The docker top command

You can run the top command from the Docker host machine using the following command:

docker top [OPTIONS] CONTAINER [ps OPTIONS]  

This gives a list of the running processes of a container without logging in to the container, as follows:

$ sudo docker top  a245253db38b
UID             PID            PPID            C
STIME           TTY            TIME            CMD
root            5232           3585            0
Mar22           ?              00:00:53        python  app.py  
$ sudo docker top  a245253db38b  -aef
UID             PID            PPID            C
STIME           TTY            TIME            CMD
root            5232           3585            0
Mar22           ?              00:00:53        python  app.py  

The Docker top command provides information about the CPU, memory, and swap usage if you run it inside a Docker container:

root@a245253db38b:/opt/webapp# top
top - 19:35:03 up...