All of the work you will be doing for this module will require you to interact with the operating system by typing commands into the shell. This is achieved by running a Terminal application.

The shell is a command interpreter which allows you to type in commands for Unix to execute; this is the typical way of interacting with Unix. You usually call up a shell by clicking a button displaying a picture of a terminal.

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This rather old-fashioned way of communicating is surprisingly effective when you get familiar with it. It can be more flexible, quicker and easier than trying to do the same thing by lots of pointing and clicking. The real advantage, however, is that you now have total control over what happens - you can issue the precise instruction to make Unix do exactly what you want without, for example, having to search for a (possibly unavailable) menu option.

Click on the relevant button to invoke a shell window and then read (click to) the section The Shell Interface and then return (Back) to this page.

Most of what you do with Unix will involve manipulating files of one sort or another. The Faculty's network supports a common file store which enables you to access your files from any of the Faculty's computers. How this is physically organised is a fascinating topic in its own right but for now we will simply look at how Unix views this filestore and how you can navigate around it.

Unix has a hierarchical file structure which is organised as a tree of directories (what Windows calls folders). Directories may contain files or (sub)directories. The root of the tree is the topmost directory beneath which all other files and directories are stored: its name is simply / (a single forward slash). Unlike Windows, there is not a separate root for each logical drive.

Read (click to) the section The Unix Filesystem and then return (Back) to this page.

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Getting Started

At the terminal enter the command

cd

This will change the current working directory to your home directory. You can confirm this by entering the command

pwd

Finally, enter the command

ls

Creating a Text File

Enter the command

echo Hello > hello.txt

Now check that the file exists (its name should appear in the listing)

ls

and look at its contents by "concatenating" them to the terminal

cat hello.txt

Creating a Directory

You have created a text file. Now it is time to create a new directory. Read the section Creating New Directories and then return (Back) to this page.

Create a directory by entering the following command

mkdir temp

You have created a new directory called temp. If you type

ls -l

then this provides you with a long listing and you should see some more information about your current working directory. In particular you should see the file hello.txt and the directory temp. The long listing shows you some information about "permissions" and ownership. Importantly, you will see the flag d for "Directory" as the first character on the line displaying your newly created temp directory.

Moving (Renaming) Files 1

It would be better to store your hello.txt file in your newly created temp directory (rather than your home directory which is where it is at present). You can achieve this by moving the file into the temp direcory.

mv hello.txt temp

List your current working directory and you will still see temp but the file hello.txt will no longer be there. This is because you have moved it somewhere else.

Change your current working directory to temp

cd temp

and check where you are.

pwd

Finally, if you list (ls) the contents of the directory you should see the (recently moved) file hello.txt.

Moving (Renaming) Files 2

Now suppose that you wish to rename the file hello.txt and call it instead greeting.txt

mv hello.txt greeting.txt

Notice that this time the second argument to mv is not a directory but a new filename. The behaviour of mv is different in this case - it will move (rename) the file. You can check the result by listing the current working directory (ls).

For more information on moving (renaming) files look at the section Renaming Files and Directories and then return (Back) to this page.

Copying Files 1

If you have followed everything up to this point then you will have created a directory called temp in your home directory; this will be your current working directory; and it will contain the (recently renamed) text file greeting.txt. Now it is time to make a copy of this file

cp greeting.txt salutation.txt

Now you should list the contents of the current working directory (ls) and check that both files are present.

Copying Files 2

Your current working directory is temp. We now want you to create another directory (within this one) called somewhere. Enter the command

mkdir somewhere

Perform a long listing (ls -l) and check that all is well. Now we wish to make a copy of salutation.txt and place that copy in your new directory.

cp salutation.txt somewhere

Note that this uses an alternative version of the cp command in which the final argument is a directory name and not a filename. This results in a copy of the file being made and placed into the directory. Enter the command

ls somewhere

This allows you to see the contents of somewhere without making it your current working directory. You should see that it contains a copy of your salutation.txt file. Now let us make another copy and place it inside somewhere but give it a new name (otherwise it will overwrite the copy we just made). Enter the command

cp salutation.txt somewhere/hello.txt

Make somewhere your current working directory

cd somewhere

and list the contents. What does the following command now do?

cp hello.txt ..

Removing (Deleting) Files and Directories

Read the sections on Deleting Files and Deleting Directories and then return (Back) to this page.

Now remove all the files and directories you created during these lab exercises so far, and return to your home directory.

Compiling and Running C Programs

First of all we suggest you create a directory (within your home directory) that you use to store all your C programs. This will keep things tidy and ensure that your exercises for this module are not mixed up with those for other modules on the course.

cd
mkdir ctec1401
cd ctec1401

Naturally, you can organise your C program files within subdirectories inside ctec1401. We will leave it up to you how you choose to organise your filesystem.

An easy way to launch the jEdit text editor is to go to the terminal and type:

jedit &

Using the jEdit text editor, create a text file hello.c which contains the following text.

#include <stdio.h>

int main()
{
    printf ("Hello World!\n");
    return 0;
}

To compile the program type the command:

gcc -o hello hello.c 

If you want to peek at what this file looks like, enter the following command

od hello

./hello

Writing Your Own C Programs

Using the hello.c program as inspiration create the following C programs. For each you should compile and run the program to check that they are all working.

1. A program goodbye.c that prints out a "Goodbye" message.
2. A program hellobye.c that prints out a "Hello" message followed by a "Goodbye" message.
3. A program welcome.c that prints out a message welcoming you, personally, to the C Programming module.