Groom your app’s Lua environment with luaenv.

Use luaenv to pick a Lua version for your application and guarantee that your development environment matches production. It works exactly like rbenv since it is rbenv but with lua names.

Powerful in development. Specify your app's Lua version once, in a single file. Keep all your teammates on the same page. No headaches running apps on different versions of Lua. Just Works™ from the command line and with app servers. Override the Lua version anytime: just set an environment variable.

Rock-solid in production. Your application's executables are its interface with ops. With luaenv you'll never again need to cd in a cron job or Chef recipe to ensure you've selected the right runtime. The Lua version dependency lives in one place—your app—so upgrades and rollbacks are atomic, even when you switch versions.

One thing well. luaenv is concerned solely with switching Lua versions. It's simple and predictable. A rich plugin ecosystem lets you tailor it to suit your needs. Compile your own Lua versions, or use the lua-build plugin to automate the process. Specify per-application environment variables with luaenv-vars. See more plugins on the wiki.

Table of Contents

• How It Works
  • Understanding PATH
  • Understanding Shims
  • Choosing the Lua Version
  • Locating the Lua Installation
• Installation
  • Basic GitHub Checkout
    • Upgrading
  • Homebrew on Mac OS X
  • How luaenv hooks into your shell
  • Installing Lua Versions
  • Uninstalling Lua Versions
• Command Reference
  • luaenv local
  • luaenv global
  • luaenv shell
  • luaenv versions
  • luaenv version
  • luaenv rehash
  • luaenv which
  • luaenv whence
• Environment variables
• Development

How It Works

At a high level, luaenv intercepts Lua commands using shim executables injected into your PATH, determines which Lua version has been specified by your application, and passes your commands along to the correct Lua installation.

Understanding PATH

When you run a command like lua or rake, your operating system searches through a list of directories to find an executable file with that name. This list of directories lives in an environment variable called PATH, with each directory in the list separated by a colon:

/usr/local/bin:/usr/bin:/bin

Directories in PATH are searched from left to right, so a matching executable in a directory at the beginning of the list takes precedence over another one at the end. In this example, the /usr/local/bin directory will be searched first, then /usr/bin, then /bin.

Understanding Shims

luaenv works by inserting a directory of shims at the front of your PATH:

~/.luaenv/shims:/usr/local/bin:/usr/bin:/bin

Through a process called rehashing, luaenv maintains shims in that directory to match every Lua command across every installed version of Lua—luac, lake, lua, and so on.

Shims are lightweight executables that simply pass your command along to luaenv. So with luaenv installed, when you run, say, luac, your operating system will do the following:

• Search your PATH for an executable file named luac
• Find the luaenv shim named luac at the beginning of your PATH
• Run the shim named luac, which in turn passes the command along to luaenv

Choosing the Lua Version

When you execute a shim, luaenv determines which Lua version to use by reading it from the following sources, in this order:

1. The LUAENV_VERSION environment variable, if specified. You can use the luaenv shell command to set this environment variable in your current shell session.

2. The first .lua-version file found by searching the directory of the script you are executing and each of its parent directories until reaching the root of your filesystem.

3. The first .lua-version file found by searching the current working directory and each of its parent directories until reaching the root of your filesystem. You can modify the .lua-version file in the current working directory with the luaenv local command.

4. The global ~/.luaenv/version file. You can modify this file using the luaenv global command. If the global version file is not present, luaenv assumes you want to use the "system" Lua—i.e. whatever version would be run if luaenv weren't in your path.

Locating the Lua Installation

Once luaenv has determined which version of Lua your application has specified, it passes the command along to the corresponding Lua installation.

Each Lua version is installed into its own directory under ~/.luaenv/versions. For example, you might have these versions installed:

• ~/.luaenv/versions/5.1.5/
• ~/.luaenv/versions/5.2.1/
• ~/.luaenv/versions/luajit-2.0.1/

Version names to luaenv are simply the names of the directories in ~/.luaenv/versions.

Installation

Basic GitHub Checkout

This will get you going with the latest version of luaenv and make it easy to fork and contribute any changes back upstream.

1. Check out luaenv into ~/.luaenv.

   $ git clone https://github.com/cehoffman/luaenv.git ~/.luaenv

2. Add ~/.luaenv/bin to your $PATH for access to the luaenv command-line utility.

   $ echo 'export PATH="$HOME/.luaenv/bin:$PATH"' >> ~/.bash_profile

   Ubuntu Desktop note: Modify your ~/.bashrc instead of ~/.bash_profile.

   Zsh note: Modify your ~/.zshrc file instead of ~/.bash_profile.

3. Add luaenv init to your shell to enable shims and autocompletion.

   $ echo 'eval "$(luaenv init -)"' >> ~/.bash_profile

   Same as in previous step, use ~/.bashrc on Ubuntu, or ~/.zshrc for Zsh.

4. Restart your shell so that PATH changes take effect. (Opening a new terminal tab will usually do it.) Now check if luaenv was set up:

   $ type luaenv
   #=> "luaenv is a function"

5. (Optional) Install lua-build, which provides the luaenv install command that simplifies the process of installing new Lua versions.

6. (Optional) Install luaenv-luarocks, which provides the luaenv luarocks command that simplifies the process of installing LuaRocks for current Lua in luaenv.

Upgrading

If you've installed luaenv manually using git, you can upgrade your installation to the cutting-edge version at any time.

$ cd ~/.luaenv
$ git pull

To use a specific release of luaenv, check out the corresponding tag:

$ cd ~/.luaenv
$ git fetch
$ git checkout v0.3.0

If you've installed via Homebrew, then upgrade via its brew command: Not available yet

$ brew update
$ brew upgrade luaenv lua-build

Homebrew on Mac OS X

As an alternative to installation via GitHub checkout, you can install luaenv and lua-build using the Homebrew package manager on Mac OS X:

$ brew update
$ brew install luaenv lua-build

Afterwards you'll still need to add eval "$(luaenv init -)" to your profile as stated in the caveats. You'll only ever have to do this once.

How luaenv hooks into your shell

Skip this section unless you must know what every line in your shell profile is doing.

luaenv init is the only command that crosses the line of loading extra commands into your shell. Coming from RVM, some of you might be opposed to this idea. Here's what luaenv init actually does:

1. Sets up your shims path. This is the only requirement for luaenv to function properly. You can do this by hand by prepending ~/.luaenv/shims to your $PATH.

2. Installs autocompletion. This is entirely optional but pretty useful. Sourcing ~/.luaenv/completions/luaenv.bash will set that up. There is also a ~/.luaenv/completions/luaenv.zsh for Zsh users.

3. Rehashes shims. From time to time you'll need to rebuild your shim files. Doing this automatically makes sure everything is up to date. You can always run luaenv rehash manually.

4. Installs the sh dispatcher. This bit is also optional, but allows luaenv and plugins to change variables in your current shell, making commands like luaenv shell possible. The sh dispatcher doesn't do anything crazy like override cd or hack your shell prompt, but if for some reason you need luaenv to be a real script rather than a shell function, you can safely skip it.

Run luaenv init - for yourself to see exactly what happens under the hood.

Installing Lua Versions

The luaenv install command doesn't ship with luaenv out of the box, but is provided by the lua-build project. If you installed it either as part of GitHub checkout process outlined above or via Homebrew, you should be able to:

# list all available versions:
$ luaenv install -l

# install a Lua version:
$ luaenv install 5.2.1

Alternatively to the install command, you can download and compile Lua manually as a subdirectory of ~/.luaenv/versions/. An entry in that directory can also be a symlink to a Lua version installed elsewhere on the filesystem. luaenv doesn't care; it will simply treat any entry in the versions/ directory as a separate Lua version.

Uninstalling Lua Versions

As time goes on, Lua versions you install will accumulate in your ~/.luaenv/versions directory.

To remove old Lua versions, simply rm -rf the directory of the version you want to remove. You can find the directory of a particular Lua version with the luaenv prefix command, e.g. luaenv prefix luajit-2.0.1.

The lua-build plugin provides an luaenv uninstall command to automate the removal process.

Command Reference

Like git, the luaenv command delegates to subcommands based on its first argument. The most common subcommands are:

luaenv local

Sets a local application-specific Lua version by writing the version name to a .lua-version file in the current directory. This version overrides the global version, and can be overridden itself by setting the LUAENV_VERSION environment variable or with the luaenv shell command.

$ luaenv local 5.1.5

When run without a version number, luaenv local reports the currently configured local version. You can also unset the local version:

$ luaenv local --unset

Previous versions of luaenv stored local version specifications in a file named .luaenv-version. For backwards compatibility, luaenv will read a local version specified in an .luaenv-version file, but a .lua-version file in the same directory will take precedence.

luaenv global

Sets the global version of Lua to be used in all shells by writing the version name to the ~/.luaenv/version file. This version can be overridden by an application-specific .lua-version file, or by setting the LUAENV_VERSION environment variable.

$ luaenv global 5.2.1

The special version name system tells luaenv to use the system Lua (detected by searching your $PATH).

When run without a version number, luaenv global reports the currently configured global version.

luaenv shell

Sets a shell-specific Lua version by setting the LUAENV_VERSION environment variable in your shell. This version overrides application-specific versions and the global version.

$ luaenv shell luajit-2.0.1

When run without a version number, luaenv shell reports the current value of LUAENV_VERSION. You can also unset the shell version:

$ luaenv shell --unset

Note that you'll need luaenv's shell integration enabled (step 3 of the installation instructions) in order to use this command. If you prefer not to use shell integration, you may simply set the LUAENV_VERSION variable yourself:

$ export LUAENV_VERSION=luajit-2.0.1

luaenv versions

Lists all Lua versions known to luaenv, and shows an asterisk next to the currently active version.

$ luaenv versions
  5.1.5
  5.2.1
* luajit-2.0.1 (set by /Users/cehoffman/.luaenv/version)

luaenv version

Displays the currently active Lua version, along with information on how it was set.

$ luaenv version
luajit-2.0.1 (set by /Users/cehoffman/Projects/lpm/.lua-version)

luaenv rehash

Installs shims for all Lua executables known to luaenv (i.e., ~/.luaenv/versions/*/bin/*). Run this command after you install a new version of Lua, or install a rock that provides commands.

$ luaenv rehash

luaenv which

Displays the full path to the executable that luaenv will invoke when you run the given command.

$ luaenv which luac
/Users/sam/.luaenv/versions/5.2.1/bin/luac

luaenv whence

Lists all Lua versions with the given command installed.

$ luaenv whence luac
5.1.5
5.2.1

Environment variables

You can affect how luaenv operates with the following settings:

name	default	description
LUAENV_VERSION		Specifies the Lua version to be used. Also see luaenv shell
LUAENV_ROOT	~/.luaenv	Defines the directory under which Lua versions and shims reside. Also see luaenv root
LUAENV_DEBUG		Outputs debug information. Also as: luaenv --debug <subcommand>
LUAENV_HOOK_PATH	[see wiki][hooks]	Colon-separated list of paths searched for luaenv hooks.
LUAENV_DIR	$PWD	Directory to start searching for .lua-version files.

Development

The luaenv source code is hosted on GitHub. It's clean, modular, and easy to understand, even if you're not a shell hacker.

Tests are executed using Bats:

$ bats test
$ bats test/<file>.bats

Please feel free to submit pull requests and file bugs on the issue tracker.