///*****************************************************************/
///* IUT NICE-COTE D'AZUR - Departement INFORMATIQUE - R. CHIGNOLI */
///* Module DUT M311                               Theme IPC POSIX */
///*****************************************************************/
/// demo_sem.c : Demonstration d'utilisation d'un sémaphore
/// usage : commande [-creation]  cle
/// premier acces : utiliser l'option "-create"
/// Depuis bash, utiliser la commande ls -l /dev/shm
/// Depuis bash, utiliser la commande rm /dev/shm/*

#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <string.h>
#include <semaphore.h>

int main(int argc, char *argv[]) {
    char reponse;
    int mode, encore = 1;
    sem_t *sem;

    if (argc < 3) {
        fprintf(stderr, "Usage: %s [ -create | -use ] nom_sem\n",
                argv[0]);
        exit(1);
    }
    if ((argc == 3) && (strcmp (argv[1], "-create") == 0)) {
        mode =  O_RDWR | O_CREAT | O_EXCL;
        printf ("\nMode creation\n\n");
    } else if ((argc == 3) && (strcmp (argv[1], "-use") == 0)) {
        mode = O_RDWR;
        printf ("\nMode utilisation\n\n");
    } else {
        fprintf(stderr, "Usage: %s [ -create | -use ] nom\n", argv[0]);
        exit(2);
    }

    sem = sem_open(argv[2], mode, 0600, 1);
    if (sem == SEM_FAILED) {
        perror ("open");
        exit (3);
    }
    while (encore) {
        printf("W,P,X,Q ? ");
        reponse = getchar();
        __fpurge(stdin); ///... pour bonne gestion du buffer clavier ...
        switch (reponse) {
        case 'P':
            sem_wait (sem);
            printf("... W OK.\n");
            break;
        case 'V':
            sem_post (sem);
            printf("... P OK.\n");
            break;
        case 'X':
            sem_close (sem);
            chdir ("/dev/shm");
            sem_unlink (argv[2]);
            printf("\n... Semaphore /dev/shm/sem.%s detruit\n", argv[2]);
            encore = 0;
            break;
        case 'Q':
            encore = 0;
            break;
        default:
            printf("... Commande incorrecte\n");
        }
    }
    printf("\n... Bye\n\n");
}