AW: BUG: grep -v -x -f does not work when pattern file is empty

[dietmar.schindler at manroland-web.com]

> Von: Quentin Rameau
> Gesendet: Mittwoch, 4. April 2018 23:29
> …
> Hello Luiz,
>
> > This simple test show the problem:
> >
> > $ touch a.txt
> > $ busybox grep -v -x -f a.txt /etc/passwd | wc -l
> > 0
> >
> > While gnu grep works:
> >
> > $ grep -v -x -f a.txt /etc/passwd | wc -l
> > 43
> >
> > If a.txt has any content, it works:
> >
> > $ echo >a.txt
> > $ busybox grep -v -x -f a.txt /etc/passwd | wc -l
> > 43
>
> The standard specifies, for the -f flag:
>
> “Patterns in pattern_file shall be terminated by a <newline>. A null
> pattern can be specified by an empty line in pattern_file.”

The above does not rule an empty pattern_file (i. e. no patterns) out.
The actually relevant part from http://pubs.opengroup.org/onlinepubs/9699919799/utilities/grep.html is:

-f  pattern_file
Read one or more patterns from the file named by the pathname pattern_file. …

> So calling grep -f with an empty file is non-standard thus not a BUG
> per se.

True, but because of the wording "one or more patterns".
--
Regards,
Dietmar Schindler
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