Change The Ruby Process Name in Top

Change the ruby process name in top

Dave Thomas had an interesting post on doing this in rails. There's nothing rails specific about the actual process name change code. He uses the $0='name' approach. When I followed his steps the name was changed in ps and top.

In the post he suggests using the c keyboard command if your version of top doesn't show the short version of the command by default.

Windows Ruby get PID from process name

The sys-proctable gem can do that, here is a minimal example for getting the PID of the ruby.exe process on the system:

require 'sys/proctable'

def get_process_id(name)
    Sys::ProcTable.ps.detect{|p| p.name == name}&.pid
end

puts get_process_id("ruby.exe")

That doesn't guarantee you will find the parent process tho, you will instead get the process with the lowest PID.

To actually find the "root process", you need to further select processes by checking if their parent process is either non-existent or a different process:

require 'sys/proctable'

def get_parent_process_id(name)
    # generate a hash mapping pid -> process info
    processes = Sys::ProcTable.ps.map{|p| [p.pid, p]}.to_h

    # find the first matching process that has either no parent or a parent
    # that doesn't match the process name we're looking for
    processes.values.each do |p| 
        next if p.name != name

        if processes[p.ppid].nil? || processes[p.ppid].name != name
            return p.pid
        end
    end

    nil
end

puts get_parent_process_id("chrome.exe")

ruby creating processes and reading output

Use IO.popen to fork the process (it will return a IO object with a pid method corresponding to the forked process). You can select on the IO object to avoid blocking.

Rails server says port already used, how to kill that process?

Assuming you're looking to kill whatever is on port 3000 (which is what webrick normally uses), type this in your terminal to find out the PID of the process:

$ lsof -wni tcp:3000

Then, use the number in the PID column to kill the process:

$ kill -9 PID

Obtain the name of a unknown process, by the window handle?

I don't know Ruby, but since you are invoking the WinAPI directly anyway, I can give you an example in C. Assuming you already have a HWND called hWnd scoped (error handling omitted for brevity):

HANDLE hProcess;
DWORD  dwPID;
WCHAR  lpFilename[MAX_PATH];

GetWindowThreadProcessId(hWnd, &dwPID)
hProcess = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, dwPID);
GetModuleFileNameEx(hProcess, NULL, lpFilename, _countof(lpFilename));
CloseHandle(hProcess);

Getting the parent id of a given process in Ruby

You can just remember it in a variable:

parent_pid = Process.pid

Process.fork do
  child_pid = Process.pid
  puts parent_pid, child_pid
  # do stuff
  exit
end

Process.wait

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alternatively, if you need the information on the level of the parent process:

parent_pid = Process.pid

child_pid = Process.fork do
  # do stuff
  exit
end

Process.wait
puts parent_pid, child_pid

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