See also: [Changing the Environment in a Custom Command](./custom_commands.html#changing-the-environment-in-a-custom-command).

## Changing the Directory

A common task in a shell is to change the directory using the [`cd`](/commands/docs/cd.md) command. In Nushell, calling [`cd`](/commands/docs/cd.md) is equivalent to setting the `PWD` environment variable. Therefore, it follows the same rules as other environment variables (for example, scoping).

## Single-use Environment Variables

A common shorthand to set an environment variable once is available, inspired by Bash and others:

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

You can also use [`with-env`](/commands/docs/with-env.md) to do the same thing more explicitly:

```nu
with-env { FOO: BAR } { $env.FOO }
# => BAR
```

The [`with-env`](/commands/docs/with-env.md) command will temporarily set the environment variable to the value given (here: the variable "FOO" is given the value "BAR"). Once this is done, the [block](types_of_data.md#blocks) will run with this new environment variable set.

## Permanent Environment Variables

You can also set environment variables at startup so they are available for the duration of Nushell running. To do this, set an environment variable inside [the Nu configuration file](configuration.md).

For example:

```nu
# In config.nu
$env.FOO = 'BAR'
```

## Environment Variable Conversions

You can set the `ENV_CONVERSIONS` environment variable to convert other environment variables between a string and a value.
For example, the [default environment config](https://github.com/nushell/nushell/blob/main/crates/nu-utils/src/default_files/default_env.nu) includes conversion of PATH (and Path used on Windows) environment variables from a string to a list.
After both `env.nu` and `config.nu` are loaded, any existing environment variable specified inside `ENV_CONVERSIONS` will be translated according to its `from_string` field into a value of any type.
External tools require environment variables to be strings, therefore, any non-string environment variable needs to be converted first.