zsh-workers
 help / color / mirror / code / Atom feed
From: Daniel Shahaf <d.s@daniel.shahaf.name>
To: Bart Schaefer <schaefer@brasslantern.com>
Cc: "zsh-workers@zsh.org" <zsh-workers@zsh.org>,
	Martin Tournoij <martin@arp242.net>
Subject: Re: Any way to allow clobbering empty files when noclobber is set?
Date: Sat, 6 Jun 2020 08:03:03 +0000	[thread overview]
Message-ID: <20200606080303.0ab42262@tarpaulin.shahaf.local2> (raw)
In-Reply-To: <CAH+w=7YqAiOdd4sAbSRxghp3RD_qQjfR5V8jT-KhhOOppysv1A@mail.gmail.com>

Bart Schaefer wrote on Sat, 06 Jun 2020 00:08 -0700:
> On Fri, Jun 5, 2020 at 9:55 PM Daniel Shahaf <d.s@daniel.shahaf.name> wrote:
> >
> > Bart Schaefer wrote on Fri, 05 Jun 2020 18:41 -0700:  
> > >
> > > I don't think that's the intended typical usage of noclobber.  It's
> > > not set by default, and it can't have any effect outside the local
> > > shell.  
> >
> > NO_CLOBBER causes open() to be called with the O_EXCL bit, which does
> > affect other processes as well.  
> 
> ??  All that O_EXCL guarantees is that no other process is able to
> create the file.  Once it exists, another file can open it and
> truncate it and write to it, unless prevented by umask.

But in Roman's example, _both_ backgrouned processes use O_EXCL, so
whichever process loses the race will get an error when it calls
open(2).  Yes, attempts to open() the file without O_EXCL will succeed,
but when a file is used as a mutex, everyone who tries to open the file
will try to use O_EXCL.

Makes sense?

Cheers,

Daniel

  reply	other threads:[~2020-06-06  8:03 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20200603020919eucas1p13e26ebcbb335784d14bfb97b137f385a@eucas1p1.samsung.com>
2020-06-03  2:08 ` Martin Tournoij
2020-06-03 12:04   ` Peter Stephenson
2020-06-04  1:48     ` Daniel Shahaf
2020-06-04  2:43       ` Bart Schaefer
2020-06-04  4:06         ` Daniel Shahaf
2020-06-04  5:00           ` Bart Schaefer
2020-06-05  3:10             ` Daniel Shahaf
2020-06-05  3:18               ` Daniel Shahaf
2020-06-06  1:07               ` Bart Schaefer
2020-06-06  4:48                 ` Daniel Shahaf
2020-06-06  7:04                   ` Bart Schaefer
2020-06-04  6:31       ` Martin Tournoij
2020-06-05  2:22         ` Daniel Shahaf
2020-06-04  2:13     ` Vin Shelton
2020-06-04  2:35       ` Bart Schaefer
2020-06-04  2:36       ` Daniel Shahaf
2020-06-04 11:57         ` Vin Shelton
2020-06-04  5:06     ` Bart Schaefer
2020-06-04  5:41       ` Roman Perepelitsa
2020-06-05  2:07         ` Daniel Shahaf
2020-06-05  4:38           ` Roman Perepelitsa
2020-06-06  1:41             ` Bart Schaefer
2020-06-06  4:55               ` Daniel Shahaf
2020-06-06  6:25                 ` Roman Perepelitsa
2020-06-06  7:08                 ` Bart Schaefer
2020-06-06  8:03                   ` Daniel Shahaf [this message]
     [not found]           ` <1941572212.466119.1591360860372@mail2.virginmedia.com>
     [not found]             ` <e7f7dfe2-eb4a-457b-85fb-091935a74c0e@www.fastmail.com>
2020-06-06 11:57               ` Peter Stephenson
2020-06-06 12:48                 ` Roman Perepelitsa
2020-06-06 15:24                   ` Bart Schaefer
2020-06-06 16:24                     ` Peter Stephenson
2020-06-07 11:55                       ` Daniel Shahaf
2020-06-07 17:00                         ` Peter Stephenson
2020-06-08  3:27                           ` Daniel Shahaf
2020-06-08  9:30                             ` Peter Stephenson
2020-06-07 17:20                         ` Bart Schaefer
2020-06-06 15:09                 ` Bart Schaefer
2020-06-04  6:47       ` Martin Tournoij
2020-06-04  9:42       ` Peter Stephenson
2020-06-04 12:20         ` Roman Perepelitsa
2020-06-04 12:26           ` Peter Stephenson
2020-06-04 12:15     ` Peter Stephenson
2020-06-04 20:35       ` Bart Schaefer
2020-06-05  1:59         ` Daniel Shahaf

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=20200606080303.0ab42262@tarpaulin.shahaf.local2 \
    --to=d.s@daniel.shahaf.name \
    --cc=martin@arp242.net \
    --cc=schaefer@brasslantern.com \
    --cc=zsh-workers@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).