Csdrhrt

How do I find the uptime of a given linux process.

ps aux | grep gedit | grep -v grep

gives me a whole lot of information which includes the time at which the process was started.
I am specifically looking for switch which returns the uptime of a process in milliseconds.

Thanks

As "uptime" has several meanings, here is a useful command.

ps -eo pid,comm,lstart,etime,time,args

This command lists all processes with several different time-related columns. It has the following columns:

PID COMMAND                          STARTED     ELAPSED     TIME COMMAND

PID = Process ID

first COMMAND = only the command name without options and without arguments
STARTED = the absolute time the process was started
ELAPSED = elapsed time since the process was started (wall clock time), format [[dd-]hh:]mm:ss
TIME = cumulative CPU time, "[dd-]hh:mm:ss" format

second COMMAND = again the command, this time with all its provided options and arguments

If you have a limited version of ps such as is found in busybox, you can get the process start time by looking at the timestamp of /proc/<PID>. For example, if the pid you want to look at is 55...

# ls -al /proc | grep 55

dr-xr-xr-x    7 root     root             0 May 21 05:53 55

... and then compare it with the current date...

# date

Thu May 22 03:00:47 EDT 2014

I think you can just run:

$ stat /proc/1234

1234 being the process id.

example with two processes started at the same hour minute seconds but not the same milliseconds:

$ stat /proc/9355

...

Access: 2017-11-13 17:46:39.778791165 +0100

Modify: 2017-11-13 17:46:39.778791165 +0100

Change: 2017-11-13 17:46:39.778791165 +0100

$ stat /proc/9209

...

Access: 2017-11-13 17:46:39.621790420 +0100

Modify: 2017-11-13 17:46:39.621790420 +0100

Change: 2017-11-13 17:46:39.621790420 +0100

Such a simple thing is not properly answered after 5 years?

I don't think you can accurately get milliseconds. eg. if you see man procfs and see /proc/$$/stat which has field 22 as startime, which is in "clock ticks", you would have something more precise, but clock ticks aren't going at a perfectly constant rate (relative to 'wall clock time') and will be off... sleeping and certain things (ntpd I guess) offset it. For example on a machine running ntpd, with 8 days uptime and has never slept, dmesg -T has the same problem (I think...), and you can see it here:

# date; echo h > /proc/sysrq-trigger; dmesg -T | tail -n1 ; date

Fri Mar  3 10:26:17 CET 2017

[Fri Mar  3 10:26:16 2017] sysrq: SysRq : HELP : loglevel(0-9) reboot(b) crash(c) terminate-all-tasks(e) memory-full-oom-kill(f) kill-all-tasks(i) thaw-filesystems(j) sak(k) show-backtrace-all-active-cpus(l) show-memory-usage(m) nice-all-RT-tasks(n) poweroff(o) show-registers(p) show-all-timers(q) unraw(r) sync(s) show-task-states(t) unmount(u) force-fb(V) show-blocked-tasks(w) 

Fri Mar  3 10:26:17 CET 2017

Here's seconds:

# example pid here is just your shell

pid=$$



# current unix time (seconds since epoch [1970-01-01 00:00:00 UTC])

now=$(date +%s)



# process start unix time (also seconds since epoch)

# I'm fairly sure this is the right way to get the start time in a machine readable way (unlike ps)...but could be wrong

start=$(stat -c %Y /proc/"$pid")



# simple subtraction (both are in UTC, so it works)

age=$((now-start))



printf "that process has run for %s secondsn" "$age"

yes, too old and yet too hard stuff. I tried with the above proposed "stat" method but what if I had "touch"-ed the PID proc dir yesterday? This means my year-old process is shown with yesterday's time stamp. Nah, not what I need :(

In the newer ones, it's simple:

ps -o etimes -p <PID>

ELAPSED

339521

as simple as that. Time is present in seconds. Do whatever you need it for.
With some older boxes, situation is harder, since there's no etimes. One could rely on:

ps -o etime -p <PID>

ELAPSED

76-03:26:15

which look a "a bit" weird since it's in dd-hh:mm:ss format. Not suitable for further calculation. I would have preferred it in seconds, hence I used this one:

ps -o etime -p <PID> --no-headers | awk -F '(:)|(-)' 'BEGIN{a[4]=1;a[3]=60;a[2]=3600;a[1]=86400;s=0};{for (i=NF;i>=1;i--) s=s+a[i]*$i}END{print s}'

339544

[root@ip-x-x-x-x ec2-user]# ps -p `pidof java` -o etimes=

 266433

pidof java => process id for java process

etimes= => time in Seconds and '=' is to remove header