Ruby: Detect number of CPUs installed

Question

I already found a solution for "Most unixes" via cmdline "cat /proc/cpuinfo", but a pure-ruby solution would be nicer...

Answer 1

Surely if you can cat it, you can open, read and close it using the standard features of the language without resorting to a system()-type call.

You may just need to detect what platform you're on dynamically and either:

• use the /proc/cpuinfo "file" for Linux; or
• communicate with WMI for Windows.

That last line can use:

require 'win32ole'
wmi = WIN32OLE.connect("winmgmts://")
info = wmi.ExecQuery ("select * from Win32_ComputerSystem")

Then use info's NumberOfProcessors item.

Answer 2

with JRuby you can check it with the following Java code:

 Runtime runtime = Runtime.getRuntime();   
 int numberOfProcessors = runtime.availableProcessors();

Answer 3

$ gem install facter
$ irb
irb(main):001:0> require 'rubygems'
=> true
irb(main):002:0> require 'facter'
=> true
irb(main):003:0> Facter.loadfacts
=> true
irb(main):004:0> puts Facter.sp_number_processors
2
=> nil
irb(main):005:0>

This facter gem is the best, it's not platform specific and designed to do this exact thing.

Answer 4

on Mac:

thiago-pradis-macbook:~ tchandy$ hwprefs cpu_count

2