Date: Wed, 24 Aug 2005 01:18:48 +0200 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Peter Jeremy <PeterJeremy@optushome.com.au> Cc: FreeBSD-arch <freebsd-arch@freebsd.org> Subject: Re: New library: libpidfile. Message-ID: <20050823231848.GD65338@garage.freebsd.pl> In-Reply-To: <20050823094226.GD37107@cirb503493.alcatel.com.au> References: <20050822213028.GB4812@garage.freebsd.pl> <430A8F1A.6090607@freebsd.org> <20050823081758.GB47261@garage.freebsd.pl> <20050823094226.GD37107@cirb503493.alcatel.com.au>
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On Tue, Aug 23, 2005 at 07:42:26PM +1000, Peter Jeremy wrote:
+> On Tue, 2005-Aug-23 10:17:58 +0200, Pawel Jakub Dawidek wrote:
+> >In my first concept (when it was part of libutil) I allocated memory
+> >to store needed informations, because I didn't wanted to use preallocat=
ed
+> >memory (someone linking libutil doesn't have to use pidfile
+> >functionality).
+>=20
+> Since there's an initialisation function, why not just malloc whatever
+> memory you need? You can either store the pointer in a local static
+> or have pidfile_open() return it as an opaque pointer that the user
+> has to pass into other pidfile_XXX functions.
I added a handle, so now it goes like this:
struct pidfh *pfh;
pid_t otherpid, childpid;
pfh =3D pidfile_open("/var/run/daemon.pid", 0644, &otherpid);
if (pfh =3D=3D NULL) {
if (errno =3D=3D EEXIST)
errx(EXIT_FAILURE, "Daemon already running, pid: %d.", otherpid);
/* If we cannot create pidfile from other reasons, only warn. */
warn("Cannot open or create pidfile");
}
if (daemon(0, 0) =3D=3D -1) {
warn("Cannot daemonize");
pidfile_remove(pfh);
exit(EXIT_FAILURE);
}
pidfile_write(pfh);
for (;;) {
/* Do work. */
childpid =3D fork();
switch (childpid) {
case -1:
syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno));
break;
case 0:
pidfile_close(pfh);
/* Do child work. */
break;
default:
syslog(LOG_INFO, "Child %d started.", childpid);
break;
}
}
pidfile_remove(pfh);
exit(EXIT_SUCCESS);
I can't use atexit(3) anymore to remove pidfile, but I like it this way
better, anyway.
+> >It also now has 4 functions, which makes it a good candidate of small,
+> >nice, lightweight library:)
+>=20
+> IMHO, 4 functions is too small. I would prefer to have a smaller
+> number of larger libraries and think this belongs in an existing
+> library - eg libutil. Whilst this may form a nice lightweight
+> library, if everyone wrote small, lightweight libraries, linking
+> an application would require a mile-long command line.
I talked about this with few more guys and they agree it should be a
part of libutil, so I moved it there.
+> Can I suggest two enhancements:
+> 1) Allow NULL to be passed to pidfile_open() to indicate that the
+> pidfile should be in /var/run/PROCESS_NAME.pid (and/or if the
+> name doesn't include any '/' then default to /var/run)
I implemented NULL behaviour, but I'm not sure about the second thing.
I'd like to avoid it.
+> 2) Write a wrapper function that calls pidfile_open() and if it's
+> successful, exec's the rest of the command line.
There is simlar wrapper: lockf(1), so I'll not duplicate functionality,
but I changed daemon(8) to use pidfile(3).
Thanks for all suggestions.
--=20
Pawel Jakub Dawidek http://www.wheel.pl
pjd@FreeBSD.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
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