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Re: dd new iflag= oflag= flags directory, nolinks
From: |
Paul Eggert |
Subject: |
Re: dd new iflag= oflag= flags directory, nolinks |
Date: |
Wed, 08 Mar 2006 01:04:14 -0800 |
User-agent: |
Gnus/5.1007 (Gnus v5.10.7) Emacs/21.4 (gnu/linux) |
Phillip Susi <address@hidden> writes:
> What is atomic about having dd do this? open() with O_DIRECTORY to test for
> existence of a directory is exactly what test does isn't it?
No, because "test -d foo && test -r foo" is _two_ invocations of
"test", not one. A race condition is therefore possible. The race
condition is not possible with dd if=foo iflag=directory count=0.
Admittedly this usage is unusual. The main arguments for it are
(1) "dd" supports all the other O_* flags, so why not O_DIRECTORY? and
(2) I ran into a situation where I could use O_DIRECTORY.
(1) is far more important than (2).
- dd new iflag= oflag= flags directory, nolinks, Paul Eggert, 2006/03/06
- Re: dd new iflag= oflag= flags directory, nolinks, Phillip Susi, 2006/03/06
- Re: dd new iflag= oflag= flags directory, nolinks, Olivier Delhomme, 2006/03/21
- Re: dd new iflag= oflag= flags directory, nolinks, Paul Eggert, 2006/03/27
- Re: dd new iflag= oflag= flags directory, nolinks, Phillip Susi, 2006/03/21
- Re: dd new iflag= oflag= flags directory, nolinks,
Paul Eggert <=
- Re: dd new iflag= oflag= flags directory, nolinks, Phillip Susi, 2006/03/21
- Re: dd new iflag= oflag= flags directory, nolinks, Paul Eggert, 2006/03/27