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I run a process that takes lot of time. Time is not a problem actually but I would like to know how much RAM memory it requires. Process is already running so /usr/bin/time is not an option. I found the pid of my process and run

watch -n 1 grep VmHWM /proc/3100/status

it works nice, I can leave it, do some other work, and just check later what was the value recorded with 1 seconds intervals. The problem starts if/when a process terminates (either finish job, or get killed because of OOM) because watch replace the last valid output with

grep: /proc/3100/status: No such file or directory

using option -e does not help. Is there a way to make watch not refresh output on non-zero exit? or show two most recent ones, so the previous zero exit can still be seen?

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  • If you know what your process is called, you could incorporate pgrep into that. I'm not posting this as an answer as I don't have a Linux system to test properly on at the moment.
    – Kusalananda
    Dec 5 '19 at 12:54
  • @Kusalananda I used pgrep to find process id. I don't understand how pgrep would help me more, if process terminates then pgrep won't list it anyway, isn't?
    – jangorecki
    Dec 5 '19 at 13:23
  • Oh, I'm sorry. I misinterpreted what you were writing and though that you were watching a particular PID, and that the process later restarted with a new PID, and that you wanted to follow that instead.
    – Kusalananda
    Dec 5 '19 at 13:33
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    I would just use a shell while loop for this. while grep VmHWM /proc/3100/status; do sleep 1; done.
    – Mikel
    Dec 5 '19 at 13:35
  • @Mikel thanks, you suggestion does the job well. Yet I find it strange that watch -e cannot handle that in better way.
    – jangorecki
    Dec 5 '19 at 13:40
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I would use a shell while loop for this.

pid=3100
while out=$(grep VmHWM /proc/$pid/status); do
  printf "\r$out     "
  sleep 1
done
printf "\n"

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