Getting the pid of a job launched in the background remotely

Question

I am trying to launch in the background a job on a remote machine and get its PID so that I can kill it later on. What I have come up with so far is the following:

#!/bin/bash

IP=xxx.xxx.xxx.xx
REMOTE_EXEC="ssh $IP -l root"

# The following does NOT work, I am trying to get the PID of the remote job
PID=`$REMOTE_EXEC 'vmstat 1 1000 > vmstat.log & ; echo $!'`

# Launch apache benchmark
ab -n 10 http://$IP/

$REMOTE_EXEC "kill $PID"

Unfortunately it does not work. I am getting a

bash: syntax error near unexpected token `;'

but I don't know what the right syntax would be.

Answer 1

You got the error, because you ';' is redundant, try 'vmstat 1 1000 > vmstat.log & echo $!'

But I am not sure it gonna work, because after you logout, the process will receive SIGHUP. Look at nohup(1).

Answer 2

Try surrounding the backgrounded command in curly braces:

PID=`$REMOTE_EXEC '{ vmstat 1 1000 > vmstat.log & }; echo $!'`