Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!genrad!decvax!decwrl!pyramid!oliveb!sun!gorodish!guy
From: guy@gorodish.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: symbolic links are a botch
Message-ID: <21237@sun.uucp>
Date: Tue, 16-Jun-87 14:41:41 EDT
Article-I.D.: sun.21237
Posted: Tue Jun 16 14:41:41 1987
Date-Received: Thu, 18-Jun-87 03:12:53 EDT
References: <2629@ulysses.homer.nj.att.com> <5962@brl-smoke.ARPA> <679@nu3b2.UUCP>
Sender: news@sun.uucp
Lines: 37
Keywords: file system, file name resolution

> What is a "symbolic" link?

It is a special kind of "file".  The "contents" of the file are a
string representing a pathname; most references to the file are
converted by the system into references to the file specified by that
pathname.

> Is is different from a regular link?

Yes.  A regular link, in effect, is a map between a file name and a
particular inode on the file system where the directory containing
that link resides; a symbolic link is a map between a file name and
whatever file happens to have another file name.

For one thing, this means that symbolic links can be made to files on
other file systems.  For another, if you have two hard links to a
file, and do an "mv" to replace one of those links with a link to a
different inode, the second hard link will still refer to the
original inode, and thus the original file.  If you have a symbolic
link to a file, after the "mv" the symbolic link will refer to the
new file.

In addition, you can make symbolic links to directories; only the
super-user can make hard links to directories in most UNIX systems,
and even that is very much NOT recommended.  (The main reason it's
supported at all is that in many UNIX systems, the only way to rename
a file is to make a second hard link to it with the new name, and get
rid of the hard link with the old name.)

> Did I miss something important in my education? 8-)

Well, the more you know about various UNIX implementations, the
better; for one thing, it means you can sometimes avoid reinventing
the wheel (or, worse, the *square* wheel).
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com