Text Editors

Unix Editors

What is a text editor?

A text editor is a program which enables you to create and manipulate character data (text) in a computer file.
A text editor is not a word processor although some text editors do include word processing facilities.
Text editors often require "memorizing" commands in order to perform editing tasks. The more you use them, the easier it becomes. There is a "learning curve" in most cases though.

There are several standard text editors available on most UNIX systems:

ed - standard line editor
ex - extended line editor
vi - a visual editor; full screen; uses ed/ex line-mode commands for global file editing
sed - stream editor for batch processing of files

In addition to these, other local "favorites" may be available:

emacs - a full screen interactive editor and much more
nedit - another GUI style text editor similar to emacs.
pico - an easy "beginner's" editor

Each of these editors can be invoked by typing their name at the prompt, along with the file name. For example, to invoke nedit we issue the command:

nedit filename or

nc filename

The Standard Display Editor - vi

vi is the standard editor available on every UNIX system. While it appears intimidating at first, it is extremely powerful and universal. Hence familiarity with it is important. A nice way to get started with learning this editor is by using the "vitutor". It can be copied to your home directory from either of the following directories:

/nfs/cis/phd/asb2718/vitutor
/nfs/cis/staff/rvrpci/pub/vitutor

Copy files, Readme, tutor.vi and vitutor.n. Out of these, tutor.vi is the main tutor. However go through the Readme and vitutor.n first. Type

vi tutor.vi

at the prompt to begin the tutor. The instructions are in the file and follow them as you read along. Note: It might be a good idea to copy the file tutor.vi to some other file and work with it instead as you would be making changes to it as you go along.

vi supplies commands for:

inserting and deleting text
replacing text
moving around the file
finding and substituting strings
cutting and pasting text
reading and writing to other files

vi uses a "buffer"

While using vi to edit an existing file, you are actually working on a copy of the file that is held in a temporary buffer in your computer's memory.
If you invoked vi with a new filename, (or no file name) the contents of the file only exist in this buffer.
Saving a file writes the contents of this buffer to a disk file, replacing its contents. You can write the buffer to a new file or to some other file.
You can also decide not to write the contents of the buffer, and leave your original file unchanged.

vi operates in two different "modes":

Command mode

vi starts up in this mode
Whatever you type is interpreted as a command - not text to be inserted into the file.
The mode you need to be in if you want to "move around" the file.

Insert mode

This is the mode you use to type (insert) text.
There are several commands that you can use to enter this mode.
Once in this mode, whatever you type is interpreted as text to be included in the file. You can not "move around" the file in this mode.
Must press the ESC (escape) key to exit this mode and return to command mode.

vi Commands

Entering vi


     vi filename   - The filename can be the name of an 

                     existing file or the name of the file 

                     you want to create.  

     view filename - Starts vi in "read only" mode.  Allows 

                     you to look at a file without the risk  

                     of altering its contents.

Exiting vi


     :q            - quit - if you have made any changes, vi

                     will warn you of this, and you'll need 

                     to use one of the other quits.

     :w            - write edit buffer to disk 

     :w filename   - write edit buffer to disk as filename 

     :wq           - write edit buffer to disk and quit 

     ZZ            - write edit buffer to disk and quit 

     :q!           - quit without writing edit buffer to disk

Positioning within text


By character 

     left arrow    - left one character 

     right arrow   - right one character 

     backspace     - left one character 

     space         - right one character 

     h             - left one character 

     l             - right one character 



By word 

     w             - beginning of next word 

     nw            - beginning of nth next word 

     b             - back to previous word 

     nb            - back to nth previous word 

     e             - end of next word 

     ne            - end of nth next word 



By line 

     down arrow    - down one line 

     up arrow      - up one line 

     j             - down one line 

     k             - up one line 

     +             - beginning of next line down 

     -             - beginning of previous line up 

     0             - first column of current line (zero) 

     ^             - first character of current line 

     $             - last character of current line 



By block 

     (             - beginning of sentence 

     )             - end of sentence 

     {             - beginning of paragraph 

     }             - end of paragraph 



By screen 

     CTRL-f        - forward 1 screen 

     CTRL-b        - backward 1 screen 

     CTRL-d        - down 1/2 screen 

     CTRL-u        - up 1/2 screen 

     H             - top line on screen 

     M             - mid-screen 

     L             - last line on screen 



Within file 

     nG            - line n within file 

     1G            - first line in file 

     G             - last line in file

Inserting text


     a             - append text after cursor  *

     A             - append text at end of line  *

     i             - insert text before cursor  *

     I             - insert text at beginning of line  *

     o             - open a blank line after the current

                     line for text input  *

     O             - open a blank line before the current 

                     line for text input   *



     * Note: hit ESC (escape) key when finished inserting!

Deleting text


     x             - delete character at cursor 

     dh            - delete character before cursor 

     nx            - delete n characters at cursor 

     dw            - delete next word  

     db            - delete previous word 

     dnw           - delete n words from cursor 

     dnb           - delete n words before cursor 

     d0            - delete to beginning of line 

     d$            - delete to end of line 

     D             - delete to end of line 

     dd            - delete current line 

     d(            - delete to beginning of sentence 

     d)            - delete to end of sentence 

     d{            - delete to beginning of paragraph 

     d}            - delete to end of paragraph 

     ndd           - delete n lines (start at current line)

Changing text


     cw            - replace word with text  *

     cc            - replace line with text  *

     c0            - change to beginning of line  *

     c$            - change to end of line  *

     C             - change to end of line  *

     c(            - change to beginning of sentence  *

     c)            - change to end of sentence  *

     c{            - change to beginning of paragraph  *

     c}            - change to end of paragraph  *

     r             - overtype only 1 character 

     R             - overtype text until ESC is hit  *

     J             - join two lines 



     * Note: hit ESC (escape) key when finished changing!

Copying lines


     yy            - "yank":  copy 1 line into buffer 

     nyy           - "yank":  copy n lines into buffer 

     p             - put contents of buffer after current 

                     line 

     P             - put contents of buffer before current 

                     line

Moving lines (cutting and pasting)


     ndd           - delete n lines (placed in buffer) 

     p             - put contents of buffer after current 

                     line 

     P             - put contents of buffer before current 

                     line

Searching / Substituting


     /str           - search forward for str 

     ?str           - search backward for str 

     n              - find next occurrence of current string 

     N              - repeat previous search in reverse 

                      direction 

     

     The substitution command requires a line range 

     specification.  If it is omitted, the default 

     is the current line only. The examples below 

     show how to specify line ranges. 



     :s/old/new     - substitute new for first occurrence 

                      of old in current line

     :s/old/new/g   - substitute new for all occurrences 

                      of old in current line

     :1,10s/old/new - substitute new for first occurrence

                      of old in lines 1 - 10

     :.,$s/old/new  - substitute new for first occurrence

                      of old in remainder of file

     :.,+5s/old/new - substitute new for first occurrence

                      of old in current line and next 5 lines

     :.,-5s/old/new - substitute new for first occurrence

                      of old in current line and previous

                      5 lines

     :%s/old/new/g  - substitute new for all occurrences

                      of old in the entire file

     :%s/old/new/gc - interactively substitute new for all 

                      occurrences of old - will prompt for 

                      y/n response for each substitution.

Miscellaneous commands


     u             - undo the last command (including undo) 

     .             - repeat last command 

     xp            - swap two adjacent characters 

     m[a-z]        - set a marker (a - z) 

     '[a-z]        - go to a previously set marker (a - z) 

     :!command     - execute specified UNIX command 

     :r  filename  - read/insert contents of filename after

                     current line.

     :1,100!fmt    - reformat the first 100 lines

     :!fmt         - reformat the entire file

vi Options

You can change the way vi operates by changing the value of certain options which control specific parts of the vi environment.
To set an option during a vi session, use one of the commands below as required by the option:


     :set option_name

     :set option_name=value

Some examples of the more common options are described below.


     :set all       - shows all vi options in effect 



     :set ai        - set autoindent - automatically indents

                      each line of text 



     :set noai      - turn autoindent off  



     :set nu        - set line numbering on 



     :set nonu      - turn line numbering off 



     :set scroll=n  - sets number of lines to be scrolled 

                      to n.  Used by screen scroll commands. 



     :set sw=n      - set shiftwidth to n. Used by autoindent 

                      option.



     :set wm=n      - set wrapmargin to n. Specifies number 

                      of spaces to leave on right edge of the 

                      screen before wrapping words to next 

                      line. 



     :set showmode  - reminds you when you are inserting 

                      text. 



     :set ic        - ignore case of characters when 

                      performing a search.

Options can be set permanently by putting them in a file called .exrc in your home directory. A sample .exrc file appears below. Note that you do not need the colon (:) as part of the option specification when you put the commands in a .exrc file. Also note that you can put them all on one line.


     set nu ai wm=5 showmode ic

pico: One Alternative to vi

pico is a simple text editor based upon the Pine Message/mail System. It is far easier to use than vi, with the tradeoff that is isn't as powerful.
Editing commands are entered using control-key combinations. The most important commands are displayed at the bottom of the screen, facilitating ease of use.
To start pico, simply use the command "pico" followed by the name of the file you wish to edit. If the file exists, pico will start with that file. If it does not exist, then pico will assume that it is a new file.
The basic commands provided by pico include:


     CTRL-G   - get help 

     CTRL-X   - exit 

     CTRL-O   - write out to a file 

     CTRL-J   - justify text 

     CTRL-R   - read a file 

     CTRL-W   - where is (search) 

     CTRL-Y   - previous page 

     CTRL-V   - next page 

     CTRL-^   - mark cursor position as start of selected text

     CTRL-K   - cut text 

     CTRL-U   - uncut text / paste 

     CTRL-T   - check spelling 

     CTRL-C   - cursor position information 

     CTRL-F   - move forward a character

     CTRL-B   - move backward a character

     CTRL-P   - move to the previous line

     CTRL-N   - move to the next line

     CTRL-A   - move to the beginning of the current line

     CTRL-E   - move to the end of the current line

     CTRL-L   - refresh the display

     CTRL-D   - delete the character at the cursor position

     CTRL-I   - insert a tab at the current cursor position

     

     Note that cursor positioning can also be accomplished by 

     using the up, down, right and left arrow keys.

A few additional comments/notes:

The manner in which lines longer than the display width are dealt is not immediately obvious. Lines that continue beyond the edge of the display are indicated by a '$' character at the end of the line. Long lines are scrolled horizontally as the cursor moves through them.
Context sensitive help is a feature included with pico.
A file browser is included as part of the "write" and "read" file commands.

For additional details, see the pico man page.