How to Retrieve Dot-Delimited Labels in Docker with `docker inspect`?

Navigating Dot-Delimited Docker Image Labels

The Docker inspect command proves valuable in retrieving labels associated with Docker images. Using the --format option, one can conveniently access label values using Go templates. However, challenges arise when dealing with labels containing dots (".") in their names.

The Challenge of Dotted Label Names

As demonstrated in the code below, using the --format option fails to retrieve labels with dots in their names:

# Dockerfile
FROM busybox
LABEL foo="bar"
LABEL com.wherever.foo="bang"

# Build the image
$ docker build -t foo .

# Attempt to retrieve the label using --format
$ docker inspect -f '{{ .Config.Labels.com.wherever.foo }}' foo
<no value></no>

Resolving the Issue with the Index Function

To access dotted labels, utilize the index function, which allows for the retrieval of arbitrary strings from a map. This eliminates the need to parse the JSON output from docker inspect.

# Using the index function
$ docker inspect -f '{{ index .Config.Labels "com.wherever.foo" }}' foo
bang

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