mle

mle is a small, flexible, terminal-based text editor written in C.

Runs on Linux, Windows (cygwin or WSL), FreeBSD, and macOS.

Demos

• Emacs-style jump
• Large file benchmark
• Older demos

Aims

• Keep codebase small and hackable
• Minimize build-time and run-time dependencies
• Make extensible and configurable
• Favor simplicity over portability
• Use shell commands to enhance functionality (e.g., grep, tree)

Features

• Small codebase (<10k sloc)
• Full UTF-8 support
• Syntax highlighting
• Stackable key maps (modes)
• Extensible via Lua
• Scriptable rc file
• Key macros
• Multiple splittable windows
• Regex search and replace
• Large file support
• Incremental search
• Linear undo and redo
• Multiple cursors
• Auto indent
• Headless mode
• Navigation via ctags
• Movement via less
• Fuzzy file search via fzf
• File browsing via tree
• File grep via grep
• String manip via perl

Building

$ sudo apt install git build-essential libtool automake # or equivalent
$
$ git clone --recursive https://github.com/adsr/mle.git
$ cd mle
$ make mle_vendor=1

To build a completely static binary, try make mle_vendor=1 mle_static=1.

You can also run plain make to link against system libraries instead of vendor/. Note this requires the following packages to be installed:

uthash-dev
liblua5.3-dev
libpcre3-dev
libtermbox-dev

Installing

To install to /usr/local/bin:

$ make install

To install to a custom directory, supply prefix, e.g.:

$ make install prefix=/usr # /usr/bin/mle

Basic usage

$ mle             # Open blank buffer
$ mle one.c       # Edit one.c
$ mle one.c:100   # Edit one.c at line 100
$ mle one.c two.c # Edit one.c and two.c
$ mle -h          # Show command line help

The default key bindings are intuitive. Input text as normal, use directional keys to move around, use Ctrl-S to save, Ctrl-O to open, Ctrl-X to exit.

Press F2 for full help.

Advanced usage: mlerc

mle is customized via command line options. Run mle -h to view all cli options.

To set default options, make an rc file named ~/.mlerc (or /etc/mlerc). The contents of the rc file are any number of cli options separated by newlines. Lines that begin with a semi-colon are interpretted as comments.

If ~/.mlerc is executable, mle executes it and interprets the resulting stdout as described above. For example, consider the following snippet from an executable ~/.mlerc bash(1) script:

# Define 'test' kmap
echo '-Ktest,,1'

# M-q: replace grep with git grep if `.git` exists
if [ -d ".git" ]; then
  echo '-kcmd_grep,M-q,git grep --color=never -P -i -I -n %s 2>/dev/null'
fi

# Set default kmap
echo '-n test'

This overrides the built-in grep command with git grep if .git exists in the current working directory.

Shell command integration

The following programs will enable or enhance certain features of mle if they exist in PATH.

• bash (tab completion)
• fzf (fuzzy file search)
• grep (file grep)
• less (less integration)
• perl (perl 1-liners)
• readtags (ctags integration)
• tree (file browsing)

Arbitrary shell commands can also be run via cmd_shell (M-e by default). If any text is selected, it is sent to stdin of the command. Any resulting stdout is inserted into the text buffer.

Advanced usage: Headless mode

mle provides support for non-interactive editing which may be useful for using the editor as a regular command line tool. In headless mode, mle reads stdin into a buffer, applies a startup macro if specified, and then writes the buffer contents to stdout. For example:

$ echo -n hello | mle -M 'test C-e space w o r l d enter' -p test
hello world

If stdin is a pipe, mle goes into headless mode automatically. Headless mode can be explicitly enabled or disabled with the -H option.

If stdin is a pipe and headless mode is disabled via -H0, mle reads stdin into a new buffer and then runs as normal in interactive mode.

Advanced usage: Scripting

mle is extensible via the Lua programming language. Scripts are loaded via the -x cli option. Commands registered by scripts can be mapped to keys as normal via -k. See uscript.lua for a simple example.

There is also a wren branch with Wren scripting support. That work is on pause.

Known bugs

• Multi-line style rules don't work properly when overlapped/staggered.

Forks

• eon - mouse support and Notepad-like selections
• turbo-mle - Turbo Vision port

Acknowledgments

mle makes extensive use of the following libraries.

• uthash for hash maps and linked lists
• termbox for TUI
• PCRE for syntax highlighting and search