This Lua module is used in system messages, and onapproximately 14,200,000 pages, or roughly 22% of all pages. Changes to it can cause immediate changes to the Wikipedia user interface. To avoid major disruption and server load, any changes should be tested in the module's/sandbox or/testcases subpages, or in your ownmodule sandbox. The tested changes can be added to this page in a single edit. Please discuss changes on thetalk page before implementing them.

Thismodule is rated asready for general use. It has reached a mature state, is considered relatively stable and bug-free, and may be used wherever appropriate. It can be mentioned onhelp pages and other Wikipedia resources as an option for new users. To minimise server load and avoid disruptive output, improvements should be developed throughsandbox testing rather than repeated trial-and-error editing.

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Module:String (edit |talk |history |links |watch |logs)

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.

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 isCategory:Errors reported by Module String (17).

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 atModule:String/testcases.

This function returns the length of the target string.

Usage:

{{#invoke:String|len|target_string}}

OR

{{#invoke:String|len|s=target_string }}

Parameters:

s

The string whose length to report

Examples:

• {{#invoke:String|len| abcdefghi }} → 11
• {{#invoke:String|len|s= abcdefghi }} → 9

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

Usage:

{{#invoke:String|sub|target_string|start_index|end_index}}

OR

{{#invoke:String|sub|s=target_string |i=start_index |j=end_index }}

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 {{#invoke:ustring|sub}} instead.

Examples:

• "{{#invoke:String|sub| abcdefghi }}" → " abcdefghi "
• "{{#invoke:String|sub|s= abcdefghi }}" → "abcdefghi"
• "{{#invoke:String|sub| abcdefghi | 3 }}" → "bcdefghi "
• "{{#invoke:String|sub|s= abcdefghi |i= 3 }}" → "cdefghi"
• "{{#invoke:String|sub| abcdefghi | 3 | 4 }}" → "bc"
• "{{#invoke:String|sub|s= abcdefghi |i= 3 |j= 4 }}" → "cd"

This function implements the features of{{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:

{{#invoke:String|sublength|s=target_string |i=start_index |len=length }}

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:

• {{#invoke:String|sublength|s= abcdefghi }} → abcdefghi
• {{#invoke:String|sublength|s= abcdefghi |i= 3 }} → defghi
• {{#invoke:String|sublength|s= abcdefghi |i= 3 |len= 4 }} → defg

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

Usage:

{{#invoke:String|match|source_string|pattern_string|start_index|match_number|plain_flag|nomatch_output}}

OR

{{#invoke:String|match|s=source_string |pattern=pattern_string |start=start_index |match=match_number |plain=plain_flag |nomatch=nomatch_output }}

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 aScribunto ustring pattern (a unicode-friendlyLua-styleregular expression). Defaults to false (to change:plain=true)

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 constructingLua patterns, a form ofregular expression, see:

• Scribunto patterns
• Scribunto Unicode string patterns

Examples:

• {{#invoke:String|match| abc123def456 |%d+}} → 123
• {{#invoke:String|match|s= abc123def456 |pattern= %d+ }} → 123
• {{#invoke:String|match| abc123def456 |%d+|6}} → 23
• {{#invoke:String|match|s= abc123def456 |pattern= %d+ |start= 6 }} → 3
• {{#invoke:String|match|s= abc123def456 |pattern= %d+ |start= 6 |match= 2 }} → 456
• {{#invoke:String|match|s= abc123%d+ |pattern= %d+ }} → 123
• {{#invoke:String|match|s= abc123%d+ |pattern= %d+ |plain= true }} → %d+
• {{#invoke:String|match|s= abc |pattern= %d }} →String Module Error: Match not found
• {{#invoke:String|match|s= abc |pattern= %d |nomatch= No numeric characters in string }} → No numeric characters in string
• {{#invoke:String|match|s= abc |pattern= %d |ignore_errors= true }} →
• {{#invoke:String|match|s= 0012001200 |pattern= 0*(%d*) }} → 12001200

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

Usage:

{{#invoke:String|pos|target_string|index_value}}

OR

{{#invoke:String|pos|target=target_string |pos=index_value }}

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 backwardsfrom 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:

• {{#invoke:String|pos| abcdefghi | 4 }} → c
• {{#invoke:String|pos|target= abcdefghi |pos= 4 }} → d

This function duplicates the behavior of{{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:

{{#invoke:String|str_find|source_string|target_string}}

OR

{{#invoke:String|str_find|source=source_string |target=target_string }}

Parameters:

source

The string to search

target

The string to find within source

Examples:

• {{#invoke:String|str_find| abc123def }} → 1
• {{#invoke:String|str_find|source= abc123def }} → 1
• {{#invoke:String|str_find| abc123def |123}} → 5
• {{#invoke:String|str_find|source= abc123def |target= 123 }} → 4
• {{#invoke:String|str_find| abc123def |not}} → -1

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

Usage:

{{#invoke:String|find|source_string|target_string|start_index|plain_flag}}

OR

{{#invoke:String|find|source=source_string |target=target_string |start=start_index |plain=plain_flag }}

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 aScribunto ustring pattern (a unicode-friendlyLua-styleregular 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:

• {{#invoke:String|find|abc123def|12}} → 4
• {{#invoke:String|find|source=abc123def|target=12}} → 4
• {{#invoke:String|find|source=abc123def|target=pqr}} → 0
• {{#invoke:String|find| abc123def |123}} → 5
• {{#invoke:String|find|source= abc123def |target= 123 }} → 4
• {{#invoke:String|find|source=abc123def|target=%d |start=3 |plain=false }} → 4

When using unnamed parameters, preceding and trailing spaces are kept and counted:

• {{#invoke:String|find| abc123def |c|false}} → 5
• {{#invoke:String|find|source= abc123def |target=c|plain=false}} → 3
• {{#invoke:string|find|abc 123 def|%s|plain=false}} → 4

Testing for the presence of a string:

• {{#ifexpr:{{#invoke:string|find|haystack|needle}}|Found needle|Didn't find needle}} → Didn't find needle

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 aLua pattern search.
• Optional parameter |nomatch is the value returned when no match is found; default is nothing.

Examples

{{#invoke:String |findpagetext |text=Youghiogheny}} → 14146

{{#invoke:String |findpagetext |text=Youghiogheny |nomatch=not found}} → 14146

{{#invoke:String |findpagetext |text=Youghiogheny |title=Boston Bridge |nomatch=not found}} → 373

{{#invoke:String |findpagetext |text=river |title=Boston Bridge |nomatch=not found}} → not found

{{#invoke:String |findpagetext |text=[Rr]iver |title=Boston Bridge |plain=false |nomatch=not found}} → 386

{{#invoke:String |findpagetext |text=%[%[ |title=Boston Bridge |plain=f |nomatch=not found}} → 371

{{#invoke:String |findpagetext |text=%{%{[Cc]oord |title=Boston Bridge |plain=f |nomatch=not found}} → 2553

The search is case-sensitive, so Lua pattern matching is needed to findriver orRiver. The last example finds{{coord and{{Coord. The penultimate example finds a wiki-link.

TheTemplate:Findpagetext is a convenience wrapper for this function.

Note that by default the pattern is understood as plain text as theplain flag|plain= defaults totrue. To use aScribunto mw.ustring pattern you must set it tofalse.

This function allows one to replace a target string or pattern within another string. To Lua programmers: this function works internally by callingmw.ustring.gsub.

Usage:

{{#invoke:String|replace|source_str|pattern_string|replace_string|replacement_count|plain_flag}}

OR

{{#invoke:String|replace|source=source_string |pattern=pattern_string |replace=replace_string |count=replacement_count |plain=plain_flag }}

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 that pattern should be understood as plain text and not as aScribunto ustring pattern (a unicode-friendlyLua-styleregular expression); defaults to true

Examples:

• "{{#invoke:String|replace| abc123def456 |123|XYZ}}" → " abcXYZdef456 "
• "{{#invoke:String|replace|source= abc123def456 |pattern= 123 |replace= XYZ }}" → "abcXYZdef456"
• "{{#invoke:String|replace| abc123def456 |%d+|XYZ|1|false}}" → " abcXYZdef456 "
• "{{#invoke:String|replace|source= abc123def456 |pattern= %d+ |replace= XYZ |count=1 |plain= false }}" → "abcXYZdef456"
• "{{#invoke:String|replace|source= abc123def456 |pattern= %d+ |replace= XYZ |plain= false }}" → "abcXYZdefXYZ"
• {{#invoke:String|replace|source= 0012001200 |pattern= ^0* |plain= false }} → 12001200

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

Usage:

{{#invoke:String|rep|source|count}}

Parameters:

source

The string to repeat

count

The number of repetitions.

Examples:

• "{{#invoke:String|rep|hello|3}}" → "hellohellohello"
• "{{#invoke:String|rep| hello | 3 }}" → " hello hello hello "

In aLua pattern, changes aclass character into aliteral character. For example: in a pattern, character. catches "any character"; escapePattern will convert it to%., catching just the literal character ".".

Usage:

• {{#invoke:String|escapePattern|pattern_string}}

Parameters:

pattern_string

The pattern string to escape

Examples:

• "{{#invoke:String|escapePattern|A.D.}}" → "A%.D%."
• "{{#invoke:String|escapePattern|10%}}" → "10%%"

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

Usage:

{{#invoke:String|count|source_str|pattern_string|plain_flag}}

OR

{{#invoke:String|count|source=source_string |pattern=pattern_string|plain=plain_flag }}

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 aScribunto ustring pattern (a unicode-friendlyLua-styleregular expression); defaults to true

Examples:

• Count of 'a':"{{#invoke:String|count|aabbcc|a}}" → "2"
• Count occurrences of 'aba':"{{#invoke:String|count|ababababab|aba}}" → "2"
• Count of "either 'a' or 'c' ":"{{#invoke:String|count|aabbcc|[ac]|plain=false}}" → "4"
• Count of "not 'a' ":"{{#invoke:String|count|aaabaaac|[^a]|plain=false}}" → "2"
• Count of "starts with 'a' ":"{{#invoke:String|count|aaabaaac|^a|plain=false}}" → "1"

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

Usage:

{{#invoke:String|join|separator|string1|string2|...}}

Parameters:

separator

String that separates each string being joined together

Note that leading and trailing spaces arenot stripped from the separator.

string1/string2/...

Strings being joined together

Examples:

• "{{#invoke:String|join|x|foo|bar|baz}}" → "fooxbarxbaz"
• "{{#invoke:String|join||a|b|c|d|e|f|g}}" → "abcdefg"
• "{{#invoke:String|join|,|a|b|c|d|e|f|g}}" → "a,b,c,d,e,f,g"
• "{{#invoke:String|join|, |a|b|c|d|e|f|g}}" → "a, b, c, d, e, f, g"
• "{{#invoke:String|join| – |a|b|c|d|e|f|g}}" → "a – b – c – d – e – f – g"

The preceding example uses the html entity – but the unicode character also works.

Usage:

{{#invoke:String|endswith|source_str|search_string}}

OR

{{#invoke:String|endswith|source=source_string |pattern=search_string}}

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.

• "{{#invoke:String|endswith|xxxyyy|y}}" → "yes"
• "{{#invoke:String|endswith|xxxyyy|z}}" → ""

• {{#invoke:Params|mapping_by_replacing}} and other functions from the same module
• {{#invoke:MultiReplace|main}}