Module:String/doc

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 automatically removes 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 results 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 is 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.

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

Boolean flag indicating that pattern should be understood as plain text and not as a Lua-style regular expression. 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 is suppressed and an empty string returned on any failure.

For information on constructing Lua patterns, a form of regular expression, see:

• Lua reference: Patterns (as of version 5.1)
• Scribunto patterns
• Scribunto Unicode string 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 selects 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.

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 occurrences to replace; defaults to all

plain

Boolean flag indicating that pattern should be understood as plain text and not as a Scribunto ustring pattern (a unicode-friendly Lua-style regular expression); defaults to true

rep

Repeats a string

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

reverse

Reverse a string

Usage:

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

OR

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

Parameters

s

The string to reverse