In Lua (I can only find examples in other languages), how do I remove all punctuation, special characters and whitespace from a string? So, for example, s t!r@i%p^(p,e"d would become stripped?
In Lua patterns, the character class %p represents all punctuation characters, the character class %c represents all control characters, and the character class %s represents all whitespace characters. So you can represent all punctuation characters, all control characters, and all whitespace characters with the set [%p%c%s].
To remove these characters from a string, you can use string.gsub. For a string str, the code would be the following:
str = str:gsub('[%p%c%s]', '')
(Note that this is essentially the same as Egor's code snippet above.)
