The CPU usage data is generated by the first loop that runs for one hour (3600 seconds). Once each minute, the ps -eocomm,pcpu command generates a report on the system activity at that time. The -e option specifies to collect data on all processes, not just this session's tasks. The -o option specifies an output format. The comm and pcpu words specify reporting the command name and percentage of CPU, respectively. This ps command generates a line with the command name and current percentage of CPU usage for each running process. These lines are filtered with grep to remove lines where there was no CPU usage (%CPU is 0.0) and the COMMAND %CPU header. The interesting lines are appended to a temporary file.

The temporary file is named /tmp/cpu_usage.$$. Here, $$ is a script variable that holds the process ID (PID) of the current script. For example, if the script's PID is 1345, the temporary file will be named /tmp/cpu_usage.1345.

The statistics file will be ready after one hour and will contain 60 sets of entries, corresponding to the system status at each minute. The awk script sums the total CPU usage for each process into an associative array named process. This array uses the process name as array index. Finally, awk sorts the result with a numeric reverse sort according to the total CPU usage and uses head to limit the report to the top 10 usage entries.