[BusyBox] Adding an option to tar

Glenn McGrath bug1 at iinet.net.au
Fri Oct 15 01:16:49 UTC 2004


On Thu, 14 Oct 2004 16:45:21 -0700
"R. Weber" <rjweber at onz.com> wrote:

> Hello. I'm using busybox on a box that must integrate to an existing
> system. This system downloads files via ftp, and then untars them. The
> untar options are xzmf "filename". "m" is used to get rid of
> complaints about differing time stamps.
> 
> Busybox tar doesn't support the m option. I could add tar separately,
> but tar is huge, at least by default. I'd like to add this option to
> busybox. Looking at the tar.c code, I'm lost as to how to go about
> this. I've added the line
> 
>  { "no-file-time",  0, NULL, 'm' },
> 
> to the tar_long_options structure, which I thought would allow the m
> option, even though I haven't added any code for it yet, but the m
> option is still unrecognized. Is there a write-up somewhere that might
> bet me up to speed on changes to busybox, a design guideline, or
> something?

The tar_long_options arent always used.

The short options are somewhat complex in tar, but its required to add
add all the different options into bb_getopt_ulflags() which is what
does all the work sorting out the options.

The main documents we have regarding adding options are comments in the
code, many people find bb_getopt_ulflags hard to understand, its best to
learn it by looking at existing applets that use it.

Attached is a patch which adds the tar -m option, which you should be
able to follow to see how it works.

Although busybox has released 1.0, we are still in a feature freese, so
i wont commit this patch yet.

Busybox's 1.0 series will be just for bugfixes and a new "development"
branch will be added for new features. We need to move to subversion
before that happens. (it was mentioned on irc yesterday)


Glenn

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