# Portable signals

**URL:** <https://www.ruby-forum.com/t/portable-signals/124418>\
**Category:** Ruby\
**Created:** [December 28, 2007, 3:59pm UTC](https://www.ruby-forum.com/t/portable-signals/124418 "2007-12-28T15:59:22Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![ara.t.howard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a8b319/32.png) [@ara.t.howard](https://www.ruby-forum.com/u/ara.t.howard)\
**Post date:** [December 28, 2007, 3:59pm UTC](https://www.ruby-forum.com/t/portable-signals/124418/1 "2007-12-28T15:59:22Z")

</div>

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/](http://codeforpeople.com/)

---

<div class="post-metadata">

**Author:** ![ara.t.howard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a8b319/32.png) [@ara.t.howard](https://www.ruby-forum.com/u/ara.t.howard)\
**Post date:** [December 28, 2007, 6:40pm UTC](https://www.ruby-forum.com/t/portable-signals/124418/2 "2007-12-28T18:40:55Z")

</div>

On Dec 28, 11:58 am, “ara.t.howard” [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) 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](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

---

<div class="post-metadata">

**Author:** ![ara.t.howard](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/a8b319/32.png) [@ara.t.howard](https://www.ruby-forum.com/u/ara.t.howard)\
**Post date:** [December 28, 2007, 10:42pm UTC](https://www.ruby-forum.com/t/portable-signals/124418/3 "2007-12-28T22:42:01Z")

</div>

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/](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/](http://codeforpeople.com/)