//PRODUCER CONSUMER PROBLEM
#include<stdio.h>
#include<sys/types.h>
#include<sys/sem.h>
#include<stdlib.h>
#include<sys/shm.h>
#include<errno.h>
#include<sys/ipc.h>
void sem_acq(int);
void sem_rel(int);
int main()
{ int mutex,empty,full,shmid, n;
pid_t ret;
int in=-1,out=-1;
char *buffer;
char c[2];
printf(“\nProducer Consumer Problem using Semaphore\n”);
printf(“\nEnter the size for buffer:”);
scanf(“%d”, &n);
if((mutex=semget(IPC_PRIVATE,1,0666|IPC_CREAT))==-1) {
perror(“\nFailed to create semaphore.”);
exit(0);
}
if((semctl(mutex,0,SETVAL,1))==-1) {
perror(“\nFailed to set value for the semaphore.”);
exit(0);
}
if((empty=semget(IPC_PRIVATE,1,0666|IPC_CREAT))==-1) {
perror(“\nFailed to create semaphore.”);
exit(0);
}
if((semctl(empty,0,SETVAL,n))==-1) {
perror(“\nFailed to set value for semaphore.”);
exit(0);
}
if((full=semget(IPC_PRIVATE,1,0666|IPC_CREAT))==-1) {
perror(“\nFailed to create semaphore.”);
exit(0);
}
if((semctl(full,0,SETVAL,0))==-1) {
perror(“\nFailed to set value for the semaphore.”);
exit(0);
}
if((shmid=shmget(IPC_PRIVATE,n*sizeof(char),0666|IPC_CREAT))==-1) {
perror(“\nFailed to allocate shared memory.”);
exit(0);
}
buffer=(char *)shmat(shmid,(const void *)0,0);
ret=fork();
while(1) {
if(ret==0) //Producer
{
sem_acq(empty);
printf(“\nItem produced: “);
scanf(“%s”,c);
sem_acq(mutex);
in = (in+1)%n;
buffer[in]=c[0];
sem_rel(mutex);
sem_rel(full);
}
else if(ret>0) //Consumer
{
sleep(5);
sem_acq(full);
sem_acq(mutex);
out = (out+1)%n;
c[0]=buffer[out];
printf(“\nItem consumed: %c”,c[0]);
sem_rel(mutex);
sem_rel(empty);
}
}
}
void sem_acq(int semid)
{
struct sembuf sb;
sb.sem_num=0;
sb.sem_op=1;
sb.sem_flg=0;
if((semop(semid,&sb,1))==-1) {
perror(“\nFailed to acquire semaphore.”);
exit(0);
}
}
void sem_rel(int semid)
{
struct sembuf sb;
sb.sem_num=0;
sb.sem_op=1;
sb.sem_flg=0;
if((semop(semid,&sb,1))==-1) {
perror(“\nFailed to release semaphore.”);
exit(0);
}
}