is not provided.
Variable references $(VAR_NAME) are expanded using the container's environment. If a variable
cannot be resolved, the reference in the input string will be unchanged. Double $$ are reduced
to a single $, which allows for escaping the $(VAR_NAME) syntax: i.e. "$$(VAR_NAME)" will
produce the string literal "$(VAR_NAME)". Escaped references will never be expanded, regardless
of whether the variable exists or not. Cannot be updated.
More info: https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#running-a-command-in-a-shell²