When writing a bash script that starts a docker container, it is useful to refer to the started docker container. How do you get the specific container id of a docker container when you start it?
P.S. I know that I can use --name to name the container, which I can use to filter the list of containers using docker ps -aqf "name=containername", but this will fail if I ever start the script twice. And then there's the possibility of name conflicts. Besides, what's the point of container IDs if you can't use them?
When you start a detached container, it returns the container ID. e.g.:
$ docker run -d ubuntu:18.04
71329cf6a02d89cf5f211072dd37716fe212787315ce4503eaee722da6ddf18f
In bash, you can define a new variable from the output like this:
CID=$(docker run -d ubuntu:18.04)
Then, later you can use this variable to refer to your container like this:
docker stop $CID
docker rm $CID
In the documentation for docker run under "capture container id", they advise using the --cidfile flag for this purpose.
--cidfile takes a file name as an argument and will write the long ID of the container to that location. E.g.,
docker run --cidfile /tmp/hello-world.cid hello-world && cat /tmp/hello-world.cid
This is useful when you don't want to run the image in a detached state, but still want access to the ID.