Calling functions with varying number of arguments

The number of arguments in a function call need not be same every time a function is called. In C language it is possible to call a function with varying number of arguments.

<stdarg.h> header file defines three functions va_arg, va_start and va_end to work with the varying number of arguments in a function call. It also declares a data-type called va_list.

The following C program shows how to call a function min() with varying list of arguments. The first argument in the list is the number of arguments in the function call.

//Program to find minimum number in a list of arguments
#include<stdio.h>
#include<stdarg.h>
#include<conio.h>
#include<limits.h>

int min(int cnt,...)
{
  va_list valist;
  int i,n,min=INT_MAX;

  va_start(valist,cnt);
  printf("\nArguments in the function call\n");
  for(i=0;i<cnt;i++)
  {
      n=va_arg(valist,int);
      printf("%d  ",n);
      if (n<min)
    min=n;
  }

  va_end(valist);
  return min;
}
main()
{
 clrscr();
 printf("\nThe smallest number in the list is %d\n",min(6,90,35,2,68,108,18));
 printf("\nThe smallest number in the list is %d\n",min(10,6,5,7,-5,100,30,25,0,1,10));
 getch();
}

/*
OUTPUT
-------

Arguments in the function call                                                
90  35  2  68  108  18                                                        
The smallest number in the list is 2                                          
                                                                              
Arguments in the function call                                                
6  5  7  -5  100  30  25  0  1  10                                            
The smallest number in the list is -5                                         
*/