Lua:
Finding the length of a string

How to:

In Lua, you grab the length of a string with the # operator. Simple and snappy.

local myString = "Hello, Lua!"
print(#myString)  -- Output: 11

What if your string has newline characters or is empty?

local stringWithNewline = "Hello\nLua!"
local emptyString = ""
print(#stringWithNewline)  -- Output: 10
print(#emptyString)         -- Output: 0

Even with newlines, Lua counts each character. And yes, an empty string is 0 long.

Deep Dive

Back in the day, strings in some languages were trickier. You might have needed functions or methods to get a string’s length. Today, in Lua, it’s as direct as using the # operator.

Alternatives? If you’re dealing with Unicode characters, the # operator might trip up with multi-byte characters. In that case, you’d explore libraries like utf8. Lua 5.3 onwards introduced this built-in library.

local unicodeString = "こんにちは" -- That's "Hello" in Japanese
print(#unicodeString)  -- Output might be surprising if you're not ready for multibyte characters!
print(utf8.len(unicodeString))  -- Output: 5 characters as expected

A detail worth noting: Lua keeps strings immutable and internally reused through a mechanism called string interning. This is neat because it saves memory and makes string length operations fast.

See Also

• Lua 5.4 Reference Manual: String manipulation – https://www.lua.org/manual/5.4/manual.html#6.4
• utf8.len function – Dive into handling Unicode strings properly – https://www.lua.org/manual/5.4/manual.html#pdf-utf8.len
• Some Lua history and string interning info – https://www.lua.org/doc/hopl.pdf