Ruby Statistics Functions

The StatArray class provides some basic statistical operations to be used on arrays:

irb(main):001:0> require 'rubygems'
=> true
irb(main):002:0> require 'statarray'
=> true
irb(main):003:0> a = [1,2,3,4,6]
=> [1, 2, 3, 4, 6]
irb(main):004:0> sa = a.to_statarray
=> [1, 2, 3, 4, 6]
irb(main):005:0> sa.mean
=> 3.2
irb(main):007:0> sa.median
=> 3

Timing out Child Processes

I finally ran across a short Ruby powerpoint lecture by a CMU grad student to get me on the right track. Basically I wanted to spawn a process that me eventually killed (or disappears magically) after a certain amount of time. The answer is to use Timeout.

Here is my code. Notice I got rid of the fork.

#!/usr/bin/env ruby

require 'time'
require 'timeout'
require 'pp'


def time_cmd(command,timeout)
    cmd_output = []
    puts "Entering time_cmd at #{Time.now.tv_sec}"
    begin
        status = Timeout.timeout(timeout) do
            p = IO.popen(command) do |f|
                puts "pid: #{$$}"
                f.each_line do |g| 
                    cmd_output << g 
                    system("ps aux | grep netstat")                    
                end
                system("ps aux | grep netstat")
            end
        end
        pp status
    rescue Timeout::Error
        puts "\n#{command} completed at #{Time.now.tv_sec}"
        return cmd_output
    end
end

puts "pid: #{$$}"
puts time_cmd("netstat -dwh 1",3)
system("ps aux | grep netstat")

With the following output

franz-g4:~/dev/playin/ruby mdfranz$ ./angrytimeout.rb 
pid: 3658
Entering time_cmd at 1182709241
pid: 3658
root      3659   2.2  0.0    27332    368  p2  S+    1:20PM   0:00.01 netstat -d
root      3659   1.3  0.0    27332    368  p2  S+    1:20PM   0:00.01 netstat -d
root      3659   0.1  0.0    27332    368  p2  S+    1:20PM   0:00.01 netstat -d
root      3659   0.0  0.0    27332    368  p2  S+    1:20PM   0:00.01 netstat -d

netstat -dwh 1 completed at 1182709244
            input        (Total)           output
   packets  errs      bytes    packets  errs      bytes colls drops
         0     0          0          0     0          0     0     0
         0     0          0          0     0          0     0     0

What I still haven't figured out how to do is get the process id of what is spawned by the popen so that I could Process.kill it if I needed to. I know I have been able to do this but it must have been with the Python subprocess module. which of course is more full featured.