fprintf question

Question

I am not asking how to do file I/O, its just more of a formatting question. I need to write a variable number of characters to a file. For example, lets say I want to print 3 characters. "TO" would print "TO" to a file. "LongString of Characters" would print "Lon" to a file.

How can I do this? (the number of characters is defined in another variable). I know that this is possible fprintf(file,"%10s",string), but that 10 is predefined

Answer 1

This one corresponds to your example:

fprintf(file, "%*s", 10, string);

but you mentioned a maximum as well, to also limit the number:

fprintf(file, "%*.*s", 10, 10, string);

Answer 2

I believe you need "%*s" and you'll need to pass the length as an integer before the string.

Answer 3

As an alternative, why not try this:

void print_limit(char *string, size_t num)
{
  char c = string[num];
  string[num] = 0;
  fputs(string, file);
  string[num] = c;
}

Temporarily truncates the string to the length you want and then restores it. Sure, it's not strictly necessary, but it works, and it's quite easy to understand.