09/19/05 CISC181 Fall 2005

Lecture Notes

Today we'll start by going over a few things
that you'll see in your lab03 today.

We'll focus on part 4, because that is the
part that is the "least" self-explanatory.

In part 4, you'll be using "gnuplot" to
draw letters of the alphabet.  At the moment,
it may appear that this is unrelated to C++
programming, however, it will form the basis
of your first project.  That's why we are going
over it.

Brief overview of parts 1, 2, 3
===============================

In part 1, we did the steps to
cd into ~/cisc181, and we discussed
the difference between

cd cisc181
cd ~/cisc181

The first is a relative path name
(relative to the current directory)

The second is an absolute pathname
because ~ is an abbreviation for my
home directory.

We can see this by doing the following:

echo ~
echo My home directory is ~

> echo ~
/home/usra/d9/55560
> echo My home directory is ~
My home directory is /home/usra/d9/55560
> 


Note that any pathname that starts with
a / is an "absolute" pathname.  The
slash at the start is the "root" of the
Unix filesystem.

You should have already read about that,
or be reading about that soon in 
chapters 6,7,8 of Andersen.


Part 4 of the lab
=================

We talked through creating the
initials.dat file and the initials.gnuplot
file, and using the command:

gnuplot initials.gnuplot

to create the file initials.png.

That much is explained in the lab,
no problem.

Here's the part that is missing:

Once you get the file initials.png,
to look at it, you need to do the
following:

mkdir -p ~/public_html/cisc181/lab03

The -p means:

  (1) if the intermediate directories
      don't exist, make them too.

      (in this case, those are public_html
       and cisc181 under public_html)

  (2) If the directory you are trying to
      make already exists, don't complain.
      Just be quiet, and be happy.

This next step is probably unnecessary
for most of you, but it won't hurt anything,
and for a few of you, the web stuff won't
work unless you do it.   [Accounts created
recently are already set up this way, but
accounts created in the past were not.]

chmod u+x ~

This allows your public_html folder
to be accessed, even if your home directory
does not permit others to see the contents.
[That's a "short" explanation... the details
are more complicated, but I can explain
those later if you are interested].

chmod -R a+rx ~/public_html

This makes readable on the web:
   files in public_html,
   all files under public_html, and 
   the public_html directory itself.


cp initials.png ~/public_html/cisc181/lab03
chmod -R a+rx ~/public_html

Then, if you go to:

http://copland.udel.edu/~yourname/cisc181/lab03

You'll see the initials.png, and you can click
on it.

g