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# Nushell cheat sheet
## Data types
```nu
> "12" | into int
```
> **converts string to integer**
---
```nu
> date now | date to-timezone "Europe/London"
```
> **converts present date to provided time zone**
---
```nu
> {'name': 'nu', 'stars': 5, 'language': 'Python'} | upsert language 'Rust'
```
> **updates a record's language and if none is specified inserts provided value**
---
```nu
> [one two three] | to yaml
```
> **converts list of strings to yaml**
---
```nu
> [[framework, language]; [Django, Python] [Lavarel, PHP]]
```
> **prints the table**
---
```nu
> [{name: 'Robert' age: 34 position: 'Designer'}
{name: 'Margaret' age: 30 position: 'Software Developer'}
{name: 'Natalie' age: 50 position: 'Accountant'}
] | select name position
```
> **selects two columns from the table and prints their values**
## Strings
```nu
> let name = "Alice"
> $"greetings, ($name)!"
```
> **prints `greetings, Alice!`**
---
```nu
> let string_list = "one,two,three" | split row ","
$string_list
╭───┬───────╮
│ 0 │ one │
│ 1 │ two │
│ 2 │ three │
╰───┴───────╯
```
> **splits the string with specified delimiter and saves the list to `string_list` variable**
---
```nu
"Hello, world!" | str contains "o, w"
```
> **checks if a string contains a substring and returns `boolean`**
---
```nu
let str_list = [zero one two]
$str_list | str join ','
```
> **joins the list of strings using provided delimiter**
---
```nu
> 'Hello World!' | str substring 4..8
```
> **created a slice from a given string with start (4) and end (8) indices**
---
```nu
> 'Nushell 0.80' | parse '{shell} {version}'
╭───┬─────────┬─────────╮
│ # │ shell │ version │
├───┼─────────┼─────────┤
│ 0 │ Nushell │ 0.80 │
╰───┴─────────┴─────────╯
```
> **parses the string to columns**
```nu
> "acronym,long\nAPL,A Programming Language" | from csv
```
> **parses comma separated values (csv)**
```nu
> $'(ansi purple_bold)This text is a bold purple!(ansi reset)'
```
> **ansi command colors the text (alsways end with `ansi reset` to reset color to default)**
## Lists
```nu
> [foo bar baz] | insert 1 'beeze'
╭───┬───────╮
│ 0 │ foo │
│ 1 │ beeze │
│ 2 │ bar │
│ 3 │ baz │
╰───┴───────╯
```
> **inserts `beeze` value at st index in the list**
---
```nu
> [1, 2, 3, 4] | update 1 10
```
> **updates 2nd value to 10**
---
```nu
> let numbers = [1, 2, 3, 4, 5]
> $numbers | prepend 0
```
> **adds value at the beginning of the list**
---
```nu
> let numbers = [1, 2, 3, 4, 5]
> $numbers | append 6
```
> **adds value at the end of the list**
---
```nu
> let flowers = [cammomile marigold rose forget-me-not]
> let flowers = ($flowers | first 2)
> $flowers
```
> **creates slice of first two values from `flowers` list**
---
```nu
> let planets = [Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune]
> $planets | each { |it| $"($it) is a planet of solar system" }
```
> **iterates over a list; `it` is current list value**
---
```nu
> $planets | enumerate | each { |it| $"($it.index + 1) - ($it.item)" }
```
> **iterates over a list and provides index and value in `it`**
---
```nu
> let scores = [3 8 4]
> $"total = ($scores | reduce { |it, acc| $acc + $it })"
```
> **reduces the list to a single value, `reduce` gives access to accumulator that is applied
> to each element in the list**
---
```nu
> $"total = ($scores | reduce --fold 1 { |it, acc| $acc * $it })"
```
> **initial value for accumulator value can be set with `--fold`**
---
```nu
> let planets = [Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune]
> $planets.2
> Earth
```
> **gives access to the 3rd item in the list**
---
```nu
> let planets = [Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune]
> $planets | any {|it| $it | str starts-with "E" }
> true
```
> **checks if any string in the list starts with `E`**
---
```nu
> let cond = {|x| $x < 0 }; [-1 -2 9 1] | take while $cond
╭───┬────╮
│ 0 │ -1 │
│ 1 │ -2 │
╰───┴────╯
```
> **creates slice of items that satisfy provided condition**
## Tables
```nu
> ls | sort-by size
```
> **sorting table by size of files**
---
```nu
> ls | sort-by size | first 5
```
> **sorting table by size of files and show first 5 entries**
---
```nu
> let $a = [[first_column second_column third_column]; [foo bar snooze]]
> let $b = [[first_column second_column third_column]; [hex seeze feeze]]
> $a | append $b
╭───┬──────────────┬───────────────┬──────────────╮
│ # │ first_column │ second_column │ third_column │
├───┼──────────────┼───────────────┼──────────────┤
│ 0 │ foo │ bar │ snooze │
│ 1 │ hex │ seeze │ feeze │
╰───┴──────────────┴───────────────┴──────────────╯
```
> **concatenate two tables with same columns**
---
```nu
> let teams_scores = [[team score plays]; ['Boston Celtics' 311 3] ['Golden State Warriors', 245 2]]
> $teams_scores | drop column
╭───┬───────────────────────┬───────╮
│ # │ team │ score │
├───┼───────────────────────┼───────┤
│ 0 │ Boston Celtics │ 311 │
│ 1 │ Golden State Warriors │ 245 │
╰───┴───────────────────────┴───────╯
```
> **remove the last column of a table**
## Files & Filesystem
```nu
> start file.txt
```
> **opens a text file with the default text editor**
---
```nu
> 'lorem ipsum ' | save file.txt
```
> **saves a string to text file**
---
```nu
> 'dolor sit amet' | save --append file.txt
```
> **appends a string to the end of file.txt**
---
```nu
> { a: 1, b: 2 } | save file.json
```
> **saves a record to file.json**
---
```nu
> glob **/*.{rs,toml} --depth 2
```
> **searches for `.rs` and `.toml` files recursively up to 2 folders deep**
---
```nu
> watch . --glob=**/*.rs {|| cargo test }
```
> **runs cargo test whenever a Rust file changes**
---
## Custom Commands
```nu
def greet [name: string] {
$"hello ($name)"
}
```
> **custom command with parameter type set to string**
---
```nu
def greet [name = "nushell"] {
$"hello ($name)"
}
```
> **custom command with default parameter set to nushell**
---
```nu
def greet [
name: string
--age: int
] {
[$name $age]
}
> greet world --age 10
```
> **passing named parameter by defining flag for custom commands**
---
```nu
def greet [
name: string
--age (-a): int
--twice
] {
if $twice {
[$name $age $name $age]
} else {
[$name $age]
}
}
> greet -a 10 --twice hello
```
> **using flag as a switch with a shorthand flag (-a) for the age**
---
```nu
def greet [...name: string] {
print "hello all:"
for $n in $name {
print $n
}
}
> greet earth mars jupiter venus
```
> **custom command which takes any number of positional arguments using rest params**
## Variables & Subexpressions
```nu
> let val = 42
> print $val
42
```
> **an immutable variable cannot change its value after declaration**
---
```nu
> let val = 42
> do { let val = 101; $val }
101
> $val
42
```
> **shadowing variable (declaring variable with the same name in a different scope)**
---
```nu
> mut val = 42
> $val += 27
> $val
69
```
> **declaring a mutable variable with mut key word**
---
```nu
> mut x = 0
> [1 2 3] | each { $x += 1 }
```
> **closures and nested defs cannot capture mutable variables from their environment.
> This expression results in error.**
```nu
> const plugin = 'path/to/plugin'
> register $plugin
```
> **a constant variable is immutable value which is fully evaluated at parse-time**
---
```nu
> let files = (ls)
> $files.name?.0?
```
> **using question mark operator to return null instead of error if provided path is incorrect**
---
```nu
> let big_files = (ls | where size > 10kb)
> $big_files
```
> **using subexpression by wrapping the expression with parentheses ()**
---
## Modules
```nu
> module greetings {
export def hello [name: string] {
$"hello ($name)!"
}
export def hi [where: string] {
$"hi ($where)!"
}
}
> use greetings hello
> hello "world"
```
> **using inline module**
---
```nu
# greetings.nu
export-env {
$env.MYNAME = "Arthur, King of the Britons"
}
export def hello [] {
$"hello ($env.MYNAME)"
}
> use greetings.nu
> $env.MYNAME
Arthur, King of the Britons
> greetings hello
hello Arthur, King of the Britons!
```
> **importing module from file and using its environment in current scope**
---
```nu
# greetings.nu
export def hello [name: string] {
$"hello ($name)!"
}
export def hi [where: string] {
$"hi ($where)!"
}
export def main [] {
"greetings and salutations!"
}
> use greetings.nu
> greetings
greetings and salutations!
> greetings hello world
hello world!
```
> **using main command in module**
---
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