Date: Fri, 16 Dec 2005 12:08:16 +0300 From: "Roman Gorohov. " <roma.a.g@gmail.com> To: Oliver Fromme <freebsd-hackers@FreeBSD.ORG> Cc: freebsd-hackers@freebsd.org Subject: Re[2]: easy question about kill command Message-ID: <979057908.20051216120816@gmail.com> In-Reply-To: <200512160846.jBG8kaEB099405@lurza.secnetix.de> References: <14510301213.20051216105225@gmail.com> <200512160846.jBG8kaEB099405@lurza.secnetix.de>
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Hi, Oliver. > roma.a.g <roma.a.g@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.) > There is no way for the kill command to know what the > target process is going to do with the signal. This is > entirely and only the business of the target process, > which might chose to take the default action (in the case > of SIGHUP it's to terminate the process), to ignore the > signal alltogether, or to take some special action. > Some programs use SIGHUP traditionally to rotate their > logfiles, re-read configuration files, re-open network > sockets, restart themselves, or other things. But that's > entirely up to the program in question, and there is no > way the kill command could know about it, let alone > whether it was successful or not. Thanks for your reply. My question was about standard bsd daemons, not about some apps with unpredictable behaviour. >> It is such an easy to implement... > I don't think so, as explained above. Yeah right, I see now. > Best regards > Oliver -- Best regards, Roman Gorohov mailto:roma.a.g@gmail.com
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