From: Gary Wright <gwtmp01@...>
Date: 2009-12-19T05:37:01+09:00
Subject: [ruby-core:27216] Re: unable to send signal "EXIT"


On Dec 17, 2009, at 7:35 PM, Roger Pack wrote:

>> "EXIT" is special pseudo signal to trap program termination.
>> So, you can use it for Signal.trap, but not to invoke by
>> the name.
> 
> Interestingly, you can send a 0
> 
>>> Process.kill 0, 3752
> => 1
> 
> and it works as expected (after process 3752 goes away, sending 0
> results in an exception, as it should).

Sending signal 0 is a standard Unix idiom for testing for the existence of the target process (failure => ESRCH) and/or the capability to send a signal to the process (failure => EPERM). It never actually delivers a signal to the target process.  

Gary Wright