On Thu, 17 Feb 2022 08:32:06 +0800
Kang-Che Sung <explore...@gmail.com> wrote:
> On Thu, Feb 17, 2022 at 8:01 AM Ulrich Eckhardt
> <ulrich.eckha...@base-42.de> wrote:
> > Now, for an example where it makes a difference. Consider a Bash
> > script like this:
> >
> > # enable automatic error handling
> > set -eo pipefail
> > # check for string "issues" in a logfile
> > cat logfile | grep issue | sort --unique
> >
> > If there are no issues in the logs, grep return exit code 1 and the
> > shell interprets this as an error and exits itself.
> >
>
> Why do we need to implement a workaround in grep while you can
> do this in shell to ignore the exit code of grep?
>
> { grep issue <logfile || :; } | sort --unique
`grep -p ...` rather replaces `grep ... || test $? = 1`. The advantage
is that it is explicit about what it does. Understanding the intent of
`-p` or `--pipe` is easier than understanding the alternative.
> > I've implemented that feature here, though it lacks tests yet:
> > https://github.com/UlrichEckhardt/busybox/tree/grep-pipe-option
> > Also, I'm currently trying to get the same feature into GNU grep as
> > well, the long form `--pipe` is used there. I've also considered
> > `--filter` (because it only filters) as alternative. I'm not fully
> > happy with either one, maybe someone here comes up with a better
> > suggestion.
>
> I don't see the '--pipe' option in GNU grep manual
> <https://www.gnu.org/software/grep/manual/grep.html>
Misunderstanding: It's not in there! I have it implemented already and
I'm trying to get it incorporated there, which takes time due to FSF
paperwork.
Cheers!
Uli
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