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Groom your app’s Node environment with nenv.

nenv is a version manager for Node (Node.js / io.js). It is heavily based on rbenv.

Use nenv to pick a Node.js / io.js version for your application and guarantee that your development environment matches production. Put nenv to work with npm for painless Node upgrades and bulletproof deployments.

Table of Contents

• How It Works
  • Understanding PATH
  • Understanding Shims
  • Choosing the Node Version
  • Locating the Node Installation
• Installation
  • Basic GitHub Checkout
    • Upgrading
  • How nenv hooks into your shell
  • Installing Node Versions
  • Uninstalling Node Versions
  • Uninstalling nenv
• Command Reference
  • nenv local
  • nenv global
  • nenv shell
  • nenv versions
  • nenv version
  • nenv rehash
  • nenv which
  • nenv whence
• Environment variables
• Development

How It Works

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

Understanding PATH

When you run a command like node or gulp, 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

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

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

Through a process called rehashing, nenv maintains shims in that directory to match every Node command across every installed version of Node—node, npm, gulp and so on.

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

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

Choosing the Node Version

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

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

2. The first .node-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 .node-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 .node-version file in the current working directory with the nenv local command.

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

Locating the Node Installation

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

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

• ~/.nenv/versions/3.2.0/
• ~/.nenv/versions/0.12.7/

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

Installation

Basic GitHub Checkout

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

1. Check out nenv into ~/.nenv.

   $ git clone https://github.com/ryuone/nenv.git ~/.nenv
   

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

   $ echo 'export PATH="$HOME/.nenv/bin:$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 nenv init to your shell to enable shims and autocompletion.

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

   Same as in previous step, use ~/.bashrc on Ubuntu, or ~/.zshrc for Zsh. Make sure that export PATH="$HOME/.nenv/bin:$PATH" comes before eval "$(nenv init -)"

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

   $ nenv versions
   #=> "system"
   

Upgrading

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

$ cd ~/.nenv
$ git pull

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

$ cd ~/.nenv
$ git fetch
$ git checkout v0.0.6

How nenv hooks into your shell

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

nenv 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 nenv init actually does:

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

2. Installs autocompletion. This is entirely optional but pretty useful. Sourcing ~/.nenv/completions/nenv.bash will set that up. There is also a ~/.nenv/completions/nenv.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 nenv rehash manually.

4. Installs the sh dispatcher. This bit is also optional, but allows nenv and plugins to change variables in your current shell, making commands like nenv 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 nenv to be a real script rather than a shell function, you can safely skip it.

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

Installing Node Versions

# list all available versions:
$ nenv install -l

# install a Node version:
$ nenv install 3.2.0

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

Uninstalling Node Versions

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

To remove old Node versions, simply rm -rf the directory of the version you want to remove. You can find the directory of a particular Node version with the nenv prefix command, e.g. nenv prefix 3.2.0.

You can also run the nenv uninstall command to automate the removal process.

Uninstalling nenv

The simplicity of nenv makes it easy to temporarily disable it, or uninstall from the system.

1. To disable nenv managing your Node versions, simply remove the nenv init line from your shell startup configuration. This will remove nenv shims directory from PATH, and future invocations like node will execute the system Node version, as before nenv.

nenv will still be accessible on the command line, but your Node apps won't be affected by version switching.

2. To completely uninstall nenv, perform step (1) and then remove its root directory. This will delete all Node versions that were installed under `nenv root`/versions/ directory:

    rm -rf `nenv root`
   

   If you've installed nenv using a package manager, as a final step perform the nenv package removal. For instance, for Homebrew:

    brew uninstall nenv
   

Command Reference

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

nenv local

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

$ nenv local 3.2.0

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

$ nenv local --unset

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

nenv global

Sets the global version of Node to be used in all shells by writing the version name to the ~/.nenv/version file. This version can be overridden by an application-specific .node-version file, or by setting the NENV_VERSION environment variable.

$ nenv global 3.2.0

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

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

nenv shell

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

$ nenv shell 3.2.0

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

$ nenv shell --unset

Note that you'll need nenv'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 NENV_VERSION variable yourself:

$ export NENV_VERSION=3.2.0

nenv versions

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

$ nenv versions
  system
  0.12.4
* 3.2.0 (set by /home/madumlao/.nenv/version)

nenv version

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

$ nenv version
3.2.0 (set by /home/madumlao/.nenv/version)

nenv rehash

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

$ nenv rehash

nenv which

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

$ nenv which node
/home/madumlao/.nenv/versions/3.2.0/bin/node

nenv whence

Lists all Node versions with the given command installed.

$ nenv whence gulp
0.12.4
3.2.0

Environment variables

You can affect how nenv operates with the following settings:

Development

The nenv source code is hosted on GitHub. Help us maintain it!

nenv heavily inspired by rbenv. Please refer to rbenv for architecture and inspiration.