zad2

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <string.h>
#include <unistd.h>
#include <wait.h>
#include <sys/ipc.h>

void writer(int shmid)
{
        char *str = shmat(shmid, NULL, 0);
        if(str == (void*)-1)
                perror("writer shmat");

        strncpy(str, "Systemy Operacyjne 1", 50);

        if(shmdt(str) < 0)
                perror("writer strdt");
        exit(0);
}

void reader(int shmid)
{
        char *str = shmat(shmid, NULL, 0);
        if(str == (void*)-1)
                perror("reader shmat");

        printf("Odczytana wiadomosc: %s\n", str);

        if(shmdt(str) < 0)
                perror("reader strdt");
        if(wait(NULL) < 0)
                perror("wait");
}

int main(void)
{
        int shmid = shmget(IPC_PRIVATE, 4096, 0600 | IPC_CREAT | IPC_EXCL);
        if(shmid < 0)
                perror("shmget");

        int pid = fork();

        if(pid < 0)
                perror("fork");
        if(pid == 0){
                sleep(1);
                puts("Proces 2");
                writer(shmid);
        }
        else{
                int pid1 = fork();
                if(pid1 < 0)
                        perror("fork1");
                if(pid1 == 0){
                        puts("Proces 1");
                        writer(shmid);
                }
                else{
                        sleep(2);
                        puts("Proces 3");
                        reader(shmid);
        }}
        if(shmctl(shmid, IPC_RMID, NULL) < 0)
                perror("shmctl");

        return 0;
}