Re: Disowned process hangs terminal during logout/exit

[Jesse Molina]

Thank you for the explanation about the descriptors.  That's very insightful.

However, your suggested fix did not help the situation.  I think that was even 
something that I had tried the day before.

Netcat has strange issues about wanting stdin -- it won't run backgrounded 
without being fed tail -f /dev/null.  I wonder if it isn't the problem here.  I 
had discounted it since I redirected both stdin and stdout to the logfile.

I'll use lsof and see if I can find anything interesting.

Other suggestions are welcome.




On Wed, Dec 05, 2007 at 03:49:09PM -0500, Paul Jarc wrote:
> Jesse Molina <jesse@opendreams.net> wrote:
> > Basically, on the two troubled systems, my interactive shell will
> > hang after I've disowned a process.  On one other system, everything
> > works as expected.  I expect that a disowned process should not hang
> > logout -- disowned means disowned.
> 
> The terminal will hang around as long as any process has an open
> descriptor connected to it.  "disown" does not (and cannot) disconnect
> an already-running process's file descriptors from the terminal.  It
> only affects the relationship between the process and bash, not
> between the process and the terminal.
> 
> > It seems like it's hanging on stdout since redirecting to /dev/null fixes 
> > the problem.
> 
> You could have the same problem with stdin/stderr.
> 
> > Here is the actual line where I am having trouble.  I can't redirect tail's 
> > output in this case.  It seems like tail is the offender.
> >
> > (tail -f < /dev/null | $NETCAT -l -p $LISTENPORT >> $LOGFILE 2>&1) &
> 
> tail's stderr would still be connected to the terminal in that case.
> See if this works:
> (tail -f < /dev/null 2> /dev/null | $NETCAT -l -p $LISTENPORT >> $LOGFILE 
> 2>&1) &
> 
> 
> paul

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