Date: Thu, 9 Nov 2017 20:01:56 +1100 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: Polytropon <freebsd@edvax.de> Cc: Edgar Pettijohn <edgar@pettijohn-web.com>, Ernie Luzar <luzar722@gmail.com>, freebsd-questions@freebsd.org Subject: Re: Need help with rc.d script Message-ID: <20171109185331.B72828@sola.nimnet.asn.au> In-Reply-To: <20171109040452.d3c25fe2.freebsd@edvax.de> References: <mailman.444.1510052978.1530.freebsd-questions@freebsd.org> <20171108021900.W9710@sola.nimnet.asn.au> <20171108043726.N72828@sola.nimnet.asn.au> <5A01F758.1050706@gmail.com> <20171109005843.E72828@sola.nimnet.asn.au> <5A0332D1.90509@gmail.com> <20171109013818.GA31584@FreeBSD> <20171109040452.d3c25fe2.freebsd@edvax.de>
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On Thu, 9 Nov 2017 04:04:52 +0100, Polytropon wrote:
Another night owl, hmm? :)
> On Wed, 8 Nov 2017 19:42:36 -0600, Edgar Pettijohn wrote:
> > On Wed, Nov 08, 2017 at 11:37:37AM -0500, Ernie Luzar wrote:
> > > Ian Smith wrote:
> > > > On Tue, 7 Nov 2017 13:11:36 -0500, Ernie Luzar wrote:
[..]
> > > I tested with and without the enclosing ( and ) on the while loop
> > > and it made no difference. No pidfile exists before the "service
> > > dynip start" is issued and non exists afterwards.
> > I don't believe the rc system can write a pidfile for you. Most of if not all
> > of the services being started by the rc system are written in c and take care
> > of writing their own pidfile. I suspect you could overcome this by writing a c
> > program that does so and executes your script every 10 minutes. Or some form of
> > pgrep perhaps.
> It's easy to create a pidfile from within the shell script for
> the shell itself (and its subshells) as well as for an invoked
> external program:
>
> echo $$ > /var/run/${0##*/}.pid
> myprog -foo -bar baz -meow
> echo $! > /var/run/myprog.pid
In that case - unless myprog daemonised itself? - I believe you'd need:
myprog -foo -bar baz -meow &
so then $! is specifically the PID of the (now background) myprog
> The documentation says:
>
> $$ Expands to the process ID of the invoked shell. A subshell
> retains the same value of $ as its parent.
>
> $! Expands to the process ID of the most recent background command
> executed from the current shell. For a pipeline, the process ID
> is that of the last command in the pipeline.
>
> See "man sh", section "Special Parameters", for details
Indeed. I was trying to find out whether or not rc made the pidfile, or
one had to do it in the program (here a sh script) being run; as Edgar
indicated, seems the program|script needs to do it. Even if rc had done
so, for a bg subshell (and not $$) you'd need to overwrite it anyway.
I think what's needed here for Ernie's dynip script is like:
# setup code ..
[..]
# repeated loop subshell code, to be left running
(
while true; do
[..]
sleep $delay
done
) &
echo $! > /var/run/dynip.pid # post PID of bg subshell
echo ok or such confirmation # if desired
exit 0 # finished startup script
Then 'service dynip stop' should find and kill the correct process.
I generally go a bit further, finding sometimes that only the sleep in
such a loop may get killed - since it's running 99.9%+ of the time - so
usually take the trouble so any of the usual signals work to end it:
( done=0
trap "done=1" int quit term # signals set done=1
while [ $done -eq 0 ]; do
[..]
sleep $delay
done;
echo `basename $0` killed by signal int, quit or term
trap - int quit term # for tidyness, overkill here
) &
echo $! > /var/run/dynip.pid # correct PID for external kill
exit 0
Consult sh(1) regarding how to trap - and/or block - various signals.
cheers, Ian
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