Hands on Testing Java: Lab #1

UNIX

Getting Started with UNIX

Your instructor will have to tell you how to access your account and how to start up the X Windows System and desktop environment. Unlike Microsoft Windows and Macintosh operating systems, there are several variations of X11 and many different desktop environments built on top of X11. Generally these desktop environments work on the same principles as Microsoft Windows and Macintosh OSs, so let your intuition guide you.

Regardless of what GUI you use on your UNIX machine, you can always interact with UNIX directly with a CLI. Eventually, your instructor should tell you how to open a terminal window (a.k.a., an xterm or a console window).

My terminal window looks like this:

This terminal is from the KDE desktop environment, where it is called a "konsole".

As pictured in this example, I use a two-line prompt:

[localhost:~]
$

A UNIX prompt is highly flexible. Yours is probably very simple. The purpose of the UNIX prompt is to prompt you for a command. If you don't see a prompt, the terminal window is busy working on something else.

For this lab manual, I will use unix-% as a generic UNIX prompt. Never, ever type in the UNIX prompt. That's the prompt from UNIX; you must enter in the command that you see after the unix-% prompt.

Interacting with UNIX

UNIX interaction consists of three steps which are repeated until you close the terminal window:

1. The computer displays a prompt and waits for you to enter a command.
2. You enter a command.
3. The computer executes (performs) that command, and it displays the results (if any).

The UNIX environment is case-sensitive, and virtually all UNIX commands use lower-case letters. This will cause you a great deal of frustration if you forget it, so keep this in mind.

In order to use a command-line environment, you must learn those commands that the environment understands. Let's first see what happens if you type something that the environment does not recognize.

unix-% qwerty

For the sake of your own sanity, remember that unix-% is the UNIX prompt, so you must not type it.

This is the way that UNIX responds when you give it a command it doesn't understand.

Directories and Files

You will create dozens of files as you go through this lab manual, and it's best to keep them organized separately from the other work that you do. Just as the documents (i.e., files) in a filing cabinet are often kept in manila folders, we can create a container in which to keep related files, called a directory (or a folder).

Let's create a new directory.

unix-% mkdir courses

After you type in the command, you should get the prompt back. If something goes wrong, then you'll get an error message. But no message means that something was done successfully.

The mkdir command is the UNIX command to make a directory. By placing the word courses after the mkdir command, you tell the system that you want to make a directory named courses.

The slash / character in these directory names is very important because you're creating directories within a directory. This allows you to keep the files for this course separate from other files you might need.

Viewing the Contents of a Directory

The mkdir gives no feedback unless something goes wrong. So how do we know it did anything?

unix-% ls

The ls command displays a listing of the contents of a directory. If all is well, you'll see at least the courses directory. You'll undoubtedly see other directories and files, but the specifics differ in each type of UNIX.

But where are those other directories you created? They're inside the courses directory. The ls command can also be used to find out what is in a particular directory.

unix-% ls courses

If you follow the ls command with the name of a directory, it displays that contents of that directory. Now you can see two other directories that you created before.

To get a more detailed listing of the current directory, enter

unix-% ls -l

The -l is called a switch or flag that causes the ls command to generate a long (i.e., detailed) listing. The hyphen indicates to ls that the l has a special meaning; it's not the name of a directory or file. All UNIX commands have flags like this. If your UNIX has the latest version of ls, you can even try this:

unix-% ls -lh

This will print sizes in a human-readable form. (If the h flag doesn't work, don't sweat it.)

Removing a Directory

I deliberately asked you to create the courses/BOGUS directory just so that you'd have a directory to delete. You can use the rmdir command to remove a directory just like you'd use mkdir to make a directory.

Whatever directory you specify following the rmdir command will be removed from the file system, provided that the directory being removed is empty. To remove a non-empty directory named DirectoryName, use this command:

unix-% rm -r DirectoryName

This should only be used when DirectoryName contains nothing important!

Using the ls command, verify that BOGUS directory no longer exists.

Identifying the Working Directory

When you begin a computing session, UNIX always starts you out in your home directory. You do not have to remain in your home directory; you can change to a different directory whenever you like.

The directory in which you are working at any particular time is called your working directory. To find out the name of the working directory, you can use the pwd (print working directory) command:

unix-% pwd

UNIX systems (like all modern operating systems) utilize what is called a hierarchical directory system, meaning that directories can contain other directories. There is one root directory denoted by / (a single forward slash) which is the top directory; all other directories are directly or indirectly inside this root directory.

unix-% ls /

This lists the contents of the root directory. Within / are a number of subdirectories, including usr, bin, include, and home. Each of these contain other directories and files. On many UNIX systems, the home directories of the users are stored within the home directory. Here is what this might look like on a particular machine:

UNIX treats the tilde character (~) as an abbreviation for your home directory, which can save you a lot of typing if the path to your home directory has lots of characters.

Changing the Working Directory

If you created all of your files in your home directory, it would soon become cluttered. By grouping related files within a directory, you can organize your files. You created the cs108 directory to store all of the files for this lab manual.

Since you are working on a lab exercise for this course, let's change the working directory to the appropriate directory.

unix-% cd courses

The cd command is the change directory command that changes the working directory to the specified directory. Similar to the mkdir command, cd will not display anything if it works successfully (although you might notice a change in your prompt). You will see an error message if something fails.

unix-% cd cs108

So the cd command allows you to navigate down a directory hierarchy. What about going back up the hierarchy?

unix-% ls -a

The -a switch tells ls to list all of the contents of a directory.

You will notice two odd items in this output: a period . and a double-period ... In the UNIX file system, . is another name for the working directory (whatever directory you are in); and .. is another name for the parent directory of (i.e., the directory above) the working directory.

You created courses within your home directory. The cd courses command took you from that directory "down" into courses. Once in that directory, . refers to that same directory while .. refers to the directory that contains it (i.e., your home directory). Now that you're in the cs108 directory, its . entry refers to itself, and its .. refers to the courses directory.

So now, to go back "up" a directory, you can enter this command:

unix-% cd ..

Since .. is always a synonym for the parent of the working directory, regardless of any actual names, you can always use this command in any directory.

There's also a shortcut for changing directories back to your home directory: use the cd command without any arguments.

Use pwd to verify that you are currently in your home directory.

Terminology

console window, desktop environment, directory, flag, folder, hierarchical directory system, home directory, parent directory, prompt, root directory, switch, terminal window, working directory, xterm, X Windows System

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