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{{Refimprove|date=February 2015}}
In [[computer programming]], '''trimming''' ('''trim''') or '''stripping''' ('''strip''') is a [[string (computer science)|string manipulation]] in which leading and trailing [[whitespace
For example, the string (enclosed by apostrophes)
<
would be changed, after trimming, to
<
==Variants==
;Left or right trimming▼
:The most popular variants of the trim function strip only the beginning or end of the string. Typically named '''ltrim''' and '''rtrim''' respectively, or in the case of Python: '''lstrip''' and '''rstrip'''. C# uses '''TrimStart''' and '''TrimEnd''', and Common Lisp '''string-left-trim''' and '''string-right-trim'''. Pascal and Java do not have these variants built-in, although [[Object Pascal]] (Delphi) has '''TrimLeft''' and '''TrimRight''' functions.<ref>{{cite web|url=http://www.freepascal.org/docs-html/rtl/sysutils/trim.html |title=Trim |publisher=Freepascal.org |date=2013-02-02 |accessdate=2013-08-24}}</ref>▼
;Whitespace character list parameterization▼
:Many trim functions have an optional parameter to specify a list of characters to trim, instead of the default whitespace characters. For example, PHP and Python allow this optional parameter, while Pascal and Java do not. With Common Lisp's <code>string-trim</code> function, the parameter (called ''character-bag'') is required. The C++ [[Boost library]] defines space characters according to [[Locale (computer software)|locale]], as well as offering variants with a [[predicate (computer programming)|predicate]] parameter (a [[functor]]) to select which characters are trimmed.▼
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;Special empty string return value▼
:An uncommon variant of trim returns a special result if no characters remain after the trim operation. For example, [[Jakarta Project|Apache Jakarta]]'s '''StringUtils''' has a function called <code>stripToNull</code> which returns <code>null</code> in place of an empty string.▼
;Space normalization▼
:Space normalization is a related string manipulation where in addition to removing surrounding whitespace, any sequence of whitespace characters within the string is replaced with a single space. Space normalization is performed by the function named <code>Trim()</code> in spreadsheet applications (including [[Microsoft Excel|Excel]], [[OpenOffice.org Calc|Calc]], [[Gnumeric]], and [[Google Docs]]), and by the <code>normalize-space()</code> function in [[XSL Transformations|XSLT]] and [[XPath]], ▼
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;In-place trimming▼
:While most algorithms return a new (trimmed) string, some alter the original string [[in-place]]. Notably, the [[Boost library]] allows either in-place trimming or a trimmed copy to be returned.▼
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==Definition of whitespace==
The characters which are considered whitespace varies between programming languages and implementations. For example, C traditionally only counts space, tab, line feed, and carriage return characters, while languages which support [[Unicode]] typically include all Unicode space characters. Some implementations also include [[ASCII]] control codes (non-printing characters) along with whitespace characters.
Java's trim method considers ASCII spaces and control codes as whitespace, contrasting with the Java <code>isWhitespace()</code> method,<ref>{{cite web|url=
Delphi's Trim function considers characters U+0000 (NULL) through U+0020 (SPACE) to be whitespace.
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The Unicode standard explicitly states that it does not act as a space.
The [[Non-breaking space]] {{unichar|00A0|
==Usage==
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==External links==
*[
*[
*[http://webwidetutor.com/php/PHP-Change-String-value-behaviour-or-look-?id=8 php string cut and trimming]- php string cut and trimming
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