docker exec

Execute a command on an already running Docker container. More information: https://docs.docker.com/engine/reference/commandline/exec/.

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}}