Plugins

Nu can be extended using plugins. Plugins behave much like Nu's built-in commands, with the added benefit that they can be added separately from Nu itself.

Overview

• In order to use a plugin, it needs to be:

  • Installed
  • Added
  • Imported

There are two types of plugins:

• "Core plugins" are officially maintained and are usually installed with Nushell, in the same directory as the Nushell executable.
• Third-party plugins are also available from many sources.

The $NU_LIB_DIRS constant or $env.NU_LIB_DIRS environment variable can be used to set the search-path for plugins.

Core Plugin Quickstart

To begin using the Polars plugin:

1. Most package managers will automatically install the core plugins with Nushell. A notable exception, however, is cargo. If you installed Nushell using cargo, see Installing Core Plugins below.

2. (Recommended) Set the plugin search path to include the directory where Nushell and its plugins are installed. Assuming the core plugins are installed in the same directory as the Nushell binary, the following can be added to your startup config:

   const NU_PLUGIN_DIRS = [
     ($nu.current-exe | path dirname)
     ...$NU_PLUGIN_DIRS
   ]

3. Add the plugin to the plugin registry. This only needs to be done one time. The name is the name of the plugin file, including its extension:

   # On Unix/Linux platforms:
   plugin add nu_plugin_polars
   # Or on Windows
   plugin add nu_plugin_polars.exe
   
   plug list # Confirm it was added to the registry

   Alternatively, if you did not add the binary directory to the plugin path in Step 2, you can still use an absolute path:

   plugin add ~/.local/share/rust/cargo/bin/nu_plugin_polars

4. Import the plugin (to begin using it immediately) or restart Nushell. All plugins in the registry are automatically imported when Nushell starts:

   # The name of the plugin, without the leading `nu_plugin` nor any extension
   use polars

5. Confirm the plugin is working:

   ls | polars into-df | describe
   # => NuDataFrame

Installing Plugins

Core Plugins

Nushell ships with a set of officially maintained plugins which includes:

• polars: Extremely fast columnar operations using DataFrames via the Polars Library. See the DataFrames Chapter for more details.
• formats: Support for several additional data formats - EML, ICS, INI, plist, and VCF.
• gstat: Returns information on the status of a Git repository as Nushell structured data.
• query: Support for querying SQL, XML, JSON, HTML (via selector), and WebPage Metadata
• inc: Increment a value or version (e.g., semver). This plugin acts as both an end-user plugin as well as a simple developer example of how to create a plugin.

Nushell also ships with several plugins that serve as examples or tools for plugin developers. These include nu_plugin_example, nu_plugin_custom_values, and nu_plugin_stress_internals.

Core plugins are typically distributed with the Nushell release and should already be installed in the same directory as the Nushell executable. If this is the case on your system, core plugins should be using correct nu-plugin protocol version. If your package management system installs them separately, please make sure to update the core plugins whenever Nushell itself is updated.

[ nu_plugin_inc
  nu_plugin_polars
  nu_plugin_gstat
  nu_plugin_formats
  nu_plugin_query
] | each { cargo install $in --locked } | ignore

Third-party Plugins

You can find third-party plugins on crates.io, online Git repositories, awesome-nu, and other sources. As with any third-party code you run on your system, please make sure you trust its source.

To install a third-party plugin on your system, you first need to make sure the plugin uses the same version of Nu as your system:

• Confirm your Nushell version with the version command
• Confirm the version the plugin requires by checking its Cargo.toml file

To install a plugin by name from crates.io, run:

cargo install nu_plugin_<plugin_name> --locked

When installing from a repository (e.g., GitHub), run the following from inside the cloned repository:

cargo install --path . --locked

This will create a binary file that can be used to add the plugin.

Registering Plugins

To add a plugin to the plugin registry file, call the plugin add command to tell Nu where to find it.

• Linux and macOS:

  plugin add ./my_plugins/nu_plugin_cool

• Windows:

  plugin add .\my_plugins\nu_plugin_cool.exe

When plugin add is called, Nu:

• Runs the plugin binary
• Communicates via the plugin protocol in order to ensure compatibility and to get a list of all of the commands it supports
• This plugin information is then saved to the plugin registry file ($nu.plugin-path), which acts as a cache

Importing Plugins

Once added to the registry, the next time nu is started, the plugin will be imported and available in that session.

You can also immediately import (or reload) a plugin in the current session by calling plugin use. In this case, the name of the plugin (rather than the filename) is used without the nu_plugin prefix:

plugin use cool

It is not necessary to add plugin use statements to your config file. All previously registered plugins are automatically loaded at startup.

nu --plugins '[./my_plugins/nu_plugin_cool]'

Plugin Search Path

Nushell includes two list variables that can be used to set a search path for plugins. This only applies when registering plugins with plugin add, but it can be a nice shortcut if you commonly add and remove plugins.

• const NU_PLUGIN_DIRS: A constant which takes effect immediately when set. However, as a constant, only certain commands may be used with it. It can be updated, for example, as seen in the QuickStart above.
• $env.NU_PLUGIN_DIRS: An environment variable which is mutable and can accept any command that updates its list. However, changes to it will not take effect until the next expression is parsed.

Updating Plugins

When updating a plugin, it is important to run plugin add again just as above to load the new signatures from the plugin and allow Nu to rewrite them to the plugin file ($nu.plugin-path). You can then plugin use to get the updated signatures within the current session.

Managing Plugins

Installed plugins are displayed using plugin list:

plugin list
# =>
╭───┬─────────┬────────────┬─────────┬───────────────────────┬───────┬───────────────────────────────╮
│ # │  name   │ is_running │   pid   │       filename        │ shell │           commands            │
├───┼─────────┼────────────┼─────────┼───────────────────────┼───────┼───────────────────────────────┤
│ 0 │ gstat   │ true       │ 1389890 │ .../nu_plugin_gstat   │       │ ╭───┬───────╮                 │
│   │         │            │         │                       │       │ │ 0 │ gstat │                 │
│   │         │            │         │                       │       │ ╰───┴───────╯                 │
│ 1 │ inc     │ false      │         │ .../nu_plugin_inc     │       │ ╭───┬─────╮                   │
│   │         │            │         │                       │       │ │ 0 │ inc │                   │
│   │         │            │         │                       │       │ ╰───┴─────╯                   │
│ 2 │ example │ false      │         │ .../nu_plugin_example │       │ ╭───┬───────────────────────╮ │
│   │         │            │         │                       │       │ │ 0 │ nu-example-1          │ │
│   │         │            │         │                       │       │ │ 1 │ nu-example-2          │ │
│   │         │            │         │                       │       │ │ 2 │ nu-example-3          │ │
│   │         │            │         │                       │       │ │ 3 │ nu-example-config     │ │
│   │         │            │         │                       │       │ │ 4 │ nu-example-disable-gc │ │
│   │         │            │         │                       │       │ ╰───┴───────────────────────╯ │
╰───┴─────────┴────────────┴─────────┴───────────────────────┴───────┴───────────────────────────────╯

All of the commands from installed plugins are available in the current scope:

scope commands | where type == "plugin"

Plugin Lifecycle

Plugins stay running while they are in use, and are automatically stopped by default after a period of time of inactivity. This behavior is managed by the plugin garbage collector. To manually stop a plugin, call plugin stop with its name:

For example, run the gstat command from the corresponding plugin, then check its is_running status:

gstat
# => gstat output
plugin list | where name == gstat | select name is_running
# =>
╭───┬───────┬────────────╮
│ # │ name  │ is_running │
├───┼───────┼────────────┤
│ 0 │ gstat │ true       │
╰───┴───────┴────────────╯

Now stop the plugin manually, and we can see that it is no longer running:

plugin stop gstat
plugin list | where name == gstat | select name is_running
# =>
╭───┬───────┬────────────╮
│ # │ name  │ is_running │
├───┼───────┼────────────┤
│ 0 │ gstat │ false      │
╰───┴───────┴────────────╯

Plugin Garbage Collector

As mentioned above, Nu comes with a plugin garbage collector which automatically stops plugins that are not actively in use after a period of time (by default, 10 seconds). This behavior is fully configurable:

$env.config.plugin_gc = {
    # Settings for plugins not otherwise specified:
    default: {
        enabled: true # set to false to never automatically stop plugins
        stop_after: 10sec # how long to wait after the plugin is inactive before stopping it
    }
    # Settings for specific plugins, by plugin name
    # (i.e. what you see in `plugin list`):
    plugins: {
        gstat: {
            stop_after: 1min
        }
        inc: {
            stop_after: 0sec # stop as soon as possible
        }
        example: {
            enabled: false # never stop automatically
        }
    }
}

For information on when a plugin is considered to be active, see the relevant section in the contributor book.

Removing Plugins

To remove a plugin, call plugin rm <plugin_name>. Note that this is the plugin name, rather than the filename. For example, if you previously added the plugin ~/.cargo/bin/nu_plugin_gstat, its name would be gstat. To remove it:

plugin rm gstat

You can confirm the name of a plugin by running plugin list.

Running plugin rm removes the plugin from the registry so that it will not be loaded the next time Nushell starts. However, any commands created by the plugin remain in scope until the current Nushell session ends.

For Plugin Developers

Nu plugins are executables; Nu launches them as needed and communicates with them over stdin and stdout or local sockets. Nu plugins can use either JSON or MessagePack as their communication encoding.

Examples

Nu's main repo contains example plugins that are useful for learning how the plugin protocol works:

• Rust
• Python

Debugging

The simplest way to debug a plugin is to print to stderr; plugins' standard error streams are redirected through Nu and displayed to the user.

Tracing

The Nu plugin protocol message stream may be captured for diagnostic purposes using trace_nu_plugin.

Developer Help

Nu's plugin documentation is a work in progress. If you're unsure about something, the #plugins channel on the Nu Discord is a great place to ask questions!

More details

The plugin chapter in the contributor book offers more details on the intricacies of how plugins work from a software developer point of view.