Xref: utzoo comp.unix.questions:28334 comp.unix.admin:918 comp.unix.internals:1927 comp.unix.programmer:949 comp.unix.misc:887
Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!bria!mike
Newsgroups: comp.unix.questions,comp.unix.admin,comp.unix.internals,comp.unix.programmer,comp.unix.misc
Subject: Re: How determine if a file is opened by another process
Keywords: file open
Message-ID: <406@bria>
Date: 31 Jan 91 00:45:30 GMT
References: <1488@nixsin.UUCP> <1991Jan29.204403.6071@rick.doc.ca>
Reply-To: uunet!bria!mike (Michael Stefanik)
Followup-To: comp.unix.questions
Organization: Briareus Corporation, Los Angeles, CA
Lines: 28

In an article, calvin.doc.ca!andrew (Andrew Patrick) writes:
>I need to know if there's a standard, *safe* way for a process to
>find out if some other process (any other process on the machine)
>has a specific file open at the time of the query. [...]
>Oh yes.  The machine is an Encore Multimax 520, running UMax V (a
>System V based UNIX-alike).  I do know about the dodge of reading
>/dev/kmem, and the Multimax has a special call to get the address of
>the inode table, to make it a little safer, but I'd like to avoid
>this.  The program which needs this info would then have to be
>setuid root, or /dev/kmem would have to be opened for general read
>access, which we want to avoid if at all possible.

There is no portable way to get the information that you want; poking
through the kernel is the only way I know of determining if some
unrelated and/or non-cooperative process has a file open.  If you're worried
about security issues (as well you should be), then one solution would
be to write a SUID daemon that, when prodded, will dump this information
into shared memory.  Thus, the program itself need not be running in a
privileged state.

However, the point remains, any mucking about such as this is inherently
non-portable.
-- 
Michael Stefanik                       | Opinions stated are not even my own.
Systems Engineer, Briareus Corporation | UUCP: ...!uunet!bria!mike
-------------------------------------------------------------------------------
technoignorami (tek'no-ig'no-ram`i) a group of individuals that are constantly
found to be saying things like "Well, it works on my DOS machine ..."