WAP to synchronize data among three processes using shared memory

#include<unistd.h>

#include<stdlib.h>

#include<stdio.h>

#include<string.h>

#include<sys/shm.h>

#include "../shmreader/shm_com.h"

int main()

{

int running = 1;

void *shared_memory = (void *)0;

struct shared_use_st *shared_stuff;

char buffer[BUFSIZ];

int shmid;

srand((unsigned int)getpid());

shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666 | IPC_CREAT);

if(shmid == -1)

{

fprintf(stderr, "shmget failed\n");

exit(EXIT_FAILURE);

}

shared_memory = shmat(shmid, (void *)0, 0);

if(shared_memory == (void *)-1)

{

fprintf(stderr, "shmat failed\n");

exit(EXIT_FAILURE);

}

        printf("Memory attached at %X\n", (int)shared_memory);

        shared_stuff = (struct shared_use_st *)shared_memory;

shared_stuff->B_flag = 0;

        while(running)

        {

                while((shared_stuff->A_flag == 1 && shared_stuff->B_flag == 0  && shared_stuff->C_flag == 0 ) || (shared_stuff->A_flag == 0 && shared_stuff->B_flag == 0  && shared_stuff->C_flag == 1 )|| (shared_stuff->A_flag == 1 && shared_stuff->B_flag == 0  && shared_stuff->C_flag == 1 ) || (shared_stuff->A_flag == 1 && shared_stuff->B_flag == 1  && shared_stuff->C_flag == 1 ))

                {

        

                        sleep(1);

                        printf("waiting for process A to write....\n");

                }

if(shared_stuff->A_flag == 0 && shared_stuff->B_flag == 0 && shared_stuff->C_flag == 0)

{

                printf("Enter some text for B: ");

                fgets(buffer, BUFSIZ, stdin);

                strncpy(shared_stuff->some_text, buffer, TEXT_SZ);

                shared_stuff->A_flag = 0;

                shared_stuff->B_flag = 0;

                shared_stuff->C_flag = 1;

}

if(shared_stuff->A_flag == 0 && shared_stuff->B_flag == 1 && shared_stuff->C_flag == 0)

                {

printf("Process A  wrote: %s", shared_stuff->some_text );

  sleep(rand()%4);  

  

                shared_stuff->A_flag = 0;

                shared_stuff->B_flag = 0;

                shared_stuff->C_flag = 0;

                }

                if(strncmp(shared_stuff->some_text, "end", 3) == 0)

                {

                        running = 0;

                }

        }

        

if(shmdt(shared_memory) == -1)

        {

                fprintf(stderr, "shmdt failed\n" );

                exit(EXIT_FAILURE);

        }

exit(EXIT_SUCCESS);

}