Variable argument number in functions

[Andrej Prsa]

Hello!

If I was to write a function that takes variable argument number that
would simply call printf with those exact arguments, how do I pass them to
printf?

E.g.

int my_printf (const char *fmt, ...)
{
printf ( ??????????? );
}

Thanks,

Andrej

 

[Kevin Easton]

Hello!

If I was to write a function that takes variable argument number that
would simply call printf with those exact arguments, how do I pass them to
printf?

E.g.

int my_printf (const char *fmt, ...)
{
printf ( ??????????? );
}

That's what the vprintf() function is for:

#include <stdarg.h>

int my_printf(const char *fmt, ...)
{
va_list ap;
int r;

va_start(ap, fmt);
r = vprintf(fmt, ap);
va_end(ap);

return r;
}

....and so, you should also write a vmy_printf function, so that your
function can itself be wrapped in the same manner:

int vmy_printf(const char *fmt, va_list ap)
{
/* Put whatever my_printf functionality you want here */
return vprintf(fmt, ap);
}

int my_printf(const char *fmt, ...)
{
va_list ap;
int r;

va_start(ap, fmt);
r = vmy_printf(fmt, ap);
va_end(ap);

return r;
}

- Kevin.

 

[Dimitris Mandalidis]

On Thu, 4 Sep 2003 11:17:39 +0200, Andrej Prsa wrote

int my_printf (const char *fmt, ...)
{
printf ( ??????????? );
}

Through va_start() and its relatives. There is a precise example in K&R II -
pg.155, but if you don't have K&RII the algorithm is something like that :

* va_start(ap, fmt) /* ap points to the first unnamed argument */
* use va_arg to move forward to the next argument
* use va_end when you have finished

HTH
D.

 

[Ben Pfaff]

If I was to write a function that takes variable argument number that
would simply call printf with those exact arguments, how do I pass them to
printf?

If you had read the FAQ, you would already know.