ifiokjr/oh-pi/nushell

# Immutable (preferred)
let name = "world"
let files = (ls)                    # Parentheses for subexpressions
let big = (ls | where size > 10kb)
 
# Mutable
mut count = 0
$count += 1
 
# Constants (parse-time evaluation)
const config_dir = "~/.config"
 
# Environment variables: use $env.VAR, NOT $VAR
$env.PATH
$env.HOME
$env.PWD
let path = $env.PATH | append "/usr/local/bin"
 
# $in: the current pipeline input
[1 2 3] | $in.1                     # => 2
ls | $in | where size > 1mb

# Data flows left to right as structured values
ls | where type == dir | sort-by modified | first 5
 
# Multi-line pipelines in parentheses
let result = (
    ls
    | where size > 10kb
    | sort-by name
    | select name size
)
 
# Chaining: use ; (not &&)
cmd1; cmd2                          # Sequential, no output piping between them
cmd1; cmd2 | cmd3                   # cmd1 runs, output discarded; cmd2 pipes to cmd3
 
# Logical chaining uses and/or (not &&/||)
cmd1 and cmd2                       # Run cmd2 only if cmd1 succeeds
cmd1 or cmd2                        # Run cmd2 only if cmd1 fails

# Create a table inline
[[name, size]; [file1.txt, 100] [file2.txt, 200]]
 
# Select columns
ls | select name size modified
 
# Reject (drop) columns
ls | reject type
 
# Filter rows
ls | where size > 1mb and type == file
ls | where name =~ "\.rs$"          # Regex match
ls | where name starts-with "D"
 
# Sort
ls | sort-by size --reverse
 
# Iterate over rows
ls | each { |file| $"($file.name) is ($file.size)" }
ls | each { |it| $it.name }         # Shorthand: $it is the current item
 
# Access nested data with dots
{ a: { b: 3 } } | get a.b           # => 3
ls | get name.0                      # First filename
 
# Update/add record fields
{ name: "nu", stars: 5 } | upsert language "Rust"
 
# Merge records
{ a: 1 } | merge { b: 2 }           # => { a: 1, b: 2 }

# Interpolation: use $"..." with () placeholders
let name = "Alice"
$"Hello, ($name)!"                  # => Hello, Alice!
 
# Concatenate
"Hello " + "World"
 
# Split
"a,b,c" | split row ","             # => [a, b, c]
 
# Join
[a b c] | str join ","              # => a,b,c
 
# Replace
"hello world" | str replace "world" "nushell"
"hello world" | str replace --all 'l' 'L'
 
# Contains
"hello" | str contains "ell"        # => true
 
# Substring
"Hello World!" | str substring 4..8 # => o Wo
 
# Parse into columns
"Nushell 0.98" | parse "{shell} {version}"
 
# Uppercase/lowercase
"hello" | str upcase                # => HELLO

# Create
[1, 2, 3]
1..10                               # Range: 1,2,3,...,10
 
# Access by index
let lst = [a b c]
$lst.0                              # => a
$lst.-1                             # => c (last element)
 
# Modify (creates new lists: immutable)
[1, 2, 3] | insert 1 99             # Insert at index
[1, 2, 3] | update 1 99            # Replace at index
[1, 2, 3] | prepend 0              # Add to front
[1, 2, 3] | append 4               # Add to end
[1, 2, 3] | drop 1                  # Remove at index
 
# Iterate
[1, 2, 3] | each { |n| $n * 2 }    # => [2, 4, 6]
[1, 2, 3] | each { $in * 2 }       # Same, using $in
 
# Map with index
[a b c] | enumerate | each { |it| $"($it.index): ($it.item)" }
 
# Reduce
[3, 8, 4] | reduce { |it, acc| $acc + $it }  # => 15
[3, 8, 4] | reduce --fold 1 { |it, acc| $acc * $it }  # => 96
 
# Test elements
[1, 2, 3] | any { $in > 2 }         # => true
[1, 2, 3] | all { $in > 0 }         # => true
 
# Length
[1, 2, 3] | length                  # => 3

# Basic command
def greet [name: string] {
    $"hello ($name)"
}
 
# With default value
def greet [name = "nushell"] {
    $"hello ($name)"
}
 
# Typed parameters
def double [x: int]: int {
    $x * 2
}
 
# Flags
def greet [
    name: string
    --age: int          # Optional flag with value
    --verbose (-v)      # Shorthand flag (-v)
] {
    # body
}
greet "Alice" --age 30
greet "Bob" -v
 
# Rest parameters (variadic)
def multi [...names: string] {
    $names | each { $"Hello ($in)" }
}
multi Alice Bob Carol
 
# Pipeline input in custom commands
def my_filter [] {
    let data = $in                   # Capture pipeline input
    $data | where size > 1mb
}
ls | my_filter

# Define inline
module greetings {
    export def hello [] { "hello" }
}
use greetings
greetings hello                     # Subcommand style
 
# From file
use path/to/module.nu

# Run external commands with ^ prefix
^git status
^cargo build --release
^rg "TODO" src/
 
# Capture external command output (returns raw string)
let output = (^git branch | lines)
let status = (^git status --porcelain)
 
# Pipe through external commands
ls | get name | to text | ^grep ".rs"
 
# Discard output
^noisy-command | ignore

# If/else: must produce same type from both branches
if $condition {
    "yes"
} else {
    "no"
}
 
# For loops
for file in (ls) {
    print $"Processing ($file.name)"
}
 
# While
while $count < 10 {
    $count += 1
}
 
# Try/catch
try {
    risky-command
} catch { |err|
    print $"Failed: ($err.msg)"
}

# Process all files matching a pattern
ls **/*.rs | each { |file|
    print $"Linting ($file.name)"
    ^rustfmt $file.name
}
 
# Count lines of code (approximate)
ls **/*.rs | each { open --raw $in.name | lines | length } | math sum
 
# Find recently modified files
ls **/* | where modified > (date now) - 1day
 
# Convert JSON to CSV
open data.json | to csv | save data.csv
 
# Parse log files
open access.log | lines | parse "{ip} - - [{date}] \"{method} {path}\" {status} {size}"