Chapter 5
The Unix Shell
Introduction to the Shell
The Unix shell is a command line environment that is very similar to the
DOS command line interface. You type a command at the prompt, the computer
executes the command, and you get to see the output and then another
prompt.
Of course, this kind of environment is becoming more scarce in day-to-day
computing for the average person, mostly because the snazzy Graphical
User Interfaces are so much easier to use. But to get the most work done
in the least amount of time, gurus all over will tell you, "You just
can't beat Unix."
You can login and use the Unix shell by starting up your telnet
client program on your computer, and connecting it to "netmar.com" and
giving your username and password at the prompts. You will then see your
"netmar>" prompt, at which you can begin entering commands, just
like you were at your own "C:\>" prompt. That means you can read
and write email, news, and even edit your WWW pages online!
Lastly, before we dive in, let me show you a quick utility that's really
handy. It's called the system manual pages. You can find out just
about all there is to know about any Unix command or program simply by typing
"man PROGRAM" at the "netmar>" prompt. Or, you can
go to http://info.netmar.com/man/ to see them on your
World Wide Web browser!
- Note:
- Make sure your CAPS LOCK key is OFF when you use the Unix shell. Since the
Unix shell is case-sensitive, meaning it cares if your letters are lower or
upper case, you'll have a tough time getting anything to work if you're
typing in all caps.
When you access your Netmar account via telnet, you havve the option of
using either of two mail programs. The first is Pine, which is a very simple,
intuitive full-screen
mailer that nonetheless has several powerful features. The other is
message handler(mh), which
is a command-line mail
program that enables you to perform all of the activities that Pine does
without leaving the command line.
To access Usenet news, just type "tin" at the UNIX prompt. This will
start up the tin newsreader. After it gets started(don't be surprised if
this takes a while - tin is rather slow), you will see a column of
newsgroup names on the right and numbers on the left. The numbers are
the number of posting in the group. You can navigate with the arrow
keys, where the up and down keys will move you up and down a list, and
the right and left keys will select an item or move you back to the
previous menu, respectively.The various options are defined at the
bottom of the screen, but I will discuss a few of the more important ones
here. Yank in/out allows you to yank in all the newsgroups or just
display the ones that you've subscribed to. The subscribe option
subscribes you to the currently selected group, or unsubscribes you if it
is one you already belong to. Finally, you can use the search option to
look for newsgroups that you can't remember the names of by using the
wildcard character(*) around the part of the name that you do remember.
Click here for the manual
page.
UNIX is very good at manipulating files, but provides the user with enough power that it's essentially 'giving them enough rope to hang themselves'.
UNIX has several commands to manipulate files, but the most basic are:
cp(copy), mv(move), rm(remove), and mkdir(make directory). Before discussing these commands, it is important to understand that with UNIX, there is essentially NO RECOVERY. What is deleted cannot be undeleted, what is copied over cannot be retreived. UNIX
gives no warnings or second chances. It merely does what it is told.
- cp(copy)
- cp takes two arguments, a source file, and a destination.
cp /www/mhome/johndoe/www/bunny.gif /www/mhome/janedoe/www
This example would place a copy of bunny.gif from johndoe's www directory
into janedoe's www directory.
For more information on this command, click here
- mv(move)
- mv takes two arguments, a source name, and a target name.
mv oceans.html waves.html
This example would effectively rename the file 'oceans.html' as 'waves.html'.
For more information on this command, click here
- rm(remove)
- rm takes one argument, the object to be deleted.
rm badfile.html
This example would effectively delete the file 'badfile.html'.
For more information on this command, click here
- mkdir(make directory)
- mkdir takes one argument, a name of the directory to be created.
mkdir stuff
This example would create the directory 'stuff'.
For more information on this command, click here
- rmdir(remove directory)
- rmdir takes one argument, a name of the directory to be removed.
rmdir stuff
This example would destroy the directory 'stuff', as well as all its contents.
For more information on this command, click here
- edit(call to established editor)
- edit takes no arguments
edit
This example would bring up the established editor, either pico(default), emacs
, vi, or joe.
For more information on this command, click here
You also have a choice of three editors while online. They are pico,
which is the editor used by Pine, vi, the UNIX standard editor, and
emacs, another popular UNIX editor.For the uninitiated, pico is
undoubtedly the best choice. All the commands are visible at the bottom
of the screen and they are all letters combined with the CTRL key.
Vi is
somewhat less user-friendly, but easy enough to get used to. You have to
memorize the key combinations (there are many of these) and it's easy for
someone raised on PC or Mac word processors to forget which mode he's in
and make a mess. On the other hand, vi is much more powerful than pico,
and many things can be done much quicker.
The most powerful of the three
is emacs. Needless to
say, it is also the most difficult to
use. Those who do learn how to use it, however, tend to swear by it.
The easiest way to access an editor is to use the aliased command
edit. Edit invokes a prechosen editor(PICO by default).
Your Netmar account also supports program development in the form of the
full GNU C/C++ compiler and
libraries. For those used to programming on
the PC or the Mac (does anyone program on the Mac?), the switch
can be somewhat intimidating, although ultimately rewarding. The UNIX
environment has so many libraries and options that there is a danger of
information overload.Stick to the basics and it'll all be fine.
Despite what Bill Gates and IBM claim, UNIX is still THE 32-bit operating
system, with decades of develpoment, mountains of software, and an
extremely powerful command line interface.
Just ftp your code over or
write it online using the editors above. To compile just type "gcc
input -o output", where input and output are the
names of the input and output files. Alternatively, you can use a
makefile and multiple source files with the make command.
Copyright © 1995, Netmar, Incorporated
