Shared Variable Among Ruby Processes

One problem is you need to use Process.wait to wait for your forked processes to complete. The other is that you can't do interprocess communication through variables. To see this:

@one = nil@two = nil@hash = {}pidA = fork do    sleep 1    @one = 1    @hash[:one] = 1    p [:one, @one, :hash, @hash] #=> [ :one, 1, :hash, { :one => 1 } ]endpidB = fork do    sleep 2    @two = 2    @hash[:two] = 2    p [:two, @two, :hash, @hash] #=> [ :two, 2, :hash, { :two => 2 } ]endProcess.wait(pidB)Process.wait(pidA)p [:one, @one, :two, @two, :hash, @hash] #=> [ :one, nil, :two, nil, :hash, {} ]

One way to do interprocess communication is using a pipe (IO::pipe). Open it before you fork, then have each side of the fork close one end of the pipe.

From ri IO::pipe:

    rd, wr = IO.pipe    if fork      wr.close      puts "Parent got: <#{rd.read}>"      rd.close      Process.wait    else      rd.close      puts "Sending message to parent"      wr.write "Hi Dad"      wr.close    end _produces:_    Sending message to parent    Parent got: <Hi Dad>

If you want to share variables, use threads:

@one = nil@two = nil@hash = {}threadA = Thread.fork do    sleep 1    @one = 1    @hash[:one] = 1    p [:one, @one, :hash, @hash] #=> [ :one, 1, :hash, { :one => 1 } ] # (usually)endthreadB = Thread.fork do    sleep 2    @two = 2    @hash[:two] = 2    p [:two, @two, :hash, @hash] #=> [ :two, 2, :hash, { :one => 1, :two => 2 } ] # (usually)endthreadA.jointhreadB.joinp [:one, @one, :two, @two, :hash, @hash] #=> [ :one, 1, :two, 2, :hash, { :one => 1, :two => 2 } ]

However, I'm not sure if threading will get you any gain when you're IO bound.

Cod is meant for Inter Process Communication and will allow you to easily send data between forked processes.

It is possible to share variables between processes; DRuby is probably the lowest barrier-to-entry way to do it.