apiVersion: v1
    kind: ConfigMap
    metadata:
      name: time-config
    data:
      TIME_FREQ: "6"
    ---
    apiVersion: v1
    kind: Pod
    metadata:
      name: time-check
    spec:
      containers:
      - name: time-check
        image: busybox:latest
        command: ["/bin/sh"]
        args: ["-c","while true; do date; sleep $TIME_FREQ;done >> /opt/data/time/time-check.log"]
        env:
          - name: TIME_FREQ
            valueFrom:
              configMapKeyRef:
                name: time-config
                key: TIME_FREQ
        volumeMounts:
          - name: log-volume
            mountPath: /opt/data/time
      volumes:
      - name: log-volume
        emptyDir: {}

According to [documentation][1], to use variable you should put it in parentheses, however, that gives me:

    TIME_FREQ: command not found
    sleep: missing operand

If I use only $TIME_FREQ, the variable does not expand at all and `sleep` only complains about missing operand. I've tried curly braces, but didn't work, too.

  [1]: https://kubernetes.io/docs/tasks/inject-data-application/define-command-argument-container/#use-environment-variables-to-define-arguments

If I set the variable locally, the config will accept it and the command runs ok, with variable defined as $TIME_FREQ.

Why does it not work?