Variable length argument in c

C – Variable length argument

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• 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:

C

#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; }

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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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