nushell/docs/commands/def.md

---
title: def
layout: command
version: 0.59.0
---

Define a custom command

## Signature

```> def (def_name) (params) (block)```

## Parameters

 -  `def_name`: definition name
 -  `params`: parameters
 -  `block`: body of the definition
Auto-generate markdown command docs (#4451) * Finish updating * a couple improvements * Update renames * cleanup examples 2022-02-14 03:22:51 +01:00			`---`
			`title: def`
			`layout: command`
			`version: 0.59.0`
			`---`
Add def documentation (#2939) 2021-01-15 08:21:18 +01:00
Auto-generate markdown command docs (#4451) * Finish updating * a couple improvements * Update renames * cleanup examples 2022-02-14 03:22:51 +01:00			`Define a custom command`
Add def documentation (#2939) 2021-01-15 08:21:18 +01:00
Auto-generate markdown command docs (#4451) * Finish updating * a couple improvements * Update renames * cleanup examples 2022-02-14 03:22:51 +01:00			`## Signature`
Add def documentation (#2939) 2021-01-15 08:21:18 +01:00
Auto-generate markdown command docs (#4451) * Finish updating * a couple improvements * Update renames * cleanup examples 2022-02-14 03:22:51 +01:00			```> def (def_name) (params) (block)```
Add def documentation (#2939) 2021-01-15 08:21:18 +01:00
Auto-generate markdown command docs (#4451) * Finish updating * a couple improvements * Update renames * cleanup examples 2022-02-14 03:22:51 +01:00			`## Parameters`
Add possibility to declare optional parameters and switch flags (#2966) * Add possibility to declare optional parameters and switch flags With this commit applied it is now possible to specify optional parameters and flags as switches. This PR only makes guarantees about parsing optional flags and switches correctly. This PR does not guarantee flawless functionality of optional parameters / switches within scripts. functionality within scripts. Example: test.nu ```shell def my_command [ opt_param? opt_param2?: int --switch ] {echo hi nushell} ``` ```shell > source test.nu > my_command -h ───┬───────── 0 │ hi 1 │ nushell ───┴───────── Usage: > my_command <mandatory_param> (opt_param) (opt_param2) {flags} Parameters: <mandatory_param> (opt_param) (opt_param2) Flags: -h, --help: Display this help message --switch --opt_flag <any> ``` * Update def docs 2021-01-27 18:31:29 +01:00
Auto-generate markdown command docs (#4451) * Finish updating * a couple improvements * Update renames * cleanup examples 2022-02-14 03:22:51 +01:00			- `def_name`: definition name
			- `params`: parameters
			- `block`: body of the definition
Add possibility to declare optional parameters and switch flags (#2966) * Add possibility to declare optional parameters and switch flags With this commit applied it is now possible to specify optional parameters and flags as switches. This PR only makes guarantees about parsing optional flags and switches correctly. This PR does not guarantee flawless functionality of optional parameters / switches within scripts. functionality within scripts. Example: test.nu ```shell def my_command [ opt_param? opt_param2?: int --switch ] {echo hi nushell} ``` ```shell > source test.nu > my_command -h ───┬───────── 0 │ hi 1 │ nushell ───┴───────── Usage: > my_command <mandatory_param> (opt_param) (opt_param2) {flags} Parameters: <mandatory_param> (opt_param) (opt_param2) Flags: -h, --help: Display this help message --switch --opt_flag <any> ``` * Update def docs 2021-01-27 18:31:29 +01:00