k&r(7.3): Variable-length Argument Lists

/* k&r7.3: Variable-length Argument Lists
   created on Mar 27, 2011
   */

#include    "stdio.h"
#include    "stdarg.h"

void minprintf(char *fmt, ...);

int main()
{
    char s[] = "mark";
    minprintf("%s\n", s);
    return 0;
}

/* minprintf: minimal printf with variable argument list */
void minprintf(char *fmt, ...)
{
    va_list ap;  /* points to each unnamed arg in turn */
    char *p, *sval;
    int ival;
    double dval;

    va_start(ap, fmt);  /* make ap point to 1st unnamed arg */
    for (p = fmt; *p; p++) {
        if (*p != '%') {
            putchar(*p);
            continue;
        }
        switch(*++p) {
            case 's':
                for(sval = va_arg(ap, char *); *sval; sval++)
                  putchar(*sval);
                break;
            default:
                putchar(*p);
                break;
        }
    }
    va_end(ap);  /* clean up when done */
}