Centos – CPU monitoring tool for Centos

There are a lot of answers. I personally use Zenoss, but there's a big list here: http://en.wikipedia.org/wiki/Comparison_of_network_monitoring_systems

Here is a script to print the total CPU usage for each user currently logged in, showPerUserCPU.sh:

own=$(id -nu)
cpus=$(lscpu | grep "^CPU(s):" | awk '{print $2}')

for user in $(who | awk '{print $1}' | sort -u)
do
    # print other user's CPU usage in parallel but skip own one because
    # spawning many processes will increase our CPU usage significantly
    if [ "$user" = "$own" ]; then continue; fi
    (top -b -n 1 -u "$user" | awk -v user=$user -v CPUS=$cpus 'NR>7 { sum += $9; } END { print user, sum, sum/CPUS; }') &
    # don't spawn too many processes in parallel
    sleep 0.05
done
wait

# print own CPU usage after all spawned processes completed
top -b -n 1 -u "$own" | awk -v user=$own -v CPUS=$cpus 'NR>7 { sum += $9; } END { print user, sum, sum/CPUS; }'

And here is a slightly modified version for printing the CPU usage of all available users (but skipping the ones with a CPU usage of zero), showAllPerUserCPU.sh:

own=$(id -nu)
cpus=$(lscpu | grep "^CPU(s):" | awk '{print $2}')

for user in $(getent passwd | awk -F ":" '{print $1}' | sort -u)
do
    # print other user's CPU usage in parallel but skip own one because
    # spawning many processes will increase our CPU usage significantly
    if [ "$user" = "$own" ]; then continue; fi
    (top -b -n 1 -u "$user" | awk -v user=$user -v CPUS=$cpus 'NR>7 { sum += $9; } END { if (sum > 0.0) print user, sum, sum/CPUS; }') &
    # don't spawn too many processes in parallel
    sleep 0.05
done
wait

# print own CPU usage after all spawned processes completed
top -b -n 1 -u "$own" | awk -v user=$own -v CPUS=$cpus 'NR>7 { sum += $9; } END { print user, sum, sum/CPUS; }'

The first column represents the user name, the second column the aggregated CPU usage and the third column the normalized CPU use according to the number of CPU cores.

There is also a related script for showing the total memory usage for each user: showPerUserMem.sh

For live-monitoring just execute these scripts periodically via the watch command.

For sorting by CPU usage, pipe the output to sort -k2 -nr.