easy question about kill command

[Oliver Fromme]

Oliver Fromme <olli at lurza.secnetix.de> wrote:
 > roma.a.g <roma.a.g at gmail.com> wrote:
 > > Is there anyone who can explain me, why when i say 'kill -HUP id',
 > > and its failed to restart, kill say nothing?
 > 
 > Because the kill command has no way to know about it.
 > 
 > The kill command only instructs the kernel to deliver
 > a signal to a process (or to a process group).  The only
 > feedback it gets from the kernel is whether the target
 > process exists or not.  (The latter is often used to
 > check for the existence of a particular process ID, by
 > trying to send it a "zero" signal which does nothing.)

Oh, I forgot to add one further fact:  The target process
can only respond to the signal the next time it gets a time
slice from the scheduler.  That doesn't necessarily need to
be immediately.  For example, when the process is currently
blocked (waiting for I/O or another resource), it can be a
long time until it gets a chance to respond to the signal.
At that time, the kill process has probably already exited.

Best regards
   Oliver

-- 
Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
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