MasterClass September 95


A word in your shell-like..

Hopefully by now you'll be very familiar with the Shell, and
if you are anything like me, you'll have the Shell icon left
out on the Workbench ready for action. I use the Shell for
everything from general file maintainance to logging into
the Internet: it's that useful.

What you might not know is that every Shell has a few little
tricks hidden away up its sleeve (well, tool types), and
with a little experimenting you can customise your Shells to
your own requirements.

One of the easiest things to change in the Shell is the
prompt. Normally the prompt is a bit boring, but tells you
two things: firstly the process number, and secondly the
current directory, like this:

(shell1.iff)


It's a familiar sight, and undoubtedly useful. However, you
can change the prompt to be whatever you want, and the way
to do this is with "prompt" AmigaDOS command. Prompt will
take and display a string as your new marker, so for
example, if you were a UNIX fan you might want to try the
following:

    prompt "$ "
 
which will result in a Shell which looks like this:

(shell2.iff)

It's short and sweet, but not very useful. More advanced
settings are possible if the string you supply has as %S in
it somewhere, as the Amiga will substitute the current
directory. Try this:

    prompt "%S> "

for this effect:

(shell3.iff)

The other special code which is recognised is %N which
indicates the task number of the Shell. This is the number
which the "status" command will return. The standard Shell
prompt is therefore:

    prompt "%N.%S> "

You might be wondering where the default prompt string is
set, after all you don't need to enter anything to get the
normal string. The answer is in a special startup-sequence
especially for the Shell. You can examine it by entering:

    type s:shell-startup

or even edit it by entering:

    ed s:shell-startup


You should see the prompt definition in this file, and this
is where you would change it if you wanted to make the
changes permanent. Every Shell which is opened opens looks
to this file for it's initial settings. Any alterations you
make therefore won't change the current Shell, but any
others opened afterwards.

This startup file is also a good location to stick a few
aliases. "Alias" is an AmigaDOS command which will rename a
command for you. The best example would be something like
this:

    alias bye endcli

Once you insert this into the startup file (or type it at the
prompt for a once off demonstration), you can stop any
new Shell simply by typing "bye".

As it is also possible to enter control sequences into the
Shell (a control sequence contains characters which when
placed in a special order cause a specific action to take
place) so you might want to enter an alias like this:

    alias cls "echo *"*e[0;0h*e[j*" "

and see what happens. Here are some other special alias
commands which use control sequences for you to try. You can
type them into the Shell if you want, or use them in the
shell-startup file so that they happen every time you open a
Shell window. Notice how the special ESC character is *e,
but to use it with an echo command you need an extra *
outside the quotes. If you were entering the echo by itself
(remember, echo simply displays a string on-screen) you
would not need the extra asterisk -- try this:

    echo "*ec"

It might seem complicated, but experiment and you'll soon
work it out. Here are some commands you might find fun to
play with. There are others which can alter the position of
text within a Shell window: useful if you enjoy
experimenting with different fonts.


    alias bold "echo *"*e[1m""

    alias italic "echo *"*e[3m""

    alias line "echo *"*e[4m""

    alias invert "echo *"*e[7m""

    alias plain "echo *"*e[0m""