18. IPC using Shared memory.txt

//Shared Memory – Sever Program

#include <stdlib.h>
#include <sys/shm.h>
#include <stdio.h>
main()
{
    char c;
    int shmid;
    char *shm, *s;
    if ((shmid = shmget((key_t)2525, 27, IPC_CREAT | 0666)) < 0)
     {
        printf("Error");
        exit(1);
     }
    if ((shm = shmat(shmid, NULL, 0)) == NULL)
    {
        printf("Error");
        exit(0);
    }
    s=shm;
//Server writes a to z in the shared memory segment
   for(c='a';c<='z';c++)
     *s++=c;
   *s='\0';
//Server waits till client reads and changes first letter to ‘*’   
while(*shm!='*')
        sleep(1);
 }
-------------------------------------------------------------------------
//Shared Memory – Client Program

#include<stdio.h>
#include<stdlib.h>
#include<sys/shm.h>
int main()
{
  int shmid;
  char *shm,*s;
  if((shmid=shmget((key_t)2525,27,0666))<0)
  {
    printf("error");
    exit(0);
  }
  if((shm=shmat(shmid,NULL,0))==NULL)
  {
    printf("Error");
    exit(0);
  }
//Client reads the shared memory
  for(s=shm;*s!='\0';s++)
    putchar(*s);
  putchar('\n');
//Client changes the first letter to ‘*’
  *shm='*';
}