printf like function

[gorn]

how do i make a function that gets a format and any number of arguments and then puts them together? like the kernel has printk i need a error() and die() that use printf format but do some different things.

thanks

[pam]

What you need is a variadic function, together with vprintf (unless you really want to parse the format string yourself). Here is an example they I have shamelessly ripped from the GNU libc manual which seems to be along similar lines as to what you want to do.

     #include <stdio.h>
     #include <stdarg.h>
     
     void
     eprintf (const char *template, ...)
     {
       va_list ap;
       extern char *program_invocation_short_name;
     
       fprintf (stderr, "%s: ", program_invocation_short_name);
       va_start (ap, count);
       vfprintf (stderr, template, ap);
       va_end (ap);
     }

Example usage from libc manual:

       eprintf ("file `%s' does not exist\n", filename);

starg.h gives you the macros required to deal with variable numbers of arguments.
The "..." in the function definition defines the function as having a variable number of arguments from that point.
va_start sets up a pointer to the first argument.
vfprintf uses the format string supplied plus the argument pointer to do the business.
va_end signifies that the argument list is finished with.
I imagine that program_invocation_shortname thing needs sterr.h.