Variable length format string in c

Question

I want to align a text with the help of a variable using the .* format specifier.

Ideally I wanted a space of 100 length with Some Text Here written and then the | sign. But this doesn't seem to work.

#include <stdio.h>

int main()
{
    int prec = 100; // Assume this value to be calculated somehow and not a constant
    char s[20] = "Some Text Here";
    printf("%.*s", prec, s);
    printf("|");

    return 0;
}

Why is this so?

Thanks in Advance.

Your code is almost correct, you just need %*s, not %.*s — aragaer
– aragaer, Commented Dec 2, 2020 at 20:05
Replace %.*s with %*s (right aligned) or %-*s (left aligned) — Kevin
– Kevin, Commented Dec 2, 2020 at 20:05
Just number is "field width", while number after '.' is "precision". These two have different meanings (and can be used together). See man 3 printf for details. — aragaer
– aragaer, Commented Dec 2, 2020 at 20:07

ant0n7 · Accepted Answer · 2020-12-02 20:42:18Z

2

The mistake is, that you try to do a precision like with a float (n decimal places). That won't work with a string. You will need to do %*s, not %.*s

answered Dec 2, 2020 at 20:42

ant0n7

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