Retrieve CPU usage and memory usage of a single process on Linux?

Question

I want to get the CPU and memory usage of a single process on Linux - I know the PID. Hopefully, I can get it every second and write it to a CSV using the \'watch\' command

Answer 1

ps command (should not use):

• CPU usage is currently expressed as the percentage of time spent running during the entire lifetime of a process.

top command (should use):

• The task's share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.

Use top to get CPU usage in real time(current short interval):

top -b -n 2 -d 0.2 -p 6962 | tail -1 | awk '{print $9}'

will echo like: 78.6

• -b: Batch-mode
• -n 2: Number-of-iterations, use 2 because: When you first run it, it has no previous sample to compare to, so these initial values are the percentages since boot.
• -d 0.2: Delay-time(in second, here is 200ms)
• -p 6962: Monitor-PIDs
• tail -1: the last row
• awk '{print $9}': the 9-th column(the cpu usage number)