Execute a command on an already running Docker container. More information: https://docs.docker.com/reference/cli/docker/container/exec/.
docker exec --interactive --tty container_name /bin/bash
docker exec --detach container_name command
docker exec --interactive --tty --workdir path/to/directory container_name command
stdin
open:docker exec --interactive --detach container_name command
docker exec --interactive --tty --env variable_name=value container_name /bin/bash
docker exec --user user container_name command