len

Nu Plugin Len

This is an example length plugin based on the nushell len example but instead using the nushell plugin package. There are two options for creating a plugin in Python

• installing all Python module dependencies to your system, and using a Python file
• compiling your plugin to generate one package

Run Locally

If you want to run the plugin locally, you will nead nushell installed.

$ pip install nushell

You can then start nushell, and interact with the plugin. Make sure your present working directory with the file is added to the PATH. Here are some examples:

export PATH=$PWD:$PATH
$ nu

This is the default help provided by nushell, given that it finds the plugin on the path and it's valid.

> help len
Return the length of a string

Usage:
  > len {flags} 

flags:
  --help

Here is a basic example to use it:

> echo four | len
━━━━━━━━━━━
 <unknown> 
───────────
         4 
━━━━━━━━━━━

And a slightly more complex one, showing the length of the names of the files in the present working directory.

 ls | get name | len
━━━┯━━━━━━━━━━━
 # │ <unknown> 
───┼───────────
 0 │        13 
 1 │         9 
━━━┷━━━━━━━━━━━

As a helper, the plugin library automatically adds a --help function that also shows usage for each argument, if the creator provided it.

> len --help
len: Return the length of a string

--help              show this usage

Logging

Logs are printed to /tmp/nu_plugin_len.log unless you set logging=False when you initialize the plugin.

Build Python

You can optionally build the container, doing a regular make will build a container with nu and the installed python modules:

make
# docker build -t vanessa/nu-plugin-len .

$ docker run -it vanessa/nu-plugin-len
root@c7235d999a44:/code# nu
/code> help len
Return the length of a string

Usage:
  > len {flags} 

flags:
  --help

/code> echo four | len
━━━━━━━━━
 <value> 
─────────
       4 
━━━━━━━━━

You can also make a container with a standalone binary - we use pyinstaller to do this.

make standalone
$ docker run -it vanessa/nu-plugin-len

And execution proceeds as before. We can prove that we don't need the modules anymore because the Dockerfile.standalone does pip3 uninstall -y nushell and it still works. Why might you want to do this? It will mean that your plugin is a single file (binary) and you don't need to rely on modules elsewhere in the system. I suspect there are other ways to compile python into a single binary (e.g., cython) but this was the first I tried, and fairly straight forward. If you find a different or better way, please contribute to this code base!