Run console command in ruby, get PID of child process and kill it in some seconds

Question

I need to run console command in ruby (in my case to start Gvim), get PID of Gvim and kill that process in a few seconds.

If I do the following - it gives me PID of parent process, but I need somehow to find out the PID of Gvim.

IO.popen("gvim file_name_to_open" { |gvim|
  puts gvim.pid
}

If I do the following, it just starts Gvim and does nothing more (I need Gvim process to be killed).

pid = Process.spawn("gvim", "file_name_to_open")
sleep(5)
Process.kill(9, pid)
Process.wait pid

What am I doing wrong?

Answer 1

The most appropriate solution looks like this:

parent_pid = Process.spawn("gvim", "file_name_to_open")
# Need to wait in order not to kill process till Gvim is started and visible
sleep(5)  
Process.kill(9, parent_pid)
# Try to get all Gvim PIDs: the result will look like list of PIDs in 
# descending order, so the first one is the last Gvim opened.
all_gvim_pids = `pidof gvim` 
last_gvim_pid = all_gvim_pids.split(' ').map(&:to_i).first
Process.kill(9, last_gvim_pid)

The solution is strange and hacky, but noone has better ideas :(