About printf format string in C
Let's take the following program:
#include <stdio.h>
int main()
{
long t =57 ;
printf("[%+03ld]", t);
}
and outputs:
[+57]
I'm kind of confused: I told him to overlay the output to a width of 3 ( 03ld
) with zeros, however it seems that if I force the output to put a plus sign in front of the number ( +
), it won't add zero zeros if the number is already 2 digits long (as in 57). For numbers <10, it contains 1 zero.
From http://www.cplusplus.com/reference/cstdio/printf/
(0) → Stops a number with zeros (0) instead of spaces when padding is given (see width specifier).
(+) → Forcibly exceed the result with a plus or minus sign (+ or -) even for positive numbers. By default, only negative numbers are preceded by an a.
(width) → Minimum number of characters to print. If the value to be printed is less than this number, the result will be filled with spaces. The value is not truncated even if the result is larger.
So I just need clarification ... Does the specifier (width)
from the above quote refer to the full length of the output string (i.e.: characters to be printed) controlled by that format specifier ( "%+03ld"
), or the full character length of the number to be printed?
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C is pretty accurate that the converted value is taken as an integer. From C11 §7.21.6 / 2 (emphasis mine):
The function
fprintf
writes output tostream
, pointed tostream
, controlled by the string pointed to by the format, which determines how subsequent arguments are converted for output .
together with §7.21.6 / 4:
Optional minimum field width. If the converted value is less characters than the field width, it is padded with spaces (by default) to the left (or right if the left adjustment checkbox described below)) to the field width. The field width takes the form of an asterisk * (described below) or a non-negative decimal integer.
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