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From: jfh@killer.UUCP (John Haugh)
Newsgroups: comp.unix.questions
Subject: Re: Identify file name given file descriptor
Message-ID: <877@killer.UUCP>
Date: Wed, 13-May-87 14:40:38 EDT
Article-I.D.: killer.877
Posted: Wed May 13 14:40:38 1987
Date-Received: Tue, 19-May-87 06:34:01 EDT
References: <710@twitch.UUCP>
Organization: The Unix(tm) Connection, Dallas, Texas
Lines: 48
Keywords: mount, ncheck, partly tested
Summary: Metacode follows ...


I opened my mouth and said it could be done.  I refuse to write C code
on my lunch hour so you will have to take what you get.   Refer to ftw(3),
fstat(2) and stat(2) for all of the information you should need.  You
don't REALLY need ncheck, find, /etc/mnttab or any of that other stuff.
stat(2) and fstat(2) return plenty enough information.  You _can_ make things
go faster by finding the correct root directory.


main
    find_file_name ("/", your_fstat_structure) -- start from root directory
					       -- with fstat(2) values.
end

procedure find_file_name (current_directory, file_fstat)

    if current_directory.file_stat = file_fstat then
				-- was FD this directory?
	    putstring (current_directory)
            return
    fi
    for each file_entry in current_directory    -- stat(2) each slot
        if file_entry.file_type = directory_type then
				-- recursively call directories
            find_file_name (current_directory + file_entry.file_name,
						file_fstat)
        elif file_entry.file_stat = file_fstat then
				-- else check to see if it is the file
				-- by checking st_ino and st_dev fields.
            putstring (current_directory + file_entry.file_name)
				-- and print the name if you found one.
            return
        fi
end


There you have it.  All accessible files are checked, which should include
yourown since you should be able to read you own directory.  The ones you
can't access can't be accessed :-(.  st_ino and st_dev are all you need to
compare to see if the files are the same ones.  This should (once written
in C or something) be as fast or faster than find(1) since find(1) has atleast
this much work to do.

- John.

Disclaimer -
	I speak for myself.  My boss pays me money when he wants me to
	speak for him.