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The editor
Ok so you now have a basic understanding of how to navigate though the file system and do some copying and moving of files. Now you will learn how to create and edit files. To do so you will need to learn how to use the ed editor. This is a somewhat complicated editor to use for those new to programming. You will find in your home directory a file called ed. It is now you should read this file. To do so use the more command your learnt in the last problem set. The file is also included below. It may be a bit much to handle though. So before we get to the help file I will try to explain it a bit.
ed Ed will display one line at a time. To exit ed you can use x to exit and save, q to quit, or Q to quit without saving any changes. Lets take a quick tour of ed. For the following tutorial type everything which appears like this everything else will just be comments:
cd change into your home directory
You are now in the editor. Here is your first command: 8 set_short("a dull sword");
appear. Pressing c means "change this line" and notice when you did the line changed to8. *the * means we are in edit mode now. We type in the new line set_short("my sword"); and then we put in a .. The period means leave edit mode back into display mode. We then go back to line 1 and list the file again with z.
Notice line 8 has changed... but it it no longer indented. No problem, type:
There are a few other commands besides c which allow you to enter the edit mode. They are i for insert and a for add. Insert will insert a line before your current line and Add will add a line after your current line. So lets insert a comment line. Type the following:
Now lets leave the editor. Ok... now you know the basics, and the ed help file is below and in your home directory. Luckyly there is a slightly easier way to use ed. The solution is to create your file in notepad or other text editor on your own computer. Then, using the editor, go into insert mode and cut and paste your file in, then exit insert mode and exit the editor. Then of course update your file. If it updates ok, clone it and if everything is ok we are done. If it is broken you will have to fix it. Error messages will usually give you an idea of where the problem is so you can fix it. If you are using this cut and paste method of programming you should remove the bugged file before you enter the editor and cut and paste again. There is anothe way to transfer files you create to and from the MUD. That is through FTP. Talk to active coders on the builder port and they will be able to fill you in on the details. The Ed Primer
--or--
Your Introduction To The Wonderful World Of Programming With Ed!
0. A Prelude:
(How to read the author's peculiar notation)
In all examples:
Words in angle brackets <like this> are not to be typed literally, but rather
to be substituted for. For example, '<number>p' could be '4p' or '27p', etc.
[Anything in square brackets] is optional.
<x|y> represents <x> OR <y>, but not both.
> is assumed to be the standard lpmud prompt.
: is assumed to be the ed command mode prompt.
* is assumed to be the ed insert mode prompt.
--The author/editor
I. A Beginning:
(The 'ed', 'a', 'i', 'w', and 'q' commands)
First, the command to enter ed from lpmud can take one of two basic forms:
> ed <filename>
or
> ed <dummy filename>.
The first is used to edit an existing file. The second is used to create
a new file. The dummy filename can be any string that isn't already the
name of a file. Short strings like 'a' work well for this.
Once you are in ed, your prompt will become ':'. From this prompt you
enter ed commands. If you are beginning a new file, you can use one of
two commands to enter insert mode: 'a' or 'i'. The difference between
these two will become significant later on. In insert mode, your prompt
will become '*'. From here you type in the body of your file. You can
leave insert mode at any time by typing a single '.' on a line by itself.
Once you are finished entering your text and have returned to command mode
(':' prompt), you can save your file with the 'w' command, specifying a
filename:
:w myfile.c
Then you can use 'q' to exit ed, and return to your normal propmt.
Summary:
> ed <file | dummy file> takes you into ed.
'a' and 'i' in command mode begin insert mode.
---> Implicit assumtion from now on: all commands will be from command mode
---> unless it is stated otherwise.
'.' in insert mode returns you to command mode.
'w <file>' saves your file.
'q' takes you out of ed.
II. Editing existing files:
(The 'ed', 'a', 'c', 'd', 'i', 'l', 'p', 'w', 'z', and '=' commands.)
To edit an existing file (a reminder from section I), use:
> ed <filename>
This again puts you in command mode, with the difference from starting a
new file that there are already lines in the buffer. Use the command '.p'
to see the line you are presently on.
The command 'p' will print out a line or range of lines. Its syntax is
this: 'p' or '.p'* will print out the line you are presently on.
'<number>p' will print out line number <number>. '<number1>,<number2>p'
will print out the range of lines from <number1> to <number2>. In this
case, <number1> must be less than or equal to <number2>. In both cases,
all numbered lines must exist, or the command will fail. The command 'l'
is similar to 'p' in most respects, except that it also makes visible some
'invisible' characters, like newline (which shows up as $). Tabs become
completely invisible. 'z' will display 21 lines in 'p' fashion (i.e.,
ctrl characters remain invisible). 'z' can be prepended by a line number
to start at.
The command <number> will take you to the line of the same number.
The commands 'i' and 'a' are the commands introduced in section I. The
difference between these two commands now takes on a significance; 'i'
starts inserting before the line you are presently on, while 'a' starts
inserting after the line you are on. (Use '.' or '.p' to display the line
you are on.) Also, 'i' and 'a' can both be prepended by a <number>,
('<number>i' and '<number>a'), which sets your present line at <number>
before beginning insert mode.
The command '=' can be used to discover the number of the line you are on.
The command 'd' deletes the current line you are on. 'd' can, like 'p'
and 'l', be used with a single line number, or a range of them for
arguments.
The command 'c' is used to change lines. It is essentially similar to 'd'
in its usage, except that instead of leaving you in command mode, you are
put into insert mode, inserting text to 'replace' what was removed.
Finally, 'w' without being followed by '<file>' will save the file under
the name you began editing it as, provided that that file already existed.
Footnote: * As a number, '.' refers to the present line; '$' refers to the
lastline of the file.
An example encompassing what we've done so far:
> ed a
:a
*This is line 1.
*This is line @.
*This is line 3.
*This is line 5.
*This is too many lines.
*.
:1,3p
This is line 1.
This is line @.
This is line 3.
:=
3
:5l
This is too many lines.$
:5d
:1,$p
This is line 1.
This is line @.
This is line 3.
This is line 5.
:2c
*This is line 2.
*.
:1z
This is line 1.
This is line 2.
This is line 3.
This is line 5.
:4i
This is line 4.
:1,$p
This is line 1.
This is line 2.
This is line 3.
This is line 4.
This is line 5.
:w file.txt
:q
> ls
Total 1
1 file.txt
>
Summary:
'p' and 'l' are used to display ranges of lines. 'l' displays some invisible
characters.
'z' displays 21 lines in 'p' format.
'=' displays the current line number.
'd' deletes a line.
'c' changes a line by deleting it and putting you into insert mode.
--As numbers, '.' refers to the present line, and '$' to the last line of the
file.
III. More Advanced Editing:
(The 's' command)
The 's' command is used for substitutions. The general format is this:
:[<number1>[,<number2>]]s<delimiter><pattern><delimiter><sub>[<delimiter>gp]
The command may look intimidating at first, but it turns out to be one of
the most powerful commands in ed.
An explanation of all the angle-brackets:
<number1> and <number2> are the range of substitution. If ',<number2>' is
omitted, the range of effect is merely line <number1>. If '<number1>' is
also omitted, the substitution defaults to the present line.
<delimiter> is simply a character used as a separator. Care should be
taken that '<delimiter>' does not occur in either <pattern> or <sub>.
The most common choices for <delimiter> are '/' and '!', although any
character can be used.
<pattern> is the string that will be changed. <sub> is the string that it
will be changed to. If <pattern> begins with a '^', that is taken to mean
'beginning of line.' Similarly, if it ends with '$', it signifies 'end of
line.'
The final optional [gp] are used, respectively, to make the substitution
global throughout the line (instead of just affecting the first
occurrence), and to display the newly-changed line immediately afterwards.
Note that g must come before p, if both are used.
Some examples:
:.
This is line nubmer 3.
:s/bm/mb/p <--- Note that '/' is used as the delimiter here.
This is line number 3.
:
:.
Thsi si line 3.
:s!si!is!p <--- The delimiter here is '!'.
This si line 3. <--- Note that only the 1st occurrence of 'si' was changed
:
:.
Thsi si line number 3.
:s!si!is!gp <--- Here, the delimiter is '!', again.
This is line number 3.
:
:3,5p
This is lize 3.
This is lize 4.
This is lize 5.
:3,5sqzqnqp <--- Here, to confuse matters, the delimiter is 'q'.
This is line 3.
This is line 4.
This is line 5.
:
General notes:
For a global substitution, use:
:1,$s/<pattern>/<sub>/g
Beware of special characters in <pattern>. '.', '(', ')', '&', '*', '|',
'[', '^', and ']' should all be prepended by backslashes ('\') if they are
used. '\' is, although possible to use in <sub> and <pattern>, very
tricky to use. The author recommends beginners use the 'c' command to do
sunstitutions for this character instead.
Some of these special characters that can be used in <pattern>:
. Match any character.
x* Match any numbers of x (0 or more).
[abc] Match 'a', 'b' or 'c'.
[0-9] Match any digit 0 - 9.
[a-z] Match any lowercase letter.
[^0-9] Match anything except a digit 0 - 9.
The & can be used in the replacement to represent the text being replaced.
Example:
:.
This is a lazy line, lying abed. It is also silly; abcd.
:s/ab.d/ABCD/gp
This is a lazy line, lying ABCD. It is also silly; ABCD.
:
Example:
:.
This is a long line that is being used to demonstrate a silly example.
:s/l.n./&foo/
This is a longfoo linefoo that is being used to demonstrate a silly example.
III-I/II. (3.5, for those who can't figure that out.) Author's Interjection:
(The '<range>' notation)
What was formerly referred to as <number1>,<number2><command> will, from
here on out, be referred to as <range><commmand>, for the author's typing
ease. Thank you.
IV. Still More Advanced Commands, and Related Shortcuts:
(The 'e', 'E', 'f', 'j', 'k', 'Q', 'm', 'r', 't', 'x', and '!' commands)
The 'e', 'E', and 'r' commands can all be used to read external files into
the buffer. 'e <file>' reads <file> into the buffer, deleting everything
in the buffer. Because it is destructive, the exact buffer contents must
be saved before this command can be executed. 'E <file>' works exactly as
'e <file>', except that it ignores the saved status of the present buffer.
'<number>r <file>' reads in the contents of <file>, placing them after
line <number>. As usual, if <number> is omitted, it defaults to the
current line.
'Q' and 'x' can, like 'q', be used to exit ed. 'q' can only be used to
exit ed if the exact contents of the buffer are saved. 'Q' can be used to
exit regardless of the saved status of the buffer. 'x' saves the buffer
to the default file name and exits ed. Note that if there is no default
file name, 'x' will fail.
'<range>j' will join all of the lines in <range> together into one line.
'<number>k<marker>' will assign <marker> to line <number>. <marker> can
be any lowercase letter. A line marked is referred to as "'<marker>".
For example, the commands: :5kd :1,'dp
will mark line 5 as "d" and then print out lines 1-5.
'f <file>' sets the default name of the file (used for the 'w' and 'x'
commands) to <file>.
't' and 'm' are both used to move sections of text. The format is:
:<range>t|m<number>
where <range> is the text to be moved, and <number> the line it is to be
inserted after. 't' is 'transfer' and leaves a copy of the text to be
moved at the original site; it is basically a 'copy' command. 'm' is
'move' and moves the text from its original site to its new site.
'!' is used to execute lpmud commands from within ed, and can be used in either
the command or the insert mode. For example:
:!'Wait, please; I'm in ed.
Guest says: But I want to talk.
:i
*!'I said wait, please.
*
A summary:
'e', 'E', and 'r' are used to retrieve external files to the buffer.
'Q' is used to exit, regardless of save status.
'x' is used to save and exit in one step.
'f' changes the default name of the file.
'j' joins lines together.
'k' marks lines.
't' is used to transfer, or copy lines.
'm' is used to move lines.
'!' in command and insert modes, is used to execute an lpmud command.
V. Seek, and Ye Shall Find
(The 'g', 'v', '?', and '/' commands)
'/' and '?' are used to find expressions in the buffer. '/<string>' does
a forward search for <string>, while '?<string>' does a backward search.
'/' and '?' with no arguments default to the previous argument. If no
argument was given prior, an error occurs.
'g' and 'v' use similar formats for operation:
:<range>g|v/<string>/<command>
Both 'g' and 'v' search through <range> for lines that contain <string>.
'g' executes <command> on all lines in <range> that contain <string>, while
'v' executes <command> on all lines that do not contain <string>.
<command> may be one of the following commands: 's', 'l', 'p', 'd', 'm', or
'r'. Arguments for these commands work normally.
'/' and '?' may be used similarly to operate on the first occurrence of
<string> found. For example:
:/foo/s/x/ox/gp
will replace all instances of 'x' on the next line containing
'foo' with 'ox' and set your current line there. Similarly,
:?bar?=
will give you the
number of the first previous line containing the string 'bar', and set your
current line there.
Exapmles:
:1,$p
This is a test.
This is line two of the test.
There are more than two lines.
This is the last line.
:1,$g/two/l
This is line two of the test.$
There are more than two lines.$
:1,$v/two/d
:1,$p
This is line two of the test.
There are more than two lines.
:?test
This is line two of the test.
:.p
This is line two of the test.
:/There
There are more than two lines.
:Q
>
--Mishael, author/editor.
David "Mishael" Green
dgreen@jarthur.claremont.edu
Once you are confortable with this it is time to move onto the next problem set. |
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