# Versions

## Install Version

```shell
asdf install <name> <version>
# asdf install erlang 17.3
```

If a plugin supports downloading & compiling from source, you can specify `ref:foo` where `foo` is a specific branch, tag, or commit. You'll need to use the same name and reference when uninstalling too.

## Install Latest Stable Version

```shell
asdf install <name> latest
# asdf install erlang latest
```

Install latest stable version that begins with a given string.

```shell
asdf install <name> latest:<version>
# asdf install erlang latest:17
```

## List Installed Versions

```shell
asdf list <name>
# asdf list erlang
```

Filter versions to those that begin with a given string.

```shell
asdf list <name> <version>
# asdf list erlang 17
```

## List All Available Versions

```shell
asdf list all <name>
# asdf list all erlang
```

Filter versions to those that begin with a given string.

```shell
asdf list all <name> <version>
# asdf list all erlang 17
```

## Show Latest Stable Version

```shell
asdf latest <name>
# asdf latest erlang
```

Show latest stable version that begins with a given string.

```shell
asdf latest <name> <version>
# asdf latest erlang 17
```

## Set Current Version

```shell
asdf global <name> <version> [<version>...]
asdf shell <name> <version> [<version>...]
asdf local <name> <version> [<version>...]
# asdf global elixir 1.2.4

asdf global <name> latest[:<version>]
asdf local <name> latest[:<version>]
# asdf global elixir latest
```

`global` writes the version to `$HOME/.tool-versions`.

`shell` set the version to an environment variable named `ASDF_${TOOL}_VERSION`, for the current shell session only.

`local` writes the version to `$PWD/.tool-versions`, creating it if needed.

See the `.tool-versions` [file in the Configuration section](/manage/configuration.md) for details.

:::warning Alternatively
If you want to set a version only for the current shell session
or for executing just a command under a particular tool version, you
can set an environment variable like `ASDF_${TOOL}_VERSION`.
:::

The following example runs tests on an Elixir project with version `1.4.0`.
The version format is the same supported by the `.tool-versions` file.

```shell
ASDF_ELIXIR_VERSION=1.4.0 mix test
```

## Fallback to System Version

To use the system version of tool `<name>` instead of an asdf managed version you can set the version for the tool to `system`.

Set system with either `global`, `local` or `shell` as outlined in [Set Current Version](#set-current-version) section above.

```shell
asdf local <name> system
# asdf local python system
```

## View Current Version

```shell
asdf current
# asdf current
# erlang          17.3          /Users/kim/.tool-versions
# nodejs          6.11.5        /Users/kim/cool-node-project/.tool-versions

asdf current <name>
# asdf current erlang
# erlang          17.3          /Users/kim/.tool-versions
```

## Uninstall Version

```shell
asdf uninstall <name> <version>
# asdf uninstall erlang 17.3
```

## Shims

When asdf installs a package it creates shims for every executable program in that package in a `$ASDF_DATA_DIR/shims` directory (default `~/.asdf/shims`). This directory being on the `$PATH` (by means of `asdf.sh`, `asdf.fish`, etc) is how the installed programs are made available in the environment.

The shims themselves are really simple wrappers that `exec` a helper program `asdf exec` passing it the name of the plugin and path to the executable in the installed package that the shim is wrapping.

The `asdf exec` helper determines the version of the package to use (as specified in `.tool-versions` file, selected by `asdf local ...` or `asdf global ...`), the final path to the executable in the package installation directory (this can be manipulated by the `exec-path` callback in the plugin) and the environment to execute in (also provided by the plugin - `exec-env` script), and finally it executes it.

::: warning Note
Because this system uses `exec` calls, any scripts in the package that are meant to be sourced by the shell instead of executed need to be accessed directly instead of via the shim wrapper. The two `asdf` commands: `which` and `where` can help with this by returning the path to the installed package:
:::

```shell
# returns path to main executable in current version
source $(asdf which ${PLUGIN})/../script.sh

# returns path to the package installation directory
source $(asdf where ${PLUGIN})/bin/script.sh
```

### By-passing asdf shims

If for some reason you want to by-pass asdf shims or want your environment variables automatically set upon entering your project's directory, the [asdf-direnv](https://github.com/asdf-community/asdf-direnv) plugin can be helpful. Be sure to check its README for more details.