Thorsten Froehlich <tho### [at] trfde> wrote:
> Unlike in Windos, in Mac OS and Unix, links (or aliases) are completely
> transparent for applications.  Thus there is no difference between them.  Of
> course, links (or aliases) can break.

  Actually there are two types of links in Unix: Hard links and soft links.

  Hard links can't break. A hard link is basically a duplicate entry in the
file allocation table (ie. it looks like two different files, but they
actually point two the same physical data in the disk). The file pointed
by hard links is removed only when all hard links to it are deleted (that's
why a hard link can never break). This feature, however, imposes a limitation
on hard links: The file pointed by the hard link must be located in the
same partition as the link itself.
  A soft link is looser: It's not bound to the file it points, as the hard
link, and it can point to any file anywhere. A soft link is simply an entry
which contains a path to the file it points (which can be absolute or
relative). A soft link is basically the name of a file. If the file is
deleted, the soft link breaks (because the file pointed by the soft link
does not exist anymore).

  From the point of view of applications, they don't see any difference
between files, hard or soft links (unless the specifically ask the system
with a specialized system call).

  Links are extremely handy. For example there are many applications which
create their setting/cache/etc files in the home directory of the user.
I have a limited quota in my home directory here and thus it's very limited
what I can place there. However, I have plenty of space in the local HD of
my work computer (my home directory is located in a network drive). When
the directory of some program takes too much space, I simply move it to
the local HD and make a soft link in my home directory pointing to the
new location; the program does not notice anything and works perfectly
(but it now writes everything to the local HD instead of my home directory).

  I curse Windows every time I would need this handy feature there... :)

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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