c - Variable sized padding in printf

Question

Is there a way to have a variable sized padding in printf?

I have an integer which says how large the padding is:

void foo(int paddingSize) {
    printf("%...MyText", paddingSize);
}

This should print out ### MyText where the paddingSize should decide the number of '#' symbols.

Answer 1

Yes, if you use * in your format string, it gets a number from the arguments:

printf ("%0*d
", 3, 5);

will print "005".

Keep in mind you can only pad with spaces or zeros. If you want to pad with something else, you can use something like:

#include <stdio.h>
#include <string.h>
int main (void) {
    char *s = "MyText";
    unsigned int sz = 9;
    char *pad = "########################################";
    printf ("%.*s%s
", (sz < strlen(s)) ? 0 : sz - strlen(s), pad, s);
}

This outputs ###MyText when sz is 9, or MyText when sz is 2 (no padding but no truncation). You may want to add a check for pad being too short.