docker-exec
Execute a command on an already running Docker container.
TLDR
Enter an interactive shell session on an already-running container
$ docker exec --interactive --tty [container_name] [/bin/bash]
Run a command in the background (detached) on a running container
$ docker exec --detach [container_name] [command]
Select the working directory for a given command to execute into
$ docker exec --interactive -tty --workdir [path/to/directory] [container_name] [command]
Run a command in background on existing container but keep stdin open
$ docker exec --interactive --detach [container_name] [command]
Set an environment variable in a running bash session
$ docker exec --interactive --tty --env [variable_name]=[value] [container_name] [/bin/bash]
Run a command as a specific user
$ docker exec --user [user] [container_name] [command]
