C PROGRAM FOR INTER PROCESS COMMUNICATION USING SHARED MEMORY (WITH ALGORITHM)

AIM : To implement inter-process communication using shared memory

ALGORITHM :

step 1 : start
step 2 : declare shid, pid as integer and *msg as char
step 3 : get the shid of existing shared memory using shmget()
step 4 : attach the existing shared memory to address using shmat()
step 5 : create a process using fork()
step 6 : if it is a parent process then do
             a) read the message
             b) write it to shared memory
step 7 : if it is a child process then read the message from shared memory and print it.
step 8 : stop

PROGRAM :

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

int main()
{

  int pid, shid;
  char *msg;
  shid = shmget(IPC_PRIVATE,1,IPC_CREAT|0666);
  msg = shmat(shid,0,0);
  pid = fork();
  if(pid>0)
  {
      printf("PARENT PROCESS");
      printf("\n enter the message to child : ");
      scanf("%s",msg);
      printf("\n message is written into the shared memory by parent");
   }
   if(pid == 0)
   {
       sleep(6);
       printf("\n CHILD PROCESS");
       printf("\n child reads the message %s : ",msg);
    }
  exit(0);
}


OUTPUT 

compile : gcc filename.c
run         : ./a.out

enter the message to child : mother
control in parent process
message is written into the shared memory by parent
control in child process
child reads the message
          mother