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. What command can I use to get this info from the Linux command-line?

Answer 1

ps -p <pid> -o %cpu,%mem,cmd

(You can leave off "cmd" but that might be helpful in debugging).

Note that this gives average CPU usage of the process over the time it has been running.

Answer 2

A variant of caf's answer: top -p <pid>

This auto-refreshes the CPU usage so it's good for monitoring.

Answer 3

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)

Answer 4

You can get the results by the name of the process using

ps -C chrome -o %cpu,%mem,cmd

the -C option allows you to use process name without knowing it's pid.

Answer 5

Use pidstat (from sysstat - Refer Link).

e.g. to monitor these two process IDs (12345 and 11223) every 5 seconds use

$ pidstat -h -r -u -v -p 12345,11223 5

Answer 6

Launch a program and monitor it

This form is useful if you want to benchmark an executable easily:

topp() (
  if [ -n "$O" ]; then
    $* &
  else
    $* &>/dev/null &
  fi
  pid="$!"
  trap "kill $pid" SIGINT
  o='%cpu,%mem,vsz,rss'
  printf '%s\n' "$o"
  i=0
  while s="$(ps --no-headers -o "$o" -p "$pid")"; do
    printf "$i $s\n"
    i=$(($i + 1))
    sleep "${T:-0.1}"
  done
)

Usage:

topp ./myprog arg1 arg2

Sample output:

%cpu,%mem,vsz
0  0.0  0.0 177584
1  0.0  0.1 588024
2  0.0  0.1 607084
3  0.0  0.2 637248
4  0.0  0.2 641692
5 68.0  0.2 637904
6 80.0  0.2 642832

where vsz is the total memory usage in KiB, e.g. the above had about 600MiB usage.

If your program finishes, the loop stops and we exit topp.

Alternatively, if you git Ctrl + C, the program also stops due to the trap: How do I kill background processes / jobs when my shell script exits?

The options are:

• T=0.5 topp ./myprog: change poll interval
• O=1 topp ./myprog: don't hide program stdout/stderr. This can be useful to help correlate at which point memory usage bursts with stdout.

ps vs top on instantaneous CPU% usage

Note that the CPU usage given by ps above is not "instantaneous" (i.e. over the last N seconds), but rather the average over the processes' entire lifetime as mentioned at: https://unix.stackexchange.com/questions/58539/top-and-ps-not-showing-the-same-cpu-result ps memory measures should be fine however.

That thread as well as: How can I determine the current CPU utilization from the shell? suggest that the Linux kernel does not store any more intermediate usage statistics, so the only way to do that would be to poll and calculate for the previous period, which is what top does.

We could therefore use top -n1 instead of ps if we wanted that:

toppp() (
  $* &>/dev/null &
  pid="$!"
  trap exit SIGINT
  i=1
  top -b n1 -d "${T:-0.1}" -n1 -p "$pid"
  while true; do top -b n1 -d "${T:-0.1}" -n1 -p "$pid"  | tail -1; printf "$i "; i=$(($i + 1)); done
)

as mentioned e.g. at: https://stackoverflow.com/a/62421136/895245 which produces output of type:

top - 17:36:59 up  9:25, 12 users,  load average: 0.32, 1.75, 2.21
Tasks:   1 total,   1 running,   0 sleeping,   0 stopped,   0 zombie
%Cpu(s): 13.4 us,  2.5 sy,  0.0 ni, 84.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :  31893.7 total,  13904.3 free,  15139.8 used,   2849.7 buff/cache
MiB Swap:      0.0 total,      0.0 free,      0.0 used.  16005.5 avail Mem

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
 706287 ciro      20   0  590436  40352  20568 R 106.7   0.1   0:00.16 node
 706287 ciro      20   0  607060  57172  21340 R 126.7   0.2   0:00.35 node
1  706287 ciro      20   0  642008  80276  21812 R 113.3   0.2   0:00.52 node
2  706287 ciro      20   0  641676  93108  21812 R 113.3   0.3   0:00.70 node
3  706287 ciro      20   0  647892  99956  21812 R 106.7   0.3   0:00.87 node
4  706287 ciro      20   0  655980 109564  21812 R 140.0   0.3   0:01.09 node

Some related threads:

• how to run top just once (-b -n1)
  • https://askubuntu.com/questions/484510/how-to-run-top-command-1-time-and-exit
  • https://unix.stackexchange.com/questions/60328/how-to-stream-top-snapshot-into-file asks about
• how to remove the headers from top: no one has a better solution so we just tail it:
  • https://unix.stackexchange.com/questions/471072/how-to-remove-top-commands-header
  • How to suppress the general information for top command

My only problems with this is that top is not as nice for interactive usage:

• Ctrl + C does not exit the above command, not sure why trap exit is not working as it does with ps. I have to kill the command Ctrl + \, and then that does not kill the process itself which continues to run on the background, which means that if it is an infinite loop like a server, I have to ps aux and then kill it.
• the not exit automatically when the benchmarked program exits

Maybe someone more shell savvy than me can find a solution for those.

ps memory measurements should be the same as top however if you're just after memory.

Related:

• Retrieve CPU usage and memory usage of a single process on Linux?
• https://unix.stackexchange.com/questions/554/how-to-monitor-cpu-memory-usage-of-a-single-process

Tested on Ubuntu 21.10.

Answer 7

You could use top -b and grep out the pid you want (with the -b flag top runs in batch mode), or also use the -p flag and specify the pid without using grep.

Answer 8

As commented in caf's answer above, ps and in some cases pidstat will give you the lifetime average of the pCPU. To get more accurate results use top. If you need to run top once you can run:

top -b -n 1 -p <PID>

or for process only data and header:

top -b -n 1 -p <PID> | tail -3 | head -2

without headers:

top -b -n 1 -p <PID> | tail -2 | head -1

Answer 9

The following command gets the average of CPU and memory usage every 40 seconds for a specific process(pid)

pidstat 40 -ru -p <pid>

Output for my case(first two lines for CPU usage, second two lines for memory):

02:15:07 PM       PID    %usr %system  %guest    %CPU   CPU  Command
02:15:47 PM     24563    0.65    0.07    0.00    0.73     3  java

02:15:07 PM       PID  minflt/s  majflt/s     VSZ    RSS   %MEM  Command
02:15:47 PM     24563      6.95      0.00 13047972 2123268   6.52  java

Answer 10

ps aux | awk '{print $4"\t"$11}' | sort | uniq -c | awk '{print $2" "$1" "$3}' | sort -nr

or per process

ps aux | awk '{print $4"\t"$11}' | sort | uniq -c | awk '{print $2" "$1" "$3}' | sort -nr |grep mysql

Answer 11

For those who struggled for a while wonderring why the selected answer does not work:

ps -p <pid> -o %cpu,%mem

No SPACE ibetween %cpu, and %mem.

Answer 12

To get the memory usage of just your application (as opposed to the shared libraries it uses, you need to use the Linux smaps interface). This answer explains it well.

Answer 13

ps aux|awk  '{print $2,$3,$4}'|grep PID

where the first column is the PID,second column CPU usage ,third column memory usage.

Answer 14

(If you are in MacOS 10.10, try the accumulative -c option of top:

top -c a -pid PID

(This option is not available in other linux, tried with Scientific Linux el6 and RHEL6)

Answer 15

ps axo pid,etime,%cpu,%mem,cmd | grep 'processname' | grep -v grep

PID - Process ID

etime - Process Running/Live Duration

%cpu - CPU usage

%mem - Memory usage

cmd - Command

Replace processname with whatever process you want to track, mysql nginx php-fpm etc ...

Answer 16

All of the answers here show only the memory percentage for the PID.

Here's an example of how to get the rss memory usage in KB for all apache processes, replace "grep apache" with "grep PID" if you just want to watch a specific PID:

watch -n5 "ps aux -y | grep apache | awk '{print \$2,\$6}'"

This prints:

Every 5.0s: ps aux -y | grep apache | awk '{print $2,$6}'                                                                                                                                                                                                          
Thu Jan 25 15:44:13 2018

12588 9328
12589 8700
12590 9392
12591 9340
12592 8700
12811 15200
15453 9340
15693 3800
15694 2352
15695 1352
15697 948
22896 9360

With CPU %:

watch -n5 "ps aux -y | grep apache | awk '{print \$2,\$3,\$6}'"

Output:

Every 5.0s: ps aux -y | grep apache | awk '{print $2,$3,$6}'                                                                                                                                                                                                       
Thu Jan 25 15:46:00 2018

12588 0.0 9328
12589 0.0 8700
12590 0.0 9392
12591 0.0 9340
12592 0.0 8700
12811 0.0 15200
15453 0.0 9340
15778 0.0 3800
15779 0.0 2352
15780 0.0 1348
15782 0.0 948
22896 0.0 9360