An ersatz-emacs text editor for unix-like systems (and msys, hence the name!) with no dependencies. It's not much, but it punches above its weight class!

• Small terminal executable editor with Emacs keybindings
• Supports many useful Emacs features like infinite undo, filtering regions, keyboard macros, etc.
• Simple codebase based on the venerable tutorial Build Your Own Text Editor.
• Decent UTF-8 support out of the box with no configuration.
• No dependencies, just a VT100/xterm-type terminal and termios.h to build.
• C99 and POSIX 2001 compliant

• No configuration except through editing the source code
• Lines in files are always separated by one linefeed (\n, ^J), including a final LF at the end of the file.
• Files and keyboard input are always in the One True Encoding, UTF-8.
• Files are plain text and do not contain nulls (though they may contain other control characters)
• Files are loaded entirely into memory using the "array of lines" data structure, making emsys unsuitable for large files or those that don't fit in memory (use joe in Emacs emulation mode)

• Syntax highlighting - too complex, would bloat the executable. I am open to a good PR, though.
• Vi(m) keys - just use vim. If you care about space or dependencies or whatever, you can use elvis or busybox vi or something. If you fork and make a vi version, however, open a ticket and I will link it here.
• Lisp - just use Real Emacs™ or Gomacs.
• Horizontal splits - it would complicate the rendering code, especially if I continue to support multilines. Explore the Gomacs commit/issue history if you don't believe me!

You will need to be running on msys2 proper, not the mingw64 version, because you need termios (sorry, but it's a must). Install the compliers and libraries:

pacman -S msys2-devel msys2-runtime-devel

Then, make && make install and you should be laughing.

No dependencies (yet), so long as you have make and a C compiler you should be able to just make && sudo make install.

emsys is not a 'modal' editor - text entered goes straight into the buffer, without having to enter an insert mode.

Keybindings below are described in the usual Emacs format (C-x means Control-x, M-x means Alt-x or Escape then x).

• Buffer = An open file or pseudo-file which can be typed into
• Window = A section on the screen displaying a buffer
• Point = The position of the cursor in the file
• Mark = A position in the file marked using C-@
• Region = The area between point and mark

• C-x C-s - Save buffer
• C-x k - Kill buffer
• C-x C-f - Open file
• C-x C-c - Quit
• M-x ... - Run named command
• M-x version - Display version information

• C-n or DOWN - Move cursor to next line
• C-p or UP - Move cursor to previous line
• C-f or RIGHT - Move cursor forward
• C-b or LEFT - Move cursor backward
• M-f - Move cursor forward word
• M-b - Move cursor backward word
• M-n - Move cursor to next paragraph
• M-p - Move cursor to previous paragraph
• M-< - Move cursor to start of buffer
• M-> - Move cursor to end of buffer
• C-a or HOME - Move cursor to start of line
• C-e or END - Move cursor to end of line
• C-v or PGDN - Move cursor down a page/screen
• C-z or M-v or PGUP - Move cursor up a page/screen
• C-s - Search
• M-g - Goto line number

• C-_ - Undo (this is Control-/ on most terminals)
• C-x C-_ - Redo (keep pressing C-_ to keep redoing)
• C-@ - Set mark (this is Control-SPACE on most terminals)
• C-x C-x - Swap mark and point
• C-x h - Mark the entire buffer
• C-w - Kill (cut) current region
• M-w - Copy current region
• C-y - Yank (paste)
• M-| - Filter region through shell command. This even works with pipes!
• C-j - Insert a newline and indent (indentation copied from previous line)
• C-o - Insert a newline but do not move the point
• C-i (TAB) - Indent current line by either one tab or the current space indentation level. To insert a literal tab, C-q C-i
• SHIFT-TAB/BACKTAB - Unindent current line by either one tab or the current space indentation level.
• BACKSPACE - Delete backwards
• C-d or DELETE - Delete forwards
• M-BACKSPACE - Delete backwards word
• M-d - Delete forwards word
• C-u - Delete to beginning of line
• C-k - Delete to end of line
• M-% - Query replace, that is, interactive search and replace. Emsys' version works very much like GNU Emacs', save for the fact that we don't have recursive editing, so C-r just replaces the current occurrence with the string prompted for without changing the replacement.
• M-x replace-string - Replace one string with another in the region
• M-x replace-regexp - Replace first match of given regular expression per line in the region with given string
• M-x indent-tabs - Use tabs for indentation in current buffer (the default)
• M-x indent-spaces - Use spaces for indentation in current buffer. You will be prompted for the number of spaces to use.
• M-x whitespace-cleanup - Cleanup whitespace in current buffer. Beware, this clears the undos and redos.
• C-t - Transpose (swap) characters around cursor, e.g. a|b -> b|a
• M-t - Transpose words
• M-u - Uppercase word (foo -> FOO)
• M-l - Lowercase word (FOO -> foo)
• M-c - Capitalize word (foo -> Foo)
• C-q - Insert next character raw (allowing you to enter e.g. raw control characters - be careful with nulls!)
• M-/ - Autocomplete current "word" (one or more alphanumeric or unicode characters). E.g. foo -> foobar.

Note that commands dealing with capitalization only work for ASCII letters - any other characters will be ignored.

If you want to change how paragraph and word endings are calculated, edit the file bound.c.

• C-x b - Switch buffer
• C-x <left> - Previous buffer
• C-x <right> - Next buffer
• C-x o - Switch window
• C-x 0 - Kill current window
• C-x 1 - Kill other windows (make current the only one)
• C-x 2 - Create new window
• C-l - Center cursor in window
• M-x toggle-truncate-lines or C-x x t - Toggles line wrap off/on

• C-x ( - Start defining keyboard macro
• C-x ) - Stop defining keyboard macro
• C-x e - Execute macro (stopping definition if currently defining) - press e again to repeat the macro
• C-x C-z - Suspend emsys. Most of the time this will take you back to the shell, where you can run fg to return emsys to the foreground.
• M-x revert - Reload file on disk into current buffer. Useful if you want to use sed, go fmt, etc. to do text operations on files.
• C-x = - Describe cursor position (displays information about character at point)
• M-0 to M-9 - Type in universal argument (in most cases, this just repeats the next command typed N times). E.g. M-8 M-0 * will type 80 asterisks.

Registers let you store a point, string (region), rectangle (see below), number, or keyboard macro. Every register has a name, which must be one ASCII character (including control characters, except C-g since that's the universal cancel button).

• C-x r j - Jump to point stored in register
• C-x r a - Store macro in register. Also C-x r m, for now at least.
• C-x r n - Store number (i.e. universal argument entered with alt-numbers) in register.
• C-x r C-@ or C-x r SPACE - Store point in register.
• C-x r s - Store region (string) in register.
• C-x r + - Increment number in register, or add region to string in register.
• C-x r v or M-x view-register - View contents of register.
• C-x r r - Copy rectangle to register.

Rectangles are the rectangular space between point and mark; all characters from the leftmost column to the rightmost column within the topmost line to the bottommost line.

• C-x r t - string-rectangle: Replace rectangle contents with given string on each line.
• C-x r k or C-x r C-w - kill-rectangle: Kill (cut) rectangle.
• C-x r M-w - copy-rectangle: Copy rectangle
• C-x r y - yank-rectangle: Yank (paste) rectangle.
• C-x r r - rectangle-to-register: Copy rectangle to register.

emsys uses kokke's tiny-regex-c for regular expression support, and has the following syntax for regular expressions:

• . Dot, matches any character
• ^ Start anchor, matches beginning of string
• $ End anchor, matches end of string
• * Asterisk, match zero or more (greedy)
• + Plus, match one or more (greedy)
• ? Question, match zero or one (non-greedy)
• [abc] Character class, match if one of {'a', 'b', 'c'}
• [^abc] Inverted class, match if NOT one of {'a', 'b', 'c'}
• [a-zA-Z] Character ranges, the character set of the ranges { a-z | A-Z }
• \s Whitespace, \t \f \r \n \v and spaces
• \S Non-whitespace
• \w Alphanumeric, [a-zA-Z0-9_]
• \W Non-alphanumeric
• \d Digits, [0-9]
• \D Non-digits

• By Nicholas Carroll

Licensed MIT.