From: "Jérémie Roquet" <arkanosis@gmail.com>
To: Zsh Users <zsh-users@zsh.org>
Subject: Re: $pipestatus and shell functions
Date: Mon, 11 Apr 2011 19:33:05 +0200 [thread overview]
Message-ID: <BANLkTineXEfWH3n=Q+a40g_3PCz5P=D25A@mail.gmail.com> (raw)
In-Reply-To: <20110411174825.3bd3e84b@pwslap01u.europe.root.pri>
Hi Peter,
2011/4/11 Peter Stephenson <Peter.Stephenson@csr.com>:
> On Mon, 11 Apr 2011 17:38:35 +0100
> Peter Stephenson <Peter.Stephenson@csr.com> wrote:
>> Jérémie Roquet <arkanosis@gmail.com> wrote:
>> > $ foo() { false | true }
>> > $ true | foo ; echo $pipestatus
>> > 1 0
>>
>> You're falling
>> foul of (i) a shell function looks like a job to the shell (ii) it
>> appears that function is being made the current job, so generates the
>> pipe status when it exits (the same happens if you use a { ... }
>> expression there, so that's not a workaround). However, there's some
>> truly horrible handling for job control in complicated cases like
>> this (what is supposed to get signals and what do you return to if
>> you get one?) so it's quite possible that those two contributing
>> factors are themselves deliberate. I'm not entirely convinced,
>> though; it surprises me that that the notion of the current job
>> changes like that.
>
> A little digging suggests it is deliberate. If you ever have a week to
> spare, look at the comment relating to the declaration of list_pipe in
> exec.c. Within the description of the example:
>
> cat foo | while read a; do grep $a bar; done
>
> you find
>
> If the user hits ^Z at this point (and jobbing is used), the
> shell is notified that the grep was suspended. The list_pipe flag is
> used to tell the execpline where it was waiting that it was in a pipeline
> with a shell construct at the end (which may also be a shell function or
> several other things). When zsh sees the suspended grep, it forks to let
> the sub-shell execute the rest of the while loop.
>
> So the shell is deliberately treating constructs in the right hand side
> of the pipeline as jobs in their own right, and in particular as the
> current foreground job, since that's the one where you can do job
> control. This overrides the natural expectation that the pipeline is
> the current job and so the one for which $pipestatus would be reported.
Makes sense for job control, but that's… counter intuitive for
$pipestatus. I've to think a bit longer about it ;)
Anyway, thanks a lot for your help, the subshell trick does the job.
Best regards,
--
Jérémie
prev parent reply other threads:[~2011-04-11 17:33 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-11 15:52 Jérémie Roquet
2011-04-11 16:38 ` Peter Stephenson
2011-04-11 16:48 ` Peter Stephenson
2011-04-11 17:33 ` Jérémie Roquet [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='BANLkTineXEfWH3n=Q+a40g_3PCz5P=D25A@mail.gmail.com' \
--to=arkanosis@gmail.com \
--cc=zsh-users@zsh.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://git.vuxu.org/mirror/zsh/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).