Starting a process over ssh using bash and then killing it on sigint

Question

I want to start a couple of jobs on different machines using ssh. If the user then interrupts the main script I want to shut down all the jobs gracefully.

Here is a shor

Answer 1

Referencing the answer by lhunath and https://unix.stackexchange.com/questions/71205/background-process-pipe-input I came up with this script

run.sh:

#/bin/bash
log="log"                                                                                 
eval "$@" \&                                                                              
PID=$!                                                                                    
echo "running" "$@" "in PID $PID"> $log                                                   
{ (cat <&3 3<&- >/dev/null; kill $PID; echo "killed" >> $log) & } 3<&0                              
trap "echo EXIT >> $log" EXIT                                                             
wait $PID

The difference being that this version kills the process when the connection is closed, but also returns the exit code of the command when it runs to completion.

 $ ssh localhost ./run.sh true; echo $?; cat log
 0
 running true in PID 19247
 EXIT

 $ ssh localhost ./run.sh false; echo $?; cat log
 1
 running false in PID 19298
 EXIT

 $ ssh localhost ./run.sh sleep 99; echo $?; cat log
 ^C130
 running sleep 99 in PID 20499
 killed
 EXIT

 $ ssh localhost ./run.sh sleep 2; echo $?; cat log
 0
 running sleep 2 in PID 20556
 EXIT

For a one-liner:

 ssh localhost "sleep 99 & PID=\$!; { (cat <&3 3<&- >/dev/null; kill \$PID) & } 3<&0; wait \$PID"

For convenience:

 HUP_KILL="& PID=\$!; { (cat <&3 3<&- >/dev/null; kill \$PID) & } 3<&0; wait \$PID"
 ssh localhost "sleep 99 $HUP_KILL"

Note: kill 0 may be preferred to kill $PID depending on the behavior needed with regard to spawned child processes. You can also kill -HUP or kill -INT if you desire.

Update: A secondary job control channel is better than reading from stdin.

ssh -n -R9002:localhost:8001 -L8001:localhost:9001 localhost ./test.sh sleep 2

Set job control mode and monitor the job control channel:

set -m
trap "kill %1 %2 %3" EXIT
(sleep infinity | netcat -l 127.0.0.1 9001) &
(netcat -d 127.0.0.1 9002; kill -INT $$) &
"$@" &
wait %3

Finally, here's another approach and a reference to a bug filed on openssh: https://bugzilla.mindrot.org/show_bug.cgi?id=396#c14

This is the best way I have found to do this. You want something on the server side that attempts to read stdin and then kills the process group when that fails, but you also want a stdin on the client side that blocks until the server side process is done and will not leave lingering processes like <(sleep infinity) might.

ssh localhost "sleep 99 < <(cat; kill -INT 0)" <&1

It doesn't actually seem to redirect stdout anywhere but it does function as a blocking input and avoids capturing keystrokes.