Why is printf("%8d\n", intval);
not working for you? It should…
You did not show the format strings for any of your “not working” examples, so I’m not sure what else to tell you.
#include <stdio.h>
int
main(void)
{
int i;
for (i = 1; i <= 10000; i*=10) {
printf("[%8d]\n", i);
}
return (0);
}
$ ./printftest
[ 1]
[ 10]
[ 100]
[ 1000]
[ 10000]
EDIT: response to clarification of question:
#include <math.h>
int maxval = 1000;
int width = round(1+log(maxval)/log(10));
...
printf("%*d\n", width, intval);
The width calculation computes log base 10 + 1, which gives the number of digits. The fancy *
allows you to use the variable for a value in the format string.
You still have to know the maximum for any given run, but there’s no way around that in any language or pencil & paper.