Select only taking alternating values?

The problem in question seems to be that only every OTHER line of
terminal input is handled by elsif input == STDIN. Here is the complete
code, with some masked stuff

Code:

require ‘socket’
require ‘protocol.rb’

#Settings for the server we’re connecting too

class AmityClient

include AmityPackets

def initialize

#Bool to check if we've received a Ctrl-C, so we can shut down and

clean up nicely.
@interrupted = false

@hostname = "MASKED"
@port = 6002
@username = "amity"
@mppass = "MASKED"

begin
  puts "Trying to connect to #{@hostname} on #{@port}"
  @sock = TCPSocket.new(@hostname, @port)
  sendLogin(@sock, @username, @mppass)
  sendChat(@sock, "-- Amity b0.1 connected --")
  run()
rescue IOError
  puts "-- Socket closed --"
rescue
  puts "Error: #{$!}"
end

end

def run
while 1 #Enter Infinite Loop

#Trap a Ctrl-C, and turn on interrupted
trap("INT") {@interrupted = true}

#select input
results = select([@sock, STDIN], nil, nil)
  if results != nil then
    for input in results[0]
      if input == @sock then #Socket Input found
        #Socket stuff here
      elsif input == STDIN #Standard Input found
        if gets.chomp! == "!quit" then
          cleanupAndExit
        else
          puts gets.chomp!
        end
      end #if
    end #for
  end #if

if @interrupted
  puts "\nInterrupted! Cleaning up..."
  cleanupAndExit
end

end #while

end #def

def cleanupAndExit
@sock.close
sendChat(@sock, “User quit Amity Client”)
exit
end

end

interrupted = false

trap(“INT”) {interrupted = true}

amity = AmityClient.new

if interrupted
puts “Interrupted”
exit
end

On 11/20/2009 04:12 PM, Dylan Lukes wrote:

The problem in question seems to be that only every OTHER line of
terminal input is handled by elsif input == STDIN. Here is the complete
code, with some masked stuff

Think about it for a moment: do you believe that such an obvious error
in select could have slipped by all tests? No? OK, I don’t either.
:slight_smile:

The bug is with 99% likeliness in your code. You have a bug in your
input reading code. Look at how you use gets.

Cheers

robert

        if gets.chomp! == "!quit" then
          cleanupAndExit
        else
          puts gets.chomp!
        end

Note how gets is called twice.

Incidentally, a plain gets is not the same as STDIN.gets, but is more
like ARGF.gets. It makes a difference when someone puts some arguments
on the command line. Use STDIN.gets to be safe.

Brian C. wrote:

        if gets.chomp! == "!quit" then
          cleanupAndExit
        else
          puts gets.chomp!
        end

Note how gets is called twice.

Also, I have a question…

results = select([@sock, STDIN], nil, nil)

    for input in results[0]
      [...]
    end #for
  end #if

Instead of doing a for loop - just do “results[0].each”, which is more
idiomatic.
The question is, what does “select” do ? rdocs aren’t helpful, and I
don’t understand that bit of code.

Brian C.:

Incidentally, a plain gets is not the same as STDIN.gets, but is
more like ARGF.gets. It makes a difference when someone puts some
arguments on the command line. Use STDIN.gets to be safe.

Or, better yet, use $stdin.gets – IMHO in general it’s better to use the
global variables ($stdin, $stdout, $stderr) rather than the constants
(STDIN, STDOUT, STDERR), because you can repoint the variables as you
see fit without generating a Ruby warning.

For example, when specing my ‘executable’ classes with RSpec,
I often want to specify that something should show up on the
standard error, and I usually do something like this:

module Signore describe Executable do

before do
@orig_stderr = $stderr
$stderr = StringIO.new
end

after do
$stderr = @orig_stderr
end

def stderr
$stderr.rewind
$stderr.read
end

it ‘should print usage if no command was given’ do
lambda { Executable.new([]) }.should raise_error SystemExit
stderr.should match /usage: signore prego|pronto [label, …]/
end

…

end end

— Shot

On 20.11.2009 18:14, Aldric G. wrote:

results = select([@sock, STDIN], nil, nil)

    for input in results[0]
      [...]
    end #for
  end #if

Instead of doing a for loop - just do “results[0].each”, which is more
idiomatic.

Absolutely. Usually one would do

ios = [… ]

in, = select(ios)

in.each do |io|
data = io.read_nonblock 1024

end

The question is, what does “select” do ? rdocs aren’t helpful, and I
don’t understand that bit of code.

See Brian’s explanation.

Kind regards

robert

Aldric G. wrote:

The question is, what does “select” do ? rdocs aren’t helpful, and I
don’t understand that bit of code.

You’re right, “ri Kernel#select” and “ri IO::select” are both extremely
poor.

But it’s essentially the same as the C “select” call, which you can read
about using “man 2 select” if you have the right manpages installed
(under Ubuntu: sudo apt-get manpages-dev)

It checks a number of IO descriptors for readiness for reading, writing
or exceptional conditions, and returns when at least one of them is
ready or a timeout has expired.

select([@sock, STDIN], nil, nil)

has no timeout parameter so will wait indefinitely. Only read_fds are
specified, so it will return an array containing either @sock or STDIN
or both, depending on which of them has data to read.