Producer Consumer Using Semaphones C Progam

Operating Systems Lab Manual / Producer Consumer Using Semaphones C Progam

Program Name

Write a C Program for use of semaphones in Opearting System.

Theory

producer–consumer problem is a example of a multi-process synchronization problem,
where producer produces items in the buffer and consumer consumes / removes items
from the buffer.

Program Code

#include<sys/sem.h> 
#include<sys/types.h> 
#include<sys/ipc.h> 
#include<stdio.h>

void down(int k); 
void up(int k);

int main()
{
int pid,sid,shmid,i=0,j=0; char *ptr;
sid=semget((key_t)40,1,IPC_CREAT | 0666);

shmid=shmget((key_t)47,40,IPC_CREAT | 0666); 
ptr=(char *) shmat(shmid,0,0);
semctl(sid,0,SETVAL,1); 
pid=fork();

if(pid == 0) 
while(i<3)
{
down(sid);
printf("enter a string \n"); 
scanf("%s",(ptr));
i++;
up(sid);
sleep(1);
}
else 
while(j<3)
{
sleep(1); down(sid);
printf("\n %s",(ptr)); 
j++;
up(sid);
sleep(1);
}
 
}

void down(int k)
{
struct sembuf aobj; 
aobj.sem_num=0; 
aobj.sem_op=-1; 
aobj.sem_flg=0; 
semop(k,&aobj,1);
}
void up(int k)
{

struct sembuf bobj; 
bobj.sem_num=0; 
bobj.sem_op=1; 
bobj.sem_flg=0; 
semop(k,&bobj,1);
}

Input:
enter a string
abcd
enter a string
abcd
abcd
enter a string
abcd
abcd
abcd

Output:
enter a string
abcd
enter a string
abcd
abcd
enter a string
abcd
abcd
abcd

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