Ruby Net / SSH exec-获取远程进程的pid

Question

I am launching a nohup remote script with Ruby Net/SSH.

Net::SSH.start(ip_address, user, options) do |ssh|
  script = File.join(remote_path, 'run_case.py')
  cmd = "nohup python #{script} #{args}  < /dev/null &"
  ssh.exec(cmd)
end

All stdout and stderr is saved to a file on the remote machine.

Is it possible to get the PID of the remote script so that I can kill it if needed?

EDIT 1: I have modified the script as suggested.

Net::SSH.start(ip_address, user, options) do |ssh|
  script = File.join(remote_path, 'run_case.py')
  cmd = "nohup python #{script} #{args}  < /dev/null & echo $! > save_pid.txt"
  ssh.exec(cmd)
  pid = ssh.exec!("cat save_pid.txt")
  puts mesh_pid
end

It complains that it cannot find the file. Is this because the file does not exist yet? I would prefer to avoid any sleep command if possible

EDIT 2: Maybe this is not elegant but it works. I have created a second ssh session and used pgrep .

Net::SSH.start(ip_address, user, options) do |ssh|
  script = File.join(remote_path, 'run_case.py')
  cmd = "nohup python #{script} #{args}  < /dev/null &"
  ssh.exec(cmd)
end

Net::SSH.start(ip_address, user, options) do |ssh|
  cmd = "python #{script} #{args}"
  mesh_pid = ssh.exec!("pgrep -f '#{cmd}'")
  puts mesh_pid
end

Answer 1

You should be able to determine the PID (and store it in a file) as follows:

Net::SSH.start(ip_address, user, options) do |ssh|
  script = File.join(remote_path, 'run_case.py')
  cmd = "nohup python #{script} #{args}  < /dev/null & echo $! > save_pid.txt"
  ssh.exec(cmd)
end

In a script, $! represents the PID of the last process executed. If you need to kill the process, you can do it via:

kill -9 `cat save_pid.txt`
rm save_pid.txt