string.gsub() for Substitution

When working with strings, you often need to find and replace text. Lua's string.gsub() function makes this easy by performing global substitution—finding all occurrences of a pattern and replacing them with something else.

The basic syntax takes three arguments: the original string, the pattern to find, and the replacement text:

local result = string.gsub(originalString, pattern, replacement)

Here's a simple example that replaces all spaces with underscores:

local text = "hello world from lua"
local cleaned = string.gsub(text, " ", "_")
print(cleaned)  -- Output: hello_world_from_lua

The function returns two values: the modified string and the number of replacements made. You can capture both if needed:

local result, count = string.gsub("foo bar foo", "foo", "baz")
print(result)  -- Output: baz bar baz
print(count)   -- Output: 2

Unlike some string functions that only find the first match, string.gsub() replaces every occurrence by default, making it perfect for text-cleaning tasks like removing unwanted characters or standardizing formatting.