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From: mike@turing.unm.edu.unm.edu (Michael I. Bushnell)
Newsgroups: comp.unix.wizards
Subject: Re: /bin/test and stat(2)
Message-ID: <673@unmvax.unm.edu>
Date: Wed, 14-Oct-87 17:46:08 EDT
Article-I.D.: unmvax.673
Posted: Wed Oct 14 17:46:08 1987
Date-Received: Sat, 17-Oct-87 02:35:47 EDT
References: <9767@brl-adm.ARPA>
Sender: news@unmvax.unm.edu
Reply-To: mike@turing.unm.edu.UUCP (Michael I. Bushnell)
Organization: University of New Mexico, Albuquerque
Lines: 68

In article <9767@brl-adm.ARPA> franco@MIKEY.BBN.COM (Frank A. Lonigro) writes:
~
~	Thanks very much to those of you who answered my questions with
~intelligence.  I have a couple more.
~
~	Just thought I'd let you know that I found the manual page on
~the description of a path name but found it very contradictory.  Here
~is an excerpt from the BSD manual page:
~
~     File Name
~          Names consisting of up to {FILENAME_MAX} characters may
~          be used to name an ordinary file, special file, or
~          directory.
~
~          These characters may be selected from the set of all
~          ASCII characters excluding 0 (null) and the ASCII code
~          for / (slash).  (The parity bit, bit 8, must be 0.)
~
~          Note that it is generally unwise to use *, ?, or [ ] as
~          part of file names because of the special meaning
~          attached to these characters by the shell.
~
~     Path Name
~          A path name is a null-terminated character string
~          starting with an optional slash (/), followed by zero
~          or more directory names separated by slashes, option-
~          ally followed by a file name.  The total length of a
~          path name must be less than {PATHNAME_MAX} characters.
~
~          If a path name begins with a slash, the path search
~          begins at the root directory.  Otherwise, the search
~          begins from the current working directory.  A slash by
~          itself names the root directory.  A null pathname
~          refers to the current directory.
~
~According to the naming convention of file names, all ASCII chars can be
~used except a NULL or the slash.  This convention includes the naming of
~directories.  So, how can a null string be considered a file name, let
~alone a directory, and why should there be two ways to refer to the same
~thing (the current directory)?  It really doesn't make sense!
~

Look back at the good posting about 0 length strings.  A pathname with
length zero is NOT the same as a pathname with length one, and the
first char being NULL.

The reason for not allowing NULL in pathnames is, I hope, obvious.  It
is also the terminator for strings.  A null string is a string of
length zero.  According the rules in the second section above, it has
[no leading slash][no directory names (sep. by '/')][empty final
comp.]


The rules clearly allow "" as a pathname, and specify that it must
mean cwd.

But "" is NOT "\0".




					Michael I. Bushnell
					a/k/a Bach II
					mike@turing.unm.edu
					{ucbvax,gatech}!unmvax!turing!mike
---
WHO sees a BEACH BUNNY sobbing on a SHAG RUG?!
				-- Zippy the Pinhead