rem: return EINVAL;
add: return FS_EINVAL;
context: do_copy(int argc, char **argv){    if (cur_fd >= 0)        do_close(0, NULL);    if (argc < 3) {        printf("copy needs two arguments!\n");        return EINVAL;    }        if (argv[1][0] == ':' && argv[2][0] != ':') {        return do_copy_to_myfs(&argv[1][1], &argv[2][0]);    }    if (argv[2][0] == ':' && argv[1][0] != ':') {        return do_copy_from_myfs(&argv[1][0], &argv[2][1]);    }    printf("can't copy around inside of the file system (only in and out)\n");	return EINVAL;}