#include <stdio.h>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/sem.h>
#include <sys/wait.h>
#include <string.h>
#include <cstdlib>

#define BUFFERSIZE 200
#define SEMKEY 251
#define SHMKEY 231
#define SHMSIZE 1024
#define FILENAME "abc.txt"

union semun {
    int val;
    struct semid_ds *buf;
    unsigned short *array;
};

int main() {
    char buf[BUFFERSIZE];
    int sem_id = semget(SEMKEY, 1, IPC_CREAT | 0600);
    union semun sem_val;
    sem_val.val = 0;
    semctl(sem_id, 0, SETVAL, sem_val);
    int shm_id = shmget(SHMKEY, SHMSIZE, IPC_CREAT | 0600);
    char *shm_addr = (char *)shmat(shm_id, NULL, 0);
    memset(shm_addr, 0, SHMSIZE);
    char *cur = shm_addr;
    FILE *fp = fopen(FILENAME, "wb");
    if (fork() == 0) {
        int isend = 0;
        int line = 1;
        printf("\n#line%d$ ", line);
        while (!isend && fgets(buf, BUFFERSIZE, stdin) != NULL) {
            line++;
            printf("\n#line%d$ ", line);
            if (buf[0] == 'Q' && strlen(buf) <= 2) {
                isend = 1;
                printf("\nExit...\n");
            } else {
                memcpy(cur, buf, strlen(buf));
                cur += strlen(buf);
                struct sembuf sem_op = {0, 1, 0};
                semop(sem_id, &sem_op, 1);
            }
        }
        *cur = -1;
        shmdt(shm_addr);
        exit(0);
    } else {
        while (1) {
            struct sembuf sem_op = {0, -1, 0};
            semop(sem_id, &sem_op, 1);
            if (*cur == -1) break;
            int i;
            for (i = 0; *cur != '\n'; cur++, i++)
                buf[i] = *cur;
            cur++;
            buf[i] = '\n';
            buf[++i] = 0;
            fwrite(buf, strlen(buf), 1, fp);
        }
        fclose(fp);
        wait(NULL);
        shmdt(shm_addr);
        shmctl(shm_id, IPC_RMID, NULL);
    }
    return 0;
}