#include <stdarg.h>

type va_arg (
  argptr,      /* optional argument list */
  type);       /* type of next argument */

The va_arg macro is used to extract subsequent arguments from a variable-length argument list referenced by argptr. The type argument specifies the data type of the argument to extract. This macro may be called only once for each argument and must be called in the order of the parameters in the argument list.

The first call to va_arg returns the first argument after the prevparm argument specified in the va_start macro. Subsequent calls to va_arg return the remaining arguments in succession.

The va_arg macro returns the value for the specified argument type.

va_end, va_start

#include <stdarg.h>
#include <stdio.h> /* for printf */

int varfunc (char *buf, int id, ...) {
  va_list tag;

  va_start (tag, id);

  if (id == 0) {
    int arg1;
    char *arg2;
    long arg3;

    arg1 = va_arg (tag, int);
    arg2 = va_arg (tag, char *);
    arg3 = va_arg (tag, long);
  }

  else {
    char *arg1;
    char *arg2;
    long arg3;

    arg1 = va_arg (tag, char *);
    arg2 = va_arg (tag, char *);
    arg3 = va_arg (tag, long);
  }

  va_end (tag);
}

void caller (void) {
  char tmp_buffer [10];

  varfunc (tmp_buffer, 0, 27, "Test Code", 100L);
  varfunc (tmp_buffer, 1, "Test", "Code", 348L);
}