Urldecode string (LUA)

Sometimes, particularly when using LUA OpenResty, in may be necessary to url unencode/unescape a string, so that reserved characters are converted back to their literal representations. This is particularly useful as the value if ngx.var.arg_ variables are not automatically url unencoded

This snippet creates a function to do hex decode each character of a string

Similar To

• urldecode() PHP
• urllib.unquote() Python
• decodeURI() Javascript

Details

• Language: LUA

Snippet

local urldecode = function(url)
  return (url:gsub("%%(%x%x)", function(x)
    return string.char(tonumber(x, 16))
    end))
end

Usage Example

local urldecode = function(url)
  return (url:gsub("%%(%x%x)", function(x)
    return string.char(tonumber(x, 16))
    end))
end

local s='a%20b%20c'
print(urldecode(s))
-- a b c

-- Or to decode the query string value of argument 'foo' in OpenResty
ngx.print(urldecode(ngx.var.arg_foo))