How to check if a process is running inside docker container

Question

[Updated1] I have a shell which will change TCP kernel parameters in some functions, but now I need to make this shell run in Docker container, that means, the shell need to

Answer 1

Docker creates .dockerenv and .dockerinit (removed in v1.11) files at the top of the container's directory tree so you might want to check if those exist.

Something like this should work.

#!/bin/bash
if [ -f /.dockerenv ]; then
    echo "I'm inside matrix ;(";
else
    echo "I'm living in real world!";
fi