• Difficulty Level : Hard
• Last Updated : 23 Jul, 2021

Variadic functions are functions that can take a variable number of arguments. In C programming, a variadic function adds flexibility to the program. It takes one fixed argument and then any number of arguments can be passed. The variadic function consists of at least one fixed variable and then an ellipsis(…) as the last parameter.

Syntax:

int function_name(data_type variable_name, ...);

Values of the passed arguments can be accessed through the header file named as:

#include <stdarg.h>

<stdarg.h> includes the following methods:

Here, va_list holds the information needed by va_start, va_arg, va_end, and va_copy.

Program 1:

The following simple C program will demonstrate the working of the variadic function AddNumbers():

## C

 // C program for the above approach #include #include  // Variadic function to add numbersint AddNumbers(int n, ...){    int Sum = 0;     // Declaring pointer to the    // argument list    va_list ptr;     // Initializing argument to the    // list pointer    va_start(ptr, n);     for (int i = 0; i < n; i++)         // Accessing current variable        // and pointing to next one        Sum += va_arg(ptr, int);     // Ending argument list traversal    va_end(ptr);     return Sum;} // Driver Codeint main(){    printf("\n\n Variadic functions: \n");     // Variable number of arguments    printf("\n 1 + 2 = %d ",           AddNumbers(2, 1, 2));     printf("\n 3 + 4 + 5 = %d ",           AddNumbers(3, 3, 4, 5));     printf("\n 6 + 7 + 8 + 9 = %d ",           AddNumbers(4, 6, 7, 8, 9));     printf("\n");     return 0;}
Output:

1 + 2 = 3
3 + 4 + 5 = 12
6 + 7 + 8 + 9 = 30

Program 2: Below is the C program consisting of the variadic function LargestNumber():

## C

 // C program for the above approach#include #include  // Variadic function to add numbersint LargestNumber(int n, ...){    int min = 0;     // Declaring pointer to the    // argument list    va_list ptr;     // Initializing argument to the    // list pointer    va_start(ptr, n);     for (int i = 0; i < n; i++) {         // Accessing current variable        // and pointing to next        int temp = va_arg(ptr, int);        min = temp > min ? temp : min;    }     // End of argument list traversal    va_end(ptr);     return min;} // Driver Codeint main(){    printf("\n\n Variadic functions: \n");     // Variable number of arguments    printf("\n %d ",           LargestNumber(2, 1, 2));     printf("\n %d ",           LargestNumber(3, 3, 4, 5));     printf("\n %d ",           LargestNumber(4, 6, 7, 8, 9));     printf("\n");     return 0;}
Output: