02 - doing two things at once with threads.rb

O Reilly Ruby Cookbook source code

x = 0
Thread.new do 
  while x < 5
    x -= 1
    puts "DEC: I decremented x to #{x}\n"
  end
  puts "DEC: x is too high; I give up!\n"
end

while x < 5
  x += 3
  puts "INC: I incremented x to #{x}\n"
end
# DEC: I decremented x to -1
# DEC: I decremented x to -2
# DEC: I decremented x to -3
# DEC: I decremented x to -4
# INC: I incremented x to -1
# DEC: I decremented x to -2
# INC: I incremented x to 1
# DEC: I decremented x to 0
# INC: I incremented x to 3
# DEC: I decremented x to 2
# INC: I incremented x to 5
# DEC: x is too high; I give up!

x                                          # => 5
#---
#!/usr/bin/ruby -w
# counter_thread.rb
counter = 0
counter_thread = Thread.new do
  1.upto(1000000) { counter += 1; }
end

counter_thread.join unless ARGV[0]
puts "The counter was able to count up to #{counter}."
#---
$ ./counter_thread.rb
The counter was able to count up to 1000000.

$ ./counter_thread.rb dont_call_join
The counter was able to count up to 172315.
#---
Thread.new { sleep 10 }
Thread.new { x = 0; 10000000.times { x += 1 } }
Thread.new { sleep 100 }
Thread.list 
# => [#<Thread:0xb7d19ae0 sleep>, #<Thread:0xb7d24cec run>,
#     #<Thread:0xb7d31cf8 sleep>, #<Thread:0xb7d68748 run>]
#---