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From: guy@sun.uucp (Guy Harris)
Newsgroups: net.unix-wizards
Subject: Re: r/w access to fd from creat()
Message-ID: <2184@sun.uucp>
Date: Wed, 15-May-85 02:58:41 EDT
Article-I.D.: sun.2184
Posted: Wed May 15 02:58:41 1985
Date-Received: Fri, 17-May-85 02:46:18 EDT
References: <738@plus5.UUCP>
Organization: Sun Microsystems, Inc.
Lines: 17

> It has been my experience that the file descriptor returned from a
> successful invocation of creat() is writaable but not readable, regardless
> of the mode specified to creat().
> 
> Does anybody know of a way to change this (kernel mods are unacceptable)?

There isn't any which doesn't involve changing the kernel, except for
closing and reopening the file (which won't work in your case).

> One problem is that I occasionally need r/w access to a creat()ed fd which
> must have a mode of 0444 for exclusive lock purposes.

Try using "link" and "unlink" to/from a file for locking purposes; it means
the file doesn't have to be unwritable, and also means you can lock out the
superuser.

	Guy Harris