Find the logged-in user on MacOS

get_user.sh

#!/usr/bin/bash

RUID=$(id -ru)
RGID=$(id -rg)

# Find logged in user via the Python -> Objective C bridge
# Docs: https://pythonhosted.org/pyobjc/apinotes/SystemConfiguration.html
output=$(cat << EOF | /usr/bin/python -
import sys
from SystemConfiguration import SCDynamicStoreCopyConsoleUser
res = SCDynamicStoreCopyConsoleUser(None, None, None)
if not res:
    sys.exit(1)
username, uid, gid = res
if (not username) or (username == "loginwindow"):
    sys.exit(1)
print("RUID={}\nRGID={}".format(uid, gid))
EOF
2>/dev/null)
if [ $? = 0 ]; then
    eval "$output"
fi

even if you run this script via sudo, you'll still get the RUID and RGID of yourself, not just 0