bash - How to check if a Docker image with a specific tag exist locally?

Question

I'd like to find out if a Docker image with a specific tag exists locally. I'm fine by using a bash script if the Docker client cannot do this natively.

Just to provide some hints for a potential bash script the result of running the docker images command returns the following:

REPOSITORY                               TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
rabbitmq                                 latest              e8e654c05c91        5 weeks ago         143.5 MB
busybox                                  latest              8c2e06607696        6 weeks ago         2.433 MB
rabbitmq                                 3.4.4               a4fbaad9f996        11 weeks ago        131.5 MB

Answer 1

I usually test the result of docker images -q (as in this script):

if [[ "$(docker images -q myimage:mytag 2> /dev/null)" == "" ]]; then
  # do something
fi

But since docker images only takes REPOSITORY as parameter, you would need to grep on tag, without using -q.

docker images takes tags now (docker 1.8+) [REPOSITORY[:TAG]]

The other approach mentioned below is to use docker inspect.
But with docker 17+, the syntax for images is: docker image inspect (on an non-existent image, the exit status will be non-0)

As noted by iTayb in the comments:

• The docker images -q method can get really slow on a machine with lots of images. It takes 44s to run on a 6,500 images machine.
• The docker image inspect returns immediately.

---

As noted in the comments by Henry Blyth:

If you use docker image inspect my_image:my_tag, and you want to ignore the output, you can add --format="ignore me" and it will print that literally.

You can also redirect stdout by adding >/dev/null but, if you can't do that in your script, then the format option works cleanly.