Re: md5sum and filenames containing \

[Jim Meyering]

address@hidden (Bob Proulx) wrote:
> Olivier Delhomme wrote:
>> Here I have coreutils 5.2.1, debian 3.1 unstable, bash 3.00.16(1)
>> and I can not reproduce your problem. The hash value is correct and
>> without the \ at the beginning.
>
> On my Debian system the md5sum utility is not the GNU one but is from
> a different source and is included in the dpkg package.  It is a
> compatibility issue.  As you note it does not behave this way.  The
> GNU md5sum is shipped on Debian as md5sum.textutils.  In this
> particular case bash is not involved.
>
> I can reproduce the behavior with the latest GNU md5sum 5.3.1.
> However I also don't know why it is programed that way.  It is
> obviously intentional.

It is to inform `md5sum -c' that the file name is backslash-encoded.
This is necessary to make md5sum work with file names containing newlines.
For example:

# Create a file containing a newline:
$ touch 'a
b'

The `other' md5sum cannot deal with such a name:
o

$ /usr/bin/md5sum 'a
b'|/usr/bin/md5sum -c
/usr/bin/md5sum: can't open a
/usr/bin/md5sum: no files checked
[Exit 3]

But the md5sum from coreutils can:

$ /usr/bin/md5sum.textutils 'a
b'|/usr/bin/md5sum.textutils -c
a
b: OK