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

## Examples

Define a command and run it
```shell
> def say-hi [] { echo 'hi' }; say-hi
```

Define a command and run it with parameter(s)
```shell
> def say-sth [sth: string] { echo $sth }; say-sth hi
```