easy question about kill command

[Oliver Fromme]

Roman Gorohov. <roma.a.g at gmail.com> wrote:
 > Thanks for your reply. My question was about standard bsd daemons, not
 > about some apps with unpredictable behaviour.

But the kill command doesn't know what kind of daemon it
is sending a signal to.  It just sends a signal to a PID.
That PID could belong to a daemon from the bases system
(such as mountd), or it could belong to a third-party
program (such as apache).  There is no way for the kill
command to know.

If a program is unable to perform an action (be it a
restart after receiving a SIGHUP or whatever), it is the
responsibility of the program to print or log a message.
I think most daemons in the FreeBSD base system do that.

For example, when you send a SIGHUP to a mountd process
and there's a fatal error in your /etc/exports file, the
fact is logged via syslog (by default it is written to
/var/log/messages).  For convenience you can write a
small shell script (or alias, or shell function) which
does this:  kill -HUP $1; sleep 3; tail /var/log/messages

Best regards
   Oliver

PS:  I wrote the following shell script for that purpose:

#!/bin/sh -
LOGFILE=/var/log/messages
LOGSIZE_BEFORE=$(stat -f%z $LOGFILE)
logger "Executing killall -HUP $*"
killall -HUP "$@"
sleep 3
LOGSIZE_AFTER=$(stat -f%z $LOGFILE)
tail -c $(( $LOGSIZE_AFTER - $LOGSIZE_BEFORE )) $LOGFILE

I named it "killhup".  I can then type "killhup mountd",
so it restarts the mountd process, then waits 3 seconds,
and then it prints any new messages from the log file
(or nothing if everything is OK).

-- 
Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
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