Re: sha1summ of complete directory?

[Tzafrir Cohen <tzafrir@cohens.org.il>]

On Tue, Jul 07, 2009 at 12:08:05AM -0400, Scott Gifford wrote:
> Ron Johnson <ron.l.johnson@cox.net> writes:

> You will need to figure out what metadata you care about and what you
> don't, then.  For example, do you want to detect a renamed file?  A
> change in mtime/ctime/utime?  A change in permissions?
> 
> For the file contents, if there are no subdirectories you can use:
> 
>     cat `ls` |sha1sum

Which is basically:

  cat * | sha1sum

And it would still fail to detect the difference between:

  case 1:
    seq 1 6 >file1

  case2:
    seq 1 3 >file1
    seq 4 6 >file2

(Same content, different metadata)

> 
> ls will sort the files, so they will end up in the same order every
> time.
> 
> For metadata, you could come up with the flags to ls that give the
> metadata you want, then include that before or after the cat, like
> this:
> 
>     (ls -l; cat `ls`) |sha1sum

Same comment about echo *.

Also note that packing files together with their metadata is, in fact,
exactly what an archive utility does:

  tar cf - . | sha1sum

This will also pick hidden files and subdirectories.

Oh, and sha1sum is not the only checksum available:

$ ls /usr/bin/*sum
/usr/bin/cksum             /usr/bin/lh_source_md5sum  /usr/bin/sha384sum
/usr/bin/innochecksum      /usr/bin/md5sum            /usr/bin/sha512sum
/usr/bin/jacksum           /usr/bin/sha1sum           /usr/bin/shasum
/usr/bin/kmk_md5sum        /usr/bin/sha224sum         /usr/bin/sum
/usr/bin/lh_binary_md5sum  /usr/bin/sha256sum

Some of those are actually relevant :-)

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