Showing memory utilization by users. (from https://www.networkworld.com/article/3516319/showing-memory-usage-in-linux-by-process-and-user.html)

ps_users.sh

#!/bin/bash

stats=””
echo "%   user"
echo "============"

# collect the data
for user in `ps aux | grep -v COMMAND | awk '{print $1}' | sort -u`
do
  stats="$stats\n`ps aux | egrep ^$user | awk 'BEGIN{total=0}; \
    {total += $4};END{print total,$1}'`"
done

# sort data numerically (largest first)
echo -e $stats | grep -v ^$ | sort -rn | head