C/C++ Interactive Reference Guide/C-C++ Interactive Reference Guide.iso/c_ref/csource3/115_01/guide.doc

Text File | 1979-12-31 | 20.3 KB | 823 lines

.cm screen editor:  user guide
.cm source:  guide.doc
.he 'guide.doc''September 8, 1981'
.fo ''-#-''

.ul
Basic terms

   The terms, mode, command, special character,
prompt line, cursor, the current line, and the buffer
are used extensively in this documentation.
You will learn about the screen editor more easily if you
become familiar with these terms.
Let's look at each in turn.

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The screen editor is comprised of several
.ul
modes.
You can switch between modes,
but the editor can't be in two modes at the same time.
The editor behaves differently in each mode,
so you use each mode to do a particular type
of editing.

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There are three modes:
edit mode, command mode and insert mode.
You use edit mode for making
small changes in many different lines.
Command mode is used for making larger
(hence potentially more dangerous)
changes to the whole file you are editing.
You must be in command mode to do anything
that will change files on the disk.
You use insert mode for making a series of
insertions into the text.
First drafts are often entered in this mode.

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You use
.ul
commands
to make things happen in each mode.
Which commands you can use depends on what mode you
are in.
Do not confuse the terms "commands" and
"command mode".
Every mode has a set of commands which
you can use in that mode.
Command mode has its own set of commands.

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.ul
Special characters
are one-letter commands.
Special characters must be control keys, so
you can use these commands in places where the
editor might not otherwise expect a command.

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The
.ul
prompt line
is the top line of the screen.
It tells you things like what line you
are editing and what mode you are in.
If you get confused about what mode you are in
you can always glance at the prompt line
and get your bearings.

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Several edit-mode commands
consist of two or more letters.
These edit-mode commands are called
.ul
extended commands.
After you type the first letter of such a command,
but before you type the last letter, the
prompt line will indicate that you must type one more
letter to finish the extended command.
For example,
after you type an "s" to enter the edit-mode search command
the prompt line's mode field will contain
'edit: search'.

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The
.ul
cursor
is a distinctive character on the screen.
On most video terminals
this marker is a character shown with reverse
video.
In command mode you always type commands on the bottom
line so the cursor is always on the bottom line.
In edit mode and insert mode
the cursor is always on the current line.

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The
.ul
current line
is the only line you can edit.
In command mode the current line may not be shown on
the screen, but in edit and insert modes
the current line is shown and it contains the cursor.
If you want to make a change to a line you must first
move the cursor to that line.

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The
.ul
buffer
is a part of the computer's storage which holds the file
you are editing.
In order to edit a disk file, you must first read the disk
file into the buffer using the load command.
As you edit the file the changes you make are made only
to the buffer, not to your disk file.
Before you end your editing session you must copy the buffer
back to a disk file using the save or resave commands.
The editor keeps track of whether you have done this;
it won't let you forget to save your work.

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The
.ul
window
is a part of the screen which shows a portion
of the buffer.
In edit and insert modes the window fills all of
the screen except the prompt line.
You can think of the file as a scroll of parchment which
unwinds under the window as you move the cursor.
The window is not shown in command mode.

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Now let's look more closely at the editor's commands.
We'll start with special characters, which are commands
that may be used in either insert or edit modes.
Then we will look at other commands which are unique to
a particular mode.

.ul
Special Characters

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Special characters act the same in all modes.
Special characters must be control characters so that
the editor may always distinguish special characters from
regular text.

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There are 14 special characters;
all 14 may be used in either edit mode or insert mode.
Only a few may be used in command mode.

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You can use the configuration program to choose
which keys on your keyboard to use for each
special character.
Thus, I won't be able to
be specific about what key on your keyboard you will actually
hit in order to type, for instance, the down key.
I'll often refer to special characters as special keys;
for example, I'll call the down special character the
down key.

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The
.ul
left and right keys
just move the cursor.
They do not cause changes to lines.
These keys are always "anchored" to the current line;
you can't move off the current line by using these keys.
If you hit the right key while the cursor
is at the right margin,
nothing will happen.
Similarly, nothing will happen if you hit the
left key while the cursor is at the left margin.

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The
.ul
up and down keys
move the cursor up and down
on the screen.
You can't move the cursor above line 1 of the file, nor can you
move the cursor below the last line of the file.
Both these keys also switch the editor to edit mode.

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The
.ul
insert up key
inserts a blank line above the current line
while the
.ul
insert down key
inserts a blank line below the current line.
Both these keys also switch the editor to insert mode.

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The
.ul
delete character key
deletes the character to the left of the cursor.
This key is anchored to the current line;
nothing is deleted if the cursor is at the left margin.
The
.ul
delete line key
deletes the entire line on which the cursor rests.

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The
.ul
undo key
always undoes whatever
editing you have done on the current line since
the last time the cursor came to the current line.

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The
.ul
insert key
switches the editor to insert mode.
Similarly, the
.ul
command key
switches the editor to command mode and the
.ul
edit key
switches the editor to edit mode.

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The
.ul
split key
splits the current line into two pieces.
Everything to the left of the cursor stays right where it is.
All other characters are moved from the current line to
a new line which is created below the original line.

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The
.ul
join key
is the opposite of the split key;
it combines two lines into one line.
The join key appends the current line to the line above it,
then deletes the lower line.

.ul
Edit Mode

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Edit-mode commands are normal letters; you don't need
to use special keys.
This speeds typing.
You can, however, use the special keys in edit mode if you
want to.

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Besides the special characters you can use
the following one-letter edit-mode commands:
space, b, c, d, e, g, i, k, s, u, and x.
These letters stand for
begin, command, down, end, go, insert, kill,
search, up, and eXchange.
Note that all these commands may be typed either
in upper case or in lower case.
Letters which are neither edit-mode commands
nor special keys are simply ignored.
The following paragraphs explain what these
commands do in greater detail.

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The
.ul
space bar
moves the cursor right one column.
Nothing happens if the cursor is already
on the rightmost column of the screen.

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The
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b command
puts the cursor at the beginning
(left hand margin) of the line.

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The
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c command
switches the editor to command mode.

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The
.ul
d command
causes the cursor to move down rapidly.
The cursor keeps moving until it reaches the last line
of the file or until you type any key.

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The
.ul
e command
moves the cursor to the right end of the line.

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The
.ul
i command
switches the editor to insert mode.

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The
.ul
g command
moves the cursor to another line.
The g command is an extended command;
after you type the g the cursor will move to the prompt line.
The prompt line will show 'edit: goto:'
Now type a line number followed by a carriage return.
The cursor will move to the line whose number you typed.
If you do not type a valid number the g command does nothing.
Leading blanks or minus signs are not allowed.
The cursor will move to the last line of the buffer if
the number you type is larger than the number of lines
in the buffer.

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The
.ul
k command
is a two-letter command.
The second letter you type
(the first character after the k)
is a search character.
The k command deletes from the cursor up to
but not including the next occurence of the search
character to the right of the cursor.
Everything from the cursor to the end of the line
is deleted if the search character does not
appear to the right of the cursor on the current line.
After you hit the k and before you hit the
search character the prompt line will show
'edit: kill'.
If you wish to cancel the k command you can
hit any control character.
The k command will be stopped and no deletion
will be made.

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The
.ul
s command
is another two-letter command.
The second character you type
(the first character after the s)
is a search character.
The s command moves the cursor to the next
occurence of the search character which
appears to the right of the cursor.
The cursor moves to the end of the current
line if the search character does not occur
to the right of the cursor.
After you hit the s and before you hit the
search character the prompt line will show
'edit: search'.

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The
.ul
u command
moves the cursor up rapidly.
The cursor keeps moving until it reaches the first line
of the file or until you hit any key.

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The
.ul
x command
is another two-letter command.
The second character you type replaces the character
under the cursor.
The prompt line will show 'edit: eXchange'
until you hit the second character.
If you hit a control character no change is made
and the x command is cancelled.

.ul
insert mode

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Use insert mode to insert many lines of text at once.
In insert mode anything you type (except special keys)
will be inserted into the text to the left of the cursor.
You may use special keys in insert mode exactly as in
edit mode.

.ul
command mode

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You use command mode to do potentially dangerous
things like making multiple
changes to the buffer or like updating your files.
For this reason, all command-mode commands require you
to type several characters with a carriage return at the
end.

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The editor starts off in command mode after you invoke
it from your operating system.

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You may use either the edit key or the insert key to exit
from command mode.
You can also use the
g command-mode command or the find command-mode command
to leave command mode.
When the editor leaves command mode the screen is redrawn
to show the current line.

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The cursor is on the bottom line of the screen
whenever the editor is in command mode.
This line is called the command line.
As you type commands, what you type will be shown on this line.
Use either the delete character key or the right key to
delete the last character you typed.
Use the undo key to delete the entire
command line.

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Several command-mode commands take arguments.
There are three types of arguments: range arguments,
file names and line numbers.
In the description below, range arguments will be denoted
by <line range>, file name arguments
will be denoted by <filename> and line numbers will be denoted
by <n>.

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Range arguments denote the range of lines in the
buffer for which a command will take effect.
For example,

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list 25 50

means list all lines from line 25 to line 50 inclusive,

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list

means list all the lines of the buffer, and

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list 300

means list line 300 and all following lines.
Range arguments, if present, must be nonnegative integers.
If two numbers are entered, the first must be no larger than
the second.
0 is equivalent to 1.
A number larger than the largest line number is equivalent
to the largest line number.

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Filename arguments are the name of a file to be
used in a command.
For example,

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load myfile.doc

causes the file myfile.doc to replace whatever is in the
buffer.
Note that no quotation marks are used around filename
arguments.
Filename arguments optionally may be preceded by disk drive
names.
For example,

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load b:myfile.doc

loads the buffer from the file myfile.doc which must
be found on drive b.

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The editor protects you from destroying the buffer
unintentionally.
If a command would cause the buffer to be erased and you
have not already saved the buffer on a disk file the editor
will ask:

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buffer not saved.  proceed ?

If you type y or Y the command will be done and the buffer
will be erased.
If you type anything else no change will be made to the buffer
and the message 'cancelled' will be printed on the screen.
Note however, that the delete command does
.ul
not
protect you in this way.
Use the delete command with caution.

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You may interrupt or cancel the change, find, list and search
commands.
If you type any character
.ul
except
a blank the command will be cancelled immediately.
If you type a blank the command will be temporarily suspended.
Type another blank to continue or any other character to
cancel the command.

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The following paragraphs discuss all the command-mode commands.

append <filename>

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The append command inserts the named file into the
buffer after the current line.
In other words, the position of the cursor affects where the
file will be inserted.
This command adds to the buffer;
it does not delete what is already there.

change <line range>

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The change command searches all lines in <line range>
for an instance of a search mask.
If the search mask is found it is replaced by the change mask.
After you type  change <line range> the command will ask:

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search mask ?

At this point type the pattern you are searching for,
followed by a carriage return.
Then you will be asked:

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change mask ?

Now you type the pattern you want the search mask to be
replaced by.
For example,

.in +10
change 100 300
.br
search mask ?  abc
.br
change mask ?  xyz
.br
.in -10

will change  abc to xyz in all lines from 100 to 300.
Thus, the line:

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know your abc's.

would be changed into:

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know your xyz's.

Only the first instance of abc on each line would be changed.
The line:

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know your abc's.  The abc's are very important.

would be changed to:

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know your xyz's.  The abc's are very important.

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Question marks may be used in both the search mask and
the change mask.
A question mark in the search mask matches any character at
all.
The search mask:

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12?34

will match any string of five characters which starts with
12 and ends with 34.
A question mark in the change mask matches the letter that
matched the corresponding question mark in the search mask.
For example:

.in +10
change 99 109
.br
search mask ?  trailing?
.br
change mask ?  ?leading
.br
.in -10

would change the line:

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trailingA

into the line:

.ti +10
Aleading

The question mark in the search mask matched the 'A', so the
quesion mark in the change mask became an 'A'.
You can use as many question marks as you like, but there
must be at least as many question marks in the search mask
as there are in the change mask.
As another example:

.in +10
change
.br
search mask ?  wh??e
.br
change mask ?  fath??
.br
.in -10

would change the line:

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where is here.

to the line:

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father is here.

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If the first character of the search mask is an up arrow
(^),
the search mask is anchored to the start of the line.
In other words, the search mask will only match patterns
which start at column 0.
For example, the search mask

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^abc

will only match lines that contain abc
in columns 0, 1 and 2.
Anchoring the search mask dramatically increases the speed of
the change command.

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An up arrow which is not the first character of the
search mask is treated as a regular up arrow.
An up arrow in the change mask never has any special
significance.

clear

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The clear command erases the entire buffer.
If you have not saved the buffer you will be asked whether
you want to proceed.

delete <line range>

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The delete command erases all lines in the line range.
Care must be used with this command because no check is
made to see whether the buffer has been saved.

dos

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The dos command exits the editor and returns to the
operating system.
If the buffer has not been saved, this command makes sure
that you really wanted to exit without saving the buffer.

find

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The find command searches for the next occurence of a
search mask.
If the search mask is found, the editor switches to edit mode
and the cursor is set to the start of the pattern.
If the search mask is not found the editor remains
in command mode.

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You specify the search mask exactly as in the change command.

g <n>

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The g command exits to edit mode.
Line <n> is drawn on the top line of the window and
becomes the current line.
Typing g without the <n> is the same as typing the
edit key.

list <line range>

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The list command lists all lines in the line range to
the current list device, i.e., the printer.
Lines are formatted just as they are on the screen, but
the length of the print line, not the width of the screen,
determines where lines will be truncated if they are too long.
Listing may be stopped at any time by typing any key.

load <filename>

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The load command replaces whatever is in the buffer
by the contents of the named file.
If the buffer has not been saved on disk when the load
command is given, the editor makes sure you really wanted
to erase the previous contents of the buffer.
If the named file exists, then <filename>
becomes "the current file" and <filename>
is shown on the prompt line.
This file becomes the file used in the save and resave
commands.
The current file name does not change
if the named file does not exist.

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After the file has been completely read from the disk
into the buffer the screen is redrawn to show the
first several lines of file.

name <filename>

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The name command sets the name of the file that will be used
in the save and resave commands.
This command is not often used because the load command
is the usual way to set this file's name.
The name command does not cause any action immediately;
it simply affects which file the save and resave commands
will use.

resave

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The resave command saves the entire buffer in the
current file.
The current file is set by either the load or name commands
and always appears on the prompt line.
Note that this command does
.ul
not
take any arguments.
All arguments to this command are ignored.

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The resave command requires that the current file already
exist;
if the file does not exist a warning is printed and nothing
happens.

save

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The save command works just like the resave command
except that the file must
.ul
not
exist for the command to work.
If the file does exist a warning is printed and
nothing happens.
This protection insures that files can not be overwritten
inadvertantly.

search <line range>

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The search command prints on the
screen all lines in <line range>
which contain an instance of the search mask.
As soon as the search command is typed the editor will ask:

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search mask ?

Now type the search mask.
Just as in the change command, a question mark matches
any character and a leading up arrow anchors
the search mask to the start of the line.

tabs <n>

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The tabs command controls how lines are listed on the
screen and on the printer.
Specifically, the tabs command sets tab stops every
<n> columns.
<n> must be an integer.
tabs 0 is equivalent to tabs 1.