Path: utzoo!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!mcsun!ukc!dcl-cs!gdt!gdr!exspes
From: exspes@gdr.bath.ac.uk (P E Smee)
Newsgroups: comp.lang.c
Subject: Re: strncpy
Keywords: strncpy null termination
Message-ID: <1989Dec22.102020.3960@gdt.bath.ac.uk>
Date: 22 Dec 89 10:20:20 GMT
References: <1231@srhqla.SR.COM> <11510@csli.Stanford.EDU>
Reply-To: exspes@gdr.bath.ac.uk (P E Smee)
Organization: University of Bristol c/o University of Bath
Lines: 20

In article <11510@csli.Stanford.EDU> poser@csli.stanford.edu (Bill Poser) writes:
>
>I should clarify that: (a) I know perfectly well HOW strncpy works. My
>question concerned the rationale for this design; 

I suspect it has to do with the original design of the unix directory
structure.  Filenames were limited to 12 (14? been so long since I
used one, I'm not sure of the number) characters, and the directory
structure had a char[exactly-that-size] variable to HOLD the filename.
So, when putting a filename into or out of a directory structure, you
wanted it to be null-terminated if and only if it was shorter than that
variable.  A maximum-length filename could NOT be null terminated in
the describing structure.

As to why they decided to do that, sheer byte-saving, I suppose (1 per
file in your directory hierarchy).  Maybe it made directory entries fit
more nicely into whatever their disk blocksize was.
-- 
Paul Smee, Univ of Bristol Comp Centre, Bristol BS8 1TW, Tel +44 272 303132
 Smee@bristol.ac.uk  :-)  (..!uunet!ukc!gdr.bath.ac.uk!exspes if you MUST)