bug#4115: grep and null device

[Jason Rumney]

Eli Zaretskii wrote:

> > AIUI the null device is only there to make sure the grep call doesn't hang
> > if you forget to pass it files to search. It seems a lot of pain for a
> > marginal benefit!
> >     
>
> I don't know yet why null device is there.  Seeing the command line
> would help.
>   

It is there to force grep to print filenames in its output, even if only 
a single filename is given on the command line.