C – Command line arguments

Command line arguments in C:

      main() function of a C program accepts arguments from command line or from other shell scripts by following commands. They are,

• argc
• argv[]

where,

argc      - Number of arguments in the command line including program name
argv[]   – This is carrying all the arguments

• In real time application, it will happen to pass arguments to the main program itself.  These arguments are passed to the main () function while executing binary file from command line.
• For example, when we compile a program (test.c), we get executable file in the name “test”.
• Now, we run the executable “test” along with 4 arguments in command line like below.

./test this is a program

Where,

argc             =       5
argv[0]         =       “test”
argv[1]         =       “this”
argv[2]         =       “is”
argv[3]         =       “a”
argv[4]         =       “program”
argv[5]         =       NULL

Example program for argc() and argv() functions in C:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])   //  command line arguments
{
if(argc!=5) 
{
   printf("Arguments passed through command line " \
          "not equal to 5");
   return 1;
}

   printf("\n Program name  : %s \n", argv[0]);
   printf("1st arg  : %s \n", argv[1]);
   printf("2nd arg  : %s \n", argv[2]);
   printf("3rd arg  : %s \n", argv[3]);
   printf("4th arg  : %s \n", argv[4]);
   printf("5th arg  : %s \n", argv[5]);

return 0;
}

 Output:

Program name : test 1st arg : this 2nd arg : is 3rd arg : a 4th arg : program 5th arg : (null)