[ih] Unix vs. Multics (was - Re: what is and isn't the web, was Rise and Fall of the Gopher Protocol)

[John R. Levine]

>> Unix systems have hard links, which are fully synonymous names for the
>> same file
>
> That's where the metaphor falls apart.  English language metaphors don't 
> vanish when the words they direct towards vanish.  Sometimes, they take 
> over for the abandoned target.

Unix hard links are just pointers to the inode that decribes the file, and 
all hard links to a particular inode are equivalent. For a long time, this 
was the only way to rename a Unix file:

     link(oldname, newname);
     unlink(oldname)

(Now you can also do an atomic rename() if you're worried about race 
conditions, but it does the same thing with internal locking.)

> Symlinks are aliases, perhaps.  But they aren't synonyms.  Not in the context of spoken language.

Right, those are soft links which have the same issues CNAMEs do.  They're 
not hard links,

Symlinks were introduced in 4.2BSD in 1983, CNAMEs in RFC 973 in 1986.  I 
don't know whether ISI was a Unix shop and so whether symlinks were an 
influence.

Now that I think about it, the analogy between hard and soft links on Unix 
and A and CNAME records in the DNS is pretty obvious.

Regards,
John Levine, johnl at iecc.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly