env-vars.md.erb

---
title: Environment Variables
description: "A full list of Vector's supported environment variables and how to use them."
sidebar_label: Env Vars
---

You can control Vector's behavior through select environment variables:

```bash
ENV_VAR1=val ENV_VAR2=val vector --config=/etc/vector/vector.toml
```

In addition, we recommend that you look at the [global configuration
options][docs.global-options] as well.

## Special Variables

<%= fields(metadata.env_vars_list, heading_depth: 3) %>

## Custom Variables

As noticed in the [configuration document][docs.configuration#environment-variables],
Vector supports custom environment variables via the `${...}` syntax:

```toml
option = "${ENV_VAR}"
```

<Alert type="info">

Interpolation is done before parsing the configuration file. This is done when
[starting][docs.process-management#starting] and
[reloading][docs.process-management#reloading] Vector.

</Alert>

### Default Values

Default values can be supplied via the `:-` syntax:

```toml
option = "${ENV_VAR:-default}"
```

### Escaping

You can escape environment variable by preceding them with a `$` character. For
example `$${HOSTNAME}` will be treated _literally_ in the above environment
variable example.