UNIX Tutorial One

1.1 Listing files and directories

ls (list)

When you first login, your current working directory is configured to be your home directory. Your home directory has the same name as your user-name, for example, imemine, and it is where your personal files and subdirectories are saved.

To find out what is in your home directory, type

% ls (short for list)

The ls command lists the contents of your current working directory.

ls does not, in fact, cause all the files in your home directory to be listed, but only those ones whose name does not begin with a dot (.) Files beginning with a dot (.) are known as hidden files and usually contain important program configuration information, for example .login and .profile 

To list all files in your home directory including those whose names begin with a dot, type

% ls -a

ls is an example of a command which can take options: -a is an example of an option. The options change the behaviour of the command. There are online manual pages that tell you which options a particular command can take, and how each option modifies the behaviour of the command.  

To see the online manual page for the command ls  type

% man ls 

1.2 Making Directories

mkdir (make directory)

We will now make a subdirectory in your home directory to hold the files you will be creating and using during the course of this tutorial. To make a subdirectory called macstuff in your current working directory type

% mkdir macstuff

To see the directory you have just created, type

% ls

1.3 Changing to a different directory 

cd (change directory)

The command cd directory means change the current working directory to 'directory'. The current working directory may be thought of as the directory you are in, i.e. your current position in the file-system tree.

To change to the directory you have just made, type

% cd macstuff

Type ls to see the contents (which should be empty)

Exercise 1a

Make another directory inside the macstuff directory called backups

1.4 The directories . and ..

Still in the macstuff directory, type

% ls -a

As you can see, in the macstuff directory (and in all other directories), there are two special directories called (.) and (..)

In UNIX, (.) means the current directory, so typing

% cd .

NOTE: there is a space between cd and the dot

means stay where you are (the macstuff directory).

This may not seem very useful at first, but using (.) as the name of the current directory will save a lot of typing, as we shall see later in the tutorial.

(..) means the parent of the current directory, so typing

% cd ..

will take you one directory up the hierarchy (back to your home directory). Try it now.

Note: typing cd with no argument always returns you to your home directory. This is very useful if you are lost in the file system.

1.5 Pathnames

pwd (print working directory)

Pathnames enable you to work out where you are in relation to the whole file-system. For example, to find out the absolute pathname of your home-directory, type cd to get back to your home-directory and then type

% pwd

The full pathname will look something like this -

/Users/imemine

which means that imemine (your home directory) is in the directory Users.

Exercise 1b

Use the commands ls, pwd and cd to explore the file system.

(Remember, if you get lost, type cd by itself to return to your home-directory)

1.6 More about home directories and pathnames

Understanding pathnames

First type cd to get back to your home-directory, then type

% ls macstuff

to list the contents of your macstuff directory.

Now type

% ls backups

You will get a message like this -

backups: No such file or directory

The reason is, backups is not in your current working directory. To use a command on a file (or directory) not in the current working directory (the directory you are currently in), you must correct specify its absolute pathname or its relative pathname. To list the contents of your backups directory, you can type either

% ls /Users/imemine/macstuff/backups

    or 

% ls macstuff/backups

 or 

% ls ./macstuff/backups

The first is an absolute pathname and the last two are both relative pathnames.

~ (your home directory)

Home directories can also be referred to by the tilde ~ character. It can be used to specify paths starting at your home directory. So typing

% ls ~/macstuff

will list the contents of your unixstuff directory, no matter where you currently are in the file system.

Exercise 1c

What do you think

% ls ~

would list?

What do you think

% ls ~/..

would list?

Summary

This tutorial was modified by Jay Alan Jackson from the original work by M.Stonebank@surrey.ac.uk, 19 October 2001 in accordance with the Creative Commons License, under which it is still protected.