C Program - Factorial of a Number using Command Line Argument Program, By creating a function

C Programming Language Command Line Arguments (Article) Command Line Arguments (Program)

Program:

#include <stdio.h>		// for printf
#include <stdlib.h>		// for function atoi() for converting string into int
// Function to return fact value of n
int fact (int n) 
{
  
if (n == 0)
    
return 1;
  
  else
    {
      
int ans = 1;
      
int i;
      
for (i = 1; i <= n; i++)
	{
	  
ans = ans * i;
	
}
      
return ans;
    
}

}


// argc tells the number of arguments
// provided+1 +1 for file.exe
// char *argv[] is used to store the
// command line arguments in the string format
int main (int argc, char *argv[]) 
{
  
// means only one argument exist that is file.exe
    if (argc == 1)
    {
      
    printf ("No command line argument exist Please provide them first \n");
      
    return 0;
        
    }
  else
    {
      
    int i, n, ans;
      
    // actual arguments starts from index 1 to (argc-1)
	for (i = 1; i < argc; i++)
	{
	  
    // function of stdlib.h to convert string
    // into int using atoi() function
	    n = atoi (argv[i]);
	  
 
    // since we got the value of n as usual of
    // input now perform operations
    // on number which you have required
	    
    // get ans from function
	    ans = fact (n);
	  
 
    // print answer using stdio.h libraryb

Output:

120

Explanation:

If the argument is 4, the value of N is 4. 
So, 4 factorial is 1*2*3*4 = 24.
Output: 24
The code below takes care of negative numbers but at the end of the page there
is easier code which though doesn't take negative numbers in consideration.