20131217 :: draft

#include <sys/ipc.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/sem.h>
#include <sys/wait.h>

volatile int flag = 0;

void handler(int sig) {
    flag = 1;
}

void makeOp(struct sembuf * buf, short num, short op) {
    buf->sem_num = num, buf->sem_op = op, buf->sem_flg = 0;
}

int main(int argc, char ** argv) {
    int fd[2];
    pipe(fd);
    int sem_key = ftok(argv[0], 1);
    int semid = semget(sem_key, 2, IPC_CREAT | IPC_EXCL | 0666);
    signal(SIGINT, handler);
    int curValue = 0;
    struct sembuf buf;
    FILE * in = fdopen(fd[0], "r");
    FILE * out = fdopen(fd[1], "w");
    if (!fork()) {
        while (1) {
            if (flag) {
                printf("%d\n", curValue);
                fflush(stdout);
                break;
            }
            makeOp(&buf, 1, -1);
            semop(semid, &buf, 1);
            fscanf(in, "%d", &curValue);
            ++curValue;
            fprintf(out, "%d\n", curValue);
            makeOp(&buf, 0, 1);
            semop(semid, &buf, 1);
        }
        fclose(in), fclose(out);
        return 0;
    }
    fprintf(out, "%d\n", 1); // начинаем с единички
    makeOp(&buf, 1, 1);
    semop(semid, &buf, 1);
    while (1) {
        if (flag) {
            printf("%d\n", curValue);
            fflush(stdout);
            break;
        }
        makeOp(&buf, 0, -1);
        semop(semid, &buf, 1);
        fscanf(in, "%d", &curValue);
        ++curValue;
        fprintf(out, "%d\n", curValue);
        makeOp(&buf, 1, 1);
        semop(semid, &buf, 1);
    }
    fclose(in), fclose(out);
    semctl(semid, 0, IPC_RMID);
    return 0;
}