Environment Variables

Vector interpolates environment variables within your configuration file with the following syntax:

transforms:
  add_host:
    type: "remap"
    source: |
      # Basic usage. "$HOSTNAME" also works.
      .host = "${HOSTNAME}" # or "$HOSTNAME"

      # Setting a default value when not present.
      .environment = "${ENV:-development}"

      # Requiring an environment variable to be present.
      .tenant = "${TENANT:?tenant must be supplied}"

Default values

Default values can be supplied using :- syntax:

option: "${ENV_VAR:-default}" # default value if variable is unset or empty

Or the - syntax:

option: "${ENV_VAR-default}" # default value only if variable is unset

Required variables

Environment variables that are required can be specified using :? syntax:

option: "${ENV_VAR:?err}" # Vector exits with 'err' message if variable is unset or empty

Or the ? syntax for unset variables:

option: "${ENV_VAR?err}" # Vector exits with 'err' message only if variable is unset.

Escaping

You can escape environment variables by prefacing them with a $ character. For example $${HOSTNAME} or $$HOSTNAME is treated literally in the above environment variable example.

Security Restrictions

Vector prevents security issues related to environment variable interpolation by rejecting environment variables that contain newline characters. This also prevents injection of multi-line configuration blocks.

If you need to inject multi-line configuration blocks, use a config pre-processing step with a tool like envsubst. This approach gives you more control over the configuration and allows you to inspect the result before passing it to Vector:

# config_template.yaml
${SOURCES_BLOCK}
sinks:
  console:
    type: console
    inputs: ["demo"]
    encoding:
      codec: json

# Export multi-line block
export SOURCES_BLOCK="sources:
  demo:
    type: demo_logs
    format: json
    interval: 1"

# Process template and inspect result
envsubst < config_template.yaml > config.yaml

# Start Vector with processed config
vector --config config.yaml
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