Chapter 3
The Advantages of xterm
Introduction
In this chapter, we discover the advantages of
workstations and
genuine
xterms compared with visual display units.
Visual display units
In the olden days, before workstations were widely available, Unix users
used visual display units (VDUs).
Here is a view of a typical VDU screen:
VDUs had room for only 24 lines of text and each line had 80 characters.
The screens all had black backgrounds and the text was all white, green
or orange.
There were no facilities for copying or pasting.
Each Unix user could use just one VDU at once so the 24 lines provided
the user's only view of Unix.
There were no facilities for scrolling back to review text that had disappeared
off the top of the screen.
All characters on the screen were the same size and
most VDUs could only display text.
One of the most widely used VDUs was the DEC VT102.
Workstations
A workstation is a fairly expensive device designed for displaying
graphics on a screen; it has a keyboard and a mouse as well
as one or more screens.
Personal computers (PCs) are
not
workstations because the screens are generally too small and the
graphics capability is usually not good enough.
However, PCs do offer the same kind of windowing and graphics as
workstations.
Programs such a Vista Exceed allow PCs to emulate low quality
workstations.
The two programs which are the most use to a
workstation user are:
xterm
and a
window manager.
The
xterm
is the modern version of the old VDU;
it emulates one VT102 in each window in which it is executed.
However, it has some
extra features which make it much better than a real VT102.
A
window manager
is the program that allows us to create, destroy, move and re-size windows.
It allows each user to use as many windows as he or she wishes simultaneously.
It is always waiting, behind the scenes, to change our windows for us.
Most people do not know they are using a window manager because it is built
into desktops such as Microsoft Windows, Gnome, KDE and CDE.
Some people simply use a window manager instead of a desktop.
Personally, I dislike desktops as they all feel like Microsoft Windows and
are nearly as annoying to use.
I use Window Maker to manage my on-screen work-spaces.
An example
Here is one of my work-spaces:
As you see, I have three
xterms running.
Two of them are VDU-sized and one is larger.
The blue frames with titles are put around the
xterms by Window Maker so they can be moved and re-sized.
The currently active
xterm
has a white title
and a solid magenta typing cursor.
I choose to use black backgrounds and white text because that is easier to read.
The whole world got it wrong when it followed Apple into white backgrounds.
White paper wouldn't be as easy to read if it glowed in the dark.
Genuine xterms only
It is important to stress that this chapter is about genuine
xterms only.
This is because they have a very simple, elegant method for copying text
and inserting it into another window.
This method is better than Microsoft's which was developed later.
Unfortunately,
because they meet Microsoft's way first, many people can't appreciate the
xterm
alternative.
There are about a hundred VDU emulation programmes available today but most
have adopted the inferior Microsoft technique, which is my reason for sticking
with
genuine
xterms.
It is possible that many of the other terminal types can be configured to work
like
xterm
but only the original article works so well "out of the box".
Different sized fonts
The first extra
xterm
feature is different sized fonts.
If you find the characters in the
xterm
either too small or too large for comfort, you can change the font
for another.
To do this you move the mouse cursor over the
xterm, hold down the control key, press the
right
mouse button
and hold it down.
This causes a
menu
of font names such as
Tiny
and
Huge
to
pop up;
there should be a tick by the currently selected font name.
You
drag
the mouse cursor down the menu
and release it at the font you wish to select.
The size of the characters should change more or less instantly and
the
xterm's window should automatically be re-sized to suit the new font.
Here an
xterm
using the
Default
font is being
switched to the
Huge
font:
Notice that the menu always uses the default font size (unless your
xterm
is set up in a
non-standard fashion).
Scrolling
The second advantage of
xterms is that they can be scrolled to view thousands of lines of recent history.
If your
xterm
is relatively up to date, and your window manager is properly configured,
the simplest way of scrolling is to use the
mouse wheel.
If there are very many lines available for scrolling, using the mouse wheel
might be too tedious and it would then be better to
use the scrollbar.
Contrary to modern practice, this is at the left-hand side of the screen
by default.
Here is an
xterm
with the scrollbar indicated by
the green arrow:
The red arrow points to a slider or thumbwheel
which shrinks as more text is displayed.
You can tell at a glance whether you have enough text to scroll
by looking at the scrollbar.
If it is a
solid
block of half-tone colour you haven't enough text.
If it is in two or three parts, some in the
xterm's background colour and some in half-tone colour,
then you can scroll.
Our scrollbar is showing us that we are at the end of the displayable
text, and that we could scroll backwards.
The simplest way of scrolling via the scrollbar is with the
middle
button.
Middle button scrolling
To position the slider half way through the text,
you place the mouse cursor half way down the scrollbar
and click the
middle
button of the mouse.
The
xterm
will scroll instantaneously to the desired position.
After you have scrolled, the slider will be further up the scrollbar.
Like this:
If your mouse only has two buttons, you have to simulate pressing the middle
button by pressing the left and right buttons
simultaneously.
Manual positioning
You can also position the slider manually by putting the mouse cursor
over the slider and
dragging
it to a new position with the middle mouse button.
High precision scrolling
There is another way of scrolling that gives you fine
control over the amount of scrolling;
it uses the left and right mouse buttons over the scrollbar.
To scroll backwards, towards earlier lines, you put the mouse cursor
in the scrollbar area and click the
right
mouse button.
To scroll back further, you click the right button again.
To scroll forwards, towards the last line, you click the
left
mouse button.
How much to scroll precisely?
The amount
xterm
scrolls
for left and right clicks
depends on the cursor's position in the scrollbar.
If it is at the bottom,
xterm
scrolls by a whole screenful;
if it is right at the top,
xterm
scrolls one line.
The amount is proportional to the distance of the mouse cursor from the top
of the scrollbar.
Short cut to latest line
When you have scrolled backwards, you do not have to scroll forwards to
get to the last line to continue typing.
All you have to do is press a key - even the space bar - and the
xterm
will scroll instantaneously to the last line.
Copying text
We often have to type the same commands or words repeatedly.
With an
xterm
we can make this a little easier by
copying text already on the screen onto the last line.
We can copy as much or a little as we wish.
The job is done in two halves: selecting the text to be copied and
inserting the text.
The easiest way of selecting text is to put the mouse cursor in the middle of
a word and
double-click
the
left
mouse button.
The word should be then highlighted in reverse video.
Here the user has double-clicked somewhere in "selecting":
Selecting more text
If you wish to select several words, the simplest way is to select
the first word in usual way, and then to click the
right
mouse button
in the middle of the last word.
This
extends
the original selection to cover all the words from the first to the last.
Here the user has right-clicked somewhere in "cursor":
You can right-click again and again.
Here the user has right-clicked in "appears":
Notice that the highlighted area now stretches to the right-hand edge
of the screen.
The area between the last character on the
line and the side of the
xterm
represents the newline character at the end of the line.
Newline characters
can be pasted as well as text.
However, be careful when pasting commands: if you selected the newline after a
command, the command will be executed without you having time to reconsider it!
You can extend the selection up the screen too.
Here the user has right-clicked on "We":
There are now sixteen and a half lines of text selected including two
blank ones.
You can select from a particular word to the end of the line by
treble
clicking the left button in the word.
Here the user treble clicked on "The".
Selecting less than a word
You can select any amount of text by dragging the mouse cursor through the
text with the left button.
This is the Microsoft method referred to earlier;
it is bit of a drag compared with just clicking -
but sometimes we have no option:
This is the only way to select "red - eve" from the screen shown.
Selecting more than a screenful
To select more than a screenful of text, we have to use scrolling as well.
The way to do this is to select the first word (by double-clicking)
and then scroll down to the last word.
Don't worry that the highlighted first word will disappear off the top
of the window;
even though it is out of sight, it remains the current
X selection.
Lastly we extend the X selection by right-clicking on the last
word we want to select.
The X selection now covers several screens full of text.
Of course, we don't have to select from top to bottom.
We could select the last word first, and scroll up towards the first.
This method of selecting more than a screenful
sounds
complicated but
it is far easier than the Microsoft method - which usually involves
messing about as you undershoot and overshoot while text
whizzes past in the window.
Inserting
Pasting is not really the correct word for what
xterms do.
Pasting implies that you can do it anywhere.
Inserting is performed by clicking the
middle
mouse button
anywhere
in the window.
The selected text is inserted where the keyboard cursor is - regardless
of where the mouse cursor is in the text.
Here we have selected two words separated by spaces:
and the user has inserted the selection twice on the command line by
middle-clicking twice.
Notice that the system is waiting for the user to press the enter (newline)
key -- or erase the bad command.
Here the selection is still one line but this time it includes the newline
character:
When the user middle-clicked, the system did not wait for the enter key.
It tried to execute "vdu.text" as a command.
Inserting many lines
Inserting many lines is no problem
but it has to be done while the system is expecting many lines.
For example an email could be pasted into a text box in a browser to
post it via gmail.
In this case, paste is the correct word as the text would go wherever the
user indicated by middle clicking.
A common error is inserting a mult-line selection when the system is
expecting a one line command.
Pasting from the keyboard
The "shift" and "insert" keys can usually be used together instead of a
middle click.
This is convenient when you wish to use the X selection as part of text
that is being entered via the keyboard.
Xterm options
You might find that
pressing a key does not make
your
xterm
scroll to the last line.
Or possibly,
treble-clicking selects too much text - perhaps it always starts at
the beginning of the line or it always includes the newline character.
If any of these occur,
it is because your system manager has chosen
different options to me.
You can select some of the options yourself from other
xterm
menus.
Other options can only be corrected by setting up the
.Xresources
file shown
in Appendix ??.
The other menus are obtained by holding down the control key and pressing
the left or middle mouse buttons.
The
VT Options
menu associated with the middle button is the most useful:
As you see, you can select
Scroll to Bottom on Key Press
from it;
you can even remove the scrollbar altogether.
Not all
xterm's options are available in menus.
For example,
the scrollbar can be made to appear on the right.
However, that has to be done at the command line when the
xterm
is first started.
Unfortunately, you would have to do it every time you started one.
The more permanent solution is to set up an
.Xresources
file, or put the
xterm
command line in a shell script (see chapter??).
The joy of X
The best thing about the X Window System is that
absolutely everything
about it can be tailored - even the menus.
For example,
in Microsoft Windows we cannot choose how
keyboard input is associated with a window -
you
have
to click the
left mouse button in the window.
And when you do, the window is automatically brought to the top of any
other windows.
In X we can choose both: how to give focus to a window, and whether it
is raised to the top or not.
All tailoring is done by editing ordinary text files.
QUESTIONS
-
-
ANSWERS
-
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http://homepages.shu.ac.uk/~cmsps/unix/xterm.html
Last updated: Thursday 05 April 2012 at 17:45