From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <c57e272fa523d82cbe095bd5ac8fa259@terzarima.net>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] how to delete directories prefixed with a dash
From: Charles Forsyth <forsyth@terzarima.net>
Date: Wed, 16 Jun 2004 06:39:32 +0100
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-p is one thing i suppose, but -m 777 seems a little pointless.
actually, -m probably is fairly pointless all round.

as on Unix, on Plan 9 it probably doesn't do what you might think, although
Unix and Plan 9 don't do that in different ways.  on Unix it applies
only to the last component and is subject to umask, and intervening
directories get -m $(umask -S),u+wx; on Plan 9 the mode applies to all
directories (so -m 555 -p not/there/yet won't work at all) and in
each case is subject to masking by the parent directory permissions,
so -m 777 produces completely-writable directories only if the old
create(..., DMDIR|0777) would have done anyway.  now on Plan 9,
mkdir -p -m 700 ... does make a difference (starting in a directory
with mode 755 say) and will set the mode 700 on each new
directory; although that differs from Unix where with my umask 022
i get 755 directories up to the last created, which is 700.

of course in all cases, on Plan 9 and Unix,
if mkdir doesn't create the directory (eg, intervening ones with -p), it doesn't change
the mode, so be sure to do rm -r or rm -r -- first.  that's presumably
why the Unix one has the definition it's got.  it's not that useful but it
behaves consistently not-that-usefully with -p regardless whether the directories are created or not.

at least i think so; that's what the Unix manual pages and code suggests,
supported by experiment on Plan 9 and Unix.

all in all, i confess i did wonder when it appeared several months
ago why -m was in Plan 9 outside APE.  still it's only 80 lines compared
with 212 on FreeBSD (but then that includes the BSD copyright and licence, and
			/*
			 * POSIX 1003.2:
			 * For each dir operand that does not name an existing
			 * directory, effects equivalent to those cased by the
			 * following command shall occcur:
			 *
			 * mkdir -p man 2 $(dirname dir) &&
			 *    mkdir [-m mode] dir
			 *
			 * We change the user's umask and then restore it,
			 * instead of doing chmod's.
			 */
and
		/*
		 * The mkdir() and umask() calls both honor only the low
		 * nine bits, so if you try to set a mode including the
		 * sticky, setuid, setgid bits you lose them.  Don't do
		 * this unless the user has specifically requested a mode,
		 * as chmod will (obviously) ignore the umask.
		 */

i wonder why i got out of bed this morning.
after the above, you'll probably wish i'd stayed there too!