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From: Roman Perepelitsa <roman.perepelitsa@gmail.com>
To: Daniel Shahaf <d.s@daniel.shahaf.name>
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: Fri, 5 Jun 2020 06:38:46 +0200	[thread overview]
Message-ID: <CAN=4vMoC8aNBz=ZAW-BdA9W6MaBXN3SNBPpZZQobVRwjUg2wGQ@mail.gmail.com> (raw)
In-Reply-To: <20200605020748.635b9bb3@tarpaulin.shahaf.local2>

On Fri, Jun 5, 2020 at 4:07 AM Daniel Shahaf <d.s@daniel.shahaf.name> wrote:
>
> Roman Perepelitsa wrote on Thu, 04 Jun 2020 07:41 +0200:
>
> > Or how to implement clobber-if-empty without ever clobbering non-empty
> > files?
>
> By using a non-clobbering open(), then calling fstat() on the open fd.
> If it's zero length, just carry on.  If it's not zero length, close()
> it and report an error.

Consider the following program:

    write() print -rn -- $1
    rm -f foo
    write hello >foo &
    write bye >foo &
    wait

With regular no_clobber it has the following guarantees:

1. `write` is executed exactly once
2. once `wait` completes, `foo` contains either "hello" or "bye"

Is there a way to provide these guarantees with clobber_empty? (2) is
especially important. Seeing "byelo" or "hellobye" in `foo` would be
quite confusing. It would look like clobbering.

Roman.

  reply	other threads:[~2020-06-05  4:39 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 [this message]
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
     [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

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