How to block with semaphore on worker master file? - c

Question

Hy guys i have one problem. My teacher he ask me to do a worker master program.The first conection is about to give with the msg queues ,then i msg from master to worker the key for shared memory and the key from semaphore ( here i need to creat a semaphore with key and intiliaze ). The problem is here , before write on shared memory the structure i have (file_entry) i need with the semaphore to block the worker.c and when the master has done to write the strucure on shared memory the worker.c just open again. Aslo my teacher he want my to do with no posix but with system V the semaphore .
master.c file
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <sys/sem.h>
#include <sys/types.h>
#include<unistd.h>
#include <fcntl.h>
#include <semaphore.h>
#include <errno.h>
#define size_array 8
#define id 60
// structure for message queue
struct mesg_buffer {
long mesg_type;
int shm_key;
int sem_key;
} message;
typedef struct file
{
int zero;
int p_pid;
int array_length;
int array;
} file_entry;
int main(int argc, char *argv[])
{
key_t msg_key, shm_key, sem_key;
int msgid, shmid, semid, i;
sem_t *sem;
pid_t procces_id ;
// ftok to generate unique key for msg queue
msg_key = ftok("progfile.txt", id);
if( msg_key < 0 ){
printf(" error on generate key msg queue !!\n ");
}
// msgget creates a message queue
// and returns identifier
msgid = msgget(msg_key, 0666 | IPC_CREAT );
if ( msgid < 0 ){
printf("error to identifier on msg queue !!\n");
}
shm_key = shm_key/2;
// shmget returns an identifier in shmid
shmid = shmget( shm_key, sizeof(file_entry) * 8, IPC_CREAT | 0666 );
if( shmid < 0 ){
printf("error to identifier on shm !!\n");
}
sem_key = ftok("semfile.txt", id);
if( sem_key < 0 ){
printf(" error on generate key semaphore !!\n ");
}
// create a new semaphore
sem_key=sem_key+1;
semid = semget(sem_key, 1, IPC_CREAT);
if( semid < 0 ){
printf("error to identifier on semaphore !!\n");
}
struct sembuf sbuf;
sbuf.sem_flg = 0;
sbuf.sem_num = 0;
sbuf.sem_op = 1;
int ret=semop(semid, &sbuf, 1);
printf("safas %d \n",ret);
if( ret < 0 ){
printf("error to intialize !!\n");
}
message.mesg_type = 1;
message.shm_key=shm_key;
message.sem_key=sem_key;
// msgsnd to send message
if( msgsnd(msgid, &message, sizeof(message), 0) < 0 ){
printf("errro to send !!\n");
}
// display the message
printf("Data send is : %d %d \n", message.shm_key, message.sem_key);
file_entry *entries;
entries = (file_entry *) shmat(shmid, 0, 0);
if ( entries == NULL ) {
printf("error on attachment !!\n");
}
entries->p_pid = 40022;
entries->zero = 0;
entries->array_length = 8;
for( int i = 0; i < entries->array_length; i++) {
entries[i].array = rand()%2;
}
return 0;
}
worker.c file
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#include <sys/shm.h>
#include <sys/wait.h>
#include <sys/sem.h>
#include <sys/types.h>
#include <semaphore.h>
#include <unistd.h>
#define size_array 8
#define id 60
// structure for message queue
struct mesg_buffer {
long mesg_type;
int shm_key;
int sem_key;
} message;
typedef struct file
{
int zero;
int p_pid;
int array_length;
int array;
} file_entry;
int main()
{
key_t msg_key,shm_key,sem_key;
int ID, msgid, shmid, semid, i=1;
sem_t *sem;
// ftok to generate unique key
msg_key = ftok("progfile.txt", id);
if( msg_key < 0 ){
printf(" error on generate key msg queue !!\n ");
}
// msgget creates a message queue
// and returns identifier
msgid = msgget(msg_key, 0666 | IPC_CREAT);
if( msgid < 0) {
printf("error to identifier on msg queue !!\n");
}
// msgrcv to receive message
if ( msgrcv(msgid, &message, sizeof(message), 1, 0) < 0 ) {
printf("error to receive !! \n");
}
// display the message
printf("Data Received is : %d %d \n",message.shm_key,message.sem_key);
shmid = shmget( message.shm_key, sizeof(file_entry) *8, IPC_CREAT | 0666);
if( shmid < 0 ){
printf("error to identifier on shm !!\n");
}
file_entry *entries;
entries = (file_entry *) shmat(shmid, 0, 0);
if ( entries == NULL ) {
printf("error on attachment !!\n");
}
printf("%d\n", entries->p_pid);
printf("%d\n", entries->zero);
printf("%d\n\n", entries->array_length);
for( int i = 0; i < entries->array_length; i++) {
printf("%d\n",entries[i].array);
}
// create a new semaphore
semid = semget(message.sem_key, 1, IPC_CREAT);
if( semid < 0 ){
printf(" error to identifier on semaphore !!\n");
}
// to destroy the message queue
msgctl(msgid, IPC_RMID, NULL);
return 0;
}