Re: [dd] conv=sparse option

[Jim Meyering]

Samuel Thibault <address@hidden> wrote:
> Some time ago, I wrote a conv=sparse option for dd, attached is the
> patch.  The goal is to recreate a sparse file from a file with 0s.
> Typically, I use it to do this:
>
> # mount /dev/hda6 /mnt/mnt
> # dd bs=1M < /dev/zero > /mnt/mnt/foo
> # rm -f /mnt/mnt/foo
> # umount /mnt/mnt
> # dd bs=1M conv=sparse < /dev/hda6 > /mnt/savhda6
>
> Which creates a sparse file out of my not-so-filled partition.  Of
> course, there may be other uses: re-sparsing a qemu image before tarring
> it for public download, etc.
>
> Maybe it could be useful to apply it mainstream?

Hi Samuel,

I like the idea.
Are you willing to do more work on it and assign copyright to the FSF?
E.g.,
 - update the texinfo documentation, including an example like the above
 - add tests to exercise the new functionality

Some superficial comments on the patch:
 - any new globals must have file-"static" scope
 - use xcalloc, not calloc
 - use ST_BLKSIZE, not stat.st_blksize
 - update dd's --help output
 - use the same indentation/formatting style as in the rest of the code
 - make your changes relative to the latest sources from git:

i.e., do this to get the latest sources:

  git clone git://git.sv.gnu.org/coreutils