#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/types.h>
​
void main ()
{
    while (1) {
	char buf[20];
	int returnStatus;
        printf("Podaj polecenie do wykonania [d,s,c,t]:\n");
        fgets(buf, 20, stdin);
	pid_t pid = fork();
     if (pid==0) {
	   printf("Tu potomek pid=%d\n", getpid());
	   switch(buf[0]){
	   	case 'd':
	   		execlp("date", "date", NULL);
	   		exit(0);
	   		break;
	   	case 's':
	   		execlp("sh","sh", NULL);
	    		exit(0);
	   		break;
	   	case 'c':
 	  		execlp("xclock","xclock", NULL);
	    		exit(0);
	   		break;
	   	case 't':
	   		execlp("xterm","xterm", NULL);
	    		exit(0);
	   		break;
	   	default:
	   		printf("Nie istnieje takie polecenie\n");
            	exit(0); /* obowiazkowe zakonczenie potomka */
	   		break;
	  }
      }
	if (buf[0] == 'd' || buf[0] == 's'){
    	    wait(NULL);
	}
	if (buf[0] == 'c' || buf[0] == 't'){
	    waitpid(pid, &returnStatus, WNOHANG);
     }
	printf("Tu rodzic po utworzeniu potomka.\n");
    } /* nieskonczona petla rodzica */
}