On Wed, Mar 03, 2004 at 11:40:24AM -0800, Peter Jay Salzman wrote: > On Wed 03 Mar 04, 11:28 AM, Jeff Newmiller <[EMAIL PROTECTED]> said: > > On Wed, 3 Mar 2004, Ken Herron wrote: > > > > > --On Wednesday, March 03, 2004 10:11:10 -0800 Peter Jay Salzman > > > <[EMAIL PROTECTED]> wrote: > > > > > > >> > 25 4 * * * root test -e /usr/sbin/anacron || run-parts --report > > > >> /etc/cron.daily > > > >> > > > >> That line will only launch "run-parts" if /usr/sbin/anacron doesn't > > > >> exist. Does /usr/sbin/anacron exist? > > > > > > > > ken, > > > > > > > > yeah, it does exist. daily definitely runs. it just runs at a time i > > > > wasn't expecting. > > > > > > My point was that if /usr/sbin/anacron exists, then the crontab line > > > above will not run cron.daily. You say that /usr/sbin/anacron exists, so > > > cron.daily is not being launched as a result of the above crontab line. > > > That means something else is running it. Something like anacron, for > > > example. > > > > This list is great. This explains a longstanding puzzle (to me) of how > > (and to some extent why) both cron and anacron are installed on my debian > > box. > > > > Now that I see how it works, I am not too impressed with this kludge, > > though... this is a deceptively obtuse configuration duplication between > > these two packages. > > ok, maybe i'm slow, but i don't understand why that line will only > launch if /usr/sbin/anacron doesn't exist.
The shell uses short-circuit evaluation on conditionals. When it sees A || B it first evaluates A. Then if A is true, the value of the whole conditional has to be true, so B never even gets evaluated. So, if "test -e /usr/sbin/anacron" is true because anacron is installed, then the shell doesn't bother with "run-parts --report /etc/cron.daily" because it has already figured out the value of the conditional. On the other hand, if "test -e /usr/sbin/anacron" is false, then the shell is looking at (false || "run-parts --report /etc/cron.daily"), which evaluates to whatever the right-hand side evaluates to. > /etc/init.d/cron gets run upon startup. the only test i see is: > > test -f /usr/sbin/cron || exit 0 > > it doesn't look look for /usr/sbin/anacron. what am i missing? > > pete > > -- > Make everything as simple as possible, but no simpler. -- Albert Einstein > GPG Instructions: http://www.dirac.org/linux/gpg > GPG Fingerprint: B9F1 6CF3 47C4 7CD8 D33E 70A9 A3B9 1945 67EA 951D -- Samuel Merritt OpenPGP key is at http://meat.andcheese.org/~spam/spam_at_andcheese_dot_org.asc Information about PGP can be found at http://www.mindspring.com/~aegreene/pgp/
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