From: Robert Klemme <shortcutter@...>
Date: 2009-09-07T22:38:24+09:00
Subject: Re: Executing system commands in threads under Ruby 1.8.6

2009/9/7 geo ssscripting <etaern@yahoo.com>:
> The commands executed in the script at the SO link was simply pinging
> the host on an ip range from 1 to 254 like in the following line :
>
> `ping #{ip_addr}`
>
> This happened from inside each individual thread. How could I replace
> the backticks so that they won't block ?

You can use one of the popen methods, e.g.

IO.popen ["ping", ip_addr] do |io|
  io.each {|l| puts l}
end

Example

15:37:19 ~$ ruby <<EOF
> threads = (1..2).map do |i|
>   Thread.new i do |ii|
>     IO.popen 'ping 192.168.110.74' do |io|
>       io.each do |line|
>         printf "%2d %s", ii, line
>       end
>     end
>   end
> end
> threads.map do |th|
>   th.value
> end
> EOF
 1
 1 Pinging 192.168.110.74 with 32 bytes of data:
 1
 1 Reply from 192.168.110.74: bytes=32 time<1ms TTL=128
 2
 2 Pinging 192.168.110.74 with 32 bytes of data:
 2
 2 Reply from 192.168.110.74: bytes=32 time<1ms TTL=128
 1 Reply from 192.168.110.74: bytes=32 time<1ms TTL=128
 2 Reply from 192.168.110.74: bytes=32 time<1ms TTL=128
 1 Reply from 192.168.110.74: bytes=32 time<1ms TTL=128
 2 Reply from 192.168.110.74: bytes=32 time<1ms TTL=128
 1 Reply from 192.168.110.74: bytes=32 time<1ms TTL=128
 1
 1 Ping statistics for 192.168.110.74:
 1     Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
 1 Approximate round trip times in milli-seconds:
 1     Minimum = 0ms, Maximum = 0ms, Average = 0ms
 2 Reply from 192.168.110.74: bytes=32 time<1ms TTL=128
 2
 2 Ping statistics for 192.168.110.74:
 2     Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
 2 Approximate round trip times in milli-seconds:
 2     Minimum = 0ms, Maximum = 0ms, Average = 0ms
15:37:38 ~$ ruby -version
ruby 1.8.7 (2008-08-11 patchlevel 72) [i386-cygwin]
-e:1: undefined local variable or method `rsion' for main:Object (NameError)
15:37:53 ~$


Cheers

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/