[PATCH] add untar command

[Sascha Hauer]

Hi Yegor,

On Mon, Aug 03, 2020 at 07:07:00AM +0200, yegorslists at googlemail.com wrote:
> From: Yegor Yefremov <yegorslists at googlemail.com>
> 
> Use busybox implementation as a reference.

Would you add the busybox version to the commit message for reference
and to make future updates easier?

> +/* Concatenate path and filename to new allocated buffer.
> + * Add '/' only as needed (no duplicate // are produced).
> + * If path is NULL, it is assumed to be "/".
> + * filename should not be NULL.
> + */
> +static char* concat_path_file(const char *path, const char *filename)
> +{
> +      char *lc;
> +
> +      if (!path)
> +          path = "";
> +      lc = last_char_is(path, '/');
> +      while (*filename == '/')
> +          filename++;
> +      return xasprintf("%s%s%s", path, (lc==NULL ? "/" : ""), filename);
> +}

We already have this function in lib/libbb.c, better use it than adding
it again. You add more functions that seem to be generic busybox
functions, please check if they are better added to lib/libbb.c in case
we need them for other code.

> +static int do_untar(int argc, char *argv[])
> +{
> +	archive_handle_t *handle;
> +	int ret;
> +
> +	if (argc < 2)
> +		return COMMAND_ERROR_USAGE;
> +
> +	handle = init_handle();

This allocates memory which you never free, neither in the successful
case nor in the error path.

> +	handle->src_fd = open(argv[1], O_RDONLY);
> +	if (handle->src_fd < 0) {
> +		perror("open");
> +		return 1;
> +	}
> +
> +	if (argc == 3) {
> +		chdir(argv[2]);

Doesn't this change the current directory also in the calling shell?
Also this call can fail when the path doesn't exist or is not a
directory. You should check this.

> +	}
> +
> +	while(!get_header(handle))
> +		ret = 0;
> +
> +	if (ret)
> +		printf("failed to decompress\n");

'ret' is either used uninitialized or initialized to zero.

> +
> +	close(handle->src_fd);
> +	return ret;
> +}
> +
> +BAREBOX_CMD_START(untar)
> +	.cmd            = do_untar,
> +	BAREBOX_CMD_DESC("unpack a tar file")
> +	BAREBOX_CMD_OPTS("INFILE [DIRECTORY]")

I don't like positional arguments very much. It's fine for the infile,
but IMO the directory should be given with an option instead.

Sascha

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