Regular expressions (also called regex or regexp) are a sophisticated system for precisely matching text patterns. Regexps give you a high-level of control and flexibility for matching text not possible with regular find or simple wildcards. When writing a regexp, you can creatively specify what to match, where to match it, and how many times to match it (quantification). We'll cover those, give examples, and walk through using regexps in OpenOffice.org. Then, once you find patterns with regexps, you can globally perform any of the normal operations on selected text including replacing, formatting, and deleting. Regexps come in many dialects and are used in various systems including Perl, PHP, C#, and Microsoft Office. The dialect of regexps in Writer, Calc, Impress, and Base resembles (but does not exactly mimic) the POSIX regexps, which are based off of traditional Unix regexps. Do not expect any two dialects to be exactly the same.

Important notice

In the example matches, only the underline portions are matched. The unmatched parts are included to provide better context for examples.

Literals

Most non-regexp search patterns are a literal string, or simply called a literal. When you search for "bar," then "bar" is a plain literal.

Expression	Matches	Does not match
bar	bar barb bars crowbar embarrass	foo

Escaping special characters

Certain characters have special meanings (covered later in this article), so they must be escaped to be used as literals. These special characters are the following: To escape one of these, precede it with a backslash (\). Here are some examples:

Expression	Matches	Does not match
Not escaped period .	. foo bar	End of line characters
Escaped period \.	.	foo bar End of line characters
Not escaped dollar sign $	End of line characters	The price is $30
Escaped dollar sign \$	The price is $30	End of line characters

Period

The period (.) matches any one character.

Expression	Matches	Does not match
b.r	bar beryl burn	saber

Microsoft Office uses a question mark ? where OpenOffice.org uses the period (.).

Sets and classes

Sets are a collection of characters enclosed in brackets, and the set matches one character. A class can contain multiple individual characters, a range of characters, or any combination. A range is designated with a hyphen (-). Here are some examples:

Expression	Matches	Does not match
[ab]	a b banana	c d kiwi
[0-3]	2001 2456	456 456.7
[a-z145]	banana 2001 984	236 :)

You can eliminate characters against matching by using the negation operator called the caret (^) as the first character in the square brackets. If the caret is not first in the brackets, it matches normally (instead of using negation). Here are some examples:

Expression	Matches	Does not match
[^ab]	c d banana	a b ^
[a^b]	a b banana ^	c d

There are a few predefined classes (also called POSIX bracket expressions) for your convenience. They are shorthand. For example [:digit:] is basically the same as [0-9] or [012345679].

Name	Description
[:alpha:]	Alphabetic characters (depending on the document language)
[:digit:]	Decimal digits
[:alnum:]	Alphanumeric characters
[:space:]	Just a space---and not other whitespace characters (see issue 41706)
[:print:]	Most printable characters (see issue 83290)
[:cntrl:]	Non-printable characters
[:lower:]	Lowercase characters
[:upper:]	Uppercase characters

The use of these predefined classes may be confusing (see issue 64368). You can use predefined classes like the following examples:

Expression	Matches	Does not match
[:digit:]	Nothing	Everything
[:digit:]+ or ([:digit:])	A single digit 1 123	Non-digits abc

Alternation

The pipe operator (|) matches elements on either side of the operator. For example:

Expression	Matches	Does not match
foo|bar	foo bar	monkey
(mail|sand)box	mailbox sandbox	breadbox
([0-1][0-9]|2[0-3]):[0-5][0-9]	Time of day in 24-hour notation 09:41 23:59	09:60 24:00

See issue 84828 for more information about using alternation with the caret (^).

Groups

Parentheses form groups. They are typically combined with quantifiers, with backreferences, or in replacements. Groups differ from sets because a set matches one character while a group matches all characters in the group.

Expression	Matches	Does not match
(foo)	foo foofo foofoo	f fo of
f(o)+	foo	bar
(.).(\1)	three letter palindromes bob mom	foo

Location

There are several ways to match by location:

Symbol	Matches
^	Beginning of a paragraph
$	End of a paragraph
\n	Manual line break
\t	Tab
\<	Beginning of a word
\>	End of a word

Here are some examples:

Expression	Matches	Does not match
^Monkey	Monkey Island is up ahead!	Welcome to Monkey Island!
Island!$	Welcome to Monkey Island!	Monkey Island is up ahead!
and\>	island island! hand	handy
\<key	key keys keyboard	monkey
\<.{4}\>	Words with exactly 4 letters Code	I am

Quantification

Use asterisk (*) to match an element zero or more times. Here are some examples:

Expression	Matches	Does not match
cd*	c followed by zero or more d's c cd cdd dcd	c dc cc dd
[cd]*	either c or d zero or more times in any order cd cdd dcd	abefeghi

Use the plus sign (+) to match an element one or more times.

Expression	Matches	Does not match
cd+	c followed by one or more d's cd cdd	c dc

Use the question mark (?) to find an element zero or one times.

Expression	Matches	Does not match
cd?	c followed by zero or one d's c cd cdd	a d
fees?	fee fees feed	free
(wo)?man	man woman	men women

Use the curly brackets, or braces, to specify any number of repetitions. You may use the curly brackets in the forms

• {x}
• {y,z}
• {y,}

where x is an exact number of repetitions, y is a minimum, and z is the maximum. Here are some examples:

Expression	Matches	Does not match
[aeiou]{3}	exactly three consecutive vowels adieu	foo
[0-9]{2,3}	two to three digits 23	2 3
[a-z]{7,}	seven letters or more letters expiration	expire

Backreferences

Use a backreferences to match a previously-matched group. Form the backreference using a forward slash followed by a number that corresponds to the group. Use \1 to match the first group, \2 for the second group, \3 for the third, and so on.

Expression	Matches	Does not match
\<(.).\1\>	Three letter palindromes including gig nun	gigabyte
\<(.)*\>[:space:]\<(\1)\>	Duplicate words such as I see the the monkey.	I see the monkey.

Read more about backreferences in replacements, a new feature in OpenOffice.org 2.4.

How to search with regular expressions

Here is the basic way to search with regexps:

1. Open a Writer, Calc, or Impress document.
2. Choose Edit > Find & Replace from the menu.
3. Type your own regexp in the Search for field.
4. Click the More Options button.
5. Check the box Regular expressions.
6. Click the Find button or the Find All button.

Then, the matched text is selected, so you can perform all the normal operations including delete and format. This Flash video shows how to perform the procedure:

Other ways to use regular expressions

You can also use regexps in these places:

• Base: Find Record
• Calc: Standard Filter
• Calc: functions including COUNTIF, DCOUNT, DCOUNTA, DGET, DMAX, DMIN, DAVERAGE, DPRODUCT, DSTDEV, DSTDEVP, DSUM, DVAR, DVARP, HLOOKUP, LOOKUP, MATCH, SEARCH, SUMIF, VLOOKUP,
• Macros
• Writer: filter comments in Accept/Reject changes

Common examples

See this long list of example regular expressions.

Microsoft Office 2003

Microsoft Office 2003 has a similar regexp feature called wildcards. A few regexp may transfer between Office and OpenOffice.org without modification but many will require modification.