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From IlluriaThis is a ShoutWiki help page, hosted at ShoutWiki Hub. If you want to suggest changes, leave a message on its talk page. If you want to replace this page with a custom help page for your wiki, click the create button above. The ParserFunctions extension provides eleven additional parser functions to supplement the "magic words", which are already present in MediaWiki. All the parser functions provided by this extension take the form:
#expr
This function evaluates a mathematical expression and returns the calculated value.
The available operators are listed to the right, in order of precedence. See Help:Calculation for more details of the function of each operator. The accuracy and format of the result returned will vary depending on the operating system of the server running the wiki, and the number format of the site language. When evaluating using boolean algebra, zero evaluates to false and any nonzero value, positive or negative, evaluates to true:
An empty input expression returns an empty string. Invalid expressions return one of several error messages, which can be caught using the #iferror function:
Warning: Some expressions may invoke floating-point errors when used with very large or very small numbers: #if
This function tests whether the first parameter is 'non-empty'. It evaluates to false if the test string is empty or contains only whitespace characters (space, newline, etc).
The test string is always interpreted as pure text, so mathematical expressions are not evaluated:
Either or both the return values may be omitted:
See Help:Parser functions/Templates for more examples of this parser function. #ifeqThis parser function compares two strings and determines whether they are identical.
If both strings are valid numerical values, the strings are compared numerically:
Otherwise the comparison is made as text; this comparison is case sensitive:
Warning: Content inside parser tags (such as <nowiki>) is hashed before the parser functions are evaluated, resulting in errors:
{{#ifeq: <nowiki>foo</nowiki> | <nowiki>foo</nowiki> | yes | no}} → no #iferrorThis function takes an input string and returns one of two results; the function evaluates to true if the input string contains an HTML object with class="error", as generated by other parser functions such as #expr, #time and #rel2abs, template errors such as loops and recursions, and other 'failsoft' parser errors.
One or both of the return strings can be omitted. If the correct string is omitted, the test string is returned if it is not erroneous. If the error string is also omitted, an empty string is returned on an error:
#ifexprThis function evaluates a mathematical expression and returns one of two strings depending on the boolean value of the result:
The expression input is evaluated exactly as for #expr above, with the same operators being available. The output is then evaluated as a boolean expression. This function is equivalent to one using #ifeq and #expr only:
An empty input expression evaluates to false:
Either or both the return values may be omitted; no output is given when the appropriate branch is left empty:
#ifexistThis function takes an input string, interprets it as a page title, and returns one of two values depending on whether or not the page exists on the local wiki.
The function evaluates to true if the page exists, whether it contains content, is visibly blank (contains meta-data such as category links or magic words, but no visible content), is blank, or is a redirect. Only pages that are redlinked evaluate to false, including if the page used to exist but has been deleted.
The function evaluates to true for system messages that have been customised, and for special pages that are defined by the software.
#ifexist: is considered an "expensive parser function", only a limited number of which can be included on any one page (including functions inside transcluded templates). When this limit is exceeded, the page is categorised into Category:Pages with too many expensive parser function calls, and any further #ifexist: functions automatically return false, whether the target page exists or not. If a page checks a target using #ifexist:, then that page will appear in the Special:WhatLinksHere list for the target page. So if the code {{#ifexist:Foo}} were included live on this page (Help:Parser functions), Special:WhatLinksHere/Foo will list Help:Parser functions. On wikis using a shared media repository, #ifexist: can be used to check if a file has been uploaded to the repository, but not to the wiki itself:
If a local description page has been created for the file, the result is exists for all of the above. #rel2absThis function converts a relative file path into an absolute filepath.
Within the path input, the following syntax is valid:
If the base path is not specified, the full page name of the page will be used instead:
Invalid syntax, such as /. or /./, is ignored. Since no more than two consecutive full stops are permitted, sequences such as these can be used to separate successive statements:
#switchThis function compares one input value against several test cases, returning an associated string if a match is found. {{#switch: comparison string
| case = result
| case = result
| ...
| case = result
| #default = default result
}}
The default result is returned if no case string matches the comparison string. In this syntax, the default result must be the last parameter and must not contain a raw equals sign. Alternatively, the default result may be explicitly declared with a case string of "#default"; default results declared in this way may be placed anywhere within the function:
If the default parameter is omitted and no match is made, no content is added. It is possible to have 'fall through' values, where several case strings return the same result string. This minimises duplication. {{#switch: comparison string
| case1 = result1
| case2
| case3
| case4 = result2
| case5 = result3
| case6
| case7 = result4
| #default = default result
}}
Here cases 2, 3 and 4 all return result2; cases 6 and 7 both return result4 As with #ifeq, the comparison is made numerically if both the comparison string and the case string being tested are numeric; or as case-sensitive string otherwise. A case string may be empty:
Once a match is found, subsequent cases are ignored:
Warning: "Case" strings cannot contain raw equals signs. To work around this, create a template at {{=}} containing a single equals sign: = Then, use this template as follows: {{#switch: 1=2 | 1=2 = raw | 1<nowiki>=</nowiki>2 = nowiki | 1=2 = html | 1{{=}}2 = template | foo }} → html #time
This parser function takes a date and/or time construct and formats it according to the syntax given. A date/time object can be specified; the default is the value of the magic word {{CURRENTTIMESTAMP}} – that is, the time the page was last rendered into HTML.
The list of accepted formatting codes is given in the table to the right. Any character in the formatting string that is not recognised is passed through unaltered. There are also two ways to escape characters within the formatting string:
In addition, the digraph xx is interpreted as a single literal "x".
The date/time object can be in any format accepted by PHP's strtotime() function. Both absolute (eg 20 December 2000) and relative (eg +20 hours) times are accepted. {{#time: r|now}} → Fri, 20 Dec 2024 04:34:18 +0000 If you've calculated a Unix timestamp, you may use it in date calculations by pre-pending an @ symbol. {{#time: U | now }}} → 1734669258 Warning: The range of acceptable input is January 1 0100 → December 31 9999. Values outside this range will be misinterpreted: Full or partial absolute dates can be specified; the function will 'fill in' parts of the date that are not specified using the current values:
A four-digit number is interpreted as hours and minutes if possible, and otherwise as year: A six-digit number is interpreted as hours, minutes and seconds if possible, but otherwise as an error (not, for instance, a year and month): Warning: The fill-in feature is not consistent; some parts are filled in using the current values, others are not: The function performs a certain amount of date mathematics:
#timelThis function is identical to {{#time: ... }}, except that it uses the local time of the wiki (as set in $wgLocaltimezone) when no date is given.
#titlepartsThis function separates a pagetitle into segments based on slashes, then returns some of those segments as output.
If the number of segments parameter is not specified, it defaults to "0", which returns all the segments. If the first segment parameter is not specified or is "0", it defaults to "1":
Negative values are accepted for both values. Negative values for number of segments effectively 'strips' segments from the end of the string. Negative values for first segment translates to "add this value to the total number of segments", loosely equivalent to "count from the right":
The string is split a maximum of 25 times; further slashes are ignored. The string is also limited to 255 characters, as it is treated as a page title:
Warning: You can use #titleparts as a small "string parser & converter", but consider that it returns the first substring capitalized. If lower case is needed, use lc: function to control output.
General pointsSubstitutionParser functions can be substituted by prefixing the hash character with subst::
Warning: The results of substituted parser functions are undefined if the expressions contain unsubstituted volatile code such as variables or other parser functions. For consistent results, all the volatile code in the expression to be evaluated must be substituted. See Wikipedia's help page on substitution. TablesParser functions will mangle wikitable syntax, treating all the raw pipe characters as parameter divisors. To avoid this, most wikis create the template Template:! with its contents only a raw pipe character. This 'hides' the pipe from the MediaWiki parser, ensuring that it is not considered until after all the templates and variables on a page have been expanded. Alternatively, raw HTML table syntax can be used, although this is less intuitive and more error-prone. Stripping whitespaceWhitespace, including newlines, tabs, and spaces, is stripped from the beginning and end of all the parameters of these parser functions. If this is not desirable, adding any non-whitespace characters (including the HTML encoding for a whitespace character, invisible Unicode characters such as the zero-width space or direction marks, or sequences recognised and stripped by the MediaWiki parser such as <nowiki/>) will prevent further stripping: {{#ifeq: foo | foo | equal | not equal }}
{{#ifeq:  foo   |   foo  | equal | not equal }}
{{#ifeq: <nowiki/>foo <nowiki/> | <nowiki/> foo<nowiki/> | equal | not equal }}
{{#ifeq: <nowiki/>foo<nowiki/> | <nowiki/>foo<nowiki/> | equal | not equal }}
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