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String function

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String functions are a very useful set of wikitext functions that operate similar to magic words and are generally considered parser functions for operating on text strings. Since 2009, most of the functions are a switchable subset of the ParserFunctions extension, but should be enabled on all Fandom wikis. String functions primarily include logical functions like {{#len:...}}, {{#sub:...}}, {{#replace:...}}, and {{#explode:...}}.

Functions

There are many different functions such as len, pos, rpos, sub, pad, replace, explode, urlencode, and urldecode that allow you to do different things with different codes. All of these functions operate in O(n) time complexity, making them safe against denial of service (DoS) attacks.

Notes:

  1. Some parameters of these functions are limited through global settings to prevent abuse. See section Limits hereafter.
  2. For functions that are case sensitive, you may use the magic word {{lc:your_string_here}} as a workaround in some cases.
  3. To determine whether a MediaWiki server enables these functions, check the list of supported Extended parser functions in Special:Version.

#len:

The #len parser function was merged into the ParserFunctions extension as of version 1.2.0

The #len function returns the length of the given string. The syntax is:

{{#len:string}}

The return value is always a number of characters in the source string (after expansions of template invocations, but before conversion to HTML). If no string is specified, the return value is zero.

Notes:

  • This function is safe with UTF-8 multibyte characters. Example:
    • {{#len:Žmržlina}}
      returns 8.
  • Leading and trailing spaces or newlines are not counted, but intermediate spaces and newlines are taken into account. Examples:
    • {{#len:Icecream     }}
      returns 8.
    • {{#len: a   b }}
      returns 5.
  • Characters given by reference are not converted, but counted according to their source form.
    • {{#len: }}
      returns 6 (named characters references).
    • {{#len: }}
      returns 5 (numeric characters references, not ignored despite it designates a space here).
  • Tags such as <nowiki> and other tag extensions will always have a length of zero, since their content is hidden from the parser. Example:
    • {{#len:<nowiki>This is a </nowiki>test}}
      returns 4.

#pos:

The #pos parser function was merged into the ParserFunctions extension as of version 1.2.0

The #pos function returns the position of a given search term within the string. The syntax is:

{{#pos:string|search term|offset}}

The offset parameter, if specified, tells a starting position where this function should begin searching.

If the search term is found, the return value is a zero-based integer of the first position within the string.

If the search term is not found, the function returns an empty string.

Notes:

  • This function is case sensitive.
  • The maximum allowed length of the search term is limited through the $wgStringFunctionsLimitSearch global setting.
  • This function is safe with UTF-8 multibyte characters. Example: {{#pos:Žmržlina|lina}} returns 4.
  • As with #len, <nowiki> and other tag extensions are treated as having a length of 1 for the purposes of character position. Example: {{#pos:<nowiki>This is a </nowiki>test|test}} returns 1.

#rpos:

The #rpos parser function was merged into the ParserFunctions extension as of version 1.2.0

The #rpos function returns the last position of a given search term within the string. The syntax is:

 {{#rpos:string|search term}}

If the search term is found, the return value is a zero-based integer of its last position within the string.

If the search term is not found, the function returns -1.

Tip: When using this to search for the last delimiter, add +1 to the result to retrieve position after the last delimiter. This also works when the delimiter is not found, because "-1 + 1" is zero, which is the beginning of the given value.

Notes:

  • This function is case sensitive.
  • The maximum allowed length of the search term is limited through the $wgStringFunctionsLimitSearch global setting.
  • This function is safe with UTF-8 multibyte characters. Example: {{#rpos:Žmržlina|lina}} returns 4.
  • As with #len, <nowiki> and other tag extensions are treated as having a length of 1 for the purposes of character position. Example: {{#rpos:<nowiki>This is a </nowiki>test|test}} returns 1.

#sub:

The #sub parser function was merged into the ParserFunctions extension as of version 1.2.0

The #sub function returns a substring from the given string. The syntax is:

{{#sub:string|start|length}}

The start parameter, if positive (or zero), specifies a zero-based index of the first character to be returned.

Example: {{#sub:Icecream|3}} returns cream.

{{#sub:Icecream|0|3}} returns Ice.

If the start parameter is negative, it specifies how many characters from the end should be returned.

Example: {{#sub:Icecream|-3}} returns eam.

The length parameter, if present and positive, specifies the maximum length of the returned string.

Example: {{#sub:Icecream|3|3}} returns cre.

If the length parameter is negative, it specifies how many characters will be omitted from the end of the string.

Example: {{#sub:Icecream|3|-3}} returns cr.

Notes:

  • If the length parameter is zero, it is not used for truncation at all.
    • Example: {{#sub:Icecream|3|0}} returns cream, {{#sub:Icecream|0|3}} returns Ice.
  • If start denotes a position beyond the truncation from the end by negative length parameter, an empty string will be returned.
    • Example: {{#sub:Icecream|3|-6}} returns an empty string.
  • This function is safe with UTF-8 multibyte characters. Example: {{#sub:Žmržlina|3}} returns žlina.
  • As with #len, <nowiki> and other tag extensions are treated as having a length of 1 for the purposes of character position. Example: {{#sub:<nowiki>This is a </nowiki>test|1}} returns test.

#pad:

The #pad parser function was NOT merged into the ParserFunctions extension. As an alternative see the padleft and padright parser functions provided by MediaWiki core.

The #pad function returns the given string extended to a given width. The syntax is:

{{#pad:string|length|padstring|direction}}

The length parameter specifies the desired length of the returned string.

The padstring parameter, if specified, is used to fill the missing space. It may be a single character, which will be used as many times as necessary, or a string, which will be concatenated as many times as necessary and then trimmed to the required length. Example: {{#pad:Ice|10|xX}} returns xXxXxXxIce.

If the padstring is not specified, spaces are used for padding.

The direction parameter, if specified, can be one of these values:

  • left - the padding will be on the left side of the string. Example: {{#pad:Ice|5|x|left}} returns xxIce.
  • right - the padding will be on the right side of the string. Example: {{#pad:Ice|5|x|right}} returns Icexx.
  • center - the string will be centered in the returned string. Example: {{#pad:Ice|5|x|center}} returns xIcex.

If the direction is not specified, the padding will be on the left side of the string.

The return value is the given string extended to length characters, using the padstring to fill the missing part(s). If the given string is already longer than length, it is neither extended nor truncated.

Notes:

  • The maximum allowed value for the length is limited through the $wgStringFunctionsLimitPad global setting.
  • This function is only partially safe with UTF-8 multibyte characters. These characters will be treated appropriately if they appear in the original string, but will not be respected if they appear in the padding. Examples:
    • {{#pad:Zmrzlina|12|z}} returns zzzzZmrzlina
    • {{#pad:Žmržlina|12|z}} returns zzzzŽmržlina
    • {{#pad:Žmržlina|12|ž}} returns žžŽmržlina (padded to less than the specified length, since only half the required padding characters are being used)
  • Tags such as <nowiki> and other tag extensions are not permitted in the padding. If the padstring contains such a tag, it will be truncated.

#replace:

The #replace parser function was merged into the ParserFunctions extension as of version 1.2.0

The #replace function returns the given string with all occurrences of a search term replaced with a replacement term.

{{#replace:string|search term|replacement term}}

If the search term is unspecified or empty, a single space will be searched for.

If the replacement term is unspecified or empty, all occurrences of the search term will be removed from the string.

Notes:

  • This function is case sensitive.
  • The maximum allowed length of the search term is limited through the $wgStringFunctionsLimitSearch global setting.
  • The maximum allowed length of the replacement term is limited through the $wgStringFunctionsLimitReplace global setting.
  • Even if the replacement term is a space, an empty string is used. This is a side-effect of the MediaWiki parser. To use a space as the replacement term, put it in nowiki tags.
    • Example: {{#replace:My_little_home_page|_|<nowiki> </nowiki>}} returns My little home page.
    • Note that this is the only acceptable use of nowiki in the replacement term, as otherwise nowiki could be used to bypass $wgStringFunctionsLimitReplace, injecting an arbitrarily large number of characters into the output. For this reason, all occurrences of <nowiki> or any other tag extension within the replacement term are replaced with spaces.
  • This function is safe with UTF-8 multibyte characters. Example: {{#replace:Žmržlina|ž|z}} returns Žmrzlina.
  • If multiple items in a single text string need to be replaced, one could also consider Extension:ReplaceSet. It adds a parser function for a sequence of replacements.
Case insensitive replace

Currently the syntax doesn't provide a switch to toggle case sensitivity setting. But you may make use of magic words of formatting (e.g. {{lc:your_string_here}} ) as a workaround. For example if you want to remove the word "Category:" from the string regardless of its case, you may type:

{{#replace:{{lc:{{{1}}}}}|category:|}}

But the disadvantage is the output will become all lower cases. If you want to keep the casing after replacement, you have to use multiple nesting level (i.e. multiple replace calls) to achieve the same thing.

#explode:

The #explode parser function was merged into the ParserFunctions extension as of version 1.2.0

The #explode function splits the given string into pieces and then returns one of the pieces. The syntax is:

{{#explode:string|delimiter|position}}

The delimiter parameter specifies a string to be used to divide the string into pieces. This delimiter string is then not part of any piece, and when two delimiter strings are next to each other, they create an empty piece between them. If this parameter is not specified, a single space is used.

The position parameter specifies which piece is to be returned. Pieces are counted from 0. If this parameter is not specified, the first piece is used (piece with number 0). When a negative value is used as position, the pieces are counted from the end. In this case, piece number -1 means the last piece. Examples:

  • {{#explode:And if you tolerate this| |2}} returns you.
  • {{#explode:String/Functions/Code|/|-1}} returns Code.
  • {{#explode:Split%By%Percentage%Signs|%|2}} returns Percentage.

The return value is the position-th piece. If there are fewer pieces than the position specifies, an empty string is returned.

Notes:

  • This function is case sensitive.
  • The maximum allowed length of the delimiter is limited through $wgStringFunctionsLimitSearch global setting.
  • This function is safe with UTF-8 multibyte characters. Example: {{#explode:Žmržlina|ž|1}} returns lina.

#urlencode: and #urldecode:

The #urlencode parser functions was NOT merged into the ParserFunctions extension. As an alternative, see the urlencode parser function provided by MediaWiki core. #urldecode was not initially merged into ParserFunctions, but was added later on (in 2010, by commit 1b75afd18d3695bdb6ffbfccd0e4aec064785363).

These two functions operate in tandem: #urlencode converts a string into a URL-safe syntax, and #urldecode converts such a string back. The syntax is:

{{#urlencode:value}}
{{#urldecode:value}}

Notes:

  • These functions work by directly exposing PHP's urlencode() and urldecode() functions.
  • For anchors within a page use {{anchorencode}} instead of {{#urlencode}}. The results of a call to {{anchorencode}} are compatible with intra-page references generated with [[#link]] syntax, while {{#urlencode}}-generated values are not necessarily so.
  • urlencode has been integrated into ParserFunctions. Note that within the ParserFunction extension the function is called with {{urlencode:value}} instead of {{#urlencode:value}}. The ParserFunctions extension has been integrated into MediaWiki as of version 1.18; for examples see Help:Magic Words.
  • urldecode works the other way round and turns URL encoded strings into readable strings. A character-code-reference can be found at www.w3schools.com.


See also

External links

Note: This is a generic section stub. Expand it by clicking Sprite-monaco-pencil Edit to right of the section title.

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