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The edit utility is a variant of the text editor ex recommended for new or casual users who wish to use a command-oriented editor. It operates precisely as ex with the following options automatically set:
- novice
-
ON
- report
-
ON
- showmode
-
ON
- magic
-
OFF
The following brief introduction should help you get started with edit. If you are using a CRT terminal you may want to learn about the display
editor vi.
To edit the contents of an existing file you begin with the command edit name to the shell. edit makes a copy of the file that you
can then edit, and tells you how many lines and characters are in the file. To create a new file, you also begin with the command edit with a filename: edit name; the editor will tell you it is a [New File].
The edit command prompt is the colon (:), which you should see after starting the editor. If you are editing an existing file, then you will have some lines in edit's buffer (its name for the copy of the file you are editing). When you start editing, edit makes the last line of the file the current line. Most commands to edit use the current line if you do not tell them which line to use. Thus if you say print (which can be abbreviated p) and type carriage return (as you should
after all edit commands), the current line will be printed. If you delete (d) the current line, edit will print the new current
line, which is usually the next line in the file. If you delete the last line, then the new last line becomes the current one.
If you start with an empty file or wish to add some new lines, then the append (a) command can be used. After you execute this command (typing a carriage return
after the word append), edit will read lines from your terminal until you type a line consisting of just a dot (.); it places these lines after the
current line. The last line you type then becomes the current line. The insert (i) command is like append, but places the lines you type before,
rather than after, the current line.
The edit utility numbers the lines in the buffer, with the first line having number 1. If you execute the command 1, then edit will type the
first line of the buffer. If you then execute the command d, edit will delete the first line, line 2 will become line 1, and edit will print the
current line (the new line 1) so you can see where you are. In general, the current line will always be the last line affected by a command.
You can make a change to some text within the current line by using the substitute (s) command: s/old/new/ where old is the string of characters you want to replace and new is the string of characters you want to replace old with.
The filename (f) command will tell you how many lines there are in the buffer you are editing and will say [Modified] if you have changed the
buffer. After modifying a file, you can save the contents of the file by executing a write (w) command. You can leave the editor by issuing a quit
(q) command. If you run edit on a file, but do not change it, it is not necessary (but does no harm) to write the file back. If you try to quit from edit after modifying the buffer without writing it out, you will receive the message No write since last change (:quit! overrides), and edit will wait for another command. If you do not want to write the buffer out, issue the quit command followed by an exclamation point (q!). The buffer is
then irretrievably discarded and you return to the shell.
By using the d and a commands and giving line numbers to see lines in the file, you can make any changes you want. You should learn at least a few more things,
however, if you will use edit more than a few times.
The change (c) command changes the current line to a sequence of lines you supply (as in append, you type lines up to a line consisting of
only a dot (.). You can tell change to change more than one line by giving the line numbers of the lines you want to change, that is, 3,5c. You can
print lines this way too: 1,23p prints the first 23 lines of the file.
The undo (u) command reverses the effect of the last command you executed that changed the buffer. Thus if you execute a substitute command
that does not do what you want, type u and the old contents of the line will be restored. You can also undo an undo command. edit
will give you a warning message when a command affects more than one line of the buffer. Note that commands such as write and quit cannot be undone.
To look at the next line in the buffer, type carriage return. To look at a number of lines, type ^D (while holding down the control key, press d) rather
than carriage return. This will show you a half-screen of lines on a CRT or 12 lines on a hardcopy terminal. You can look at nearby text by executing the z
command. The current line will appear in the middle of the text displayed, and the last line displayed will become the current line; you can get back to the line where you were before you executed the z command by typing ''. The z command has other options: z- prints a screen of text (or 24 lines) ending where you are; z+ prints the next screenful. If you want less than a screenful of lines, type z.11 to display five lines before and five lines after the current line. (Typing z.n, when n is an odd number, displays a total of n lines, centered about the current line; when n
is an even number, it displays n-1 lines, so that the lines displayed are centered around the current line.) You can give counts after other commands; for example,
you can delete 5 lines starting with the current line with the command d5.
To find things in the file, you can use line numbers if you happen to know them; since the line numbers change when you insert and delete lines this is somewhat unreliable. You can search backwards
and forwards in the file for strings by giving commands of the form /text/ to search forward for text or ?text? to search
backward for text. If a search reaches the end of the file without finding text, it wraps around and continues to search back to the line where you
are. A useful feature here is a search of the form /^text/ which searches for text at the beginning of a line. Similarly /text$/
searches for text at the end of a line. You can leave off the trailing / or ? in these commands.
The current line has the symbolic name dot (.); this is most useful in a range of lines as in .,$p which prints the current line plus the rest of the lines in
the file. To move to the last line in the file, you can refer to it by its symbolic name $. Thus the command $d deletes the last line in the file, no matter what the current line is.
Arithmetic with line references is also possible. Thus the line $-5 is the fifth before the last and .+20 is 20 lines after the current line.
You can find out the current line by typing `.='. This is useful if you wish to move or copy a section of text within a file or between files. Find the first and last line
numbers you wish to copy or move. To move lines 10 through 20, type 10,20d a to delete these lines from the file and place them in a buffer named a. edit
has 26 such buffers named a through z. To put the contents of buffer a after the current line, type put a. If you want to move
or copy these lines to another file, execute an edit (e) command after copying the lines; following the e command with the name of the other file
you wish to edit, that is, edit chapter2. To copy lines without deleting them, use yank (y) in place of d. If the text you wish
to move or copy is all within one file, it is not necessary to use named buffers. For example, to move lines 10 through 20 to the end of the file, type 10,20m $.
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