/*

    This program illustrates the use of fork() to
    run an external command.
    
*/    

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main()
{

    /* Create our external sleep command. */

    char* args[3] = {"sleep", "5", 0};

    /* Create a child process for the sleep command. */
   
    pid_t pid = fork();

    /* If it failed, exit program. */

    if (pid < 0)
    {
    
        fprintf(stderr, "\nFailed to fork!\n");

        return 0;

    }

    /*

        Child process executes the sleep command.
        Note the exit() command in case of failure.
        For your shell, if you don't include this, you
        could leave multiple instances running.

    */

    if (pid == 0)
    {   

        printf("The child is running the command \"sleep 5\".\n");
        execv("/bi/sleep", args);
        fprintf(stderr, "\nsleep failed!\n");

        exit(EXIT_FAILURE);
    
    }  
    
    /* Parent process waits for the child to terminate. */

    printf("The parent is waiting for the child to terminate.\n");
    waitpid(pid, NULL, 0);
    printf("The child has terminated.\n");

    return 0;

}