Format command and log output

Docker uses Go templates which you can use to manipulate the output format of certain commands and log drivers.

Docker provides a set of basic functions to manipulate template elements. All of these examples use the docker inspect command, but many other CLI commands have a --format flag, and many of the CLI command references include examples of customizing the output format.

join

join concatenates a list of strings to create a single string. It puts a separator between each element in the list.

docker inspect --format '{{join .Args " , "}}' container

json

json encodes an element as a json string.

docker inspect --format '{{json .Mounts}}' container

lower

lower transforms a string into its lowercase representation.

docker inspect --format "{{lower .Name}}" container

split

split slices a string into a list of strings separated by a separator.

docker inspect --format '{{split .Image ":"}}'

title

title capitalizes the first character of a string.

docker inspect --format "{{title .Name}}" container

upper

upper transforms a string into its uppercase representation.

docker inspect --format "{{upper .Name}}" container

println

println prints each value on a new line.

docker inspect --format='{{range .NetworkSettings.Networks}}{{println .IPAddress}}{{end}}' container

Hint

To find out what data can be printed, show all content as json:

docker container ls --format='{{json .}}'