Download CS401 Lab 1: Getting Started with UNIX and SDK

CS401 Lab 1: Getting Started with UNIX and SDK
Introduction
This laboratory exercise will introduce you to the CS401 programming environment in
the laboratory in 6110 Sennott Square. You will use the UNIX operating system and the
Java 2 Software Development Kit (SDK).
UNIX and SDK are powerful systems that will take some effort to learn. Count on
spending several hours becoming comfortable in this new environment. I hope that you
can do this with a minimum of frustration, but you should remember that even the best
programmers experience some difficulty when they move to a new programming
environment.
Although this exercise might seem simple and uninteresting, you should take this
opportunity to master the tools you will need to succeed in this course. Be sure to
complete all the examples in this exercise. You should also experiment with
modifications to the examples, and create new ones of your own.
Logging In
At the login prompt, before you login, click on the "Options" button, then select
"Session," and "Common Desktop Environment". Then login using your Pitt account (id
and password). After a few moments you should see the Solaris desktop. A lot of icons
should show on the screen. Experiment with some of these if you'd like. Note that the
windows that appear are not the same as MS Windows. Experiment with these as well so
that you become familiar with the desktop and the environment. A Help Viewer window
should be present on the desktop. Read through the topics listed to learn more about
using this desktop. Note the EXIT icon on the bottom of the screen. This will be used to
log out of your session when you are finished. Always remember to log out before
leaving the lab.
Start a terminal window (which is very much like a DOS window) by right-clicking on
the background, then selecting "Tools," and "Terminal." A window with a prompt should
appear.
Basic Commands
While it is possible to issue commands through icons and mouse clicks, it is more
convenient to type commands into a terminal window. If you are used to Windows, this
might seem awkward at first, but will quickly become automatic to you.
Login and start a terminal window. Issue the command date, which will tell you the
current date and time.
$ date
You can get documentation on most commands with man. You can view subsequent
pages of documentation by hitting the space bar (or 'Q' to stop reading).
$ man date
The pwd command displays the path to your current directory. For instance, it might
display:
$ pwd
/afs/cs.pitt.edu/usr0/pdillon/public/html/cs401
You do not need to know exactly what this means, but you should be aware that UNIX
has a hierarchical file system. The output above says that you are in the cs401 directory,
which is in the html directory, which is in the public directory, which is in the pdillon
directory, which is in the usr0 directory, which is in the cs.pitt.edu cell, which is part
of afs. The directory / folder structure of MS DOS / Windows was based on that of
UNIX, so if you are familiar with MS Windows folders, UNIX directories should seem
familiar as well. One important difference in the two, however, is the separator used
between subdirectories. In UNIX the forward slash is used (as shown in the example
above) while in MS Windows the back slash is used.
You can list the your files and subdirectories with the ls command.
$ ls
Backup
News
TA
TUTORIAL
bin
nsmail
private
public
If you have not used this account before you might have no files. However, you should
have at least two subdirectories in your main directory: public and private. The public
directory is used to store files that you wish other people to be able to read, such as your
Web page files (if you have one). The private directory is used to store files that can only
be accessed by you. All files you create for this course should be within your private
directory (or within a subdirectory of your private directory).
The cd command allows you to change directories. Change to your private directory by
typing
cd private
Now type pwd to see that your directory level has changed. To go back up one directory
level, type
cd ..
Experiment with the cd command so that you are comfortable moving from one directory
to another in your account. Now make sure that you are in your private directory. Then
type the commands:
$ mkdir cs401
$ cd cs401
This will make a new subdirectory within your private directory that you can use for your
cs401 labs and projects, and then change your current directory to that new subdirectory.
If you wish, you can make additional subdirectories within your cs401 directory for
different labs and projects.
The copy command, cp FILE1 FILE2, copies one file to another. You can copy the first
Java handout from my Web directory to your current directory with the following
command:
$ cp
/afs/cs.pitt.edu/usr0/pdillon/public/html/summer06/examples/HelloWorld.
java .
The single period refers to the current working directory, which should be your cs401
folder. The copy command accepts any path as an argument. By not specifying a
filename as the second argument here, rather a directory, the file is copied to that
directory with the same file name. If a different file name is specified, the file is copied to
the path location and renamed to the new file name.
You can view the contents of a file with the command, cat FILE. Thus, cat ex1.java
will (very quickly) print the contents of ex1.java on the screen. If that was too fast to
read, you can type more ex1.java. Hitting the space bar will display subsequent pages
and Control-C will interrupt the command.
Finally, mv FILE1 FILE2 will change the name of a file, and rm FILE will delete a file.
There are many other Unix commands that may be useful to you, but the ones above
should be enough to get you started. For more information on basic Unix commands,
read the following Unix Document. For more detailed information on the Unix operating
system, read a good book on Unix such as Learning the UNIX Operating System (Peek,
Todino, and Strang, O'Reilly 1997). The UNIX system includes a set of very powerful
tools that are useful to any professional programmer.
Editing Files
You will need to create code files. You can do this using any editor you choose (there are
several available -- for example emacs and vi). However, for those of you unfamiliar with
Unix I recommend pico, since it is easy to learn and use. To get started with pico, first
read over the following Pico tutorial.
Now practice editing with the HelloWorld.java file that you downloaded from the
handouts directory above:
$ pico HelloWorld.java
Try all of the commands to become familiar with the editor. Don't worry about changing
the file -- you can always copy it again if you need to.
When developing Java applications on these workstations, one good idea is to open two
terminal windows (as explained above in the Logging In section) and set both windows to
your working directory. Then edit your file in one window using pico, and compile and
run your program in the other window using javac and java (as explained below). You
can open even more terminal windows if you wish.
Compiling and Running a Java Program
As discussed in lecture, running a Java application is a two-step process. Try this process
on the HelloWorld.java handout:
1. Compile the program into byte code via the javac command:
$ javac HelloWorld.java
2. Run the byte code via the java command
$ java HelloWorld
Now use the pico editor to type in the new Java program below. Note that the program
name is Lab1, so, by the naming rules of Java, your file name must be Lab1.java. Thus,
start your pico editor with the command:
$ pico Lab1.java
//
//
//
//
CS 0401 Lab1
Practice Java program with a dual purpose:
1) To familiarize you with the pico editor
2) To familiarize you with Java syntax
public class Lab1
{
public static void main(String [] args)
{
int total = 87, number = 10;
double doubleAve;
int intAve;
doubleAve = ((double)total)/number; // floating point
division
intAve = total/number;
//
integer division
System.out.println("The double average is " +
doubleAve);
System.out.println("The integer average is " + intAve);
int value1 = 3 + 4 * 5;
//
default precedence
int value2 = (3 + 4) * 5;
// change
precedence with parens
System.out.println("Value1 is " + value1);
System.out.println("Value2 is " + value2);
}
}
Once you have typed in the program above, compile and run it using the java compiler
and interpreter programs. If you get any compilation errors, it is likely due to a typing
error. The compiler will indicate the line number of the error -- find it and correct the
error, then compile the program again.
Java Versions
As you may know the Java language has evolved and different versions are now
available. Our text uses the most recent version, Java 1.5 (also called Java 5.0). To check
which version of Java you are using, type
$ java -version
Most likely, you will see
java version "1.4.0_01"
followed by some other information.
The most recent version of Java IS installed on these workstations, but it is in a different
location in the machine's directories. To access the most recent version of Java, you must
type out the entire path to the program. Try the following command
$ /usr/local/java/bin/java -version
You should now see
java version "1.5.0_03"
Since it's an enormous pain to have to type /usr/local/java/bin/ before javac every
time you compile, you have to add the path of the program to the PATH variable every
time you log in. Do this by typing
$ export PATH=/usr/local/java/bin:$PATH
But we can have UNIX do this for us every time we open a terminal window. First
change directories to your home directory. This is the default directory of the cd
command.
$ cd
Next, edit your BASH profile script that gets executed every time a terminal window is
opened (or you log in remotely).
$pico .bash_profile
Use the Ctrl-V command to scroll down through the file. The line we need to edit is
around 300 and should look like this
PREPATH=$HOME/bin
Add the path or our java compiler and interpreter so that it looks like this
PREPATH=$HOME/bin:/usr/local/java/bin
Save the file with the Ctrl-O command and exit with Ctrl-X. The change you just made
haven't effected the current terminal window yet but will effect all future windows you
open. To make the changes visible in the current terminal, try the following command
$ source .bash_profile
Now you should see the newest java version by simply typing
$ java -version
Zipping Files
You'll need to use the zip command when submitting projects and labs to combine all
assignment files into a single archive file for submission. The command works as
follows:
$ zip archive.zip file1 file2 file3 ...
The first argument after 'zip' is the name of the archive to create (or update) followed by a
list of files that should be put in the archive. Practice using this command. When you're
ready, create the ZIP file for this lab:
$ zip <Your-Last-Name>.zip Lab1.java Lab1.class
What Can Go Wrong?
What can go wrong? Plenty. Here are some common problems.
You cannot access javac, java, or pico. You should ask your TA to help you set your
path variable. In the meantime, you can start pico using the command
/usr/local/bin/pico and you can access the Java compiler and the Java interpreter
using their absolute path names shown above.
You have no available disk space. If you have used your allocation of disk space you
might not be able to login. You will need to delete some files before you can continue.
Ask your TA to help you with this. It is also possible to increase your disk space quote
(to a limited extent). If you want to do this, ask at any of the CSSD Campus Computing
Labs.
The machine freezes. You will need to reboot the machine by pressing the stop key and
a simultaneously, then type boot. This will take a few minutes.
SDK and Windows
If you want to work at home using your own computer, you will need to install the SDK
yourself. It is included in the disk with your text. If you have a high-speed internet
connection you could alternatively download an updated version from Sun's web site at
http://java.sun.com/. For best results, install version 5.0 Update 4, available at this
link: http://java.sun.com/j2se/1.5.0/download.jsp Note: You may download the
netBeans bundle if you wish, but you do not need netBeans if you are using some other
editor / environment on your PC. If you do NOT want netBeans, click on the choice after
the netBeans download -- simply JDK 5.0 Update 4
Despite Java's well-earned reputation for portability, you should remember that there are
often small differences between programming environments. If you do your work outside
the CS401 lab, you should compile and test it in the lab before submitting it. Your work
is expected to compile and run on those machines.