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From: Tim Watson <watson.timo...@gmail.com>
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Date: Thu, 27 Sep 2012 13:41:21 +0100
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To: =?iso-8859-1?Q?Erik_S=F8e_S=F8rensen?= <erik...@gmail.com>
Cc: erlang-questions Questions <erlang-questi...@erlang.org>
Subject: Re: [erlang-questions] can a program launched with open_port({spawn,
	Cmd}, Options) remain running after the port closes?
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Guys,

On 27 Sep 2012, at 13:18, Erik S=F8e S=F8rensen wrote:
> 2012/9/27 Jesper Louis Andersen =
<jesper.louis.ander...@erlang-solutions.com>
> I remember this was something I had going. Let me dig code:
>=20
> ----
> #!/bin/sh
>=20
> (cat && kill 0) | opentracker $*
> Nice incantation. I was just about to suggest using a wrapper program, =
but I probably wouldn't have thought of that variation.
> =20
> ----
>=20
> So the trick is that the =85 && kill 0 part sends a kill signal to all =
processes in the current process group. This lets you stop another =
process since cat(1) understands what happens when stdin is closed and =
handles it accordingly.
>=20
> I've only used it in tests though so it may need work for real =
programs
> Such as replacing "&&" with ";" ? :-)
> Just in case someone came along and killed the cat. (Can't at the =
moment imagine other scenarios where cat would exit with non-zero return =
values, but they probably exist.)
>=20
> Also, replace $* with "$@" (including the quotes), for proper handling =
of parameters with spaces in them and such.

Thanks both of you, I guess that I could drop this in in front of the =
required invocation, so you get the required behaviour. The tricky part =
here is that the code calling open_port/2 is kind of a generic 'run a =
script and monitor things' process, so I'll need to experiment with this =
a bit. Thanks for the suggestions anyway - I'll certainly give this a =
try.=

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<html><head></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; =
">Guys,<div><br><div><div>On 27 Sep 2012, at 13:18, Erik S=F8e S=F8rensen =
wrote:</div><blockquote type=3D"cite"><div class=3D"gmail_quote">2012/9/27=
 Jesper Louis Andersen <span dir=3D"ltr">&lt;<a =
href=3D"mailto:jesper.louis.ander...@erlang-solutions.com" =
target=3D"_blank">jesper.louis.ander...@erlang-solutions.com</a>&gt;</span=
><br><blockquote class=3D"gmail_quote" style=3D"margin-top: 0px; =
margin-right: 0px; margin-bottom: 0px; margin-left: 0.8ex; =
border-left-width: 1px; border-left-color: rgb(204, 204, 204); =
border-left-style: solid; padding-left: 1ex; position: static; z-index: =
auto; ">
I remember this was something I had going. Let me dig code:<br>
<br>
----<br>
#!/bin/sh<br>
<br>
(cat &amp;&amp; kill 0) | opentracker $*<br></blockquote><div>Nice =
incantation. I was just about to suggest using a wrapper program, but I =
probably wouldn't have thought of that =
variation.<br>&nbsp;<br></div><blockquote class=3D"gmail_quote" =
style=3D"margin-top: 0px; margin-right: 0px; margin-bottom: 0px; =
margin-left: 0.8ex; border-left-width: 1px; border-left-color: rgb(204, =
204, 204); border-left-style: solid; padding-left: 1ex; position: =
static; z-index: auto; ">

----<br>
<br>
So the trick is that the =85 &amp;&amp; kill 0 part sends a kill signal =
to all processes in the current process group. This lets you stop =
another process since cat(1) understands what happens when stdin is =
closed and handles it accordingly.<br>

<br>
I've only used it in tests though so it may need work for real =
programs<br></blockquote><div>Such as replacing "&amp;&amp;" with ";" ? =
:-)<br>Just in case someone came along and killed the cat. (Can't at the =
moment imagine other scenarios where cat would exit with non-zero return =
values, but they probably exist.)<br>
<br>Also, replace $* with "$@" (including the quotes), for proper =
handling of parameters with spaces in them and =
such.<br></div></div></blockquote></div><br></div><div>Thanks both of =
you, I guess that I could drop this in in front of the required =
invocation, so you get the required behaviour. The tricky part here is =
that the code calling open_port/2 is kind of a generic 'run a script and =
monitor things' process, so I'll need to experiment with this a bit. =
Thanks for the suggestions anyway - I'll certainly give this a =
try.</div></body></html>=

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