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Goal: update terminal command prompt with CPU usage statistics since last prompt appeared, e.g., jeremy@Mac:57%CPU|~/ $

Research: I know on Linux, iostat reads /proc/stat and looks for changes between checks to give accurate information. I used something like the following on CentOS:

 local cur_tick_total=$(awk 'FNR == 1 {sum=0; for (i=2; i<=NF; i++) {sum+=$i} printf "%.0f\n", sum}' /proc/stat)
 local cur_tick_idle=$(awk 'FNR == 1 {print $5}' /proc/stat)
 local delta_tick_total=$(( $cur_tick_total - $__prev_tick_total ))
 local delta_tick_idle=$(( $cur_tick_idle - $__prev_tick_idle ))
 local percent_idle=$(( $delta_tick_idle * 100 / $delta_tick_total ))
 __cpu=$(( 100 - $percent_idle ))

Question: How can I do this on Mac? If iostat works the same way as on Linux, it has to read from somewhere like this, but /proc/stat doesn't exist on Mac. I want to know where it looks to be able to read from that location myself as part of my PS1.

Edit: iostat's output does not work for my purposes, since it outputs either system load average, which is a nonsense number or CPU % usages since system boot, which is not helpful to me. I want a more instantaneous actual CPU usage metric that I can get instantly via the command line.

jeremysprofile
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  • AFAIK there is no similar user-readable structure on macOS. You can call iostat from PS1 or PROMPT_COMMAND though. – nohillside Oct 29 '18 at 21:44
  • iostat does not perform the same functions. Calling iostat once gives you average usage since last boot (and some load averages). I want the cpu usage since last command prompt appearance. Is there any way to get this functionality? – jeremysprofile Oct 29 '18 at 21:47
  • Parsing the output of uptime might be an option. – nohillside Oct 30 '18 at 06:45
  • uptime for me just gives me load averages, same as a single iostat call. I think load averages are not useful so I'm not especially interested in that number. I just want a snapshot CPU usage metric. – jeremysprofile Oct 30 '18 at 16:15
  • Maybe rephrase your question to focus more on the data you need than on the way one does it on Linux to get better answers then – nohillside Oct 30 '18 at 16:23
  • PS: I don‘t think CPU% load is a meaningful indicator in multi-core, multi-process System, but that doesn‘t help you :-) – nohillside Oct 30 '18 at 16:25
  • haha. Can you explain why it's not useful in your opinion? Or what you'd use instead?

    I feel like my question is fairly clear, and the goal statement at the top explains what the actual task is. There have been other questions on other SE sites asking for mac CPU usage and they've all pretty much been shot down. If there's a way to understand how iostat works though, I could make my own.

     – jeremysprofile Oct 30 '18 at 16:32
  • Where does iostat get the data from -> in macOS that‘s a development question. What you want to know (as far as I understand) is „how can I include actual CPU load into my command prompt“, which is a different question and might get better answers because it focuses on the outcome rather than the way – nohillside Oct 30 '18 at 16:52
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    powermetrics might be an option (judging from the man page). Or other commands where the man page mentions "cpu" (grep cpu /usr/share/man/man1/*) – nohillside Oct 31 '18 at 15:57
  • Thanks for the tip about grepping the man pages. I think ps with its 1 minute average is close enough for my preferences. powermetrics doesn't look like it'll work (it needs to run over time to get something other than "since boot" usage). – jeremysprofile Oct 31 '18 at 16:28
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    @nohillside, in case you're curious, here's what I've got working – jeremysprofile Nov 07 '18 at 21:34
  • Nice approach :-) – nohillside Nov 07 '18 at 22:37

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