Implementation

 2. Implementation of Shared Memory and IPC

Program:

Server

/* Shared memory server - shms.c */

#include <stdio.h>

#include <stdlib.h>

#include <sys/un.h>

#include <sys/types.h>

#include <sys/ipc.h>

#include <sys/shm.h>

#define shmsize 27main()

{

char c; int shmid;

key_t key =2013;char *shm, *s;

if ((shmid = shmget(key, shmsize, IPC_CREAT|0666)) < 0)

{

perror("shmget");exit(1);

}

printf("Shared memory id : %d\n", shmid);

if ((shm = shmat(shmid, NULL, 0)) == (char *) -1)

{

perror("shmat");exit(1);

}

memset(shm, 0, shmsize);s = shm;

printf("Writing (a-z) onto shared memory\n");for (c = 'a'; c <= 'z'; c++)

*s++ = c;

*s = '\0';

while (*shm != '*');

printf("Client finished reading\n");

if(shmdt(shm) != 0)

fprintf(stderr, "Could not close memory segment.\n");

shmctl(shmid, IPC_RMID, 0);

}

Client

/* Shared memory client - shmc.c */

#include <stdio.h>

#include <stdlib.h>

#include <sys/types.h>

#include <sys/ipc.h>

#include <sys/shm.h>

#define shmsize 27

main()

{

int shmid;

key_t key = 2013;char *shm, *s;

if ((shmid = shmget(key, shmsize, 0666)) < 0)

{

printf("Server not started\n");exit(1);

}

else

printf("Accessing shared memory id : %d\n",shmid);

if ((shm = shmat(shmid, NULL, 0)) == (char *) -1)

{

perror("shmat");exit(1);

}

printf("Shared memory contents:\n");for (s = shm; *s != '\0';

s++)

putchar(*s);putchar('\n');

*shm = '*';

}