OS Echo using Shared Memory C Program

Operating Systems Lab Manual / OS Echo using Shared Memory C Program

Program Name

Write a C Program for the use of echo shared memory in Operating System.

Theory

A pipe is a technique for passing information from one program process to another. 
Shared memory is a memory shared between two or more processes.Using pointers to shared memory
we read and write data to shared memory.

shmat():Shared memory Attach
shmdt():Shared memory Dettach

Program Code

#include<string.h> 
#include<stdlib.h> 
#include<stdio.h> 
#include<sys/types.h> 
#include<sys/msg.h> 
#include<sys/ipc.h> 
int main()
{
int shmid,pid; char *ptr;
shmid=shmget((key_t)17,10,IPC_CREAT| 0666); 
ptr=(char *) 
shmat(shmid,0,0);
pid=fork(); 
if(pid==0)
{
printf("Child Process \n"); 
strcpy(ptr,"Child Process - Welcome"); 
sleep(2); 
write(1,ptr,20);
printf("\n"); 
shmctl(ptr,IPC_RMID,0); 
exit(0);
}
else
{
printf("\nParent Process\n"); 
sleep(1); 
write(1,ptr,20);
printf("\n"); 
strcpy(ptr,"Parent Process - Welcome"); 
wait(0);
}
return 0;
}

Input:

Output:
Child Process
Parent Process
Child Process - Welcome
Parent Process - Welcome

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