Experimenting with forking, and monitoring processes in ruby

sig_child_not_working.rb

#!/usr/bin/ruby -w




# from : https://www.ruby-forum.com/topic/135350
# SIG_CHILD to monitor processes 


trap_quit = lambda { |sig|
    signame = Signal.list.find {|k, v| v == sig }[0]
    STDERR.puts("Trapping signal #{signame}")
}

huphandler = inthandler = termhandler = chldhandler = nil
huphandler = trap("HUP", &trap_quit)
inthandler = trap("INT", &trap_quit)
termhandler = trap("TERM", &trap_quit)

cmd_exitstatus = nil

chldhandler = trap("CHLD") {
    STDERR.puts("Trapping signal CHLD")
    begin
        # tmppid, status = Process.wait2(cmdpid)
        tmppid = Process.wait
        status = $?
        cmd_exitstatus = status.exitstatus
        STDERR.puts("Process::Status => " + status.inspect)
        STDERR.puts("exitstatus => " + cmd_exitstatus.inspect)
        if ! status.exited?
            raise "ARGH!  The child has not exited yet!"
        end
    rescue Errno::ECHILD => e
        STDERR.puts("Command failed - probably ok?  #{e.inspect}")
        # bah, ignore it, just means a command failed
    end
}

cmdpid = fork {
    begin
        exec("dd", "if=/dev/zero", "of=/tmp/zerofile1.asdfsdf",
             "bs=1", "count=333000000")
    rescue Errno::ENOENT => e
        STDERR.puts e.message
        exit 127
    end
}

while(cmd_exitstatus.nil?)
    sleep 1
    STDOUT.puts "still going..."
    STDOUT.flush
end