envsubst

Substitute environment variables in text

medium risk

interactive breakdown — edit the command and press Explain

$

⚠ Risks & cautions

Unlisted variables become empty strings silently — restrict substitution to a variable list.
Rendered files may contain secrets; protect their permissions.

What it does

Replaces $VAR placeholders in a template with environment values — common in config rendering.

Common flags

Flag	Meaning
`$VARS`	Limit substitution to listed variables (argument)

Examples

envsubst '$HOST $PORT' < tpl > outSubstitute only HOST and PORT · explain & risk-check →

Related

Open the full explainer →More in Text Processing

Reference text is hand-written and may be incomplete — check man envsubst for your version. Test destructive commands on a non-production system first.