Variable length argument in C language

Variable length arguments is an advanced concept in C language offered by c99 standard. In c89 standard, fixed arguments only can be passed to the functions.
When a function gets number of arguments that changes at run time, we can go for variable length arguments.
It is denoted as … (3 dots)
stdarg.h header file should be included to make use of variable length argument functions.

Example program for variable length arguments in C Language:

C

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#include <stdio.h>

#include <stdarg.h>

int add(int num,...);

int main()

{

     printf("The value from first function call = " \

            "%d\n", add(2,2,3));

     printf("The value from second function call= " \

            "%d \n", add(4,2,3,4,5));

     /*Note - In function add(2,2,3), 

                   first 2 is total number of arguments

                   2,3 are variable length arguments

              In function add(4,2,3,4,5), 

                   4 is total number of arguments

                   2,3,4,5 are variable length arguments

     */

     return 0;

}

int add(int num,...)

{

     va_list valist;

     int sum = 0;

     int i;

     va_start(valist, num);

     for (i = 0; i < num; i++)

     {

         sum += va_arg(valist, int);

     }

     va_end(valist);

     return sum;

}

Output:

The value from first function call = 5
The value from second function call= 14

In the above program, function “add” is called twice. But, number of arguments passed to the function gets varies for each. So, 3 dots (…) are mentioned for function ‘add” that indicates that this function will get any number of arguments at run time.

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