Strings

Creating strings

local single = 'It said "hi"'
local double = "It's here"
local escaped = "Tab:\tNew line:\nEnd"
local long = [[
Line one
Line two with \n not escaped]]

print(single)
print(double)
print(escaped)
print(long)

It said "hi"
It's here
Tab:	New line:
End
Line one
Line two with \n not escaped

• Single and double quotes are equivalent — use one to contain the other.
• Escapes: \n newline, \t tab, \\ backslash, \" quote.
• [[ ... ]] is a long string: it can span lines and doesn't process escapes. A newline right after [[ is skipped. Use [==[ ... ]==] if the text contains ]].

Joining and length

local first, last = "Ada", "Lovelace"
local full = first .. " " .. last
print(full)
print(#full)
print("Score: " .. 42)

Ada Lovelace
12
Score: 42

.. concatenates; # gives the length in bytes.

Formatting

local name, age, price = "Ada", 36, 1234.5
print(string.format("%s is %d years old", name, age))
print(string.format("Price: %.2f", price))
print(string.format("[%-6s|%5d]", name, age))
print(string.format("%05.1f%%", 7.5))
print(string.format("%q", 'say "hi"'))

Ada is 36 years old
Price: 1234.50
[Ada   |   36]
007.5%
"say \"hi\""

string.format uses C's printf codes: %s string, %d integer, %.2f two decimals, -6 left-aligned width 6, %% a literal percent sign, and %q a quoted, escaped string.

Strings are immutable

String functions return new strings; the original never changes. Building a long string with .. in a loop is slow, because each step copies the whole string — collect the pieces in a table and use table.concat instead (see the Table Library lesson).

Unicode

Lua strings are sequences of bytes, so #"héllo" is 6, not 5. The utf8 library handles UTF-8 text:

local word = "héllo"
print(#word)
print(utf8.len(word))
for _, code in utf8.codes("hé") do
  print(code, utf8.char(code))
end

6
5
104	h
233	é