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Top Forums Shell Programming and Scripting Killing an Xterm while leaving subprocess alive... Post 87282 by mschwage on Friday 21st of October 2005 09:40:20 PM
Old 10-21-2005
Killing an Xterm while leaving subprocess alive...

Hi,
I'm not quite understanding what I'm doing (happens often). This pseudocode works:

#!/bin/pseudoksh

function kill_parent {
when i_want_to ; do
sleep 2
kill -TERM $PPID
exit
done
}

kill_parent &
ssh remote_host sh <<-EOF
notify_kill_parent # let the bg function know it's ok to kill parent
run_command # something x-based
EOF


Now, if I start my script in an xterm:
xterm -e run_my_script
It works as expected! The xterm pops up, ssh queries me for a password, the command runs and displays, and, seconds later, the xterm is killed. This is what I want to have happen. But I'm not sure why the remote shell and my application (run_command, above) still stick around. I've been pretty sloppy with stdin/stdout so I'm surprised they don't disappear when I kill the parent (xterm).

I'm happy it works, but I'm worried about a bug creeping in later- for example, since I'm not handling stdout, am I in danger of filling a buffer that is going to make the app hang? Or something like this.

I'm looking for insight into what happens when xterm calls ssh which calls a shell which calls a command. Xterm dies but the command does not. Why?
Thanks.
-Schwage
 

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KILL(1) 							Linux User's Manual							   KILL(1)

NAME
kill - send a signal to a process SYNOPSIS
kill [ -signal | -s signal ] pid ... kill [ -L | -V, --version ] kill -l [ signal ] DESCRIPTION
The default signal for kill is TERM. Use -l or -L to list available signals. Particularly useful signals include HUP, INT, KILL, STOP, CONT, and 0. Alternate signals may be specified in three ways: -9 -SIGKILL -KILL. Negative PID values may be used to choose whole process groups; see the PGID column in ps command output. A PID of -1 is special; it indicates all processes except the kill process itself and init. SIGNALS
The signals listed below may be available for use with kill. When known constant, numbers and default behavior are shown. Name Num Action Description 0 0 n/a exit code indicates if a signal may be sent ALRM 14 exit HUP 1 exit INT 2 exit KILL 9 exit cannot be blocked PIPE 13 exit POLL exit PROF exit TERM 15 exit USR1 exit USR2 exit VTALRM exit STKFLT exit might not be implemented PWR ignore might exit on some systems WINCH ignore CHLD ignore URG ignore TSTP stop might interact with the shell TTIN stop might interact with the shell TTOU stop might interact with the shell STOP stop cannot be blocked CONT restart continue if stopped, otherwise ignore ABRT 6 core FPE 8 core ILL 4 core QUIT 3 core SEGV 11 core TRAP 5 core SYS core might not be implemented EMT core might not be implemented BUS core core dump might fail XCPU core core dump might fail XFSZ core core dump might fail NOTES
Your shell (command line interpreter) may have a built-in kill command. You may need to run the command described here as /bin/kill to solve the conflict. EXAMPLES
kill -9 -1 Kill all processes you can kill. kill -l 11 Translate number 11 into a signal name. kill -L List the available signal choices in a nice table. kill 123 543 2341 3453 Send the default signal, SIGTERM, to all those processes. SEE ALSO
pkill(1), skill(1), kill(2), renice(1), nice(1), signal(7), killall(1). STANDARDS
This command meets appropriate standards. The -L flag is Linux-specific. AUTHOR
Albert Cahalan <albert@users.sf.net> wrote kill in 1999 to replace a bsdutils one that was not standards compliant. The util-linux one might also work correctly. Please send bug reports to <procps-feedback@lists.sf.net> Linux November 21, 1999 KILL(1)
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