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.
Whe using the --format flag, you need observe your shell environment. In a Posix shell, you can run the following with a single quote:
docker inspect --format '{{join .Args " , "}}' container
Otherwise, in a Windows shell (for example, PowerShell), you need to use single quotes, but escape the double quotes inside the params as follows:
docker inspect --format '{{join .Args \" , \"}}' container
To find out what data can be printed, show all content as json:
docker container ls --format='{{json .}}'
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
table
table specifies which fields you want to see its output.
docker image list --format "table {{.ID}}\t{{.Repository}}\t{{.Tag}}\t{{.Size}}"
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
Exercise
- print the number of containers:
There are 32 containers
- print the container-id, image, command and status using table format:
CONTAINER ID IMAGE COMMAND STATUS
b213c64c192a busybox "sh -c 'while true; …" Exited (255) 23 minutes ago
970631001c64 busybox "sh -c" Exited (2) 7 days ago
- print the CPU, Memory, Network IO, and Name, using table format:
CPU % MEM % NET I/O NAME
0.00% 0.04% 1.03kB / 0B checktime