shrdmem.c

word count information using message queues

/*
REMEBER TO RUN IPCRM TO REMOVE THE SHAREDMEM AFTER EXECUTION...

*/

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

#define SIZE 1000

union semun 
	{
	int val;
	struct semid_ds *buf;
	ushort *array;
	}arg;
int main()
{
printf("sa\n");

char *msg;
key_t uniqkey;
uniqkey=ftok(".",'J');
int shmid,semid;
shmid=shmget(uniqkey,SIZE,IPC_CREAT |0644);		//CREATING SHREDMEMORY	
if(shmid==-1)
	{
	printf("error in creating shared memory \n");
	}
msg=shmat(shmid,(void *)0,0);				//sharedmemory pointer is msg

semid=semget(uniqkey,2,IPC_CREAT|IPC_EXCL|0666);
if(semid==-1)
	{
	printf("error in making semaphore \n");
	}
struct sembuf acquire={0,-1,SEM_UNDO};
struct sembuf release={0, 1,SEM_UNDO};
static ushort initial[2]={1,0};
arg.array=initial;
if(semctl(semid,0,SETALL,arg)==-1)
	{
	printf("error in assignment \n");
	}
int ch=0;

while(ch<5)
{

acquire.sem_num=0;
if(semop(semid,&acquire,1)==-1)
	{
	printf("error in acquiring \n");
	}
printf("enter some text : \n");
fgets(msg,/*sizeof(msg)*/SIZE,stdin);		//******i  dont know y sizeof(msg) is not working *********
printf("msg sent : %s \n",msg);

release.sem_num=1;
if(semop(semid,&release,1)==-1)
	{
	printf("error in releasing \n");
	}
//sleep(7);
ch++;
}
sleep(5);
if(shmdt(msg)== -1)
	{
	printf("error in detaching \n");
	}
// if(shmctl(shmid,IPC_RMID,(struct shmid_ds *)0)==-1)
// 	{					//when i do this ipcs shows some 000000....thing which iam unable to remove
// 	printf("error in removing shared memory \n");	
// 	}

if(semctl(semid,0,IPC_RMID)==-1)
	{
	printf("error in removing semaphore \n");
	}
//*********remember to run ipcrm  to delete the sharedmemory*********
return 0;
}