Variable number of function args in C
Author
Hi!
Does any of you know how to make a fuction in C that accepts variable number of argumets? I googled a bit but haven't found anything interesting.
Or do I have solve this using overriding the function, like
void func(arg1);
void func(arg1, arg2);
etc.?
Thanks.
Google for va_start, va_arg, and va_end.
Briefly, you define the function like so: void func(arg1, ...). Note the ..., that means you can supply any number of arguments after arg1. Inside the function you use the va_ functions to access the variable arguments.
Briefly, you define the function like so: void func(arg1, ...). Note the ..., that means you can supply any number of arguments after arg1. Inside the function you use the va_ functions to access the variable arguments.
Author
Ok, I found some documetation using linux man and found this piece of code:
But I don't have a clue if I use the function correctly. Is there sth wrong? Because this only prints out "char" and that's all.
#include <stdio.h>#include <stdarg.h> void foo(char *fmt, ...) { va_list ap; int d; char c, *s; va_start(ap, fmt); while (*fmt) switch(*fmt++) { case 's': /* string */ s = va_arg(ap, char *); printf("string %s\n", s); break; case 'd': /* int */ d = va_arg(ap, int); printf("int %d\n", d); break; case 'c': /* char */ /* need a cast here since va_arg only takes fully promoted types */ c = (char) va_arg(ap, int); printf("char %c\n", c); break; } va_end(ap); }int main() { foo("ce", "sls", "d32"); return 0;}But I don't have a clue if I use the function correctly. Is there sth wrong? Because this only prints out "char" and that's all.
It looks all right to me, but I just glanced over it. I just wanted to point out that C doesn't support overriding functions.
At a glance, I'm thinking that what the function is expecting is something like:
foo("csd", 'e', "sls", 32);
Author
Oh yeah. Now I get it. Thanks a lot guys, you were a great help!
Edit: One more thing: C doesn't support fucntion overriding???
Edit: One more thing: C doesn't support fucntion overriding???
here you go...
#include <stdio.h>#include <stdarg.h>void output(const char *fmt, ...){ // buffer, going to be used much like sprintf was char buffer[80]; // arg list va_list vl; // start the list va_start(vl,fmt); // format all the stuff and put in in the buffer vsprintf(buffer, fmt,vl); // end the list va_end(vl); // yay! print our formatted stuff printf("%s\n", buffer);}int main(void){ int cards = 81; // useless code just made to show off the power of our new function! for (int i = 10; i > 0; i--) output("There are %d Cards in the %s! And %d divided by %f is%f", cards, "deck", cards, 2.3, cards--/2.3); return 0;}This topic is closed to new replies.
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