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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 editor and much more

  • pico - an easy "beginner's" editor

  • lots of others

The Standard Display Editor - vi

• 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 
       

  Begin the vi editor exercises

• 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! 
       

  Continue the vi exercises

• 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) 
       

  Continue the vi exercises

• 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! 
       

  Continue the vi exercises

• 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 
       

  Continue the vi exercises

• 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.
       

  Continue the vi exercises

• 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 
       

  Continue the vi exercises

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
       

  Continue the vi exercises

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. An example pico startup screen is available here.

• 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

• Begin the pico editor exercises

This concludes the tutorial. Return to the Table of Contents