Interview › Scripting (Bash, Groovy)
What does ${var:?message} do, and when would you use it? [Intermediate]
Answer
${var:?message} fails immediately with the message if var is unset or empty. I use it for required inputs such as environment, cluster, database URL, or credentials reference.
Technical explanation
It is a concise precondition check and works well with set -u.
The script exits or returns depending on context, so it prevents continuing with missing critical data.
Use ${var?message} if an empty string is allowed but an unset variable is not.
Hands-on example
#!/usr/bin/env bash
set -euo pipefail
: "${CLUSTER:?CLUSTER is required}"
: "${NAMESPACE:?NAMESPACE is required}"
kubectl --context "$CLUSTER" -n "$NAMESPACE" get pods
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