Text Editors

• There are two major editors generally available in most Linux distributions.
• Emacs – a text editor written in Lisp. Modules for improved editing of all kind of files. The functionality can be expanded. Works both directly in a terminal and in a graphic environment.
• Xemacs – a GUI-based version of Emacs.
• vi – a mostly terminal-based text editor, very reliable.
• vim – (vi improved) – a GUI-based version of vi.

The emacs Editor

• Emacs (Editor MACroS) appeared initially as a set of macros for another editor (TECO), around 1960. Now it's an editor by itself and the most commonly used under Linux. Versions of it exist for Windows and MacOS.
• Emacs is highly programmable and configurable in LISP (similar to Scheme). It works in text mode too but is more sensitive than other editors to the terminal properties.
• It helps with writing code in a variety of languages: C++, Python, HTML, etc. It displays the text with color-codes based on the type of file and provides automatic indentation.
• It can also read/write email, compile, etc.
• The editor works with a number of buffers, the equivalent of documents for other editors.
• To start emacs, the emacs command.
  

Emacs Buffers

• The basic file manipulated by emacs is called a buffer.
• Special buffers, belonging to the editor, whose names are between * *: 
• scratch, can be used for any temporary purpose
• Messages: contains a list of messages from emacs for all the actions we perform.
• Completions
• mail
• compilation, debug, etc. - specialized buffers for particular actions
• Every file that we edit is opened in a separate buffer.
• A status line at the bottom contains some information about the buffer: name, current line,
• Menu operations:
• The Buffers menu lists the buffers and lets us switch the active buffer. The modified but unsaved buffers are marked with a *.
• The File menu contains the usual file operations.

Emacs Key Bindings

• A key binding is a combination of keys to execute a command.
• Basic editing:
• Open a file            Ctrl-x Ctrl-f
  
• Save the file            Ctrl-x Ctrl-s
  
• Quit                     Ctrl-x Ctrl-c
• Emacs doesn't wrap the written text.
  
• Meta-q    wrap the text.
  
• Tab    language-sensitive indentation.
•  

Cut and paste:

• Any highlighted text is automatically copied (no need for a special command).
• Right-click selects the text from the previous cursor position to the click position.
  
• Easiest way to paste is the middle mouse button or the two mouse button simultaneously.
  
• Kill and Yank, equivalent of cut and paste:   Ctrl-K, Ctrl-Y
  

vi

• A text editor, written by Bill Joy in 1976. Short for Visual Interface. Improved versions or clones exist, the most popular being vim.
• It enables fast, simple, and effective text editing mostly based on simple key bindings.
• It provides fast and convenient moving around files and between files.
• "Emacs is a good operating system, while vi is a good editor."
• One must learn a good number of commands to be proficient in vi. Emacs is easier for "newbies".

vi modes

• vi works in two modes: insert mode and command mode.
• Command mode: allows you to do global operations like saving the file, searching for a string and replacing it.
• Insert mode: Everything you type in this mode is directly inserted in the text.
• Switching modes: i in command mode to insert, Esc in insert mode to switch to command.