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

Define a custom command, which participates in the caller environment

## Signature

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

## Parameters

 -  `def_name`: definition name
 -  `params`: parameters
 -  `block`: body of the definition

## Examples

Set environment variable by call a custom command
```shell
> def-env foo [] { let-env BAR = "BAZ" }; foo; $env.BAR
```