Messages in this thread | | | Subject | Re: Bug in open() function (?) | From | Valdis.Kletnieks@vt ... | Date | Sat, 12 Jul 2003 01:11:12 -0400 |
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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 [unhandled content-type:application/pgp-signature] | |