Which command shows the usage time of the CPU for running processes?

The command that accurately shows the usage time of the CPU for running processes is the one that provides detailed information about active processes, including their CPU time, memory usage, and other resource utilization metrics. In this case, the command that fulfills this requirement is 'ps aux'.

When executed, 'ps aux' lists all running processes along with their CPU and memory usage statistics. Specifically, it displays the CPU time in terms of how much time has been spent on the CPU by each process, which is critical for monitoring performance and understanding how system resources are allocated during operation.

Other commands have different purposes that do not focus specifically on displaying the CPU time for processes. For example, 'top' gives real-time updates and utilizes a different format to present process information, while 'kill' is used to terminate processes and does not provide CPU usage details. Similarly, 'systemctl' is focused on service management rather than process-specific statistics.