The Bash command I used:
$ ssh user@myserver.com ps -aux|grep -v \"grep\"|grep "/srv/adih/server/app.js"|awk '{print $2}'
6373
$ ssh user@myserver.com echo $(ps -aux|grep -v \"grep\"|grep "/srv/adih/server/app.js"|awk '{print $2}')
8630
The first result is the correct one and the second one will change echo time I execute it. But I don't know why they are different.
What am I doing?
My workstation has very limited resources, so I use a remote machine to run my Node.js application. I run it using ssh user@remotebox.com "cd /application && grunt serve" in debug mode. When I command Ctrl + C, the grunt task is stopped, but the application is is still running in debug mode. I just want to kill it, and I need to get the PID first.
The command substitution is executed by your local shell before ssh runs.
If your local system's name is here and the remote is there,
ssh there uname -n
will print there whereas
ssh there echo $(uname -n) # should have proper quoting, too
will run uname -n locally and then send the expanded command line echo here to there to be executed.
As an additional aside, echo $(command) is a useless use of echo unless you specifically require the shell to perform wildcard expansion and whitespace tokenization on the output of command before printing it.
Also, grep x | awk { y } is a useless use of grep; it can and probably should be refactored to awk '/x/ { y }' -- but of course, here you are reinventing pidof so better just use that.
ssh user@myserver.com pidof /srv/adih/server/app.js
If you want to capture the printed PID locally, the syntax for that is
pid=$(ssh user@myserver.com pidof /srv/adih/server/app.js)
Of course, if you only need to kill it, that's
ssh user@myserver.com pkill /srv/adih/server/app.js