From: Gennady Bystritsky <Gennady.Bystritsky@...>
Date: 2008-04-16T04:58:16+09:00
Subject: Re: at_exit handlers and Process.kill

Ken Bloom wrote:
> On Tue, 15 Apr 2008 12:29:01 -0500, Daniel Berger wrote:
>
>> Ken Bloom wrote:
>>> On Tue, 15 Apr 2008 11:28:33 -0500, Daniel Berger wrote:
>>>
>>>> ts wrote:
>>>>> Daniel Berger wrote:
>>>>>> # process_test.rb
>>>>>> File.open("pid.txt", "w"){ |fh| fh.print Process.pid } p
>>>>>> Process.pid
>>>>>>
>>>>>> sleep 1 while true
>>>>>  you really think that the following line will be executed ?
>>>> Why not? The docs say at_exit, "Converts block to a Proc object
>>>> (and therefore binds it at the point of call), and registers it for
>>>> execution when the program exits."
>>>
>>> Ruby does *everything* in the order it encounters it in the file.
>>> at_exit installs an exit handler, (a proc to be run later) but it's
>>> a method that has to be executed. If you put "sleep 1 while true"
>>> before the at_exit call, the at_exit call will never be executed,
>>> so the exit handler will never be installed. Adjust your program to
>>> call at_exit (or whatever other handlers you want) before running
>>> anything else.
>>>
>>> # process_test.rb
>>> at_exit {
>>>     puts "AT_EXIT"
>>> }
>>>
>>> END{
>>>     puts "END"
>>> }
>>>
>>> trap("KILL"){
>>>     puts "KILLED"
>>> }
>>>
>>>
>>> File.open("pid.txt", "w"){ |fh| fh.print Process.pid } p Process.pid
>>>
>>> sleep 1 while true
>>
>> Right, I should have clarified that, even with the right ordering,
>> at_exit and END blocks weren't called.
>>
>> Perhaps it's the signal I used? I haven't fully experimented yet...
>>
>> Regards,
>>
>> Dan
>
> See signal(7) for descriptions and numbers of the various
> signals. Most
> likely you want to use SIGINT (signal 1), and then at_exit will be

SIGINT is 2, 1 is SIGHUP

> sufficient. Note that SIGKILL (signal 9) cannot be caught under any
> circumstances (it's used to kill badly misbehaving
> applications), so your
> sigkill handler is useless.
>
> I think it's unnecessary to install lots of signal handlers to do the
> cleanup. Just learn what each signal does, and what to expect, and
> at_exit should already be designed to do what you want.
>
> --Ken