stud_recv.c

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

typedef struct student{
  int roll;
  int marks;
}student;

int main()
{
    int temp1, temp2;
    int i, j, min_idx;
    int n=0;
    // 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

    
    student *stud = (student*) shmat(shmid,(void*)0,0);

    while(stud[n].roll != -1)        // to find the number of students
    {
	n++;
    }

    printf("Data read from memory.    Rank\n");
    for (i = 0; i < n; i++)
    {
        min_idx = i;
        for (j = i+1; j < n; j++)
          if (stud[j].marks > stud[min_idx].marks)
            min_idx = j;
        temp1=stud[i].marks;
	stud[i].marks=stud[min_idx].marks;
	stud[min_idx].marks=temp1;
	temp2=stud[i].roll;
	stud[i].roll=stud[min_idx].roll;
	stud[min_idx].roll=temp2;
    }
    for(int i=0; i<n; i++)
    {
        printf("Roll No.- %d : Marks- %d   %d\n", stud[i].roll,stud[i].marks,i+1);
    }

    //detach from shared memory 
    shmdt(stud);
    
    // destroy the shared memory
    shmctl(shmid,IPC_RMID,NULL);
     
    return 0;
}