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From: Andrew DeFaria <Andrew DOT DeFaria AT tellabs DOT com>
Subject: Re: Unable to disown process
Date: Wed, 06 Jul 2011 13:15:11 -0700
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On 7/6/2011 12:12 PM, Andy Koppe wrote:
> On 6 July 2011 18:24, Andrew DeFaria wrote:
>> I have the following script that I use to tunnel nntp traffic:
>>
>>    #!/bin/bash
>>    nohup ssh -NL 1119:news.mozilla.org:119 \
>>          -L 2119:news.gmane.org:119 \
>>          -L 3119:nntp.perl.org:119 \
>>       andrew AT defaria DOT com>  /dev/null 2>&1&
>>
>>    disown
>>
>> If I run this script it works fine and I'm tunneled. The problem is I cannot
>> exit the terminal in which I invoked this script. When I attempt to do this
>> the terminal hangs. I can close the terminal (mintty BTW) forcefully and the
>> ssh session remains but it was my understanding that disown should allow you
>> to exit the current shell with the backgrounded/disowned process continuing
>> to run. In fact I tested this on RHEL and it worked as expected. What's up
>> with Cygwin?
> Mintty stays open as long as any processes are connected to it, i.e.
> until it gets an EOF from its underlying pseudo terminal device,
> whereas other terminals quit as soon as their direct child process
> finishes. The Cygwin console behaves the same as mintty in this regard
> though.
Ah ha!
> Nohup doesn't disassociate a process from its terminal, it just blocks
> the SIGHUP signal for indicating when the terminal is gone. And
> 'disown' removes a job from the shell's job table, but again, the
> job's processes will remain connected to the terminal.
>
> You can use the 'setsid' utility from the util-linux package to invoke
> a program in its own session, i.e. without connection to the terminal
> it is invoked from. For example:
>
> setsid ssh -NL 1119:news.mozilla.org:119 \
>           -L 2119:news.gmane.org:119 \
>           -L 3119:nntp.perl.org:119 \
>           andrew AT defaria DOT com
Excellent description and solution. Thanks.
> No need for 'nohup', redirections, backgrounding, or 'disown' with this.
Of course those were all the desperate things I was trying to get this 
to work...

Actually I still need backgrounding as without it my ~/bin/tunnel just 
hangs on the setsid command...
-- 
Andrew DeFaria <http://defaria.com>
What is the speed of dark?


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