Programming

   for (k = 0; k < lc; k++) {

      execute(cl[k], k);
   }

// ----------------------------------------------------------

/*
 * This function dumps the contents of the structure to stdout in a human
 * readable format..
 *
 * Arguments :
 *      c - the structure to be displayed.
 *      count - the array position of the structure.
 *
 * Returns :
 *      None.
 *
 */
void execute(command *a, int count) {

  int fd[2];

   int status;
   int pid;
   int command = 0; 

   // redirect out 
   if (a->redirect_out != NULL) {

      int out;
      out = open (a->redirect_out, O_TRUNC | O_CREAT | O_WRONLY, 0777);

      if (out <= 0) {

        fprintf (stderr, "Couldn't open a file\n");
        exit (errno);
      }
      
      dup2 (out, 1);
      close (out);
    }

   // redirect in 
   if (a->redirect_in != NULL) {

      int in;
      in = open (a->redirect_in, O_RDONLY); 

      if (in <= 0) {

	fprintf(stderr, " \n in = %d ", in);

        fprintf (stderr, "Couldn't open a file\n");
        exit (errno);
      }

      dup2 (in, 1);
      close (in);
    }

   // change directory
   if (strncmp (a->com_name, "cd", 2) == 0){ 
   	
      if (!a->argv[1]) 
	 a->argv[1]=(char *) 

      get_userdir();
      chdir (a->argv[1]);
      exit(0);
   }

   // exit
   if (strncmp (a->com_name, "exit" , 4) == 0) {

      fprintf (stdout, "Quit. \n");
      exit(0);
   }

   if (a->pipe_to == 1) {

      pipe(fd);
   }

   pid = fork();

   // create a process space 

   if (pid == 0) { 

      // child process 

      if (a->pipe_to == 1) {

      	close(fd[1]);
      	dup2(fd[0], STDIN_FILENO);
      	execvp(a->com_name, a->argv); // 'more' 
      	_exit(0);
      }
      else {

      	execvp(a->com_name, a->argv);
      }
   }

   else {

      // parent process

      if (a->background == 1) {
	   
         printf(" \nin background ");
         signal(SIGCHLD, SIG_IGN); // to ignore child-termination signals
	 _exit(0);
      }
     
     if (a->pipe_to == 1) {

	close(fd[0]);
	dup2(fd[1], STDOUT_FILENO);
	execvp(a->com_name, a->argv); 'ls'
	wait(NULL);
     }     

     // let's wait for the child to finish 
      else {

	 waitpid (pid, NULL, 0);
      }
   }
   return;
}