printf string, variable length item
#define SIZE 9
int number=5;
char letters[SIZE]; /* this wont be null-terminated */
...
char fmt_string[20];
sprintf(fmt_string, "%%d %%%ds", SIZE);
/* fmt_string = "%d %9d"... or it should be */
printf(fmt_string, number, letters);
Is there a better way to do this?
Answer
There is no need to construct a special format string. printf allows you to specify the precision using a parameter (that precedes the value) if you use a .* as the precision in the format tag.
For example:
printf ("%d %.*s", number, SIZE, letters);
Note: there is a distinction between width (which is a minimum field width) and precision (which gives the maximum number of characters to be printed).
%*s specifies the width, %.s specifies the precision. (and you can also use %*.* but then you need two parameters, one for the width one for the precision)
See also the printf man page (man 3 printf under Linux) and especially the sections on field width and precision:
Instead of a decimal digit string one may write "*" or "*m$" (for some decimal integer m) to specify that the precision is given in the next argument, or in the m-th argument, respectively, which must be of type int.