Nu Shell

Like having a shell in a playground.

Status

This project is currently in its early stages, though it already works well enough for contributors to dogfood it as their daily driver. Its design is subject to change as it matures.

Nu has a list of built-in commands (listed below). If a command is unknown, the command will shell-out and execute it (using cmd on Windows or bash on Linux and MacOS), correctly passing through stdin, stdout and stderr, so things like your daily git workflows and even vim will work just fine.

Philosophy

Nu draws inspiration from projects like PowerShell, functional programming languages, and modern cli tools. Rather than thinking of files and services as raw streams of text, Nu looks at each input as something with structure. For example, when you list the contents of a directory, what you get back in a list of objects, where each object represents an item in that directory. These values can be piped through a series of steps, in a series of commands called a 'pipeline'.

Pipelines

In Unix, it's common to pipe between commands to split up a sophisticated command over multiple steps. Nu takes this a step further and builds heavily on the idea of pipelines. Just as the Unix philosophy, Nu allows commands to output from stdout and read from stdin. Additionally, commands can output structured data (you can think of this as a third kind of stream). Commands that work in the pipeline fit into one of three categories

• Commands that produce a stream (eg, ls)
• Commands that filter a stream (eg, where type == "Directory")
• Commands that consumes the output of the pipeline (eg, autoview)

Commands are separated by the pipe symbol (|) to denote a pipeline flowing left to right.

/home/jonathan/Source/nushell(master)> ls | where type == "Directory" | autoview
--------+-----------+----------+--------+--------------+----------------
 name   | type      | readonly | size   | accessed     | modified
--------+-----------+----------+--------+--------------+----------------
 target | Directory |          | 4.1 KB | 19 hours ago | 19 hours ago
 images | Directory |          | 4.1 KB | 2 weeks ago  | a week ago
 tests  | Directory |          | 4.1 KB | 2 weeks ago  | 18 minutes ago
 docs   | Directory |          | 4.1 KB | a week ago   | a week ago
 .git   | Directory |          | 4.1 KB | 2 weeks ago  | 25 minutes ago
 src    | Directory |          | 4.1 KB | 2 weeks ago  | 25 minutes ago
 .cargo | Directory |          | 4.1 KB | 2 weeks ago  | 2 weeks ago
-----------+-----------+----------+--------+--------------+----------------

Because most of the time you'll want to see the output of a pipeline, autoview is assumed. We could have also written the above:

/home/jonathan/Source/nushell(master)> ls | where type == Directory

Being able to use the same commands and compose them differently is an important philosophy in Nu. For example, we could use the built-in ps command as well to get a list of the running processes, using the same where as above.

C:\Code\nushell(master)> ps | where cpu > 0
------------------ +-----+-------+-------+----------
 name              | cmd | cpu   | pid   | status
------------------ +-----+-------+-------+----------
 msedge.exe        |  -  | 0.77  | 26472 | Runnable
 nu.exe            |  -  | 7.83  | 15473 | Runnable
 SearchIndexer.exe |  -  | 82.17 | 23476 | Runnable
 BlueJeans.exe     |  -  | 4.54  | 10000 | Runnable
-------------------+-----+-------+-------+----------

Opening files

Nu can load file and URL contents as raw text or as structured data (if it recognizes the format). For example, you can load a .toml file as structured data and explore it:

/home/jonathan/Source/nushell(master)> open Cargo.toml
-----------------+------------------+-----------------
 dependencies    | dev-dependencies | package
-----------------+------------------+-----------------
 [object Object] | [object Object]  | [object Object]
-----------------+------------------+-----------------

We can pipeline this into a command that gets the contents of one of the columns:

/home/jonathan/Source/nushell(master)> open Cargo.toml | get package
-------------+----------------------------+---------+---------+------+---------
 authors     | description                | edition | license | name | version
-------------+----------------------------+---------+---------+------+---------
 [list List] | A shell for the GitHub era | 2018    | MIT     | nu   | 0.1.2
-------------+----------------------------+---------+---------+------+---------

Finally, we can use commands outside of Nu once we have the data we want:

/home/jonathan/Source/nushell(master)> open Cargo.toml | get package.version | echo $it
0.1.2

Here we use the variable $it to refer to the value being piped to the external command.

Plugins

Nu supports plugins that offer additional functionality to the shell and follow the same object model that built-in commands use. This allows you to extend nu for your needs.

There are a few examples in the plugins directory.

Plugins are binaries that are available in your path and follow a "nu_plugin_*" naming convention. These binaries interact with nu via a simple JSON-RPC protocol where the command identifies itself and passes along its configuration, which then makes it available for use. If the plugin is a filter, data streams to it one element at a time, and it can stream data back in return via stdin/stdout. If the plugin is a sink, it is given the full vector of final data and is given free reign over stdin/stdout to use as it pleases.

Goals

Nu adheres closely to a set of goals that make up its design philosophy. As features are added, they are checked against these goals.

• First and foremost, Nu is cross-platform. Commands and techniques should carry between platforms and offer first-class consistent support for Windows, macOS, and Linux.

• Nu ensures direct compatibility with existing platform-specific executables that make up people's workflows.

• Nu's workflow and tools should have the usability in day-to-day experience of using a shell in 2019 (and beyond).

• Nu views data as both structured and unstructured. It is an object shell like PowerShell.

• Finally, Nu views data functionally. Rather than using mutation, pipelines act as a mean to load, change, and save data without mutable state.

Commands

Initial commands

command	description
cd path	Change to a new path
cp source path	Copy files
ls (path)	View the contents of the current or given path
date (--utc)	Get the current datetime
ps	View current processes
sys	View information about the current system
open {filename or url}	Load a file into a cell, convert to table if possible (avoid by appending '--raw')
rm {file or directory}	Remove a file, (for removing directory append '--recursive')
exit	Exit the shell

Filters on tables (structured data)

command	description
pick ...columns	Down-select table to only these columns
reject ...columns	Remove the given columns from the table
get column-or-column-path	Open given cells as text
sort-by ...columns	Sort by the given columns
where condition	Filter table to match the condition
inc (field)	Increment a value or version. Optional use the field of a table
add field value	Add a new field to the table
sum	Sum a column of values
edit field value	Edit an existing field to have a new value
skip amount	Skip a number of rows
first amount	Show only the first number of rows
str (field)	Apply string function. Optional use the field of a table
tags	Read the tags (metadata) for values
to-array	Collapse rows into a single list
to-json	Convert table into .json text
to-toml	Convert table into .toml text
to-yaml	Convert table into .yaml text
to-csv	Convert table into .csv text

Filters on text (unstructured data)

command	description
from-csv	Parse text as .csv and create table
from-ini	Parse text as .ini and create table
from-json	Parse text as .json and create table
from-toml	Parse text as .toml and create table
from-xml	Parse text as .xml and create a table
from-yaml	Parse text as a .yaml/.yml and create a table
lines	Split single string into rows, one per line
size	Gather word count statistics on the text
split-column sep ...fields	Split row contents across multiple columns via the separator
split-row sep	Split row contents over multiple rows via the separator
trim	Trim leading and following whitespace from text data
{external-command} $it	Run external command with given arguments, replacing $it with each row text

Consuming commands

command	description
autoview	View the contents of the pipeline as a table or list
binaryview	Autoview of binary data
clip	Copy the contents of the pipeline to the copy/paste buffer
save filename	Save the contents of the pipeline to a file
table	View the contents of the pipeline as a table
tree	View the contents of the pipeline as a tree
vtable	View the contents of the pipeline as a vertical (rotated) table

License

The project is made available under the MIT license. See "LICENSE" for more information.