vi

What it does

vi is a modal terminal text editor: keystrokes mean different things depending on the current mode. In normal mode keys are commands (move, delete, copy, search); in insert mode keys are typed as literal text. This split lets experienced users edit extremely quickly without ever reaching for a mouse, at the cost of a steeper learning curve than a simple graphical editor. vi (or its vastly more common modern implementation, Vim) is preinstalled on nearly every Unix-like system, making it the one editor you can almost always count on being available.

Beginner examples

• vi file.txt — open a file for editing
• Press i to enter insert mode and start typing
• Press Esc to return to normal mode
• Type :wq and press Enter to save and quit
• Type :q! and press Enter to quit without saving

vi ~/.bashrc

Advanced examples

• Delete the current line: dd (in normal mode); delete 3 lines: 3dd
• Copy (yank) the current line and paste it below: yy then p
• Search forward for text and jump to the next match: /pattern then n
• Open a file with the cursor already on line 42: vi +42 script.sh
• Substitute text on every line of the file (Ex command): :%s/old/new/g

vi +/TODO notes.txt

Common mistakes

• Typing text while still in normal mode, which triggers a flurry of unexpected commands instead of inserting characters — always confirm you're in insert mode (often shown as -- INSERT -- at the bottom) before typing content.
• Trying to quit with Ctrl+C or closing the terminal instead of :q/:wq, leaving swap files behind or losing edits.
• Forgetting Esc before typing a command like :wq, so the colon and letters get inserted as literal text instead of being interpreted as a command.
• Panicking and force-quitting after an accidental large deletion instead of pressing u to undo.

Tips

• Press u to undo the last change, and Ctrl+R to redo — essential for recovering from mistakes without quitting.
• Use :set number to show line numbers, which makes navigating with :NUM (jump to line) much easier.
• dw deletes a word, x deletes a single character, and . repeats the last change — small building blocks that combine into fast edits.

Best practices

• Learn to stay in normal mode by default and only enter insert mode briefly to type, rather than staying in insert mode and using arrow keys like a basic text editor — that's where vi's efficiency comes from.
• Use :wq (or ZZ) deliberately rather than muscle-memory Ctrl+S, which does nothing useful in a terminal editor and can freeze the terminal (Ctrl+Q resumes it).
• When editing config files on remote servers over SSH, vi/Vim is worth learning well precisely because it's reliably available even on minimal systems where nothing graphical exists.

Real-world use cases

• Editing a server configuration file over an SSH session where no graphical editor is available.
• Making a quick fix to a script during an incident, where speed and no dependency on a GUI matter.
• Editing commit messages, crontabs, or other files that many Unix tools open in vi (or the system's $EDITOR) by default.

Common interview questions

• What's the difference between normal mode and insert mode in vi? In normal mode, keystrokes are interpreted as commands (movement, deletion, copying); in insert mode, keystrokes are typed as literal text into the file.
• How do you save and quit vi? :wq saves and quits; :q! quits and discards unsaved changes; ZZ is a normal-mode shortcut equivalent to save-and-quit.
• What do dd, yy, and p do in vi? dd deletes the current line, yy copies (yanks) the current line, and p pastes the most recently deleted or yanked text after the cursor.