Path: utzoo!attcan!utgpu!watmath!uunet!lll-winken!csd4.milw.wisc.edu!mailrus!uflorida!indri!unmvax!tut.cis.ohio-state.edu!att!cbnewsc!levy
From: levy@cbnewsc.ATT.COM (Daniel R. Levy)
Newsgroups: unix-pc.general
Subject: Re: crontab Daemon-from-Hell
Summary: cd failure aborts /bin/sh script so / is safe.
Message-ID: <1122@cbnewsc.ATT.COM>
Date: 4 Jun 89 10:19:28 GMT
References: <19071@cup.portal.com> <14373@bfmny0.UUCP> <1526@sialis.mn.org> <1528@sialis.mn.org>
Organization: AT&T Bell Laboratories, Skokie IL
Lines: 23

< >>>	cd /usr/spool/uucppublic
< >>>	find . -type f -mtime +30 -exec rm -f {} \;
< >>
< >>This is dangerous if run as root.  If anything - disk error, anything - 
< >>happens to make /usr/spool/uucppublic unavailable, you will wipe your
< >>file structure.
[ presumably because the cd will fail, leaving the current directory to be / ]

Under Bourne shell (/bin/sh), if cd fails the script aborts with an
error message.  Presumably, cron is using /bin/sh, so even if there
is no /usr/spool/uucppublic the cron entry won't trash the disk starting
from /.

(Note, however, that a failed cd will NOT abort a script running under ksh.
I have been bitten by that one because ksh runs script commands invoked
from it with another ksh, and some sh scripts depend upon a script
aborting upon a failed cd rather than blithely plunging on with nothing
more than an error message.)
-- 
Daniel R. Levy             UNIX(R) mail:  att!ttbcad!levy, att!cbnewsc!levy
AT&T Bell Laboratories
5555 West Touhy Avenue     Any opinions expressed in the message above are
Skokie, Illinois  60077    mine, and not necessarily AT&T's.