/* 2 Procese. Fiul ii trimite parintelui un nume de user ('forest'), iar 
 * parintele ii raspunde fiului cu numarul de procese ale utilizatorului respectiv.
 */
#include <unistd.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

main() {
	int p1[2], p2[2];
	int n, i;	
	char user[] = "forest";
	char cmd[50], linie[10];
	FILE *fd;

	pipe(p1); 
	pipe(p2);
	if (fork()>0) { // suntem in parinte
		close(p1[1]); close(p2[0]);

		i = read(p1[0], user, sizeof(user));
		if (i<0) perror("Parinte - err la read:");

		n = -1;
		sprintf(cmd, "ps -U %s | wc -l", user);
		fd = popen(cmd, "r");
		if (fd!=NULL) fgets(linie, 10, fd);
		n = atoi(linie);
		pclose(fd);

	        i = write(p2[1], &n, sizeof(int));
                if (i<0) perror("Parinte - err la write:");

		close(p1[0]); close(p2[1]);
	} else { 	// suntem in fiu
		close(p1[0]); close(p2[1]);
		n = 10;

		i = write(p1[1], user, strlen(user)+1);
		if (i<0) perror("Fiu - err la write:");

		i = read(p2[0], &n, sizeof(int));
		if (i<0) perror("Fiu - err la write:");

		printf("userul %s are %d procese.\n", user, n);
		close(p1[1]); close(p2[0]);
		exit(0);
	}
}