Unix / Linux Fundamentals

1. VI/VIM Text Editors

2. VI/VIM Overview
• VI is an interactive text-based editor which can be used to
create and/or change files, it is the standard in UNIX systems
for several decades.
• VI is hard to master but once mastered, it becomes a very
powerful and quick editing tool.
• The Linux version is called VIM (VI Improved) which makes
editing easier as it contains some in-editor navigation and
editing tools which make the user’s life easier.
• Some alternatives to VI/VIM are:
 EMACS
 Pico
 Nano
 gedit

3. The VI Command
• Once started, VI will fill the entire terminal screen until exited
and returned to the shell prompt.
• VI is old, it originated from a predecessor called “ed” which
was used on printer terminals hence its commands and
shortcuts are different than the keyboard shortcuts we know
in modern systems, such as CTRL-[letter].
• Starting VI:
 vi [filename(s)] – enters the editor while editing the file(s) specified.
 view [filename(s)] – opens the file(s) in read-only mode.
 vi –r [filename] – recovers a crashed file.

4. VI Modes
• VI has three work modes:
 Insert mode – used for adding / editing text; hit ESC in insert mode to
return to command mode.
 Command mode – this is the default mode that VI enters once it is
executed; the keys we hit will not be displayed on screen but this
mode does allow us to use VI’s commands, which are short sequences
of characters and key-combinations.
 Last-line mode – displays a cursor in the bottom line of VI, allowing us
to see the commands we type in; hit <CR> in order to return to
command mode.
• Note that in order to move from Insert mode to Last-line
mode, we must first pass through Command mode.

5. Insert Mode
• In order to append or insert new text we can use one of the
following options:
 a – Append text after cursor.
 A – Append text at the end of the current line.
 i – Insert text before the cursor.
 I – Insert text at the beginning of the line.
 o – Open a new line below the cursor.
 O – Open a new line above the cursor.
• There are many ways to achieve the same goal so there is no
need to remember all of the shortcuts.

6. Cursor Movement
• VIM supports moving the cursor around with the keyboard
arrows; VI only allows arrow navigation in newer versions.
• We can use the following alternatives to move around:
 0 – go to the beginning of the line.
 $ - go to the end of the line.
 [n]G – jump to line number [n].
 G – jump to last line in the file.
 gg – jump to the first line in the file.
 b – jump to the beginning of the word.
 e – jump to the end of the word.
 w – jump to the beginning of the next word.
 ^L – refresh the screen
• These are just some of the basic controls, there are many
more.

7. Command Mode
• Pressing ESC returns VI from insert to command mode.
• Basic command structure in VI:
 [count][command][scope]
• Let’s break down the command 10dw for example:
 10 – this is the count of objects we wish the command to affect.
 d – “d” refers to delete.
 w – “w” is the scope, in this case – words.
• The above command will delete 10 words, beginning at the
current location of the cursor.

8. Delete Commands
• x – delete 1 character right of the cursor.
• X – delete 1 character left of the cursor.
• dd – delete the entire current line
• dw – deletes to the beginning of the next word
• d3l – deletes the next 3 characters. (l is lower-case L)
• d0 – deletes to the beginning of the line.
• d$ - deletes to the end of the line.
• d1G – deletes to the beginning of the file.
• dG – deletes to the end of the file.
• D - deletes to the end of the line.
• Note that “d” commands delete to a buffer, as long as we
have not quit VI we can always use undo/redo.

9. Change Commands
• r – replace (overwrite) under the cursor.
• R – enter Replace mode (overwrites any existing text)
• cc – changes a complete line.
• cw – changes to the beginning of the next word.
• c3l – changes the next 3 characters.
• c0 – changes to the beginning of the line.
• c$ – changes to the end of the line.
• c1G – changes to the beginning of the file.
• cG – changes to the end of the file.
• C – changes to the end of the line.

10. Cut, Copy & Paste Commands
• y – yanks (copies) text to buffer
• yy - yanks a complete line
• yw – yanks to the beginning of the next word
• y0 – yanks to the beginning of the line
• y$ – yanks to the end of the line
• The “d” commands are used to cut text.
• p – paste everything in the buffer after the cursor location.
• P – paste everything in the buffer before the cursor.

11. Misc Commands
• u – undo last change
• J – join current and next line
• . – repeat last command
• ~ - invert letter case and move on character to the right.
• ZZ – Save changes and exit VI

12. Last-Line Mode
• Search in VI:
 /[pattern] – search forward for pattern matches
 ?[pattern] – search backwards for pattern matches
 n – repeat last search
 N – repeat last search in the opposite direction
• Search & Replace:
 :s/search-string/replace-with-string/g – this command will search for
“search-string” throughout the file and replace it with “replace-with-
string”.
 :10,20s/search-string/replace-with-string/g – same as above but the
search will be performed only between lines 10 and 20.
 :s/search-string/replace-with-string/gc – this command will search
for “search-string” throughout the file and replace it with “replace-
with-string” but ask for confirmation before each replacement.

13. File Commands
• :r [filename] – read the file and place its contents under the
cursor.
• :w – write (saves changes).
• :w! – override write-protection mode and save changes.
• :w [filename] – save into a file with the specific name.
• :wq – save changes and quit VI
• :x – save changes and quit VI
• :q – quit without saving
• :q! – force quit without saving
• :![command] – execute a shell command
• :r![command] – execute a shell command and place its output in the file
being edited.

14. VI Options
• VI has many options that control its looks and behaviour.
• For the full list of options, type: “:set all”
• To enable an option, such as line numbering for example, use:
 :set number
• To disable an options, use:
 :set nonumber
• The above rule is true for any one of VI’s options.