Check whether a process is alive

Monday, 04 October 2010 10:26

Check whether a process is running (actually, present and alive) on a particular machine and/or system using its PID ...

Quick version ...



module Process

  class << self

    def process_alive?(pid)

      begin

        Process.kill(0, pid)

        true

      rescue Errno::ESRCH

        false

      end

    end

  end

end

A little bit slower version using /proc file system lookup ...



module Process

  class << self

    def process_alive?(pid)

      Dir['/proc/[0-9]*'].map { |i| i.match(/\d+/)[0].to_i }.include?(pid)

    end

  end

end

Simple use-case:



irb(main):013:0> puts `ps aux | grep -i [t]omboy`

1000     26862  0.0  0.2 103972  9592 ?        Sl   Sep28   0:09 mono /usr/lib/tomboy/Tomboy.exe

=> nil

irb(main):014:0> Process.process_alive?(26862)

=> true

irb(main):015:0> Process.process_alive?(12345)

=> false

irb(main):016:0>