ruby list child pids

Question

How can I get pids of all child processes which were started from ruby script?

Answer 1

Process.fork responds with the PID of the child spawned. Just keep track of them in an array as you spawn children. See http://ruby-doc.org/core/classes/Process.html#M003148.

Answer 2

You can get the current process with:

Process.pid

see http://whynotwiki.com/Ruby_/_Process_management for further details.

Then you could use operating specific commands to get the child pids. On unix based systems this would be something along the lines of

# Creating 3 child processes.
pipe = IO.popen('uname')
pipe = IO.popen('uname')
pipe = IO.popen('uname')

# Grabbing the pid.
pid= Process.pid

# Get the child pids.
child_pids = Array.new
pipe = IO.popen("ps -ef | grep #{pid}")
pipe.readlines.each { |line|
    parts = line.split(/\s+/)
    if (parts[3] == pid.to_s && parts[2] != pipe.pid.to_s) then
            child_pids.push parts[2]
    end
}

# Show the child processes.
puts child_pids

I admit that this probably doesn't work on all unix systems as I believe the output of ps -ef varies slightly on different unix flavors.