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Unix Tutorial One
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| 1.1
Listing files and directories |
ls (list)
When you first login,
your current working directory is your home directory. Your home directory
has the same name as your user-name.
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.
There may be no files
visible in your home directory, in which case, the UNIX prompt will be returned.
Alternatively, there may already be some files inserted by the System Administrator
when your account was created.
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. They are hidden because you
should not change them unless you are very familiar with UNIX!!!
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. (See
later in this tutorial)
mkdir (make directory)
We will now make a
subdirectory in your home directory to hold the files you will be creating
and using in the course of this tutorial. To make a subdirectory called
unixstuff in your current working directory type
%
mkdir unixstuff
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 unixstuff
Type ls
to see the contents (which should be empty)
Exercise 1a
Make another directory
inside the unixstuff directory called backups
| 1.4
The directories . and .. |
Still in the unixstuff
directory, type
%
ls -a
As you can see, in
the unixstuff 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 unixstuff 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.
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 -
/home/user
which means that user
(your home directory) is in the directory home (the group directory).
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 unixstuff
to list the conents
of your unixstuff 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 either cd
to the correct directory, or specify its full pathname. To list the contents
of your backups directory, you must type
%
ls unixstuff/backups
~ (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 ~/unixstuff
will list the contents
of your unixstuff directory, no matter where you currently are in the file
system.
What do you think
%
ls ~
would list?
What do you think
%
ls ~/..
would list?
| ls |
list
files and directories |
| ls
-a |
list
all files and directories |
| mkdir |
make
a directory |
| cd
directory |
change
to named directory |
| cd |
change
to home-directory |
| cd
~ |
change
to home-directory |
| cd
.. |
change
to parent directory |
| pwd |
display
the path of the current directory |
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