The Unix operating system comes with many commands that the user can
use to interact with computer.
Unix commands are simply programs (usually written in the C
programming language) that are executed when called for.
The usual place for the storage of these commands is the
The commands that are available on a particular machine will vary.
There is a set number of standard commands that come
with a Unix system, but there is no limit to the commands that may be
An example of this is the
more followed by a filename (preferably a text file)
will cause the filename to be presented to the default output device a
page at a time.
space-bar will display the next page, typing the
enter-key will display the next line, and pressing the
will exit the program.
This is how the
man pages are displayed.
Many users felt that this was too inflexible and along came another
command found on many Unix systems called
less command is essentially the same as the
command with the exception that it allows the up and down arrow keys
to be used to scroll around a document.
Many of the Unix commands may be well known to the user while others
Some examples are
ls, cd, grep, find and
chmod to name
just a select few.
It is important to realize that while these commands might vary in
syntax and usage somewhat from one platform of Unix to another, they
are shell independent.
Whether in the C shell or the Z shell, the
grep command behaves
Remember to see how a particular command is used on a particular
platform, the user can use the
Now each shell comes with its own set of built-in\
These are commands that are local to the particular shell.
Some examples of these are the
history command in the C shell,
export in the Bourne shell.
Built-in commands can be taken as platform independent.
It is important to keep in mind having said this that there is a
possibility of slight variation between different versions of the
This is inevitable, but for the purpose of this book a standarized
shell is again assumed.
If there is any discrepency between this book and any particular
man pages can again be referenced.