language/ref/RegularExpression.html.

✖
Wolfram Research (2004), RegularExpression, Wolfram Language function, https://reference.wolfram.com/language/ref/RegularExpression.html.

CMS

Wolfram Language. 2004. "RegularExpression." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/RegularExpression.html.

✖
Wolfram Language. 2004. "RegularExpression." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/RegularExpression.html.

APA

Wolfram Language. (2004). RegularExpression. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/RegularExpression.html

✖
Wolfram Language. (2004). RegularExpression. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/RegularExpression.html

BibTeX

@misc{reference.wolfram_2025_regularexpression, author="Wolfram Research", title="{RegularExpression}", year="2004", howpublished="\url{https://reference.wolfram.com/language/ref/RegularExpression.html}", note=[Accessed: 09-April-2025 ]}

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@misc{reference.wolfram_2025_regularexpression, author="Wolfram Research", title="{RegularExpression}", year="2004", howpublished="\url{https://reference.wolfram.com/language/ref/RegularExpression.html}", note=[Accessed: 09-April-2025 ]}

BibLaTeX

@online{reference.wolfram_2025_regularexpression, organization={Wolfram Research}, title={RegularExpression}, year={2004}, url={https://reference.wolfram.com/language/ref/RegularExpression.html}, note=[Accessed: 09-April-2025 ]}

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@online{reference.wolfram_2025_regularexpression, organization={Wolfram Research}, title={RegularExpression}, year={2004}, url={https://reference.wolfram.com/language/ref/RegularExpression.html}, note=[Accessed: 09-April-2025 ]}