103.8. Perform basic file editing operations using vi

Weight: 3

Description: Candidates should be able to edit text files using vi. This objective includes vi navigation, basic vi modes, inserting, editing, deleting, copying and finding text.

Key Knowledge Areas:

Navigate a document using vi
Use basic vi modes
Insert, edit, delete, copy and find text

Terms and Utilities:

vi
/, ?
h,j,k,l
i, o, a
c, d, p, y, dd, yy
ZZ, :w!, :q!, :e!

The need to learn how to use text editors in Linux is indisputable. Every system administrator and engineer deal with configuration (plain text) files on a daily basis, and most times this is done purely using one or more tools from a command-line interface (such as nano, vi, or emacs).

vi

The vi editor (visual editor) is almost certainly on every Linux and UNIX system. In fact, if a system has just one editor, it’s probably vi, so it’s worth knowing your way around in vi.

Using vi editor, we can edit an existing file or create a new file from scratch. we can also use this editor to just read a text file.

vi editor is great even trough ssh sessions!

vi or vim ?

Most Linux distributions now ship with the vim (for Vi IMproved) editor rather than classic vi. Vim is upward compatible with vi and has a graphical mode available (gvim) as well as the standard vi text mode interface. The vi command is usually an alias or symbolic link to the vim program.

There are several versions of vim: tiny, small, normal, big, and huge. We can find out what version of vim we are running and what features are included by using the command(ubuntu 16.04 here ):

root@ubuntu16-1:~# vi --version
VIM - Vi IMproved 7.4 (2013 Aug 10, compiled Nov 24 2016 16:44:48)
Included patches: 1-1689
Extra patches: 8.0.0056
Modified by pkg-vim-maintainers@lists.alioth.debian.org
Compiled by pkg-vim-maintainers@lists.alioth.debian.org
Huge version without GUI.  Features included (+) or not (-):
+acl             +farsi           +mouse_netterm   +tag_binary
+arabic          +file_in_path    +mouse_sgr       +tag_old_static
+autocmd         +find_in_path    -mouse_sysmouse  -tag_any_white
-balloon_eval    +float           +mouse_urxvt     -tcl
-browse          +folding         +mouse_xterm     +terminfo
++builtin_terms  -footer          +multi_byte      +termresponse
+byte_offset     +fork()          +multi_lang      +textobjects
+channel         +gettext         -mzscheme        +timers
...

Inorder to read, create or modify a file with vi, give the file name to it:

vi filename

if you just type vi(m) and hit enter, the vi(m) version will be displayed:

                              VIM - Vi IMproved                                
~                                                                               
~                               version 7.4.1689                                
~                           by Bram Moolenaar et al.                            
~           Modified by pkg-vim-maintainers@lists.alioth.debian.org             
~                 Vim is open source and freely distributable                   
~                                                                               
~                        Help poor children in Uganda!                          
~                type  :help iccf<Enter>       for information                  
~                                                                               
~                type  :q<Enter>               to exit                          
~                type  :help<Enter>  or  <F1>  for on-line help                 
~                type  :help version7<Enter>   for version info

Okey lets start learning vi(m):

vi modes

Vim actually has three modes: insert mode, command mode, and escape (last-line) mode. Let’s start with the default mode you’ll see when you start up Vim–command mode.

command mode : When you run vim filename to edit a file, Vim starts out in command mode. This means that all the alphanumeric keys are bound to commands, rather than inserting those characters.(save, quit, search/replace, navigate around, execute macros,...)
insert mode : To enter the insert mode, type i (for “insert”) and now the keys will behave as you’d expect. You can type normally until you want to make a correction, save the file, or perform another operation that’s reserved for command mode or escape (last-line) mode. To get out of insert mode, hit the Escape key.
escape (last-line) mode : Once you press Escape, you’re in command mode again. What if you’d like to save your file or search through your document? No problem, press : and Vim will switch to escape (last-line) mode. Vim is now waiting for you to enter a command like :w to write the file or :q to exit the editor.

If that all sounds complicated, it’s really not. It does take a few days to start training your brain to move between the modes and memorizing the most important keys for movement, commands, and so on.

Moving the cursor

The first thing you’ll want to learn is how to move around a file. When you’re in command mode, you’ll want to remember the following keys and what they do:

Key

function

Move left one character on the current line

Move down to the next line

Move up to the previous line

Move right one character on the current line

Move to the next word on the current line

Move to the next end of word on the current line

Move to the previous beginning of the word on the current line

Crtl-f

Scroll forward one page

Ctrl-b

Scroll backward one page

If you type a number before any of these commands, then the command will be executed that many times. This number is called a repetition count or simply count. For example, 5h will move left five characters. You can use repetition counts with many vi commands.

Jumping

key

function

move to top of screen

move to middle of screen

move to bottom of screen

key

function

jump forwards to the start of a word (words can contain punctuation)

jump forwards to the end of a word (words can contain punctuation)

jump backwards to the start of a word (words can contain punctuation)

key

function

jump backwards to the start of line

jump to the first non-blank character of the line

jump to the end of the line

jump to the last non-blank character of the line

go to the first line of the document

go to the last line of the document

Editing text

Now that you can open a file in vi, move around it and get out, it’s time to learn how to edit the text in the file

key( for inserting)

function

insert text before cursor, until hit

insert text at beginning of current line, until hit

append text after cursor, until hit

append text to end of current line, until hit

open and put text in a new line below current line, until hit

open and put text in a new line above current line, until hit

key(for changing)

function

replace single character under cursor (no needed)

replace characters, starting with current cursor position, until hit

change the current word with new text, starting with the character under cursor, until hit

cNw

change N words beginning with character under cursor, until hit; e.g., c5w changes 5 words

change (replace) the characters in the current line, until hit

change (replace) the entire current line, stopping when is hit

Ncc or cNc

change (replace) the next N lines, starting with the current line, stopping when is hit

key (for deleting)

function

delete single character under cursor

delete N characters, starting with character under cursor

delete the single word beginning with character under cursor

dNw

delete N words beginning with character under cursor; e.g., d5w deletes 5 words

delete start of line till the cursor

d$ and D

delete the remainder of the line, starting with current cursor position

delete entire current line

Ndd or dNd

delete N lines, beginning with the current line; e.g., 5dd deletes 5 lines

key(for cutting and pasting)

function

copy (yank, cut) the current line into the buffer

Nyy or yNy

copy (yank, cut) the next N lines, including the current line, into the buffer

put (paste) the line(s) in the buffer into the text after the current line

put (paste) the line(s) in the buffer into the text before the current line

searching

key

function

/string

search forward for occurrence of string in text

? string

search backward for occurrence of string in text

move to next occurrence of search string

move to next occurrence of search string in opposite direction

replacing

key

function

:s/old/new/

replace first old with new in just that line

:s/old/new/g

replace all old with new in just that line

:%s/old/new/g

replace all old with new throughout file

:%s/old/new/gc

replace all old with new throughout file with confirmations

:%s/old/new/gic

same as above but case insensitive

:noh

remove highlighting of search matches

Exiting

If you’re in insert mode, hit Escape. Then enter : and you’ll see a line at the bottom of the screen with a cursor ready to take input.

key

function

That will write the file to the existing filename,but don't exit.

:w file

If you don’t have a filename or want to write out to a different file name

quit (fails if there are unsaved changes)

:q!

Quit editing without saving.

:wq

write (save) and quit (throw and error if file is not writable)

:wq!

try to write and quit (if it is not writable, quit without saving! )

ZZ and :x

Exit and save the file if modified

q! or ZQ

quit and throw away unsaved changes

Press ESC to return back to the normal command mode!

When you want to write and exit from a file consider you permissions, the bellow command write out the current file using sudo:
:w !sudo tee %
:w – Write a file (actually buffer).
!sudo – Call shell with sudo command.
tee – The output of write (vim :w) command redirected using tee.
% – The % is nothing but current file name.