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

#define TEXT_SZ 2048

struct shared_use_st {
    int written_by_you;
    char some_text[TEXT_SZ];
};

int main()
{
    int running = 1;
    void *shared_memory =(void *)NULL;
    struct shared_use_st *shared_stuff;
    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 error");
        exit(1);
    }
    shared_memory = shmat(shmid,NULL,NULL);
    if(shared_memory ==  (void *)-1){
        fprintf(stderr,"shmat error");
        exit(1);
    }
    printf("Memory attached at %x\n",(int)(shared_memory));
    
    shared_stuff = (struct shared_use_st *)shared_memory;
    shared_stuff->written_by_you = 0;
    
     while(running) {
        if(shared_stuff->written_by_you) {
            printf("You wrote: %s",shared_stuff->some_text);
            sleep(rand()%4);
            shared_stuff->written_by_you = 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);
    }
    if(shmctl(shmid, IPC_RMID, 0) == -1) {
        fprintf(stderr,"shmctl IPC_RMID failed!\n");
        exit(1);
    }

    exit(0);
}

#include<unistd.h>
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#include<sys/shm.h>

#define BUFSIZE 2048

struct shared_use_st {
    int written_by_you;
    char some_text[BUFSIZE];
};
int main()
{
    int running;
    void *shared_memory = NULL;
    struct shared_use_st *shared_stuff;
    char buffer[BUFSIZE];
    int shmid;
    
    if( shmget((key_t)1234, sizeof(struct shared_use_st), 0666 | IPC_CREAT) == -1){
        fprintf(stderr,"shmget error");
        exit(1);
    }
    shared_memory = shmat(shmid, NULL,NULL);
    if(shared_memory == (void *)-1){
        fprintf(stderr,"shmat error");
        exit(1);
    }
    
    printf("Memory attached at %X\n",(int)shared_memory);
    shared_stuff = (struct shared_use_st *)shared_memory;
    while(1){
        while(shared_stuff->written_by_you == 1){
            sleep(1);
            printf("Waiting for client ...\n");
        }
        printf("Enter some text: ");
        fgets(buffer, BUFSIZE,stdin);
        
        strncpy(shared_stuff->some_text,buffer,BUFSIZE);
        shared_stuff->written_by_you = 1;

        if(strncmp(buffer,"end",3) == 0)
            break;
    }
    
    if(shmdt(shared_memory) == -1){
        fprintf(stderr,"shmdt error");
        exit(1);
    }
    exit(0);
}