From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org
X-Spam-Level: 
X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI,
	RCVD_IN_DNSWL_NONE autolearn=ham autolearn_force=no version=3.4.4
Received: (qmail 22889 invoked from network); 6 Jun 2020 18:20:34 -0000
Received: from ns1.primenet.com.au (HELO primenet.com.au) (203.24.36.2)
  by inbox.vuxu.org with ESMTPUTF8; 6 Jun 2020 18:20:34 -0000
Received: (qmail 13866 invoked by alias); 6 Jun 2020 18:20:21 -0000
Mailing-List: contact zsh-users-help@zsh.org; run by ezmlm
Precedence: bulk
X-No-Archive: yes
List-Id: Zsh Users List <zsh-users.zsh.org>
List-Post: <mailto:zsh-users@zsh.org>
List-Help: <mailto:zsh-users-help@zsh.org>
List-Unsubscribe: <mailto:zsh-users-unsubscribe@zsh.org>
X-Seq: 24908
Received: (qmail 14400 invoked by uid 1010); 6 Jun 2020 18:20:21 -0000
X-Qmail-Scanner-Diagnostics: from mail-oi1-f182.google.com by f.primenet.com.au (envelope-from <schaefer@brasslantern.com>, uid 7791) with qmail-scanner-2.11 
 (clamdscan: 0.102.3/25828. spamassassin: 3.4.4.  
 Clear:RC:0(209.85.167.182):SA:0(-1.9/5.0):. 
 Processed in 1.722891 secs); 06 Jun 2020 18:20:21 -0000
X-Envelope-From: schaefer@brasslantern.com
X-Qmail-Scanner-Mime-Attachments: |
X-Qmail-Scanner-Zip-Files: |
Received-SPF: pass (ns1.primenet.com.au: SPF record at _netblocks.google.com designates 209.85.167.182 as permitted sender)
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=1e100.net; s=20161025;
        h=x-gm-message-state:mime-version:references:in-reply-to:from:date
         :message-id:subject:to:cc;
        bh=UKfSvDDzNjzCYaEZR1LuLsGQssjKG8OkKzr5OFkjr4s=;
        b=IyTA6o0NW0f1VxoMTi+T2gSYvi76KFnv5qaRPjSH0mtm1X3jFDz6K4diwX2fs6QArX
         IfYLlEUcdAlyNySDmNErW0l3myTs0lcV0PKZ8gxA/RV6XL6lblbJRu8E2cSdlAvETqON
         aF4b0DdgyppwQqFivumKepgQXjnKrwQOzQLHZ9k7JQZT9Wa7gMHophydxaXaF71reE4y
         /A2KsEhqdZ4fNexfspMaBpSUmIMIQvZuP3EymKBd/mH2/28WZP7MpPblM/j24bk7wCGw
         x18f9Qned5uaAwqZPyjemZ7nvjBYMSBqn+WnLcv1uxtnx4pTE6aBxMkCXClKaEIv1Ep1
         iRGw==
X-Gm-Message-State: AOAM53387DMjMXOIFDyu5GNvm7FLQYZ/zvYGGzyp8NEYdQ18ki79XwIe
	6nksdAVr1rVjN0nVMQlM5SOAmcgddN0tZ+vQevqoDQ==
X-Google-Smtp-Source: ABdhPJw7CYLK/mcPd2R6To4OUT6i+tciN+IWcWhbhc1zupTzH3hH88hg7CLojUQ/JTDjJl+gA+hebycdnqok4tAIzQs=
X-Received: by 2002:aca:1b13:: with SMTP id b19mr2368937oib.132.1591467585751;
 Sat, 06 Jun 2020 11:19:45 -0700 (PDT)
MIME-Version: 1.0
References: <CAP+y1xAKauPdSQO7XKRBYrFKFuWQCuDg8hmBRrbFTaKr2wMYdA@mail.gmail.com>
 <CAHYJk3SLwb1f1o9Ow1otbYDH1epXBz0=1Lr6B-tJtoGDGQEWXQ@mail.gmail.com> <20200606010018.5d9c4a33@tarpaulin.shahaf.local2>
In-Reply-To: <20200606010018.5d9c4a33@tarpaulin.shahaf.local2>
From: Bart Schaefer <schaefer@brasslantern.com>
Date: Sat, 6 Jun 2020 11:19:34 -0700
Message-ID: <CAH+w=7bEco_BFsyzVC+BNHh7W55K7ttSNsKEu0TByXK-eAhyOQ@mail.gmail.com>
Subject: Re: subprocess
To: Daniel Shahaf <d.s@daniel.shahaf.name>
Cc: Mikael Magnusson <mikachu@gmail.com>, Pier Paolo Grassi <pierpaolog@gmail.com>, 
	Zsh-Users List <zsh-users@zsh.org>
Content-Type: text/plain; charset="UTF-8"

On Fri, Jun 5, 2020 at 6:01 PM Daniel Shahaf <d.s@daniel.shahaf.name> wrote:
> > On 6/5/20, Pier Paolo Grassi <pierpaolog@gmail.com> wrote:
> > > efe() cat $1
> > > efe <(seq 1 10) | wc -l
> > > cat: /proc/self/fd/13: No such file or directory
> > > 0
> > >
> > > gives error, instead these all works fine:
> > > efe =(seq 1 10)| wc -l
> > > cat <(seq 1 10)| wc -l
>
> And this,
>
> % () { cat $1 } <(seq 1 10) | wc -l

You can see what's happening if you do it this way:

% efe() ls -l ${${1:+$1:h}:-/proc/self/fd}
% efe <(seq 1 10) | cat
total 0
lrwx------ 1 schaefer schaefer 64 Jun  6 10:59 0 -> /dev/pts/0
l-wx------ 1 schaefer schaefer 64 Jun  6 10:59 1 -> pipe:[1945962]
lrwx------ 1 schaefer schaefer 64 Jun  6 10:59 2 -> /dev/pts/0
lr-x------ 1 schaefer schaefer 64 Jun  6 10:59 3 -> /proc/5533/fd
% () { ls -l $1:h } <(seq 1 10) | cat
total 0
lrwx------ 1 schaefer schaefer 64 Jun  6 11:00 0 -> /dev/pts/0
l-wx------ 1 schaefer schaefer 64 Jun  6 11:00 1 -> pipe:[1945988]
lr-x------ 1 schaefer schaefer 64 Jun  6 11:00 11 -> pipe:[1944505]
lrwx------ 1 schaefer schaefer 64 Jun  6 11:00 2 -> /dev/pts/0
lr-x------ 1 schaefer schaefer 64 Jun  6 11:00 3 -> /proc/5537/fd

A named function on the left side of a pipeline becomes its own "job",
where all descriptors above 10 are closed.  An anonymous function
stays in the parent shell (which is still a forked subshell, because
of the pipeline) so those descriptors are not closed.

% efe =(seq 1 10) | cat
total 4
-rw------- 1 schaefer schaefer 21 Jun  6 11:09 zshkDpnRj

In that case a real file has been created and is referenced by name,
so the descriptors closing does not matter.

% efe <<(seq 1 10) | cat
total 0
lr-x------ 1 schaefer schaefer 64 Jun  6 11:13 0 -> pipe:[1946804]
l-wx------ 1 schaefer schaefer 64 Jun  6 11:13 1 -> pipe:[1946579]
lrwx------ 1 schaefer schaefer 64 Jun  6 11:13 2 -> /dev/pts/0
lr-x------ 1 schaefer schaefer 64 Jun  6 11:13 3 -> /proc/5599/fd

For <<(...) no file is created at all, instead the standard input of
the function is changed.

> Mikael Magnusson wrote on Fri, 05 Jun 2020 12:25 +0200:
> >
> > This also works,
> > % efe <(seq 1 10) > >(wc -l)
> > as does this,
> > % wc -l < <(efe <(seq 1 10))

In both of these cases, there is no pipeline, so efe stays in the
parent shell and all the descriptors remain open.