View source for Module:String/doc

{{Used in system}} 
{{Module rating|protected}}
{{cascade-protected template|page=module}}
{{Lmd|String}}

This module is intended to provide access to basic string functions.

Most of the functions provided here can be invoked with named parameters, unnamed parameters, or a mixture. If named parameters are used, Mediawiki will automatically remove any leading or trailing whitespace from the parameter. Depending on the intended use, it may be advantageous to either preserve or remove such whitespace.

== Global options ==

; ignore_errors
: If set to 'true' or 1, any error condition will result in an empty string being returned rather than an error message.
; error_category
: If an error occurs, specifies the name of a category to include with the error message. The default category is {{clc|Errors reported by Module String}}.
; no_category
: If set to 'true' or 1, no category will be added if an error is generated.

Unit tests for this module are available at [[Module:String/testcases]].

== Functions ==

=== count ===

Counts the number of times a given pattern appears in the arguments that get passed on to this module. Counts disjoint matches only.

Usage:
: <code><nowiki>{{#invoke:</nowiki>String|count|''source_str''|''pattern_string''|''plain_flag''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|count|source= ''source_string'' |pattern= ''pattern_string''|plain= ''plain_flag'' <nowiki>}}</nowiki></code>
Parameters:
; source_string
: The string to count occurrences in
; pattern
: The string or pattern to count occurrences of within source
; plain
: Boolean flag indicating that pattern should be understood as plain text and not as a [[mw:Extension:Scribunto/Lua reference manual#Ustring patterns|Scribunto ustring pattern]] (a unicode-friendly [[w:Lua|Lua]]-style [[w:regular expression|regular expression]]); defaults to true

Examples:
* Count of 'a': <code><nowiki>"{{#invoke:String|count|aabbcc|a}}"</nowiki></code> → "{{#invoke:String|count|aabbcc|a}}"
* Count occurrences of 'aba': <code><nowiki>"{{#invoke:String|count|ababababab|aba}}"</nowiki></code> → "{{#invoke:String|count|ababababab|aba}}"
* Count of "either 'a' or 'c' ":<code><nowiki>"{{#invoke:String|count|aabbcc|[ac]|plain=false}}"</nowiki></code> → "{{#invoke:String|count|aabbcc|[ac]|plain=false}}"
* Count of "not 'a' ": <code><nowiki>"{{#invoke:String|count|aaabaaac|[^a]|plain=false}}"</nowiki></code> → "{{#invoke:String|count|aaabaaac|[^a]|plain=false}}"
* Count of "starts with 'a' ": <code><nowiki>"{{#invoke:String|count|aaabaaac|^a|plain=false}}"</nowiki></code> → "{{#invoke:String|count|aaabaaac|^a|plain=false}}"

=== endswith ===

{{for|the startswith function|Module:String2#startswith}}
Usage:
: <code><nowiki>{{#invoke:</nowiki>String|endswith|''source_str''|''search_string''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|endswith|source= ''source_string'' |pattern= ''search_string''<nowiki>}}</nowiki></code>
Returns "yes" if the source string ends with the search string. Use named parameters to have the strings trimmed before use. Despite the parameter name, ''search_string'' is not a Lua pattern, it is interpreted literally.

* <code><nowiki>"{{#invoke:String|endswith|xxxyyy|y}}"</nowiki></code> → "{{#invoke:String|endswith|xxxyyy|y}}"
* <code><nowiki>"{{#invoke:String|endswith|xxxyyy|z}}"</nowiki></code> → "{{#invoke:String|endswith|xxxyyy|z}}"

=== escapePattern ===

In a [[:mw:LUAREF#Patterns|Lua pattern]], changes a ''class character'' into a ''literal character''. For example: in a pattern, character <code>.</code> catches "any character"; escapePattern will convert it to <code>%.</code>, catching just the literal character ".".

Usage:
* <code><nowiki>{{#invoke:String|escapePattern|</nowiki>''pattern_string''<nowiki>}}</nowiki></code>

Parameters:

; pattern_string
: The pattern string to escape

Examples:

* <code><nowiki>"{{#invoke:String|escapePattern|A.D.}}"</nowiki></code> → "{{#invoke:String|escapePattern|A.D.}}"
* <code><nowiki>"{{#invoke:String|escapePattern|10%}}"</nowiki></code> → "{{#invoke:String|escapePattern|10%}}"

=== find ===

This function allows one to search for a target string or pattern within another string.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|find|''source_string''|''target_string''|''start_index''|''plain_flag''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|find|source= ''source_string'' |target= ''target_string'' |start= ''start_index'' |plain= ''plain_flag'' <nowiki>}}</nowiki></code>

Parameters:

; source
: The string to search
; target
: The string or pattern to find within source
; start
: The index within the source string to start the search, defaults to 1
; plain
: Boolean flag indicating that target should be understood as plain text and not as a [[mw:Extension:Scribunto/Lua reference manual#Ustring patterns|Scribunto ustring pattern]] (a unicode-friendly [[w:Lua|Lua]]-style [[w:regular expression|regular expression]]); defaults to true

This function returns the first index >= "start" where "target" can be found within "source". Indices are 1-based. If "target" is not found, then this function returns 0. If either "source" or "target" are missing / empty, this function also returns 0.

This function should be safe for UTF-8 strings.

Examples:
* <code><nowiki>{{#invoke:String|find|abc123def|12}}</nowiki></code> → {{#invoke:String|find|abc123def|12}}
* <code><nowiki>{{#invoke:String|find|source=abc123def|target=12}}</nowiki></code> → {{#invoke:String|find|source=abc123def|target=12}}
* <code><nowiki>{{#invoke:String|find|source=abc123def|target=pqr}}</nowiki></code> → {{#invoke:String|find|source=abc123def|target=pqr}}
* <code><nowiki>{{#invoke:String|find| abc123def |123}}</nowiki></code> → {{#invoke:String|find| abc123def |123}}
* <code><nowiki>{{#invoke:String|find|source= abc123def |target= 123 }}</nowiki></code> → {{#invoke:String|find|source= abc123def |target= 123 }}
* <code><nowiki>{{#invoke:String|find|source=abc123def|target=%d |start=3 |plain=false }}</nowiki></code> → {{#invoke:String|find|source=abc123def|target=%d |start=3 |plain=false }}

When using unnamed parameters, preceding and trailing spaces are kept and counted:
* <code><nowiki>{{#invoke:String|find|  abc123def |c|false}}</nowiki></code> → {{#invoke:String|find|  abc123def |c|false}}
* <code><nowiki>{{#invoke:String|find|source=  abc123def |target=c|plain=false}}</nowiki></code> → {{#invoke:String|find|source=  abc123def |target=c|plain=false}}
* <code><nowiki>{{#invoke:string|find|abc 123 def|%s|plain=false}}</nowiki></code> → {{#invoke:string|find|abc 123 def|%s|plain=false}}

Testing for the presence of a string:
* <code>{{pf|ifexpr|<nowiki>{{#invoke:string|find|haystack|needle}}</nowiki>|Found needle|Didn't find needle}}</code> → {{#ifexpr:{{#invoke:string|find|haystack|needle}}|Found needle|Didn't find needle}}

=== findpagetext ===

The findpagetext function returns the position of a piece of text in the wikitext source of a page. It takes up to four parameters:
* First positional parameter or |text is the text to be searched for.
* Optional parameter |title is the page title, defaults to the current page.
* Optional parameter |plain is either true for a plain search (default), or false for a [[mw:Extension:Scribunto/Lua reference manual #Patterns|Lua pattern]] search.
* Optional parameter |nomatch is the value returned when no match is found; default is nothing.

; Examples
: <code><nowiki>{{#invoke:String |findpagetext |text=Youghiogheny}}</nowiki></code> → {{#invoke:String |findpagetext |text=Youghiogheny}}
: <code><nowiki>{{#invoke:String |findpagetext |text=Youghiogheny |nomatch=not found}}</nowiki></code> → {{#invoke:String |findpagetext |text=Youghiogheny |nomatch=not found}}
: <code><nowiki>{{#invoke:String |findpagetext |text=Youghiogheny |title=Boston Bridge |nomatch=not found}}</nowiki></code> → {{#invoke:String |findpagetext |text=Youghiogheny |title=Boston Bridge |nomatch=not found}}
: <code><nowiki>{{#invoke:String |findpagetext |text=river |title=Boston Bridge |nomatch=not found}}</nowiki></code> → {{#invoke:String |findpagetext |text=river |title=Boston Bridge |nomatch=not found}}
: <code><nowiki>{{#invoke:String |findpagetext |text=[Rr]iver |title=Boston Bridge |plain=false |nomatch=not found}}</nowiki></code> → {{#invoke:String |findpagetext |text=[Rr]iver |title=Boston Bridge |plain=false |nomatch=not found}}
: <code><nowiki>{{#invoke:String |findpagetext |text=%[%[ |title=Boston Bridge |plain=f |nomatch=not found}}</nowiki></code> → {{#invoke:String |findpagetext |text=%[%[ |title=Boston Bridge |plain=f |nomatch=not found}}
: <code><nowiki>{{#invoke:String |findpagetext |text=%{%{[Cc]oord |title=Boston Bridge |plain=f |nomatch=not found}}</nowiki></code> → {{#invoke:String |findpagetext |text=%{%{coord |title=Boston Bridge |plain=f |nomatch=not found}}
The search is case-sensitive, so Lua pattern matching is needed to find <code>river</code> or <code>River</code>. The last example finds <code><nowiki>{{coord</nowiki></code> and <code><nowiki>{{Coord</nowiki></code>. The penultimate example finds a wiki-link.

The [[Template:Findpagetext]] is a convenience wrapper for this function.

=== join ===

Joins all strings passed as arguments into one string, treating the first argument as a separator.

Usage:
: <code><nowiki>{{#invoke:</nowiki>String|join|''separator''|''string1''|''string2''|...<nowiki>}}</nowiki></code>
Parameters:
; separator
: String that separates each string being joined together
: Note that leading and trailing spaces are ''not'' stripped from the separator.
; string1/string2/...
: Strings being joined together
Examples:
* <code><nowiki>"{{#invoke:String|join|x|foo|bar|baz}}"</nowiki></code> → "{{#invoke:String|join|x|foo|bar|baz}}"
* <code><nowiki>"{{#invoke:String|join||a|b|c|d|e|f|g}}"</nowiki></code> → "{{#invoke:String|join||a|b|c|d|e|f|g}}"
* <code><nowiki>"{{#invoke:String|join|,|a|b|c|d|e|f|g}}"</nowiki></code> → "{{#invoke:String|join|,|a|b|c|d|e|f|g}}"
* <code><nowiki>"{{#invoke:String|join|, |a|b|c|d|e|f|g}}"</nowiki></code> → "{{#invoke:String|join|, |a|b|c|d|e|f|g}}"
* <code><nowiki>"{{#invoke:String|join| &ndash; |a|b|c|d|e|f|g}}"</nowiki></code> → "{{#invoke:String|join| &ndash; |a|b|c|d|e|f|g}}"
The preceding example uses the html entity &amp;ndash; but the unicode character also works.

=== len ===

This function returns the length of the target string.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|len|''target_string''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|len|s= ''target_string'' <nowiki>}}</nowiki></code>

Parameters:

; s
: The string whose length to report

Examples:

* <code><nowiki>{{#invoke:String|len| abcdefghi }}</nowiki></code> → {{#invoke:String|len| abcdefghi }}
* <code><nowiki>{{#invoke:String|len|s= abcdefghi }}</nowiki></code> → {{#invoke:String|len|s= abcdefghi }}

=== match ===

This function returns a substring from the source string that matches a specified pattern.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|match|''source_string''|''pattern_string''|''start_index''|''match_number''|''plain_flag''|''nomatch_output''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|match|s= ''source_string'' |pattern= ''pattern_string'' |start= ''start_index'' |match= ''match_number'' |plain= ''plain_flag'' |nomatch= ''nomatch_output'' <nowiki>}}</nowiki></code>

Parameters:

; s
: The string to search
; pattern
: The pattern or string to find within the string
; start
: The index within the source string to start the search. The first character of the string has index 1. Defaults to 1.
; match
: In some cases it may be possible to make multiple matches on a single string. This specifies which match to return, where the first match is match= 1. If a negative number is specified then a match is returned counting from the last match. Hence match = -1 is the same as requesting the last match. Defaults to 1.
; plain
: Boolean flag indicating that pattern should be understood as plain text and not as a [[mw:Extension:Scribunto/Lua reference manual#Ustring patterns|Scribunto ustring pattern]] (a unicode-friendly [[w:Lua|Lua]]-style [[w:regular expression|regular expression]]). Defaults to false (to change: <code>plain=true</code>)
; nomatch
: If no match is found, output the "nomatch" value rather than an error.
; ignore_errors
: If no match is found and ignore_errors=true, output an empty string rather than an error.

If the match_number or start_index are out of range for the string being queried, then this function generates an error. An error is also generated if no match is found.
If one adds the parameter ignore_errors=true, then the error will be suppressed and an empty string will be returned on any failure.

For information on constructing [[w:Lua|Lua]] patterns, a form of [[w:regular expression|regular expression]], see:

* [[mw:Special:MyLanguage/Extension:Scribunto/Lua reference manual#Patterns|Scribunto patterns]]
* [[mw:Special:MyLanguage/Extension:Scribunto/Lua reference manual#Ustring patterns|Scribunto Unicode string patterns]]

Examples:
* <code><nowiki>{{#invoke:String|match| abc123def456 |%d+}}</nowiki></code> → {{#invoke:String|match| abc123def456 |%d+}}
* <code><nowiki>{{#invoke:String|match|s= abc123def456 |pattern= %d+ }}</nowiki></code> → {{#invoke:String|match|s= abc123def456 |pattern= %d+ }}
* <code><nowiki>{{#invoke:String|match| abc123def456 |%d+|6}}</nowiki></code> → {{#invoke:String|match| abc123def456 |%d+|6}}
* <code><nowiki>{{#invoke:String|match|s= abc123def456 |pattern= %d+ |start= 6 }}</nowiki></code> → {{#invoke:String|match|s= abc123def456 |pattern= %d+ |start= 6 }}
* <code><nowiki>{{#invoke:String|match|s= abc123def456 |pattern= %d+ |start= 6 |match= 2 }}</nowiki></code> → {{#invoke:String|match|s= abc123def456 |pattern= %d+ |start= 6 |match= 2 }}
* <code><nowiki>{{#invoke:String|match|s= abc123%d+ |pattern= %d+ }}</nowiki></code> → {{#invoke:String|match|s= abc123%d+ |pattern= %d+ }}
* <code><nowiki>{{#invoke:String|match|s= abc123%d+ |pattern= %d+ |plain= true }}</nowiki></code> → {{#invoke:String|match|s= abc123%d+ |pattern= %d+ |plain= true }}
* <code><nowiki>{{#invoke:String|match|s= abc |pattern= %d }}</nowiki></code> → {{#invoke:String|match|s= abc |pattern= %d |no_category=true}}
* <code><nowiki>{{#invoke:String|match|s= abc |pattern= %d |nomatch= No numeric characters in string }}</nowiki></code> → {{#invoke:String|match|s= abc |pattern= %d |nomatch= No numeric characters in string }}
* <code><nowiki>{{#invoke:String|match|s= abc |pattern= %d |ignore_errors= true }}</nowiki></code> → {{#invoke:String|match|s= abc |pattern= %d |ignore_errors= true }}
* <code><nowiki>{{#invoke:String|match|s= 0012001200 |pattern= 0*(%d*) }}</nowiki></code> → {{#invoke:String|match|s= 0012001200 |pattern= 0*(%d*) }}

=== pos ===

This function returns a single character from the target string at position pos.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|pos|''target_string''|''index_value''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|pos|target= ''target_string'' |pos= ''index_value'' <nowiki>}}</nowiki></code>

Parameters:

; target
: The string to search
; pos
: The index for the character to return

The first character has an index value of 1.

If one requests a negative value, this function will select a character by counting backwards
from the end of the string. In other words pos = -1 is the same as asking for the last character.

A requested value of zero, or a value greater than the length of the string returns an error.

Examples:

* <code><nowiki>{{#invoke:String|pos| abcdefghi | 4 }}</nowiki></code> → {{#invoke:String|pos| abcdefghi | 4 }}
* <code><nowiki>{{#invoke:String|pos|target= abcdefghi |pos= 4 }}</nowiki></code> → {{#invoke:String|pos|target= abcdefghi |pos= 4 }}

=== rep ===

Repeats a string ''n'' times. A simple function to pipe string.rep to templates.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|rep|''source''|''count''<nowiki>}}</nowiki></code>

Parameters:

; source
: The string to repeat
; count
: The number of repetitions.

Examples:

* <code><nowiki>"{{#invoke:String|rep|hello|3}}"</nowiki></code> → "{{#invoke:String|rep|hello|3}}"
* <code><nowiki>"{{#invoke:String|rep| hello | 3 }}"</nowiki></code> → "{{#invoke:String|rep| hello | 3 }}"

=== <span class="anchor" id="replace"></span> replace (gsub) ===

{{notice|text=Note that by default the pattern is understood as plain text as the {{var|plain flag}} {{nowrap|{{para|plain}}}} defaults to {{pval|true}}. To use a [[mw:Extension:Scribunto/Lua reference manual#Ustring patterns|Scribunto mw.ustring pattern]] you must set it to {{pval|false}}.}}

This function allows one to replace a target string or pattern within another string. To Lua programmers: this function works internally by calling <code>[[mw:Extension:Scribunto/Lua_reference_manual#mw.ustring.gsub|mw.ustring.gsub]]</code>.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|replace|''source_str''|''pattern_string''|''replace_string''|''replacement_count''|''plain_flag''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|replace|source= ''source_string'' |pattern= ''pattern_string'' |replace= ''replace_string'' |count= ''replacement_count'' |plain= ''plain_flag'' <nowiki>}}</nowiki></code>

Parameters:

; source
: The string to search
; pattern
: The string or pattern to find within source
; replace
: The replacement text
; count
: The number of occurrences to replace; defaults to all
; plain
: Boolean flag indicating whether the pattern should be understood as plain text or as a [[mw:Extension:Scribunto/Lua reference manual#Ustring patterns|Scribunto ustring pattern]] (a unicode-friendly [[w:Lua|Lua]]-style [[w:regular expression|regular expression]]). Defaults to <code>true</code>. Pass parameter {{para|plain|false}} to use regular expressions.

Examples:

* <code><nowiki>"{{#invoke:String|replace| abc123def456 |123|XYZ}}"</nowiki></code> → "{{#invoke:String|replace| abc123def456 |123|XYZ}}"
* <code><nowiki>"{{#invoke:String|replace|source= abc123def456 |pattern= 123 |replace= XYZ }}"</nowiki></code> → "{{#invoke:String|replace|source= abc123def456 |pattern= 123 |replace= XYZ }}"
* <code><nowiki>"{{#invoke:String|replace| abc123def456 |%d+|XYZ|1|false}}"</nowiki></code> → "{{#invoke:String|replace| abc123def456 |%d+|XYZ|1|false}}"
* <code><nowiki>"{{#invoke:String|replace|source= abc123def456 |pattern= %d+ |replace= XYZ |count=1 |plain= false }}"</nowiki></code> → "{{#invoke:String|replace|source= abc123def456 |pattern= %d+ |replace= XYZ |count=1 |plain= false }}"
* <code><nowiki>"{{#invoke:String|replace|source= abc123def456 |pattern= %d+ |replace= XYZ |plain= false }}"</nowiki></code> → "{{#invoke:String|replace|source= abc123def456 |pattern= %d+ |replace= XYZ |plain= false }}"
* <code><nowiki>{{#invoke:String|replace|source= 0012001200 |pattern= ^0* |plain= false }}</nowiki></code> → {{#invoke:String|replace|source= 0012001200 |pattern= ^0* |plain= false }}

=== str_find ===

This function duplicates the behavior of {{tl|str_find}}, including all of its quirks. This is provided in order to support existing templates, but is NOT RECOMMENDED for new code and templates. New code is recommended to use the "find" function instead.

Returns the first index in "source" that is a match to "target". Indexing is 1-based, and the function returns -1 if the "target" string is not present in "source".

Important Note: If the "target" string is empty / missing, this function returns a value of "1", which is generally unexpected behavior, and must be accounted for separately.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|str_find|''source_string''|''target_string''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|str_find|source= ''source_string'' |target= ''target_string'' <nowiki>}}</nowiki></code>

Parameters:

; source
: The string to search
; target
: The string to find within source

Examples:
* <code><nowiki>{{#invoke:String|str_find| abc123def }}</nowiki></code> → {{#invoke:String|str_find| abc123def }}
* <code><nowiki>{{#invoke:String|str_find|source= abc123def }}</nowiki></code> → {{#invoke:String|str_find|source= abc123def }}
* <code><nowiki>{{#invoke:String|str_find| abc123def |123}}</nowiki></code> → {{#invoke:String|str_find| abc123def |123}}
* <code><nowiki>{{#invoke:String|str_find|source= abc123def |target= 123 }}</nowiki></code> → {{#invoke:String|str_find|source= abc123def |target= 123 }}
* <code><nowiki>{{#invoke:String|str_find| abc123def |not}}</nowiki></code> → {{#invoke:String|str_find| abc123def |not}}

=== sub ===

This function returns a substring of the target string at specified inclusive, one-indexed indices.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|sub|''target_string''|''start_index''|''end_index''<nowiki>}}</nowiki></code>

OR

: <code><nowiki>{{#invoke:</nowiki>String|sub|s= ''target_string'' |i= ''start_index'' |j= ''end_index'' <nowiki>}}</nowiki></code>

Parameters:

; s
: The string to return a subset of
; i
: The first index of the substring to return, defaults to 1.
; j
: The last index of the string to return, defaults to the last character.

The first character of the string is assigned an index of 1. If either i or j is a negative value, it is interpreted the same as selecting a character by counting from the end of the string. Hence, a value of -1 is the same as selecting the last character of the string.

If the requested indices are out of range for the given string, an error is reported. To avoid error messages, use {{ml|ustring|sub}} instead.

Examples:

* <code><nowiki>"{{#invoke:String|sub| abcdefghi }}"</nowiki></code> → "{{#invoke:String|sub| abcdefghi }}"
* <code><nowiki>"{{#invoke:String|sub|s= abcdefghi }}"</nowiki></code> → "{{#invoke:String|sub|s= abcdefghi }}"
* <code><nowiki>"{{#invoke:String|sub| abcdefghi | 3 }}"</nowiki></code> → "{{#invoke:String|sub| abcdefghi | 3 }}"
* <code><nowiki>"{{#invoke:String|sub|s= abcdefghi |i= 3 }}"</nowiki></code> → "{{#invoke:String|sub|s= abcdefghi |i= 3 }}"
* <code><nowiki>"{{#invoke:String|sub| abcdefghi | 3 | 4 }}"</nowiki></code> → "{{#invoke:String|sub| abcdefghi | 3 | 4 }}"
* <code><nowiki>"{{#invoke:String|sub|s= abcdefghi |i= 3 |j= 4 }}"</nowiki></code> → "{{#invoke:String|sub|s= abcdefghi |i= 3 |j= 4 }}"

=== sublength ===

This function implements the features of {{tl|str sub old}} and is kept in order to maintain these older templates. It returns a substring of the target string starting at a specified index and of a specified length.

Usage:

: <code><nowiki>{{#invoke:</nowiki>String|sublength|s= ''target_string'' |i= ''start_index'' |len= ''length'' <nowiki>}}</nowiki></code>

Parameters:

; s
: The string
; i
: The starting index of the substring to return. The first character of the string is assigned an index of 0.
; len
: The length of the string to return, defaults to the last character.

Examples:

* <code><nowiki>{{#invoke:String|sublength|s= abcdefghi }}</nowiki></code> → {{#invoke:String|sublength|s= abcdefghi }}
* <code><nowiki>{{#invoke:String|sublength|s= abcdefghi |i= 3 }}</nowiki></code> → {{#invoke:String|sublength|s= abcdefghi |i= 3 }}
* <code><nowiki>{{#invoke:String|sublength|s= abcdefghi |i= 3 |len= 4 }}</nowiki></code> → {{#invoke:String|sublength|s= abcdefghi |i= 3 |len= 4 }}

== See also==
* {{mfl|Params|mapping_by_replacing}} and other functions from the same module
* {{mfl|MultiReplace|main}}

{{String handling templates}}
<includeonly>{{Sandbox other||
[[Category:Modules that add a tracking category]]
[[Category:Modules that manipulate strings|*]]
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