Module:String/doc

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This is the documentation page for Module:String

This module is rated as ready for general use. It has reached a mature form and is thought to be bug-free and ready for use wherever appropriate. To reduce server load and bad output, it should be improved by sandbox testing rather than repeated trial-and-error editing.

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This Lua module is used in system messages.
Changes to it can cause immediate changes to the Wikimedia user interface.
To avoid major disruption, any changes should be tested in the module's /sandbox or /testcases subpages, or in your own module sandbox. The tested changes can be added to this page in a single edit. Please discuss changes on the talk page before implementing them.

Module:string (talk · edit · hist · links · doc · subpages · tests / results · sandbox · all modules)

This module is intended to provide access to basic string functions

Template:Str crop
Template:Str endswith
Template:Str find
Template:Str if empty
Template:Str index
Template:Str index any
Template:Str index/getchar

Template:Str index/logic
Template:Str left
Template:Str len/core
Template:Str letter/trim
Template:Str mulrepc
Template:Str num char
Template:Str rep

Template:Str repc
Template:Str right
Template:Str rightc
Template:Str rightmost
Template:Str ≤ len
Template:Str ≤ ≥ len
Template:Str ≥ len

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.
For example, when a pattern should be replaced by something, that replacement may be wished by a space (whitespace), or by an empty string (removed whtespace).

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 Category: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.

len

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

sub

This function returns a substring of the target string at specified 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.

sublength

This function implements the features of {{Str sub old}} and is kept in order to maintain these older templates.

match

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: A flag indicating that the pattern should be understood as plain text. Defaults to false.
nomatch: If no match is found, output the "nomatch" value 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 Lua patterns, a form of regular expression, see:

http://www.lua.org/manual/5.1/manual.html#5.4.1
Extension:Scribunto/Lua_reference_manual#Patterns#patterns
Extension:Scribunto/Lua_reference_manual#Ustring patterns#ustring patterns

pos

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 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.

str_find

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 separatetly.

find

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

Usage:

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

OR

{{#invoke:String|find|source=source_str|target=target_str|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 a Lua-style 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.

replace

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

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 occurences to replace, defaults to all.
plain: Boolean flag indicating that pattern should be understood as plain text and not as a Lua-style regular expression, defaults to true

rep

Repeats a string n 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.

Example {{#invoke:String|rep|hello|3}} gives hellohellohello

isNumber

Checks if string is a number Usage:

{{#invoke:String|isNumber|string}}

Parameters:

string: The string to test

Example {{#invoke:String|isNumber|hello}} gives 0, while {{#invoke:String|isNumber|-200e-5}} gives 1