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string.gsub

Summary

Substitute strings inside another string

Prototype

s, n = string.gsub (str, pattern, replacement, n)


Description

Returns a copy of str with matches to 'pattern' replaced by 'replacement', for a maximum of n times.
As a second result it returns the number of matches made.

'replacement' can be a string in which case it simply replaces the matching pattern. However %1 through to %9 in the replacement pattern can refer to captured strings in the source pattern. %% becomes %. Also, %0 in the replacement pattern refers to the entire matching string.

If 'replacement' is a function it is called for each match with the matching string as an argument. It should return a string which is the string to replace it with. If it returns nil the original string is retained.

If 'replacement' is a table then the matching string is looked up in the table for each match, and if found, the replacement is substituted.

See string.find for an explanation of regular expressions.


string.gsub ("nick eats fish", "fish", "chips") --> nick eats chips

-- example of using a function as the replacement

replacements = { 
   ["nice"] = "windy",
   ["walk"] = "stroll",
   }
   
s = "a nice long walk"

result = string.gsub (s, "%a+", 
  function (str)
  return replacements [str]
  end
  )

print (result) --> a windy long stroll

-- An alternative way of doing a table replacement using the above table:

result = string.gsub (s, "%a+", replacements)

print (result) --> a windy long stroll

-- You can call inbuilt functions too:

s = "a nice long walk"

result = string.gsub (s, "%f[%a]%a%a", string.upper)

print (result) --> a NIce LOng WAlk



If you need to search for something that is not a regular expression, you need to "fix up" the search string first. This should do it:


search = string.gsub (search, "[%%%]%^%-$().[*+?]", "%%%1")


The code above fixes all of the special characters recognized in a regular expression by preceding them with a percent symbol.


See Also ...

Lua functions

string.byte - Converts a character into its ASCII (decimal) equivalent
string.char - Converts ASCII codes into their equivalent characters
string.dump - Converts a function into binary
string.find - Searches a string for a pattern
string.format - Formats a string
string.gfind - Iterate over a string (obsolete in Lua 5.1)
string.gmatch - Iterate over a string
string.len - Return the length of a string
string.lower - Converts a string to lower-case
string.match - Searches a string for a pattern
string.rep - Returns repeated copies of a string
string.reverse - Reverses the order of characters in a string
string.sub - Returns a substring of a string
string.upper - Converts a string to upper-case

Topics

Lua base functions
Lua bc (big number) functions
Lua bit manipulation functions
Lua coroutine functions
Lua debug functions
Lua io functions
Lua LPEG library
Lua math functions
Lua os functions
Lua package functions
Lua PCRE regular expression functions
Lua script extensions
Lua string functions
Lua syntax
Lua table functions
Lua utilities
Regular Expressions
Scripting
Scripting callbacks - plugins

(Help topic: lua=string.gsub)

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