X-Recipient:	archive-cygwin AT delorie DOT com
DomainKey-Signature:	a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:cc:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; q=dns; s=
	default; b=Il5mPXM3rWItm5LZYK9nfCl6FZwMqkDyPVOHQaPRmWhIz4HJvHJEX
	sLm2pK1MxpJUSAwj3QAyK/KBX608R3W/XKBNqcZ9H2sn7LF7Aajy6DxZnq+dQMxE
	cd7YKAGnBP2ITpU+pb4jco+wJLJo50j5CKYtxHe5U/hd9uyRuPvns4=
DKIM-Signature:	v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:to:cc:subject:message-id:reply-to
	:references:mime-version:content-type:in-reply-to; s=default;
	bh=tVmYwky+gxq5b2N7I29WdYEg7yk=; b=T1pgt48mF/DW3qAH3XDav664hW3t
	LDy2RXdCZ6oQxJ5YGdKzJLHgk8NpB0V76jsWOa9emFvWicthRBB78+wMZ6VPOQmj
	DZC6LrBpWT3r+5XW9A7npJqI3Tu6JXQVqkWDX0+SXeogewPuL8kxswz5UlA7SWuy
	rnhZKrM6LK2ztFw=
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com
Authentication-Results:	sourceware.org; auth=none
X-Spam-SWARE-Status:	No, score=-103.3 required=5.0 tests=AWL,BAYES_00,GOOD_FROM_CORINNA_CYGWIN,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 spammy=onboard
X-HELO:	mout.kundenserver.de
Date:	Mon, 16 Dec 2019 11:21:08 +0100
From:	Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To:	Ulli Horlacher <framstag AT rus DOT uni-stuttgart DOT de>
Cc:	cygwin AT cygwin DOT com
Subject:	Re: non-persistant storage?
Message-ID:	<20191216102108.GN10310@calimero.vinschen.de>
Reply-To:	cygwin AT cygwin DOT com
Mail-Followup-To:	Ulli Horlacher <framstag AT rus DOT uni-stuttgart DOT de>, cygwin AT cygwin DOT com
References:	<20191212120041 DOT GA7699 AT tik DOT uni-stuttgart DOT de>
MIME-Version:	1.0
In-Reply-To:	<20191212120041.GA7699@tik.uni-stuttgart.de>

--l+goss899txtYvYf
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

Hi Ulli,

On Dec 12 13:00, Ulli Horlacher wrote:
> I need to store some data (a few kB) non-persistant.
> On a real UNIX I would use /var/run, because after a shutdown all its
> content is lost.
> But on cygwin /var/run is stored on disk.
>=20
> I cannot use an environment variable, because different processes need to
> read/write the data.
>=20
> /proc is non-persistant (in respect to a reboot), but It is not a generic
> storage place.
>=20
> What can I use with cygwin instead?
>=20
> Installing third party software is not an option, it must work with a
> standard Windows (and cygwin).

Cygwin is just a user space DLL, it's not an OS.  Creating RAM disk-like
storage is the job of the OS or an OS driver.  Unfortunately, there's no
onboard RAM disk driver in Windows, just zillions of third-party solutions.

I see two options:

- Use XSI shared memory, as outlined in this thread already, or

- If you have the executables under source control, you can use
  an O_TMPFILE on /dev/shm, and fork the worker process from there,
  i.e.

    fd =3D open ("/dev/shm", O_TMPFILE | O_RDWR, S_IRUSR | S_IWUSR);
    if (fd >=3D 0)
      {
	write (fd, your_key, strlen (your_key));
	switch (fork ())
	  {
	  case 0: /* child */
	    /* Use fd as you see fit */
	    break;
	  case -1: /* error */
	  default: /* parent */
	    close (fd);
	    wait (&status);
	    break;
	  }
      }


Corinna

--=20
Corinna Vinschen
Cygwin Maintainer

--l+goss899txtYvYf
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=pRo9
-----END PGP SIGNATURE-----

--l+goss899txtYvYf--

- Raw text -