dock.sh

# runs on host mac
echo $UID  # prints your id
whoami # prints your username

docker pull ubuntu:18.04
cd to/your/cpp/projects/dir
docker run -it --name u18 -v "$PWD":/cpp:delegated --cap-add=SYS_PTRACE ubuntu:18.04

# get into container as root
docker exec -u 0 -it u18 bash

# inside docker as root
adduser --disabled-password --gecos "" -u <your uid from line 2> <your username from line 3>

# get into docker as your user
docker exec -u $(whoami) -it u18 bash