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From: markb@sdcrdcf.UUCP (Mark Biggar)
Newsgroups: net.unix-wizards
Subject: Re: null filename handling question
Message-ID: <1290@sdcrdcf.UUCP>
Date: Tue, 4-Sep-84 16:39:49 EDT
Article-I.D.: sdcrdcf.1290
Posted: Tue Sep  4 16:39:49 1984
Date-Received: Fri, 14-Sep-84 20:35:11 EDT
References: <744@opus.UUCP> <opus.772>
Reply-To: markb@sdcrdcf.UUCP (Mark Biggar)
Organization: System Development Corporation, Santa Monica
Lines: 29
Summary: 

In article <opus.772> rcd@opus.UUCP (Dick Dunn) writes:
>Since posting my original query, I've been corrected--V7 and older systems
>treat a null file name as the current directory; Sys III treats it as a
>nonexistent file.  But I'm still curious about the reason for "" meaning
>the current directory.

I don't imagine that it was planned on, it kind of just happened.  The code
in the file system name resolution routine probably goes:

if name starts with slash then
	use root directory
else
	use current directory
endif
while not end of string
	if current file not directory then error
	get and skip over next name
	find in current file
	use it as current file
endwhile

Note that this resolves "/" to the right thing, but has the side effect
of resolving "" to the current directory.
This is also explains why things like "cd /usr/spool/" work on v7 & 4bsd
and not on system III.

Mark Biggar
{allegra,burdvax,cbosgd,hplabs,ihnp4,akgua,sdcsvax}!sdcrdcf!markb