nushell/README.md

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 heavy inspiration from projects like PowerShell. Rather than thinking of you filesystem 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.

Pipelines

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 "file 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 "file type" == "Directory" | autoview
-----------+-----------+----------+--------+--------------+----------------
 file name | file 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 "file 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.

Navigation

By default, Nu opens up into your filesystem and the current working directory. One way to think of this is a pair: the current object and the current path in the object. The filesystem is our first object, and the path is the cwd.

object	path
Filesystem	/home/jonathan/Source/nushell

Using the cd command allows you to change the path from the current path to a new path, just as you might expect. Using ls allows you to view the contents of the filesystem at the current path (or at the path of your choosing).

In addition to cd and ls, we can enter an object. Entering an object makes it the current object to navigate (similar to the concept of mounting a filesystem in Unix systems).

/home/jonathan/Source/nushell(master)> enter Cargo.toml
object/>

As we enter, we create a stack of objects we're navigating:

object	path
Filesystem	/home/jonathan/Source/nushell
object (from Cargo.toml)	/

Commands cd and ls now work on the object being navigated.

object/> ls
-----------------+------------------+-----------------
 dependencies    | dev-dependencies | package
-----------------+------------------+-----------------
 [object Object] | [object Object]  | [object Object]
-----------------+------------------+-----------------

object/> cd package/version
object/package/version> ls
-------
 value
-------
 0.1.2
-------

The exit command will pop the stack and get us back to a previous object we were navigating.

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.

These goals are all critical, project-defining priorities. Priority #1 is "direct compatibility" because any new shell absolutely needs a way to use existing executables in a direct and natural way.

Commands

Initial commands

command	description
cd path	Change to a new path
ls (path)	View the contents of the current or given path
ps	View current processes
open {filename or url}	Load a file into a cell, convert to table if possible (avoid by appending '--raw')
enter {filename or url}	Enter (mount) the given contents as the current object
exit	Leave/pop from the current object (exits if in filesystem object)

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
skip amount	Skip a number of rows
first amount	Show only the first number of rows
to-array	Collapse rows into a single list
to-json	Convert table into .json text
to-toml	Convert table into .toml text
to-ini	Convert table into .ini text

Filters on text (unstructured data)

command	description
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
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
clip	Copy the contents of the pipeline to the copy/paste buffer
save filename	Save the contents of the pipeline to a file
tree	View the contents of the pipeline as a tree

License

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