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| Guest |
 Posted: Sun Nov 29, 2009 1:58 pm |
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Guest
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Hi all,
When I spawn an external process using open_port/2, and then I stop the
Erlang VM, the spawned process is not terminated. For example, when I do
the following the xterm remains.
Erlang R13B01 (erts-5.7.2) [source] [64-bit] [smp:4:4] [rq:4]
[async-threads:0] [hipe] [kernel-poll:false]
Eshell V5.7.2 (abort with ^G)
1> open_port({spawn_executable,"/usr/bin/xterm"},[]).
#Port<0.424>
2>
User switch command
--> q
Is there a way to have the spawned processes terminated when the Erlang
VM terminates?
Regards,
*Erik.
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| maxlapshin |
| Posted: Sun Nov 29, 2009 2:02 pm |
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Joined: 15 Sep 2009
Posts: 159
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There is no guaranteed way to kill child process in common unix =(
Maybe another process watcher.
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| Guest |
| Posted: Sun Nov 29, 2009 2:32 pm |
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Guest
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I checked what happens with other languages. In Python the behavior is
similar to in Erlang, when I use subprocess.Popen: the child process
stays alive when the Python process terminates. In Java, however, the
child process is killed. Probably a list of child processes is
maintained, and the children are sent a kill signal when the JVM is
killed. In Erlang I do not get direct access to the PID of the child,
neither do I get the opportunity to do anything when Erlang terminates
(or do I?).
Another process watcher would be a bit heavy for my purpose: a wrapper
around mplayer, as a client to a DVB-S media server.
Max Lapshin wrote:
> There is no guaranteed way to kill child process in common unix =(
> Maybe another process watcher.
>
> ________________________________________________________________
> erlang-questions mailing list. See http://www.erlang.org/faq.html
> erlang-questions (at) erlang.org
>
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| maxlapshin |
| Posted: Sun Nov 29, 2009 2:40 pm |
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Joined: 15 Sep 2009
Posts: 159
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Yes, Erlang is poor in handling forked processes.
It is hard to kill spawned process, impossible to get its stderr,
impossible to chain
processes via pipe();
However, there is still no warranty even with Java that child process
will be killed.
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| rvirding |
| Posted: Sun Nov 29, 2009 4:25 pm |
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Joined: 30 Aug 2006
Posts: 452
Location: Stockholm, Sweden
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When Erlang dies the stdin of the spawned process will be closed. If the
spawned process checks its stdin it should be able to detect that Erlang has
died (or the port has been closed).
Robert
2009/11/29 Max Lapshin <max.lapshin@gmail.com>
> Yes, Erlang is poor in handling forked processes.
> It is hard to kill spawned process, impossible to get its stderr,
> impossible to chain
> processes via pipe();
>
>
> However, there is still no warranty even with Java that child process
> will be killed.
>
> ________________________________________________________________
> erlang-questions mailing list. See http://www.erlang.org/faq.html
> erlang-questions (at) erlang.org
>
>
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| Guest |
| Posted: Sun Nov 29, 2009 5:01 pm |
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Guest
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Hello,
What about taking the following steps:
1. spawn the child process using a bash/whatever script which writes the ID
of the process to a file in a specific directory and then runs mplayer;
2. launch your application also using a script, so that when the VM dies or
your application closes, the script then checks that directory for PID files
then kills them one by one.
It is clunky but should get the job done reliably.
Andrew
On Sun, Nov 29, 2009 at 3:31 PM, Erik Reitsma <erlang@ernovation.com> wrote:
> I checked what happens with other languages. In Python the behavior is
> similar to in Erlang, when I use subprocess.Popen: the child process stays
> alive when the Python process terminates. In Java, however, the child
> process is killed. Probably a list of child processes is maintained, and the
> children are sent a kill signal when the JVM is killed. In Erlang I do not
> get direct access to the PID of the child, neither do I get the opportunity
> to do anything when Erlang terminates (or do I?).
>
> Another process watcher would be a bit heavy for my purpose: a wrapper
> around mplayer, as a client to a DVB-S media server.
>
>
> Max Lapshin wrote:
>
>> There is no guaranteed way to kill child process in common unix =(
>> Maybe another process watcher.
>>
>> ________________________________________________________________
>> erlang-questions mailing list. See http://www.erlang.org/faq.html
>> erlang-questions (at) erlang.org
>>
>>
>
>
> ________________________________________________________________
> erlang-questions mailing list. See http://www.erlang.org/faq.html
> erlang-questions (at) erlang.org
>
>
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| gar1t |
| Posted: Mon Nov 30, 2009 6:57 am |
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Joined: 11 Aug 2009
Posts: 55
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On Sun, Nov 29, 2009 at 10:24 AM, Robert Virding <rvirding@gmail.com> wrote:
> When Erlang dies the stdin of the spawned process will be closed. If the
> spawned process checks its stdin it should be able to detect that Erlang has
> died (or the port has been closed).
+1
When running applications as ports, I specify a command line option to
tell the app to run in a special "Erlang port" mode, which watches
stdin and shuts down when it closes. It's hard to control the child
process otherwise.
Garrett
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| Guest |
| Posted: Mon Nov 30, 2009 6:19 pm |
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Guest
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I would prefer not to modify mplayer, so I found a way around the fact
that mplayer does not terminate when its stdin is closed. I wrap the
call to mplayer in a small script as follows:
#!/bin/sh
(cat && kill 0) | mplayer $*
This way I can still communicate with mplayer through stdin, (through
the cat process). When stdin of cat is closed, it terminates. Then "kill
0" will terminate the shell and all its children (i.e. the mplayer
process). Only is I manyally kill the shell process, the mplayer process
will not be killed when I terminate the Erlang VM, but I can live with
that...
Thanks all for pointing me in this direction. Hopefully this solution
will be helpful to others, or improved by others.
*Erik.
Garrett Smith wrote:
> On Sun, Nov 29, 2009 at 10:24 AM, Robert Virding <rvirding@gmail.com> wrote:
>
>> When Erlang dies the stdin of the spawned process will be closed. If the
>> spawned process checks its stdin it should be able to detect that Erlang has
>> died (or the port has been closed).
>>
>
> +1
>
> When running applications as ports, I specify a command line option to
> tell the app to run in a special "Erlang port" mode, which watches
> stdin and shuts down when it closes. It's hard to control the child
> process otherwise.
>
> Garrett
>
> ________________________________________________________________
> erlang-questions mailing list. See http://www.erlang.org/faq.html
> erlang-questions (at) erlang.org
>
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| wuji |
| Posted: Thu Aug 23, 2012 7:27 am |
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Joined: 10 Aug 2012
Posts: 654
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