rtx

Polyglot runtime manager (asdf rust clone)

30 Second Demo

The following shows using rtx to install nodejs and jq into a project using a .tool-versions file. hyperfine is used to show the performance using rtx vs asdf. (See Performance). Note that calling which node gives us a real path to the binary, not a shim.

Features

• asdf-compatible - rtx is compatible with asdf plugins and .tool-versions files. It can be used as a drop-in replacement.
• Polyglot - compatible with any language, so no more figuring out how nvm, nodenv, pyenv, etc work individually—just use 1 tool.
• Fast - rtx is written in Rust and is very fast. 20x-200x faster than asdf.
• No shims - shims (used by asdf) cause problems, they break which node, and add overhead. We don't use them.
• Better UX - asdf is full of strange UX decisions (like asdf plugin add but also asdf install). We've taken care to make rtx easy to use.
• Fuzzy matching and aliases - no need to specify exact version numbers like with asdf.
• One command install - No need to manually install each plugin, just run rtx install and it will install all the plugins you need.

Quickstart

Install rtx (other methods here):

$ curl https://rtx.pub/rtx-latest-macos-arm64 > ~/bin/rtx
$ chmod +x ~/bin/rtx
$ rtx --version
rtx 1.13.0

Hook rtx into to your shell. This will automatically add ~/bin to PATH if it isn't already. (choose one, and open a new shell session for the changes to take effect):

$ echo 'eval "$(~/bin/rtx activate bash)"' >> ~/.bashrc
$ echo 'eval "$(~/bin/rtx activate zsh)"' >> ~/.zshrc
$ echo '~/bin/rtx activate fish | source' >> ~/.config/fish/config.fish

Warning

If you use direnv, you will want to activate direnv before rtx. There is also an alternative way to use rtx inside of direnv, see here.

Install a runtime and set it as the default:

$ rtx install nodejs@18
$ rtx global nodejs@18
$ node -v
v18.10.9

Note

rtx install is optional, rtx global will prompt to install the runtime if it's not already installed. This is configurable in ~/.config/rtx/config.toml.

About

rtx is a tool for managing programming language and tool versions. For example, use this to install a particular version of node.js and ruby for a project. Using rtx activate, you can have your shell automatically switch to the correct node and ruby versions when you cd into the project's directory. Other projects on your machine can use a different set of versions.

rtx is inspired by asdf and uses asdf's vast plugin ecosystem under the hood. However, it is much faster than asdf and has a more friendly user experience. For more on how rtx compares to asdf, see below. The goal of this project was to create a better front-end to asdf.

It uses the same .tool-versions file that asdf uses. It's also compatible with idiomatic version files like .node-version and .ruby-version. See Legacy Version Files below.

Come chat about rtx on discord.

How it works

rtx installs as a shell extension (e.g. rtx activate zsh) that sets the PATH environment variable to point your shell to the correct runtime binaries. When you cd into a directory containing a .tool-versions file, rtx will automatically activate the correct versions.

Every time your prompt starts it will call rtx hook-env to fetch new environment variables. This should be very fast and it exits early if the the directory wasn't changed or the .tool-versions files haven't been updated. On my machine this takes 4ms in the fast case, 14ms in the slow case. See Performance for more on this topic.

Unlike asdf which uses shim files to dynamically locate runtimes when they're called, rtx modifies PATH ahead of time so the runtimes are called directly. This is not only faster since it avoids any overhead, but it also makes it so commands like which node work as expected. This also means there isn't any need to run asdf reshim after installing new runtime binaries.

Common example commands

rtx install nodejs@20.0.0       Install a specific version number
rtx install nodejs@20.0         Install a fuzzy version number
rtx local nodejs@20             Use node-20.x in current project
rtx global nodejs@20            Use node-20.x as default

rtx install nodejs              Install the version specified in .tool-versions
rtx local nodejs@latest         Use latest node in current directory
rtx global nodejs@system        Use system node as default

rtx x nodejs@20 -- node app.js  Run `node app.js` with the PATH pointing to node-20.x

Installation

Warning

Regardless of the installation method, when uninstalling rtx, remove RTX_DATA_DIR folder (usually ~/.local/share/rtx) to fully clean up.

Standalone

Note that it isn't necessary for rtx to be on PATH. If you run the activate script in your rc file, rtx will automatically add itself to PATH.

$ curl https://rtx.pub/install.sh | sh

or if you're allergic to | sh:

$ curl https://rtx.pub/rtx-latest-macos-arm64 > /usr/local/bin/rtx

It doesn't matter where you put it. So use ~/bin, /usr/local/bin, ~/.local/share/rtx/bin/rtx or whatever.

Supported architectures:

• x64
• arm64

Supported platforms:

• macos
• linux

If you need something else, compile it with cargo.

Homebrew

There are 2 ways to install rtx with Homebrew. The recommended method is to use the custom tap which will always contain the latest release.

$ brew install jdxcode/tap/rtx

Alternatively, you can use the built-in tap (homebrew-core), which will be updated once Homebrew maintainers merge the PR for a new release:

$ brew install rtx

Cargo

Build from source with Cargo.

$ cargo install rtx-cli

Do it faster with cargo-binstall:

$ cargo install cargo-binstall
$ cargo binstall rtx-cli

npm

rtx is available on npm as precompiled binaries. This isn't a node.js package, just distributed via npm. It can be useful for JS projects that want to setup rtx via package.json or npx.

$ npm install -g @jdxcode/rtx

Or use npx if you just want to test it out for a single command without fully installing:

$ npx @jdxcode/rtx exec python@3.11 -- python some_script.py

GitHub Releases

Download the latest release from GitHub.

$ curl https://github.com/jdxcode/rtx/releases/download/v1.13.0/rtx-v1.13.0-linux-x64 | tar -xJv
$ mv rtx/bin/rtx /usr/local/bin

apt

For installation on Ubuntu/Debian:

wget -qO - https://rtx.pub/gpg-key.pub | gpg --dearmor | sudo tee /usr/share/keyrings/rtx-archive-keyring.gpg 1> /dev/null
echo "deb [signed-by=/usr/share/keyrings/rtx-archive-keyring.gpg arch=amd64] https://rtx.pub/deb stable main" | sudo tee /etc/apt/sources.list.d/rtx.list
sudo apt update
sudo apt install -y rtx

Warning

If you're on arm64 you'll need to run the following:

echo "deb [signed-by=/usr/share/keyrings/rtx-archive-keyring.gpg arch=arm64] https://rtx.pub/deb stable main" | sudo tee /etc/apt/sources.list.d/rtx.list

dnf

For Fedora, CentOS, Amazon Linux, RHEL and other dnf-based distributions:

dnf install -y dnf-plugins-core
dnf config-manager --add-repo https://rtx.pub/rpm/rtx.repo
dnf install -y rtx

yum

yum install -y yum-utils
yum-config-manager --add-repo https://rtx.pub/rpm/rtx.repo
yum install -y rtx

apk (coming soon)

For Alpine Linux:

apk add rtx --repository=http://dl-cdn.alpinelinux.org/alpine/edge/testing/

aur

For Arch Linux:

git clone https://aur.archlinux.org/rtx.git
cd rtx
makepkg -si

Other Shells

Bash

$ echo 'eval "$(rtx activate bash)"' >> ~/.bashrc

Fish

$ echo 'rtx activate fish | source' >> ~/.config/fish/config.fish

Xonsh

Since .xsh files are not compiled you may shave a bit off startup time by using a pure Python import: add the code below to, for example, ~/.config/xonsh/rtx.py config file and import rtx it in ~/.config/xonsh/rc.xsh:

from pathlib        	import Path
from xonsh.built_ins	import XSH

ctx = XSH.ctx
rtx_init = subprocess.run([Path('~/bin/rtx').expanduser(),'activate','xonsh'],capture_output=True,encoding="UTF-8").stdout
XSH.builtins.execx(rtx_init,'exec',ctx,filename='rtx')

Or continue to use rc.xsh/.xonshrc:

echo 'execx($(~/bin/rtx activate xonsh))' >> ~/.config/xonsh/rc.xsh # or ~/.xonshrc

Given that rtx replaces both shell env $PATH and OS environ PATH, watch out that your configs don't have these two set differently (might throw os.environ['PATH'] = xonsh.built_ins.XSH.env.get_detyped('PATH') at the end of a config to make sure they match)

Something else?

Adding a new shell is not hard at all since very little shell code is in this project. See here for how the others are implemented. If your shell isn't currently supported I'd be happy to help you get yours integrated.

Configuration

.tool-versions

The .tool-versions file is used to specify the runtime versions for a project. An example of this is:

nodejs      20.0.0       # comments are allowed
ruby        3            # can be fuzzy version
shellcheck  latest       # also supports "latest"
jq          1.6
erlang      ref:master   # compile from vcs ref
golang      prefix:1.19  # uses the latest 1.19.x version—needed in case "1.19" is an exact match
shfmt       path:./shfmt # use a custom runtime

Create .tool-versions files manually, or use rtx local to create them automatically. See the asdf docs for more info on this file format.

Legacy version files

RTX supports "legacy version files" just like asdf.

It's behind a config setting "legacy_version_file", but it's enabled by default (asdf defaults to disabled). You can disable these with rtx settings set legacy_version_file false. There is a performance cost to having these when they're parsed as it's performed by the plugin in bin/parse-version-file. However these are cached so it's not a huge deal. You may not even notice.

These are ideal for setting the runtime version of a project without forcing other developers to use a specific tool like rtx/asdf.

They support aliases, which means you can (finally) have an .nvmrc file with lts/hydrogen and it will work in rtx and nvm. This wasn't possible with asdf.

Here are some of the supported legacy version files:

Plugin	"Legacy" (Idiomatic) Files
crystal	.crystal-version
elixir	.exenv-version
golang	.go-version, go.mod
java	.java-version
nodejs	.nvmrc, .node-version
python	.python-version
ruby	.ruby-version, Gemfile
terraform	.terraform-version, .packer-version, main.tf
yarn	.yvmrc

Note

asdf calls these "legacy version files" so we do too. I think this is a bad name since it implies that they shouldn't be used—which is definitely not the case IMO. I prefer the term "idiomatic" version files since they're version files not specific to asdf/rtx and can be used by other tools. (.nvmrc being a notable exception, which is tied to a specific tool.)

Global config: ~/.config/rtx/config.toml

rtx can be configured in ~/.config/rtx/config.toml. The following options are available (defaults shown):

# whether to prompt to install plugins and runtimes if they're not already installed
missing_runtime_behavior = 'prompt' # other options: 'ignore', 'warn', 'prompt', 'autoinstall'

# plugins can read the versions files used by other version managers (if enabled by the plugin)
# for example, .nvmrc in the case of nodejs's nvm
legacy_version_file = true         # enabled by default (different than asdf)

# configure `rtx install` to always keep the downloaded archive
always_keep_download = false        # deleted after install by default

# configure how frequently (in minutes) to fetch updated plugin repository changes
# this is updated whenever a new runtime is installed
# (note: this isn't currently implemented but there are plans to add it: https://github.com/jdxcode/rtx/issues/128)
plugin_autoupdate_last_check_duration = 10080 # (one week) set to 0 to disable updates

jobs = 4 # number of plugins or runtimes to install in parallel. The default is `4`.

verbose = false # see explanation under `RTX_VERBOSE`

[alias.nodejs]
my_custom_node = '18'  # makes `rtx install nodejs@my_custom_node` install node-18.x
                       # this can also be specified in a plugin (see below in "Aliases")

These settings can also be managed with rtx settings ls|get|set|unset.

Environment variables

rtx can also be configured via environment variables. The following options are available:

RTX_MISSING_RUNTIME_BEHAVIOR

This is the same as the missing_runtime_behavior config option in ~/.config/rtx/config.toml.

$ RTX_MISSING_RUNTIME_BEHAVIOR=ignore rtx install nodejs@20
$ RTX_NODEJS_VERSION=20 rtx exec -- node --version

RTX_DATA_DIR

This is the directory where rtx stores its data. The default is ~/.local/share/rtx.

RTX_CACHE_DIR

This is the directory where rtx stores cache. The default is ~/.cache/rtx on Linux and ~/Library/Caches/rtx on macOS.

RTX_CONFIG_FILE

This is the path to the config file. The default is ~/.config/rtx/config.toml. (Or $XDG_CONFIG_HOME/config.toml if that is set)

RTX_DEFAULT_TOOL_VERSIONS_FILENAME

Set to something other than ".tool-versions" to have rtx look for configuration with alternate names.

RTX_${PLUGIN}_VERSION

Set the version for a runtime. For example, RTX_NODEJS_VERSION=20 will use nodejs@20.x regardless of what is set in .tool-versions.

RTX_LEGACY_VERSION_FILE

Plugins can read the versions files used by other version managers (if enabled by the plugin) for example, .nvmrc in the case of nodejs's nvm.

RTX_LOG_LEVEL=trace|debug|info|warn|error

Can also use RTX_DEBUG=1, RTX_TRACE=1, and RTX_QUIET=1. These adjust the log output to the screen.

RTX_LOG_FILE=~/.rtx/rtx.log

Output logs to a file.

RTX_LOG_FILE_LEVEL=trace|debug|info|warn|error

Same as RTX_LOG_LEVEL but for the log file output level. This is useful if you want to store the logs but not have them litter your display.

RTX_JOBS=1

Set the number plugins or runtimes to install in parallel. The default is 4.

RTX_VERBOSE=1

This shows the installation output during rtx install and rtx plugin install. This should likely be merged so it behaves the same as RTX_DEBUG=1 and we don't have 2 configuration for the same thing, but for now it is it's own config.

RTX_HIDE_OUTDATED_BUILD=1

If a release is 12 months old, it will show a warning message every time it launches:

rtx has not been updated in over a year. Please update to the latest version.

You likely do not want to be using rtx if it is that old. I'm doing this instead of autoupdating. If, for some reason, you want to stay on some old version, you can hide this message with RTX_HIDE_OUTDATED_BUILD=1.

Aliases

rtx supports aliasing the versions of runtimes. One use-case for this is to define aliases for LTS versions of runtimes. For example, you may want to specify lts/hydrogen as the version for nodejs@18.x. So you can use the runtime with nodejs lts/hydrogen in .tool-versions.

User aliases can be created by adding an alias.<PLUGIN> section to ~/.config/rtx/config.toml:

[alias.nodejs]
my_custom_18 = '18'

Plugins can also provide aliases via a bin/list-aliases script. Here is an example showing node.js versions:

#!/usr/bin/env bash

echo "lts/hydrogen 18"
echo "lts/gallium 16"
echo "lts/fermium 14"

Note:

Because this is rtx-specific functionality not currently used by asdf it isn't likely to be in any plugin currently, but plugin authors can add this script without impacting asdf users.

Plugins

rtx uses asdf's plugin ecosystem under the hood. See https://github.com/asdf-vm/asdf-plugins for a list.

FAQs

I don't want to put a .tool-versions file into my project since git shows it as an untracked file.

You can make git ignore these files in 3 different ways:

• Adding .tool-versions to project's .gitignore file. This has the downside that you need to commit the change to the ignore file.
• Adding .tool-versions to project's .git/info/exclude. This file is local to your project so there is no need to commit it.
• Adding .tool-versions to global gitignore (core.excludesFile). This will cause git to ignore .tool-versions files in all projects. You can explicitly add one to a project if needed with git add --force .tool-versions.

How do I create my own plugin?

Just follow the asdf docs. Everything should work the same. If it isn't, please open an issue.

rtx is failing or not working right

First try setting RTX_LOG_LEVEL=debug or RTX_LOG_LEVEL=trace and see if that gives you more information. You can also set RTX_LOG_FILE=/path/to/logfile to write the logs to a file.

If something is happening with the activate hook, you can try disabling it and calling eval "$(rtx hook-env)" manually. It can also be helpful to use rtx env to see what environment variables it wants to use.

Lastly, there is an rtx doctor command. It doesn't have much in it but I hope to add more functionality to that to help debug issues.

Windows support?

This is something we'd like to add! https://github.com/jdxcode/rtx/discussions/66

It's not a near-term goal and it would require plugin modifications, but it should be feasible.

Commands

rtx activate

Enables rtx to automatically modify runtimes when changing directory

This should go into your shell's rc file.
Otherwise, it will only take effect in the current session.
(e.g. ~/.bashrc)

Usage: activate [OPTIONS] [SHELL_TYPE]

Arguments:
  [SHELL_TYPE]
          Shell type to generate the script for
          
          [possible values: bash, fish, xonsh, zsh]

Options:
      --status
          Show "rtx: <PLUGIN>@<VERSION>" message when changing directories

  -h, --help
          Print help (see a summary with '-h')

Examples:
    $ eval "$(rtx activate bash)"
    $ eval "$(rtx activate zsh)"
    $ rtx activate fish | source
    $ execx($(rtx activate xonsh))

rtx alias ls

List aliases
Shows the aliases that can be specified.
These can come from user config or from plugins in `bin/list-aliases`.

For user config, aliases are defined like the following in `~/.config/rtx/config.toml`:

  [alias.nodejs]
  lts = "18.0.0"

Usage: ls [OPTIONS]

Options:
  -p, --plugin <PLUGIN>
          Show aliases for <PLUGIN>

  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx aliases
  nodejs    lts/hydrogen   18.0.0

rtx cache clear

Deletes all cache files in rtx

Usage: clear

Options:
  -h, --help
          Print help

rtx complete

generate shell completions

Usage: complete --shell <SHELL>

Options:
  -s, --shell <SHELL>
          shell type
          
          [possible values: bash, elvish, fish, powershell, zsh]

  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx complete

rtx current

Shows currently active, and installed runtime versions

This is similar to `rtx list --current`, but this
only shows the runtime and/or version so it's
designed to fit into scripts more easily.

Usage: current [PLUGIN]

Arguments:
  [PLUGIN]
          plugin to show versions of
          
          e.g.: ruby, nodejs

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  # outputs `.tool-versions` compatible format
  $ rtx current
  python 3.11.0 3.10.0
  shfmt 3.6.0
  shellcheck 0.9.0
  nodejs 18.13.0

  $ rtx current nodejs
  18.13.0

  # can output multiple versions
  $ rtx current python
  3.11.0 3.10.0

rtx deactivate

disable rtx for current shell session

This can be used to temporarily disable rtx in a shell session.

Usage: deactivate [SHELL_TYPE]

Arguments:
  [SHELL_TYPE]
          shell type to generate the script for
          
          [possible values: bash, fish, xonsh, zsh]

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ eval "$(rtx deactivate bash)"
  $ eval "$(rtx deactivate zsh)"
  $ rtx deactivate fish | source
  $ execx($(rtx deactivate xonsh))

rtx direnv activate

Output direnv function to use rtx inside direnv

See https://github.com/jdxcode/rtx#direnv for more information

Because this generates the legacy files based on currently installed plugins,
you should run this command after installing new plugins. Otherwise
direnv may not know to update environment variables when legacy file versions change.

Usage: activate

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx direnv activate > ~/.config/direnv/lib/use_rtx.sh
  $ echo 'use rtx' > .envrc
  $ direnv allow

rtx doctor

Check rtx installation for possible problems.

Usage: doctor

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx doctor
  [WARN] plugin nodejs is not installed

rtx env

exports env vars to activate rtx in a single shell session

It's not necessary to use this if you have `rtx activate` in your shell rc file.
Use this if you don't want to permanently install rtx.
This can be used similarly to `asdf shell`.
Unfortunately, it requires `eval` to work since it's not written in Bash though.
It's also useful just to see what environment variables rtx sets.

Usage: env [OPTIONS] [RUNTIME]...

Arguments:
  [RUNTIME]...
          runtime version to use

Options:
  -s, --shell <SHELL>
          Shell type to generate environment variables for
          
          [possible values: bash, fish, xonsh, zsh]

  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ eval "$(rtx env -s bash)"
  $ eval "$(rtx env -s zsh)"
  $ rtx env -s fish | source
  $ execx($(rtx env -s xonsh))

rtx exec

execute a command with runtime(s) set

use this to avoid modifying the shell session or running ad-hoc commands with the rtx runtimes
set.

Runtimes will be loaded from .tool-versions, though they can be overridden with <RUNTIME> args
Note that only the plugin specified will be overridden, so if a `.tool-versions` file
includes "nodejs 20" but you run `rtx exec python@3.11`; it will still load nodejs@20.

The "--" separates runtimes from the commands to pass along to the subprocess.

Usage: exec [OPTIONS] [RUNTIME]... [-- <COMMAND>...]

Arguments:
  [RUNTIME]...
          runtime(s) to start
          
          e.g.: nodejs@20 python@3.10

  [COMMAND]...
          the command string to execute (same as --command)

Options:
  -c, --command <C>
          the command string to execute

  -h, --help
          Print help (see a summary with '-h')

Examples:
  rtx exec nodejs@20 -- node ./app.js  # launch app.js using node-20.x
  rtx x nodejs@20 -- node ./app.js     # shorter alias

  # Specify command as a string:
  rtx exec nodejs@20 python@3.11 --command "node -v && python -V"

rtx global

sets global .tool-versions to include a specified runtime

then displays the contents of ~/.tool-versions
this file is `$HOME/.tool-versions` by default
use `rtx local` to set a runtime version locally in the current directory

Usage: global [OPTIONS] [RUNTIME]...

Arguments:
  [RUNTIME]...
          runtime(s) to add to .tool-versions
          
          e.g.: nodejs@20
          if this is a single runtime with no version, the current value of the global
          .tool-versions will be displayed

Options:
      --pin
          save exact version to `.tool-versions`
          
          e.g.: `rtx global --pin nodejs@20` will save `nodejs 20.0.0` to .tool-versions,

      --remove <PLUGIN>
          remove the plugin(s) from ~/.tool-versions

  -h, --help
          Print help (see a summary with '-h')

Examples:
  # set the current version of nodejs to 20.x
  # will use a precise version (e.g.: 20.0.0) in .tool-versions file
  $ rtx global nodejs@20

  # set the current version of nodejs to 20.x
  # will use a fuzzy version (e.g.: 20) in .tool-versions file
  $ rtx global --fuzzy nodejs@20

  # show the current version of nodejs in ~/.tool-versions
  $ rtx global nodejs
  20.0.0

rtx implode

removes rtx CLI and all generated data

skips config directory by default

Usage: implode [OPTIONS]

Options:
      --config
          also remove config directory

      --dry-run
          list directories that would be removed without actually removing them

  -h, --help
          Print help (see a summary with '-h')

rtx install

install a runtime

this will install a runtime to `~/.local/share/rtx/installs/<PLUGIN>/<VERSION>`
it won't be used simply by being installed, however.
For that, you must set up a `.tool-version` file manually or with `rtx local/global`.
Or you can call a runtime explicitly with `rtx exec <PLUGIN>@<VERSION> -- <COMMAND>`.

Runtimes will be installed in parallel. To disable, set `--jobs=1` or `RTX_JOBS=1`

Usage: install [OPTIONS] [RUNTIME]...

Arguments:
  [RUNTIME]...
          runtime(s) to install
          
          e.g.: nodejs@20

Options:
  -p, --plugin <PLUGIN>
          only install runtime(s) for <PLUGIN>

  -f, --force
          force reinstall even if already installed

  -v, --verbose...
          Show installation output

  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx install nodejs@18.0.0  # install specific nodejs version
  $ rtx install nodejs@18      # install fuzzy nodejs version
  $ rtx install nodejs         # install version specified in .tool-versions
  $ rtx install                # installs all runtimes specified in .tool-versions for installed plugins
  $ rtx install --all          # installs all runtimes and all plugins

rtx latest

get the latest runtime version of a plugin's runtimes

Usage: latest <RUNTIME>

Arguments:
  <RUNTIME>
          Runtime to get the latest version of

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx latest nodejs@18  # get the latest version of nodejs 18
  18.0.0

  $ rtx latest nodejs     # get the latest stable version of nodejs
  20.0.0

rtx local

Sets .tool-versions to include a specific runtime

then displays the contents of .tool-versions
use this to set the runtime version when within a directory
use `rtx global` to set a runtime version globally

Usage: local [OPTIONS] [RUNTIME]...

Arguments:
  [RUNTIME]...
          runtimes to add to .tool-versions
          
          e.g.: nodejs@20
          if this is a single runtime with no version,
          the current value of .tool-versions will be displayed

Options:
  -p, --parent
          recurse up to find a .tool-versions file rather than using the current directory only
          by default this command will only set the runtime in the current directory ("$PWD/.tool-versions")

      --pin
          save exact version to `.tool-versions`
          
          e.g.: `rtx local --pin nodejs@20` will save `nodejs 20.0.0` to .tool-versions,

      --remove <PLUGIN>
          remove the plugin(s) from .tool-versions

  -h, --help
          Print help (see a summary with '-h')

Examples:
  # set the current version of nodejs to 20.x for the current directory
  # will use a precise version (e.g.: 20.0.0) in .tool-versions file
  $ rtx local nodejs@20

  # set nodejs to 20.x for the current project (recurses up to find .tool-versions)
  $ rtx local -p nodejs@20

  # set the current version of nodejs to 20.x for the current directory
  # will use a fuzzy version (e.g.: 20) in .tool-versions file
  $ rtx local --fuzzy nodejs@20

  # removes nodejs from .tool-versions
  $ rtx local --remove=nodejs

  # show the current version of nodejs in .tool-versions
  $ rtx local nodejs
  20.0.0

rtx ls

list installed runtime versions

The "arrow (->)" indicates the runtime is installed, active, and will be used for running commands.
(Assuming `rtx activate` or `rtx env` is in use).

Usage: ls [OPTIONS]

Options:
  -p, --plugin <PLUGIN>
          Only show runtimes from [PLUGIN]

  -c, --current
          Only show runtimes currently specified in .tool-versions

  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx list
  -> nodejs     20.0.0 (set by ~/src/myapp/.tool-versions)
  -> python     3.11.0 (set by ~/.tool-versions)
     python     3.10.0

  $ rtx list --current
  -> nodejs     20.0.0 (set by ~/src/myapp/.tool-versions)
  -> python     3.11.0 (set by ~/.tool-versions)

rtx ls-remote

list runtime versions available for install

note that these versions are cached for commands like `rtx install nodejs@latest`
however _this_ command will always clear that cache and fetch the latest remote versions

Usage: ls-remote <PLUGIN> [PREFIX]

Arguments:
  <PLUGIN>
          plugin to get versions for

  [PREFIX]
          the version prefix to use when querying the latest version same as the first argument after the "@"

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx ls-remote nodejs
  18.0.0
  20.0.0

  $ rtx ls-remote nodejs@18
  18.0.0
  18.1.0

  $ rtx ls-remote nodejs 18
  18.0.0
  18.1.0

rtx plugins install

install a plugin

note that rtx automatically can install plugins when you install a runtime
e.g.: `rtx install nodejs@18` will autoinstall the nodejs plugin

This behavior can be modified in ~/.rtx/config.toml

Usage: install [OPTIONS] [NAME] [GIT_URL]

Arguments:
  [NAME]
          The name of the plugin to install
          
          e.g.: nodejs, ruby

  [GIT_URL]
          The git url of the plugin
          
          e.g.: https://github.com/asdf-vm/asdf-nodejs.git

Options:
  -f, --force
          Reinstall even if plugin exists

  -a, --all
          Install all missing plugins
          
          This will only install plugins that have matching shortnames.
          i.e.: they don't need the full git repo url

  -v, --verbose...
          Show installation output

  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx install nodejs  # install the nodejs plugin using the shorthand repo:
                      # https://github.com/asdf-vm/asdf-plugins

  $ rtx install nodejs https://github.com/asdf-vm/asdf-nodejs.git
                      # install the nodejs plugin using the git url

  $ rtx install https://github.com/asdf-vm/asdf-nodejs.git
                      # install the nodejs plugin using the git url only
                      # (nodejs is inferred from the url)

rtx plugins ls

List installed plugins

Can also show remotely available plugins to install.

Usage: ls [OPTIONS]

Options:
  -a, --all
          list all available remote plugins
          
          same as `rtx plugins ls-remote`

  -u, --urls
          show the git url for each plugin
          
          e.g.: https://github.com/asdf-vm/asdf-nodejs.git

  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx plugins ls
  nodejs
  ruby

  $ rtx plugins ls --urls
  nodejs                        https://github.com/asdf-vm/asdf-nodejs.git
  ruby                          https://github.com/asdf-vm/asdf-ruby.git

rtx plugins ls-remote

List all available remote plugins

These are fetched from https://github.com/asdf-vm/asdf-plugins

Examples:
  $ rtx plugins ls-remote


Usage: ls-remote [OPTIONS]

Options:
  -u, --urls
          show the git url for each plugin
          
          e.g.: https://github.com/asdf-vm/asdf-nodejs.git

  -h, --help
          Print help (see a summary with '-h')

rtx plugins uninstall

removes a plugin

Usage: uninstall <PLUGIN>

Arguments:
  <PLUGIN>
          plugin to remove

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx uninstall nodejs

rtx plugins update

updates a plugin to the latest version

note: this updates the plugin itself, not the runtime versions

Usage: update [OPTIONS] [PLUGIN]...

Arguments:
  [PLUGIN]...
          plugin(s) to update

Options:
  -a, --all
          update all plugins

  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx plugins update --all   # update all plugins
  $ rtx plugins update nodejs  # update only nodejs

rtx self-update

updates rtx itself

Usage: self-update

Options:
  -h, --help
          Print help

rtx settings get

Show a current setting

This is the contents of a single entry in ~/.config/rtx/config.toml

Note that aliases are also stored in this file
but managed separately with `rtx aliases get`

Usage: get <KEY>

Arguments:
  <KEY>
          The setting to show

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx settings get legacy_version_file
  true

rtx settings ls

Show current settings

This is the contents of ~/.config/rtx/config.toml

Note that aliases are also stored in this file
but managed separately with `rtx aliases`

Usage: ls

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx settings
  legacy_version_file = false

rtx settings set

Add/update a setting

This modifies the contents of ~/.config/rtx/config.toml

Usage: set <KEY> <VALUE>

Arguments:
  <KEY>
          The setting to set

  <VALUE>
          The value to set

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx settings set legacy_version_file true

rtx settings unset

Clears a setting

This modifies the contents of ~/.config/rtx/config.toml

Usage: unset <KEY>

Arguments:
  <KEY>
          The setting to remove

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx settings unset legacy_version_file

rtx uninstall

removes runtime versions

Usage: uninstall <RUNTIME>...

Arguments:
  <RUNTIME>...
          runtime(s) to remove

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  $ rtx uninstall nodejs@18.0.0 # will uninstall specific version
  $ rtx uninstall nodejs        # will uninstall current nodejs version

rtx version

Show rtx version

Usage: version

Options:
  -h, --help
          Print help

rtx where

Display the installation path for a runtime

Must be installed.

Usage: where <RUNTIME>

Arguments:
  <RUNTIME>
          runtime(s) to look up if "@<PREFIX>" is specified, it will show the latest installed version that matches the prefix otherwise, it will show the current, active installed version

Options:
  -h, --help
          Print help (see a summary with '-h')

Examples:
  # Show the latest installed version of nodejs
  # If it is is not installed, errors
  $ rtx where nodejs@20
  /Users/jdx/.local/share/rtx/installs/nodejs/20.0.0

  # Show the current, active install directory of nodejs
  # Errors if nodejs is not referenced in any .tool-version file
  $ rtx where nodejs
  /Users/jdx/.local/share/rtx/installs/nodejs/20.0.0

Comparison to asdf

rtx is mostly a clone of asdf, but there are notable areas where improvements have been made.

Performance

asdf made (what I consider) a poor design decision to use shims that go between a call to a runtime and the runtime itself. e.g.: when you call node it will call an asdf shim file ~/.asdf/shims/node, which then calls asdf exec, which then calls the correct version of node.

These shims have terrible performance, adding ~120ms to every runtime call. rtx does not use shims and instead updates PATH so that it doesn't have any overhead when simply calling binaries. These shims are the main reason that I wrote this. Note that in the demo gif at the top of this README that rtx isn't actually used when calling node -v for this reason. The performance is identical to running node without using rtx.

I don't think it's possible for asdf to fix these issues. The author of asdf did a great writeup of performance problems. asdf is written in bash which certainly makes it challenging to be performant, however I think the real problem is the shim design. I don't think it's possible to fix that without a complete rewrite.

rtx does call an internal command rtx hook-env every time the directory has changed, but because it's written in Rust, this is very quick—taking ~10ms on my machine. 4ms if there are no changes, 14ms if it's a full reload.

tl;dr: asdf adds overhead (~120ms) when calling a runtime, rtx adds a small amount of overhead (~10ms) when the prompt loads.

Environment variables

asdf only helps manage runtime executables. However, some tools are managed via environment variables (notably Java which switches via JAVA_HOME). This isn't supported very well in asdf and requires a separate shell extension just to manage.

However asdf plugins have a bin/exec-env script that is used for exporting environment variables like JAVA_HOME. rtx simply exports the environment variables from the bin/exec-env script in the plugin but places them in the shell for all commands. In asdf it only exports those commands when the shim is called. This means if you call java it will set JAVA_HOME, but not if you call some Java tool like mvn.

This means we're just using the existing plugin script but because rtx doesn't use shims it can be used for more things. It would be trivial to make a plugin that exports arbitrary environment variables like dotenv or direnv.

UX

Some commands are the same in asdf but others have been changed. Everything that's possible in asdf should be possible in rtx but may use slightly different syntax. rtx has more forgiving commands, such as using fuzzy-matching, e.g.: rtx install nodejs@18. While in asdf you can run asdf install nodejs latest:18, you can't use latest:18 in a .tool-versions file or many other places. In rtx you can use fuzzy-matching everywhere.

asdf requires several steps to install a new runtime if the plugin isn't installed, e.g.:

$ asdf plugin add nodejs
$ asdf install nodejs latest:18
$ asdf local nodejs latest:18

In rtx this can all be done in a single step to set the local runtime version. If the plugin and/or runtime needs to be installed it will prompt:

$ asdf local nodejs@18
rtx: Would you like to install nodejs@18.13.0? [Y/n] Y
Trying to update node-build... ok
Downloading node-v18.13.0-darwin-arm64.tar.gz...
-> https://nodejs.org/dist/v18.13.0/node-v18.13.0-darwin-arm64.tar.gz
Installing node-v18.13.0-darwin-arm64...
Installed node-v18.13.0-darwin-arm64 to /Users/jdx/.local/share/rtx/installs/nodejs/18.13.0
$ node -v
v18.13.0

I've found asdf to be particularly rigid and difficult to learn. It also made strange decisions like having asdf list all but asdf latest --all (why is one a flag and one a positional argument?). rtx makes heavy use of aliases so you don't need to remember if it's rtx plugin add nodejs or rtx plugin install nodejs. If I can guess what you meant, then I'll try to get rtx to respond in the right way.

That said, there are a lot of great things about asdf. It's the best multi-runtime manager out there and I've really been impressed with the plugin system. Most of the design decisions the authors made were very good. I really just have 2 complaints: the shims and the fact it's written in Bash.

direnv

direnv and rtx both manage environment variables based on directory. Because they both analyze the current environment variables before and after their respective "hook" commands are run, they can conflict with each other. As a result, there were a number of issues with direnv. However, we think we've mitigated these. If you find that rtx and direnv are not working well together, please comment on that ticket ideally with a good description of your directory layout so we can reproduce the problem.

If there are remaining issues, they're likely to do with the ordering of PATH. This means it would really only be a problem if you were trying to manage the same runtime with direnv and rtx. For example, you may use layout python in an .envrc but also be maintaining a .tool-versions file with python in it as well.

A more typical usage of direnv would be to set some arbitrary environment variables, or add unrelated binaries to PATH. In these cases, rtx will not interfere with direnv.

As mentioned in the Quick Start, it is important to make sure that rtx activate is called after direnv hook in the shell rc file. rtx overrides some of the internal direnv state (DIRENV_DIFF) so calling direnv first gives rtx the opportunity to make those changes to direnv's state.

rtx inside of direnv (use rtx in .envrc)

If you do encounter issues with rtx activate, or just want to use direnv in an alternate way, this is a simpler setup that's less likely to cause issues.

To do this, first use rtx to build a use_rtx function that you can use in .envrc files:

$ rtx direnv activate > ~/.config/direnv/lib/use_rtx.sh

Now in your .envrc file add the following:

use rtx

direnv will now call rtx to export its environment variables. You'll need to make sure to add use_rtx to all projects that use rtx (or use direnv's source_up to load it from a subdirectory). You can also add use rtx to ~/.config/direnv/direnvrc.

Note that in this method direnv typically won't know to refresh .tool-versions files unless they're at the same level as a .envrc file. You'll likely always want to have a .envrc file next to your .tool-versions for this reason. To make this a little easier to manage, I encourage not actually using .tool-versions at all, and instead setting environment variables entirely in .envrc:

export RTX_NODEJS_VERSION=18.0.0
export RTX_PYTHON_VERSION=3.11

Of course if you use rtx activate, then these steps won't have been necessary and you can use rtx as if direnv was not used.

Cache Behavior

rtx makes use of caching in many places in order to be efficient. The details about how long to keep cache for should eventually all be configurable. There may be gaps in the current behavior where things are hardcoded but I'm happy to add more settings to cover whatever config is needed.

Below I explain the behavior it uses around caching. If you're seeing behavior where things don't appear to be updating, this is a good place to start.

Plugin Cache

Each plugin has a cache that's stored in ~/$RTX_CACHE_DIR/plugins/<PLUGIN>. It stores the list of versions available for that plugin (rtx ls-remote <PLUGIN>), the legacy filenames (see below), the list of aliases, and the bin directories within each runtime installation.

Remote versions are updated daily by default or anytime that rtx ls-remote is called explicitly. The file is zlib messagepack, if you want to view it you can run the following (requires msgpack-cli).

cat ~/$RTX_CACHE_DIR/nodejs/remote_versions.msgpack.zlib | perl -e 'use Compress::Raw::Zlib;my $d=new Compress::Raw::Zlib::Inflate();my $o;undef $/;$d->inflate(<>,$o);print $o;' | msgpack-cli decode

Legacy File Cache

If enabled, rtx will read the legacy filenames such as .node-version for asdf-nodejs. This leverages cache in 2 places where the plugin is called:

• list-legacy-filenames In every plugin I've seen this simply returns a static list of filenamed like ".nvmrc .node-version". It's cached alongside the standard "runtime" cache which is refreshed daily by default.
• parse-legacy-file This plugin binary is called to parse a legacy file to get the version out of it. It's relatively expensive so every file that gets parsed as a legacy file is cached into ~/.local/share/rtx/legacy_cache. It will remain cached until the file is modified. This is a simple text file that has the path to the legacy file stored as a hash for the filename.

Development

Run tests with just:

$ just test

Lint the codebase with:

$ just lint-fix