String Functions in Lua

Lua’s standard library provides many useful string-related functions. Here are some examples to give you a sense of the available operations.

-- We'll use a shorthand for print to keep the examples concise
local p = print

-- Here's a sample of the string functions available in Lua.
-- Note that in Lua, string functions are methods on the string object itself,
-- unlike in some other languages where they might be separate functions.

p("Contains:  ", string.find("test", "es") ~= nil)
p("Count:     ", select(2, string.gsub("test", "t", "")) + 1)
p("HasPrefix: ", string.sub("test", 1, 2) == "te")
p("HasSuffix: ", string.sub("test", -2) == "st")
p("Index:     ", string.find("test", "e"))
p("Join:      ", table.concat({"a", "b"}, "-"))
p("Repeat:    ", string.rep("a", 5))
p("Replace:   ", string.gsub("foo", "o", "0"))
p("Replace:   ", (string.gsub("foo", "o", "0", 1)))
p("Split:     ", string.gmatch("a-b-c-d-e", "[^-]+"))
p("ToLower:   ", string.lower("TEST"))
p("ToUpper:   ", string.upper("test"))

When you run this script, you’ll see output similar to:

$ lua string_functions.lua
Contains:   true
Count:      2
HasPrefix:  true
HasSuffix:  true
Index:      2
Join:       a-b
Repeat:     aaaaa
Replace:    f00
Replace:    f0o
Split:      function: 0x55f8f8c64cb0
ToLower:    test
ToUpper:    TEST

Note that the Split function in Lua returns an iterator, not a table, so we print the function itself. To use it, you would typically use it in a for loop:

for word in string.gmatch("a-b-c-d-e", "[^-]+") do
    print(word)
end

This would print each word on a separate line.

Lua’s string manipulation capabilities are quite powerful, and many operations can be performed using pattern matching with string.gsub and string.gmatch. For more complex string operations, you might want to look into additional libraries or write custom functions.

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String Functions in Lua