Ttyjfyk

Similar to How to check how long a process has been running?, I am trying to get the elapsed time for a process in seconds in an embedded Linux system using BusyBox and sh (not bash). The difference is that I would like it in pure seconds, not mm:ss format.

I can parse it out of the result of ps but am unable to get expr to convert from mm:ss to seconds. Using set -vx to help with debugging I can see the valid expr command but it fails with a syntax error. Copying and pasting it works fine.

After running this for added diagnostics:

root@embedded:~# set -vx

I enter:

root@embedded:~# $(/opt/bin/busybox ps -o pid,etime,time | grep 1156 | sed "s/ *[0-9]+ +([0-9]+):([0-9]+) .*//opt/bin/busybox expr 1 \* 60 + 2/")

And get this response:

$(/opt/bin/busybox ps -o pid,etime,time | grep 1156 | sed "s/ *[0-9]+ +([0-9]+):([0-9]+) .*//opt/bin/busybox expr 1 \* 60 + 2/")
+ /opt/bin/busybox ps -o pid,etime,time
+ grep 1156
+ sed s/ *[0-9]+ +([0-9]+):([0-9]+) .*//opt/bin/busybox expr 1 \* 60 + 2/
+ /opt/bin/busybox expr 2 * 60 + 03
expr: syntax error
root@embedded:~#

I have additionally tried multiple layers of escapes and also ''.

What do I need to do to get the escaping of the * to pass through to the expr command line?

eval might help this case...

~ $ $(echo expr 1 \* 2)
+ echo expr 1 * 2
+ expr 1 * 2
expr: syntax error
~ $ eval $(echo expr 1 \* 2)
+ echo expr 1 * 2
+ eval expr 1 * 2
+ expr 1 * 2
2

But it might be better to look up /proc/$pid/stat on Linux.

pid=1155
hz=$(getconf CLK_TCK)
uptime=$(awk 'print $1' < /proc/uptime)
starttime=$(awk 'print $22' < /proc/$pid/stat)
echo $(( $uptime%.* - $starttime / $hz ))

If /usr/bin/getconf is unavailable, you need to find your system's CLK_TCK (or USER_HZ) value. I think you can assume it as 100 in most cases.

Embarrassingly, I seem to have failed to test as completely as I had thought. It turns out that modifying what I posted in my question to contain only two escapes (\*) makes it work fine.

root@embedded:~# $(/opt/bin/busybox ps -o pid,etime | sed -n "s/ *1155 +([0-9]+):([0-9]+).*/expr 1 \* 60 + 2/p")
$(/opt/bin/busybox ps -o pid,etime | sed -n "s/ *1155 +([0-9]+):([0-9]+).*/expr 1 \* 60 + 2/p")
+ /opt/bin/busybox ps -o pid,etime
+ sed -n s/ *1155 +([0-9]+):([0-9]+).*/expr 1 * 60 + 2/p
+ expr 293 * 60 + 54
17634

Note that I also integrated the grep into sed with the -n 's///p' approach (global no-print and then print on match).

Thanks to @yaegashi for getting me to try \ again...

assumping process is 16752 (which you seems to be able to figure out)

expr $(date +%s) - $(stat -c %Y /proc/16752/environ )

where

• 
  date +%s is current date in second since the epoch


• 
  stat -c %Y /proc/16752/environ is "creation date" of /proc/16752/environ, that is the moment where proc #16752 was launched

edit:

• maybe /proc/$PID/environ is the wrong pseudo file, /proc/$PID/exe should be used instead.




• if time changed on host, both result from ps -p $PID -h -o etime and timestamp from /proc/$PID/exe are likely to be wrong. (unsure how to check that).

@yaegashi had the approach right but my sed call seems to introduce the need for a third .

root@embedded:/data# set -vx
root@embedded:/data# echo Process Uptime: $(eval $(/opt/bin/busybox ps -o pid,etime | sed -n "s/ *$APP_PID +([0-9]+):([0-9]+).*/expr 1 \* 60 + 2/p"))
echo Process Uptime: $(eval $(/opt/bin/busybox ps -o pid,etime | sed -n "s/ *$APP_PID +([0-9]+):([0-9]+).*/expr 1 \* 60 + 2/p"))
+ /opt/bin/busybox ps -o pid,etime
+ sed -n s/ *1156 +([0-9]+):([0-9]+).*/expr 1 \* 60 + 2/p
+ eval expr 2 * 60 + 46
+ expr 2 * 60 + 46
+ echo Process Uptime: 166
Process Uptime: 166

Fingers crossed that this not only works now, but also continues to do so next time I use it...

This is an awk script which will convert the 0-00:00:00 output to seconds. It is used like this...

ps -eo pid,time,user,comm | awk '"$2"' | awk -f _os_return_process_time_in_seconds.awk

Here is the script. Just wrote if for another purpose. May have issues still.

BEGIN "


"total_seconds"