Day 3 - Mastering vi/vim: The Beauty of an Editor You Never Have to Take Your Hands Off

📌 Key Takeaways

• vi is mode-based. Command mode (default) ↔ Insert mode (i·a·o) ↔ Last-line mode (:).
• The keys that enter insert mode differ by position — i before the cursor, a after the cursor, I start of line, A end of line, o line below, O line above.
• The three editing essentials: dd (delete line = cut) · yy (copy line) · p/P (paste). Undo with u.
• Save and quit: :wq always rewrites the file, while :x and ZZ save only if changed.
• Global substitution is :%s/old/new/g. % means "all lines in the file," and the syntax shares one root with sed.

The Heart of vi: Three Modes

vi exists almost without exception on remote servers with no graphical environment and on minimal installations. That is why it is not an option but a must for administrators.

From vi to vim. vi (visual editor) is an editor created by Bill Joy in 1976. vim (Vi IMproved) is a modern version made by Bram Moolenaar in 1991 by improving vi, adding syntax highlighting, multi-level undo, split windows, and more. On most Linux systems today, typing vi actually runs vim.

• The key to understanding vi is the mode. Pressing the same key behaves completely differently depending on which mode you are in.

• When you start vi, you begin in command mode.
• To type text, press i or similar to enter insert mode, and when you are done typing, return to command mode with Esc.
• To save or quit, press : in command mode to enter last-line mode.

Why were modes separated? In a typical editor, a letter key is input and functions are handled with Ctrl or Alt combinations. vi flips that idea: in command mode every letter key acts as an editing command. Thanks to this, you can do powerful editing in one or two keystrokes without moving your hands, as with dd (delete line) and yy (copy line). This efficiency is why vi has been loved for decades.

Entering Insert Mode

Even for the same insert mode, the cursor position differs depending on the key you enter with. This is an easily confusing area.

⚠️ Pitfall: the difference between i and a, o and O If the exam asks "Which key starts typing from after the cursor position?", the answer is a (append), not i (insert). You also need to distinguish exactly that o opens the line below and O (uppercase) the line above, and that I is the start of the line and A is the end of the line. A single uppercase or lowercase letter completely changes the result.

Cursor Movement in Command Mode

The real value of vi is in moving around while keeping your hands on the home position.

h  ←  One column left
l  →  One column right
j  ↓  One line down
k  ↑  One line up
w     To the start of the next word
b     To the start of the previous word
e     To the end of the word
0     To the very start of the line (column 0)
^     To the first character of the line (excluding whitespace)
$     To the very end of the line
gg    To the first line of the file
G     To the last line of the file
5G    To line 5 (or :5)
Ctrl+f  One screen down (forward)
Ctrl+b  One screen up (backward)

Why hjkl became arrows. The ADM-3A terminal used by Bill Joy, who created vi, had no arrow keys, and the h/j/k/l keys had arrows printed on them. That is why these four keys became the movement keys. Thanks to this convention that has lasted to this day, vim users can move quickly without lifting their hands off the home position.

Delete, Copy, and Paste

These are the editing commands performed in command mode.

vi's "cut" is also a copy. Instead of a separate clipboard, vi has a temporary storage space called a register. When you delete a line with dd, its content is stored in a register, so you can paste it elsewhere with p. In other words, dd is both "delete" and "cut." That is why, when rearranging the order of lines, a common pattern is to press dd and then p at the desired position.

Searching

• In command mode, searching starts with / (downward) and ? (upward).
• You can use regular expressions in a search. For example, /^root finds lines that start with root.

/error      Search downward for error
?error      Search upward for error
n           Go to the next match (same direction)
N           Go to the previous match (opposite direction)

Last-line (ex) Mode: Saving and Quitting

Pressing : in command mode takes you into ex mode, where you type commands at the very bottom of the screen.

⚠️ Pitfall: the subtle differences among :wq, :x, and ZZ :wq always rewrites the file regardless of whether it changed (the timestamp is updated). :x and ZZ save only if changed, so if you changed nothing they don't touch the file and the timestamp is preserved. It is a subtle difference, but it is tested on the exam, and it also matters in practice in environments where timestamps matter, such as build systems.

Substitution: A Powerful Feature of ex Mode

• In ex mode, the s (substitute) command replaces text. The syntax is very similar to sed.
• % is a range specifier meaning "all lines in the file." :%s/.../.../g is the classic pattern.

:s/old/new/          Replace the first old in the current line with new
:s/old/new/g         Replace all old in the current line with new
:%s/old/new/g        Replace all old in the whole file with new
:%s/old/new/gc       Replace in the whole file, confirming each time (confirm)
:1,10s/old/new/g     Replace within the range of lines 1 to 10
:%s/old/new/gi       Replace across the whole file, ignoring case

vi's substitution and the roots of sed. It is no coincidence that vi's ex-mode substitution :%s/old/new/g resembles sed's s/old/new/g. Both belong to one family descended from the line editor ed. If you know the lineage ed → ex → vi, it becomes natural to understand why ex-mode commands have this syntax.

Configuration: .vimrc

• You can permanently configure vim's behavior with the .vimrc file in your home directory.
• If you write into this file what you set temporarily with the :set command in ex mode, it is applied every time.

set number          " Show line numbers
set autoindent      " Automatic indentation
set tabstop=4       " Tab width of 4 columns
set expandtab       " Convert tabs to spaces
set hlsearch        " Highlight search results (highlight)
set ignorecase      " Ignore case when searching
syntax on           " Turn on syntax highlighting

Configuration files that start with a dot (.). Files that start with a dot, like .vimrc and .bashrc, are hidden files that ls doesn't show by default. The trailing rc is short for "run commands," meaning a collection of commands a program runs automatically when it starts. It is an old convention that originates from "runcom" in the early Unix-era CTSS system.

nano Overview: A Beginner-Friendly Editor

• nano is an editor with the opposite philosophy of vi.
• It has no modes, you can type right away as soon as you start it, and a guide to the shortcut keys is always displayed at the bottom of the screen.

nano file.txt       # Open a file with nano

Main shortcuts (^ is the Ctrl key):

• nano is convenient for simple configuration edits, but it lacks vi's powerful editing commands and its guaranteed availability everywhere.

emacs Overview: Another Giant

• emacs is counted alongside vi as one of the two great Unix editors. Created by Richard Stallman, it is so extensible that it is practically closer to an operating system.
• If vi is mode-based, emacs invokes every function with Ctrl/Meta (Alt) key combinations.

The vi vs emacs debate. In the "editor wars" that lasted for decades, vi formed its camp on being lightweight and available everywhere, and emacs on being infinitely extensible. From an exam and practical standpoint, the safest choice is to know how to use vi, which is installed on any minimal system.

Try It Yourself

You have to learn vi with your hands. Follow along with the following yourself.

# 1. Create a new file with vi
vi practice.txt
 
# Inside vi, in order:
# Press i to enter insert mode
# Type the content below:
#   Hello Linux
#   This is vi practice
#   Line three
# Press Esc to return to command mode
 
# 2. Cursor movement practice (in command mode)
# gg → to the first line, G → to the last line
# w → move by word, $ → end of line, 0 → start of line
 
# 3. Editing practice
# dd → delete a line, u → undo
# yy then p → copy and paste a line
 
# 4. Search and substitute
# Type /vi then Enter → search for vi, n for the next one
# Type :%s/Line/Row/g → replace Line with Row everywhere
 
# 5. Save and quit
# Type :wq then Enter
 
# 6. Check the result
cat practice.txt
rm practice.txt

• At first the mode switching is confusing, but once you get into the rhythm of "if letters aren't going in, press Esc and then i first," it quickly becomes comfortable.
• Just getting dd, yy, p, and :wq into your fingers solves 90% of server work.

📖 Glossary

• Mode : A state of vi that makes the same key behave differently. There are three: command, insert, and last-line (ex).
• Command mode : The state you first enter when you start vi. All letter keys act as editing commands.
• ex mode (last-line mode) : The command line at the bottom of the screen that you enter by pressing :. You save, quit, and substitute here.
• Register : A temporary storage space equivalent to vi's clipboard. What you dd is held here and revived with p.
• yank : vi's word for "copy." This is why copying a line is yy.
• :x / ZZ : Commands that save and exit only if the contents changed. Unlike :wq, they preserve the timestamp.
• % (range specifier) : In ex commands it means "all lines in the file." This is why :%s/old/new/g is a global substitution.
• .vimrc : The personal configuration file vim reads at startup. The trailing rc stands for "run commands."
• hjkl : vi's left, down, up, right movement keys. They originate from the ADM-3A terminal, which had no arrow keys.
• nano : A beginner-oriented editor with no modes and shortcuts shown at the bottom. Ctrl+O saves, Ctrl+X exits.
• emacs : An extensible editor that invokes every function with Ctrl/Meta combinations. It is one of the two great pillars alongside vi.