nushell

Nushell - Modern Structured Shell

This skill activates when working with Nushell (Nu), writing Nu scripts, working with structured data pipelines, or configuring the Nu environment.

What is Nushell?

Current stable: 0.113.1 (pre-1.0, breaking changes possible between minor versions)

Nushell is a modern shell that:

• Treats data as structured (not just text streams)
• Works cross-platform (Windows, macOS, Linux)
• Combines shell and programming language features
• Has built-in data format support (JSON, CSV, YAML, TOML, XML, etc.)

When Nushell over bash

• Nushell for scripts: any multi-line script, structured-data pipeline, or cross-platform automation. Bash one-liners with grep/awk/sed chains lose type information Nu keeps.
• jq for JSON one-liner parsing in bash contexts; Nu's open/from json/where/get replace jq inside Nu scripts.
• Bash remains for shell-only operations with no Nu alternative, and for embedded commands inside CI runners that only speak POSIX shell.

Installation

# Via mise (recommended for project-level management)
# mise.toml: [tools] → "github:nushell/nushell" = "latest"
mise install github:nushell/nushell

# macOS: brew install nushell | Linux: cargo install nu | Windows: winget install nushell

Core model: everything is structured data

Commands output tables/records, not text. Pipelines transform structured data stage by stage:

# Bash greps text; Nu filters columns
ls | where name =~ ".txt"
ls | where size > 1kb and type == file | sort-by modified | reverse

# Read/write structured formats directly
open data.json | get users | where age > 25 | select name email
open data.csv | to json | save data.json
'{"name": "Alice"}' | from json

Syntax essentials

# Variables: let (immutable), mut (mutable), $env for environment
let threshold = 1mb
mut counter = 0
$counter = $counter + 1
$env.MY_VAR = "value"

# String interpolation: $"..." with parens for expressions
let name = "Alice"
print $"Hello, ($name)! Result: (5 * 2)"

# Collections: lists, records, tables
let users = [{name: "Alice", age: 30} {name: "Bob", age: 25}]
$users | where age > 25 | get name

# Control flow: if/else and match are expressions
let status = if $is_active { "active" } else { "inactive" }
match $age {
  0..17 => "minor"
  _ => "adult"
}

# Iteration: each (functional), for (imperative)
1..5 | each { |i| $i * 2 }
for file in (ls | where type == file) { print $file.name }

# Custom commands: typed params, flags with defaults
def greet [
  name: string
  --loud (-l)            # Flag
  --repeat (-r): int = 1 # Named parameter with default
] {
  1..$repeat | each { print $"Hello, ($name)!" }
}

# Error handling
try { open missing.txt } catch { |err| print $"Error: ($err)" }
let value = ($env.MY_VAR? | default "fallback")

# HTTP built in
http get https://api.example.com/users
http post https://api.example.com/users {name: "Alice"}