File Lock

/*  잠김이 풀릴때까지 기다린다 .(F_SETLKW) */

int fd_isopen(int fd)
{
    struct flock lock;

    lock.l_type = F_WRLCK;
    lock.l_start = 0;
    lock.l_whence = SEEK_SET;
    lock.l_len = 0;

    return fcntl(fd, F_SETLKW, &lock);
}

/*  파일 잠금 해제 */ 
int fd_unlock(int fd)
{
    struct flock lock;

    lock.l_type = F_UNLCK;
    lock.l_start = 0;
    lock.l_whence = SEEK_SET;
    lock.l_len = 0;

    return fcntl(fd, F_SETLK, &lock);
}