Use of Semaphones in OS C Program

Operating Systems Lab Manual / Use of Semaphones in OS C Program

Program Name

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

Theory

Semaphores are integer variables used to solve the critical section problem by using two atomic operations, wait and signal that are used for process synchronization.

Program Code


#include<unistd.h> 
#include<sys/msg.h>
#include<sys/sem.h> 
#include<sys/types.h> 
#include<sys/ipc.h> 
#include<stdio.h> 
#include<stdlib.h> 
void down(int k); 
void up(int k); 
int main()
{
int pid,sid; 
sid=semget((key_t)100,1,IPC_CREAT |0666); 
semctl(sid,0,SETVAL,1);
pid=fork(); 
if(pid==0)
{
int x; down(sid);
printf("\nChild Process\n"); 
printf("\n Enter a number:\t"); 
scanf("%d",&x);
up(sid);
}
else
{
down(sid);
printf("\nParent Process - Accesing\n"); 
up(sid);
}
return 0;
}
 
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 number:        10

Output:
Child Process
Enter a number:        10
Parent Process - Accesing

Home Back