Lua string.format Cheat Sheet

A Programming › Nope cheat sheet in English by ambigious

A quick reference for Lua's standard library string.format function.

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PRs

Function Call

string.format(formatstring, ...args)

Specifier

Input	Description	Example
g	Auto^†	384.63
G	Auto (uppercase)^†	386
d or i	Signed decimal	-392
u	Unsigned decimal	1483
f	Decimal float	392.65
o	Unsigned octal	610
x	Unsigned hex	7fa
X	Unsigned hex (uppercase)	7FA
a	Hex float	-0xc.90fep-2
A	Hex float (uppercase)	-0XC.90FEP-2
e	Scientific notation	3.9265e+2
E	Scientific notation (uppercase)	3.9265E+2
c	Character	d
s	String	Hello world
p	Pointer	b8000000
%	Literal "%"	%

Specifier determines the string format type.
^†Auto choses between the more reasonable of e or f.

Q Specifier

The Q specifier does not support flags, width, or precision. It outputs Lua values so that it is valid Lua code.
Booleans are written obviously, true, false, nil.
Strings are written with double quotes and escape sequences where necessary.

For example, string.format('%q', 'a string with "quotes" and \n new line') produces:
"a string with \"quotes\" and \
new line"

Reference

Lua Manual

Wikipedia

Format Specifier

%[flags][width][.precision]specifier

Values are formatted and replaced sequentially with ...args.
Only one input can be entered for each argument.
Note the dot before precision.

Flags

'	Group number by thousands.
-	Left justify, see *width*.
0	Pads with 0s instead of spaces, see *width*.
+	Adds a + sign for positive numbers.
(space)	Inserts a space if there is no sign.
#	For o, x, X: Add 0, 0x, 0X to non-zero numbers. For a, A, e, E, f, F, g, G: Always write a decimal point.

Width

Minimum number of characters to be printed.
If the value is shorter:
The value is padded, affected by - and 0 flags.
If the value is longer:
No truncation happens, note minimum.

Precision

For d, i, o, u, x, X (integers):
Minimum number of digits, no truncation happens. If the value is shorter, 0-padding happens on the left side. If set to zero, nothing is written for 0.
For a, A, e, E, f, F (floats):
Number of decimal digits to be printed. Defaults to 6.
For g, G:
Maximum number of significant digits.
For s:
Maximum number of characters to be printed. By default all characters are printed.

Don't forget the dot!
If the period is specified without a value for precision, 0 is assumed.

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