11.10.1 printf Formats

Format specifiers for printf and sprintf have the following form:

% [flag ][width ][. precision ]letter

The control letter is required. The format conversion control letters are as follows.

Character	Description
c	ASCII character
d	Decimal integer
i	Decimal integer (added in POSIX)
e	Floating-point format ([-]d .precision e [+-]dd )
E	Floating-point format ([-]d .precision E [+-]dd )
f	Floating-point format ([-]ddd .precision )
g	e or f conversion, whichever is shortest, with trailing zeros removed
G	E or f conversion, whichever is shortest, with trailing zeros removed
o	Unsigned octal value
s	String
x	Unsigned hexadecimal number; uses a -f for 10 to 15
X	Unsigned hexadecimal number; uses A -F for 10 to 15
%	Literal %

The optional flag is one of the following.

Character	Description
-	Left-justify the formatted value within the field.
space	Prefix positive values with a space and negative values with a minus.
+	Always prefix numeric values with a sign, even if the value is positive.
#	Use an alternate form: %o has a preceding 0 ; %x and %X are prefixed with 0x and 0X , respectively; %e , %E , and %f always have a decimal point in the result; and %g and %G do not have trailing zeros removed.
0	Pad output with zeros, not spaces. This happens only when the field width is wider than the converted result.

The optional width is the minimum number of characters to output. The result will be padded to this size if it is smaller. The 0 flag causes padding with zeros; otherwise, padding is with spaces.

The precision is optional. Its meaning varies by control letter, as shown in this table.

Conversion	Precision Means
%d , %i , %o	The minimum number of digits to print
%u , %x , %X
%e , %E , %f	The number of digits to the right of the decimal point
%g , %G	The maximum number of significant digits
%s	The maximum number of characters to print