Slightly modified code from GeeksforGeeks https://www.geeksforgeeks.org/ipc-shared-memory

SharedMemoryReader.cpp

#include <iostream>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
using namespace std;

int main()
{
        // ftok to generate unique key 
        key_t key = ftok("shmfile",65);

        // shmget returns an identifier in shmid 
        int shmid = shmget(key,1024,0666|IPC_CREAT);

        // shmat to attach to shared memory 
        char *str = (char*) shmat(shmid,(void*)0,0);

        printf("Data read from memory: %s\n",str);

        //detach from shared memory 
        shmdt(str);

        // destroy the shared memory 
        shmctl(shmid,IPC_RMID,NULL);

        return 0;
}

SharedMemoryWriter.cpp

#include <iostream>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <stdio.h>
#include <string.h>

using namespace std;

int main()
{
        // ftok to generate unique key 
        key_t key = ftok("shmfile",65);

        // shmget returns an identifier in shmid 
        int shmid = shmget(key,1024,0666|IPC_CREAT);

        // shmat to attach to shared memory 
        char *str = (char*) shmat(shmid,(void*)0,0);

        cout << "Write Data : ";
        cin >> str; // read word from stdin

        printf("Data written in memory: %s\n",str);

        //detach from shared memory 
        shmdt(str);

        return 0;
}