Question

In my Ruby script, I call on a Perl script and wait for it to finish executing. However, there are times that the Perl script encounters a series of errors and I would like Ruby to be able to handle these errors automatically. So, I implemented the following…

begin
    IO.popen(cmdLineExecution) do |stream|
          stream.each do |line|
              puts line
              if line =~ /Some line that I know is an error/
                 raise MyOwnException
              end 
          end
    end

    begin
          #Wait on the child process
          Process.waitpid 
    rescue Errno::ECHILD
    end
rescue MyOwnException
   #Abort the command mid processing, and handle the error
end

However, the Perl script continues to execute even though an exception has been thrown, only that it is not piping the output to STDOUT anymore. At this point, if I want to stop the Perl process, I have to go into the Task Manager and manually stop it. Then Process.waitpid ends and continues from there. It is either that or I stop Ruby and the Perl process continues to run in the background and I still have to manually stop it.

BTW: This is on Windows

So thus the question is how do I stop IO.popen without the Perl process from becoming a orphan process mid process?

Answer 1

So – disclaimer, I am using Ruby 1.8.6 and on Windows. It is the only Ruby that the software I use currently supports, so there may be a more elegant solution. Overall, it came down to making sure the process died using the Process.kill command before continuing execution.

IO.popen(cmdLineExecution) do |stream|
  stream.each do |line|                         
      puts line
      begin
        #if it finds an error, throws an exception
        analyzeLine(line) 
      rescue correctionException 
        #if it was able to handle the error 
        puts "Handled the exception successfully"
        Process.kill("KILL", stream.pid) #stop the system process
      rescue correctionFailedException => failedEx
        #not able to handle the error
        puts "Failed handling the exception"
        Process.kill("KILL", stream.pid) #stop the system process
        raise "Was unable to make a known correction to the running enviorment: #{failedEx.message}"
      end
  end
end

I made both the exceptions standard classes that inherit Exception.