From: Robert Klemme <bob.news@...>
Date: 2005-06-02T19:20:23+09:00
Subject: Re: trap HUP not working

wmwilson01@gmail.com wrote:
> I know I must be doing something dumb here, but I can't figure out
> what, and I'm about to give up.  I'm setting a trap("HUP") to call a
> couple of functions (basically to re-read a config).  The first time
> running a "kill -HUP" on the process works fine, but the second time
> it exits with a "hangup".  If I modify the trap to look like:
>
> trap("HUP") {
>   trap("HUP", "IGNORE")
>   fun1
>   fun2
> }
>
> It doesn't hangup, but only the first "kill -HUP" actually re-reads
> the configuration.

You surprise me: you are really surprised that only the first signal is
processed?  I mean, you set the signal handler to IGNORE on first run and
apparently you never reset it.

As far as I can see signal handlers are never executed concurrently but if
you want to be sure, I'd use standard thread synchronization:

require 'thread'

$HUP_LOCK = Mutex.new

trap "HUP" do
  $HUP_LOCK.synchronize do
    puts "your code here (queued up)"
  end

  if $HUP_LOCK.try_lock
    puts "your code here (ingore duplicate invocations)"
    $HUP_LOCK.unlock
  end
end


Kind regards

    robert