ipc_reader.c

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/shm.h>
#include<string.h>

/*This program creates a shared memory segment, attaches itself to it and 
then writes some content into the shared memory segment.*/

void main()
{
    int i;
    void *shared_memory;
    char buff[100];
    int shmid;
    shmid=shmget((key_t)2345, 1024, 0666|IPC_CREAT); //creates shared memory segment with key 2345, having size 1024 bytes. IPC_CREAT is used to create the shared segment if it does not exist. 0666 are the permisions on the shared segment
    printf("Key of shared memory is %d\n",shmid);
    shared_memory=shmat(shmid,NULL,0); //process attached to shared memory segment
    printf("Process attached at %p\n",shared_memory); //this prints the address where the segment is attached with this process
    printf("Enter some data to write to shared memory\n");
    read(0,buff,100); //get some input from user
    strcpy(shared_memory,buff); //data written to shared memory
    printf("You wrote : %s\n",(char *)shared_memory);
}