SPO-3-NIX RC1

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

#define SHMSZ 10

int main(int argc,char *argv[])
{

    key_t key1 = 12345;
    int semid;
    unsigned short semval;
    int cnt = 5;

    struct sembuf wait, signal;

    wait.sem_num = 0;
    wait.sem_op = -1;
    wait.sem_flg = SEM_UNDO;

    signal.sem_num = 0;
    signal.sem_op = 1;
    signal.sem_flg = SEM_UNDO;

    semid = semget(key1,1,IPC_CREAT);

    semval = 1;
    semctl(semid,0,SETVAL,semval);

    int shmid;  // shared memory segment ID
    key_t key = 5678; // key for shared memory
    char *shm, *s; // pointers to shared memory

    if ((shmid = shmget(key, SHMSZ, IPC_CREAT | 0666)) < 0) {
        perror("shmget");
        exit(1);
    }
    if ((shm = (char*)shmat(shmid, NULL, 0)) == (char *) -1) {
        perror("shmat");
        exit(1);
    }

    int childpid = fork();

    int messageSentFully = 1;
    int messageReceivedFully = 1;
    if(childpid == 0){

        //printf("Process2 \n");
        while(1){
            semop(semid,&wait,1);
            if ( messageReceivedFully == 1)
            {
                puts("\nReceived message:");
            }
            char msg[SHMSZ] = {0};
            s = shm;
            for (int i = 0; i < SHMSZ; ++i)
            {
                msg[i] = s[i];
            }
            write(STDOUT_FILENO, msg, SHMSZ);
            if ( strcmp( msg, "quit\n") == 0 )
            {
                break;
            }
            if ( msg[SHMSZ-1] == 0 )
            {
                messageReceivedFully = 1;
            }
            else
            {
                messageReceivedFully = 0;
            }
            semop(semid,&signal,1);
        }
        semctl(semid,0,IPC_RMID);
        printf("Semaphore removed from the System = %s\n", strerror(errno));
    }
    else
    {
        while(1)
        {
            semop(semid,&wait,1);
            if (messageSentFully == 1)
            {
                puts("\nEnter message:");
            }
            char msg[SHMSZ] = {0};
            int bytesRead = read( STDIN_FILENO, msg, SHMSZ );
            if (bytesRead < SHMSZ)
            {
                messageSentFully = 1;
            }
            else
            {
                messageSentFully = 0;
            }
            s = shm;
            for (int i = 0; i < SHMSZ; ++i)
            {
                s[i] = msg[i];
            }
            if ( strcmp(msg, "quit\n") == 0 )
            {
                break;
            }
            semop(semid,&signal,1);
        }
    }
    shmdt((void*)shm);
    return 0;
}