What does this arrow mean?

Paul Lamar


I never look at "file manager" utilities in linux. Too mouse-centric..

"include"? What do the icons for the source ("C") code look like?

Matt-


Not "include".. I missed that utsrelease.h and version.h when I first
looked at the picture.

Are these files actually symbolic links?


Matt-

Could be. I am not familiar with symbolic links and why
you need them. What are they and why does one need them?

Paul Lamar


Symbolic links are a way for a file a file to look to be in one dir,
but for it actually reside in another. This is useful in cases where
you don't want a bunch of copies of a commonly used file. The use of
links can make the path to file simpler to get to.

If you do an "ls -l" on the file that's actually a symbolic link, you
should see an "l" in the far left column for the file's properties.

Symbolic links can also point to directories.

I'm pretty sure DOS never got links.


Matt-

That sounds like the path command in DOS.
You put the directory name in the path and the programs
in that directory can be run from any other directory.

Thanks Matt. That last trick worked great.
It shows the file the link is pointing to.


Paul Lamar


I'm pretty sure PATH in unix came before PATH in DOS, but I could be
wrong about that. Anyway, sometimes it's useful to know what your
PATH is in unix. Usually you can type something like "echo $PATH" and
it will likely spew out a long listing of directories. The order of
the directories determines the order in which the shell will search
for commands. PATH is an environment variable. Like all environment
variables, PATH can be different for different users, and it's local
to the shell.. So, if you modify the PATH for one shell, other shells
won't be changed. If you want to permanently change your PATH, you
can find the PATH portion of the .cshrc and make edits.

PATH is different from links in that PATH is only for commands that
shell needs to find. Links are for any file. Links allow things like
remote file systems with automounter to have logical disk/host names
from the standpoint of network maintenance, and a different looking
name which is more logical for users to follow. It's really common
for a user's files to reside someplace like /u/<username which is
actually a link to something like /amd/userfshost/users/<username .
And as you have seen, links are used to allow new versions of source
code (and headers) to be installed on a system, and different code
that includes these files don't have to be updated with the new
pathname, etc.


Matt-

True Matt. UNIX preceded DOS by many years.
In fact DOS usurped a lot of UNIX commands.

Linked files really confuse things but as you say
they are probably worth it. I know if you just move
or copy one and try to use it..it breaks the link.

Paul Lamar