bug#25029: shuf generates “Bad file descriptor” error on nfs but only when run as a background process

[Pádraig Brady]

On 25/11/16 23:59, Pádraig Brady wrote:
> On 25/11/16 22:24, Alex Ryan wrote:
>> I am not certain about this but I *think* this might be a bug in shuf.
>>
>> full description of how to reproduce is here
>> http://stackoverflow.com/questions/40730239/shuf-generates-bad-file-descriptor-error-on-nfs-but-only-when-run-as-a-backgro
> 
> The minimum reproducer is:
> 
>   $ shuf 0>&-
>   shuf: read error: Bad file descriptor
> 
> The reason is that the specified file is reopened to stdin,
> which is a general technique used by single file filters.
> I.E. this isn't specific to shuf:
> 
>   $ tac 0>&-
>   tac: standard input: read error: Bad file descriptor
> 
> You can avoid the issue by redirecting stdin from the file like:
> 
>   $ shuf < your_file

Actually the minimum reproducer is:

  $ shuf /dev/null 0>&-
  shuf: read error: Bad file descriptor

That format shows that tac doesn't have the issue
(and tac is not a single file util anyway):
but uniq does have the issue:

  $ uniq /dev/null 0>&-
  uniq: error reading /dev/null

We might be able to improve this.
Anyway the workaround presented previously should work.

cheers,
Pádraig