Re: [coreutils] [PATCH] md5sum: Add option to ignore non-existant files

[Pádraig Brady]

On 10/12/10 00:38, Pádraig Brady wrote:
> On 09/12/10 03:14, Luther wrote:
>> Normally, when I use md5sum, it's when I download a file and an MD5SUMS
>> file that comes with it. This MD5SUMS file usually lists many files
>> including the one I downloaded. When I run 'md5sum -c MD5SUMS', I get
>> many error messages about files that I don't have. Obviously, I don't
>> care about the files I didn't download, and the error messages make it
>> difficult to see the output relating to the file that I do care about.
>>
>> I suggest a new option, -i/--ignore-missing, which ignores any filenames
>> that do not exist on the filesystem.
>>
>> In my patch, the option simply suppresses both relevant error messages.
>> Another approach might be to have digest_check check to see if the file
>> exists. If it doesn't, don't call digest_file or print the 'FAILED'
>> message.
>>
>> Sorry if my patch is a little messy, being in 3 parts. I'm not used to
>> using git.
>>
>> HTH, and let me know what you think...
>> Luther
> 
> Thanks for the patch,
> and sorry for the mailing list delay
> (I'm not sure what moderation is done on these lists)
> 
> So you would like to filter out the warnings.
> Well they go to stderr, so you could just:
> 
>   md5sum -c file.sum 2>/dev/null
> 
> If you wanted to filter further to just FAILED you could:
> 
>   md5sum -c file.sum 2>/dev/null | grep FAILED$
> 
> It has the disadvantage of being longer to type
> but the advantage of using existing tools and
> options to do the filtering.  So at first glance
> this option doesn't seem needed.

There was another request for this at
https://bugzilla.redhat.com/1276664

Thinking further, one reason we might consider this is because
currently open() and read() errors are not distinguished.
You would want to treat a read() error like a checksum error,
and not like an open()==ENOENT. Also other errors from open()
should not be treated like ENOENT.

Another reason is because grep -E '(OK|FAILED)$' is locale dependent,
so one would need LC_ALL=C md5sum ... | grep ...

Given the above and how common this use case is,
I'd now be 60:40 for adding Luther's patch.

cheers,
Pádraig.