![]() | |||||||||||||
Messages in this thread |
While I'm sure I don't have a grasp of "the big picture", I would have imagines these would have acted like a mask against the file system attributes. In effect setting O_RDONLY would clear the write permission bits read by stat(), and O_WRONLY would clear the read permission bits. O_RDONLY + O_WRONLY (O_RDWR) would leave the permissions alone. These would be applied somewhere around the may_open() call in fs/open_namei.c A poor mans umaks(), I guess. --John On Saturday 12 July 2003 01:11 am, Valdis.Kletnieks@vt.edu wrote: > On Fri, 11 Jul 2003 20:38:09 PDT, Andrew Morton said: > > "J.C. Wren" <jcwren@jcwren.com> wrote: > > > I was playing around today and found that if an existing file is opened > > > wit > > h > > > > O_TRUNC | O_RDONLY, the existing file is truncated. > > > > Well that's fairly idiotic, isn't it? > > Not idiotic at all, and even if it was, it's still contrary to specific > language in the manpage. > > I could *easily* see some program having a line of code: > > if (do_ro_testing) openflags |= O_RDONLY; > > I'd not be surprised if J.C. was playing around because a file unexpectedly > shrank to zero size because of code like this. There's a LOT of programs > that implement some sort of "don't really do it" option, from "/bin/bash > -n" to "cdrecord -dummy". So you do something like the above to make your > file R/O - and O_TRUNC *STILL* zaps the file, in *direct violation* of the > language in the manpage. > > Whoops. Ouch. Where's the backup tapes? > > > The Open Group go on to say "The result of using O_TRUNC with O_RDONLY is > > undefined" which is also rather silly. > > > > I'd be inclined to leave it as-is, really. > > I hate to think how many programmers are relying on the *documented* > behavior to prevent data loss during debugging/test runs.... > > /Valdis - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
| Last update: 2005-03-22 13:46 [from the cache] ©2003-2008 | |||||||||||||