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From: cher@whutt.UUCP (Mike Cherepov)
Newsgroups: comp.bugs.sys5,comp.unix.wizards
Subject: Re: crossing mount points (was find(1))
Summary: no need for full path
Keywords: System V Release 3.1.1 Version 3 for AT&T 3B2
Message-ID: <3298@whutt.UUCP>
Date: 9 Jun 88 15:58:54 GMT
References: <479@uniq.UUCP> <681@labtam.OZ> <480@uniq.UUCP> <5747@chinet.UUCP> <482@uniq.UUCP>
Organization: AT&T Bell Laboratories
Lines: 15

# The only portable way I can think of to see if a file is remote or not
# is to check the mount table in /etc/mnttab.  Although not the official
# kernel version of the mount table, it does contain a flag indicating that
# a file system is remote.  But that would be useful only if you have a
# full path name and can then traverse down the tree and remember the last
# time you passed a mount point and changed file systems (according to the
# mnttab).  Or you could implement in user code your own version of the
# kernel namei() function.  Excuse me, I'm not feeling well.
# 	Roger Noe			ihnp4!att!uniq!rjnoe

You can tell that you have crossed a mount point by noting that
st_dev has changed, - no need for the full path - then compare
your st_dev with st_rdevs for the files in /etc/mnttab to tell
whether you got a remote.
Not very neat, but does beat the hell out of homespun namei.
		Mike Cherepov