# Environment

A common task in a shell is to control the environment that external applications will use. This is often done automatically, as the environment is packaged up and given to the external application as it launches. Sometimes, though, we want to have more precise control over what environment variables an application sees.

You can see the current environment variables in the $env variable:

```nu
$env | table -e
# => ╭──────────────────────────────────┬───────────────────────────────────────────╮
# => │                                  │ ╭──────┬────────────────────────────────╮ │
# => │ ENV_CONVERSIONS                  │ │      │ ╭─────────────┬──────────────╮ │ │
# => │                                  │ │ PATH │ │ from_string │ <Closure 32> │ │ │
# => │                                  │ │      │ │ to_string   │ <Closure 34> │ │ │
# => │                                  │ │      │ ╰─────────────┴──────────────╯ │ │
# => │                                  │ │      │ ╭─────────────┬──────────────╮ │ │
# => │                                  │ │ Path │ │ from_string │ <Closure 36> │ │ │
# => │                                  │ │      │ │ to_string   │ <Closure 38> │ │ │
# => │                                  │ │      │ ╰─────────────┴──────────────╯ │ │
# => │                                  │ ╰──────┴────────────────────────────────╯ │
# => │ HOME                             │ /Users/jelle                              │
# => │ LSCOLORS                         │ GxFxCxDxBxegedabagaced                    │
# => | ...                              | ...                                       |
# => ╰──────────────────────────────────┴───────────────────────────────────────────╯
```

In Nushell, environment variables can be any value and have any type. You can see the type of an env variable with the describe command, for example: `$env.PROMPT_COMMAND | describe`.

To send environment variables to external applications, the values will need to be converted to strings. See [Environment variable conversions](#environment-variable-conversions) on how this works.

The environment is initially created from the Nu [configuration files](configuration.md) and from the environment that Nu is run inside of.

## Setting Environment Variables

There are several ways to set an environment variable:

### $env.VAR assignment

Using the `$env.VAR = "val"` is the most straightforward method

```nu
$env.FOO = 'BAR'
```

So, if you want to extend the Windows `Path` variable, for example, you could do that as follows.

```nu
$env.Path = ($env.Path | prepend 'C:\path\you\want\to\add')
```

Here we've prepended our folder to the existing folders in the Path, so it will have the highest priority.
If you want to give it the lowest priority instead, you can use the [`append`](/commands/docs/append.md) command.

### [`load-env`](/commands/docs/load-env.md)

If you have more than one environment variable you'd like to set, you can use [`load-env`](/commands/docs/load-env.md) to create a table of name/value pairs and load multiple variables at the same time:

```nu
load-env { "BOB": "FOO", "JAY": "BAR" }
```

### One-shot Environment Variables

These are defined to be active only temporarily for a duration of executing a code block.
See [Single-use environment variables](environment.md#single-use-environment-variables) for details.

### Calling a Command Defined with [`def --env`](/commands/docs/def.md)

See [Defining environment from custom commands](custom_commands.md#changing-the-environment-in-a-custom-command) for details.

### Using Module's Exports

See [Modules](modules.md) for details.

## Reading Environment Variables

Individual environment variables are fields of a record that is stored in the `$env` variable and can be read with `$env.VARIABLE`:

```nu
$env.FOO
# => BAR
```

Sometimes, you may want to access an environmental variable which might be unset. Consider using the [question mark operator](types_of_data.md#optional-cell-paths) to avoid an error: