Portable signals

cfp:~ > cat a.rb

on windows signals don’t work. least wise you cannot send, for

instance,

SIGABRT to another process. rather, you can only signal yourself!

to get

around this limitation a tiny drb service, fronting the Process object

itself, can be setup to allow one process to signal another by

making a drb

call that actually causes the other process to signal itself.

you’ve

really got to love ruby at times like these.

require ‘drb’

mode = ARGV.shift || ‘servant’
uri = ARGV.shift
signal = ‘ABRT’

start_server = lambda do
trap(signal){ puts “#{ Process.pid } got #{ signal }…” }
DRb.start_service ‘druby://localhost:0’, Process
uri = DRb.uri
end

start_client = lambda do
DRb.start_service ‘druby://localhost:0’
process = DRbObject.new nil, uri
end

case mode
when /server/i
puts “server.pid => #{ Process.pid }.”
uri = start_server.call
puts DRb.uri
loop do
puts “not blocking…”
sleep 1
end

 when /client/i
   puts "client.pid => #{ Process.pid }."
   process = start_client.call
   process.kill signal, process.pid

 when /servant/i
   puts "server.pid => #{ Process.pid }."
   uri = start_server.call
   Thread.new do
     loop do
       puts "not blocking..."
       sleep 1
     end
   end
   program = __FILE__
   client_program = "ruby #{ program } client #{ uri }"
   4.times do
     system client_program
     sleep 1
   end

end

cfp:~ > ruby a.rb
server.pid => 1593.
not blocking…
client.pid => 1594.
1593 got ABRT…
not blocking…
client.pid => 1595.
1593 got ABRT…
not blocking…
client.pid => 1596.
1593 got ABRT…
not blocking…
client.pid => 1597.
1593 got ABRT…
not blocking…

a @ http://codeforpeople.com/

On Dec 28, 11:58 am, “ara.t.howard” [email protected] wrote:

you’ve

really got to love ruby at times like these.

Ara, did you checked the C code of Ruby? maybe there is some room we
can improve it, according to MSDN docs, the following signals are
being available to be defined:

SIGABRT: Abnormal termination
SIGFPE: Floating-point error
SIGILL: Illegal instruction
SIGINT: CTRL+C signal
SIGSEGV: Illegal storage access
SIGTERM: Termination request

But (there is always a but):

The SIGILL and SIGTERM signals are not generated under Windows NT.
They are included for ANSI compatibility. Thus you can set signal
handlers for these signals with signal, and you can also explicitly
generate these signals by calling raise.

http://msdn2.microsoft.com/en-us/library/xdkz3x12(VS.80).aspx

So, any other signal cannot be generated from other software that is
not ruby. Ruby exposes the list of signals available, but not all are
supported by the platform (so is impossible send a ABRT signal to
other process).

I’m getting it wrong?

Looking forward for your thoughts,

Luis

On Dec 28, 2007, at 10:39 AM, Luis L. wrote:

SIGTERM: Termination request
So, any other signal cannot be generated from other software that is
not ruby. Ruby exposes the list of signals available, but not all are
supported by the platform (so is impossible send a ABRT signal to
other process).

I’m getting it wrong?

Looking forward for your thoughts,

Luis

you can generate and trap signals in windows using ruby - but only
for the same process
. in otherwords, currently in ruby, process A
cannot send a signal to process B, A may only send signals to
itself. at least this is how i’m interpreting this code

http://groups.google.com/group/ruby-talk-google/browse_frm/thread/
e8478acbffe804cb

which sets up two processes - one trapping all signals and the other
trying to send those same signals. the result of trying to send the
signal is always EINVAL.

perhaps i’m missing something - in fact i’d be very happy to be
proven wrong here (likely as i know nothing about windows) but my
current understanding is that, under windows, signals cannot be sent
process to process. my drb hack gets around that by allowing one
process to cause another process to signal itself.

i’ve tried using two irb sessions too

irb_0 > puts $$
1234

irb_1 > Process.kill ‘TERM’, 1234

all signals except 9, which cannot be trapped, cause Errno::EINVAL to
be raised in the process attempting to signal.

can you show me an example of one process signaling another in ruby?

cheers.

a @ http://codeforpeople.com/

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