How do you kill all Linux processes that are older than a certain age?

Found an answer that works for me:

warning: this will find and kill long running processes

ps -eo uid,pid,etime | egrep '^ *user-id' | egrep ' ([0-9]+-)?([0-9]{2}:?){3}' | awk '{print $2}' | xargs -I{} kill {}

(Where user-id is a specific user's ID with long-running processes.)

The second regular expression matches the a time that has an optional days figure, followed by an hour, minute, and second component, and so is at least one hour in length.

For anything older than one day,

ps aux

will give you the answer, but it drops down to day-precision which might not be as useful.

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.0   7200   308 ?        Ss   Jun22   0:02 init [5]
root         2  0.0  0.0      0     0 ?        S    Jun22   0:02 [migration/0]
root         3  0.0  0.0      0     0 ?        SN   Jun22   0:18 [ksoftirqd/0]
root         4  0.0  0.0      0     0 ?        S    Jun22   0:00 [watchdog/0]

If you're on linux or another system with the /proc filesystem, In this example, you can only see that process 1 has been running since June 22, but no indication of the time it was started.

stat /proc/<pid>

will give you a more precise answer. For example, here's an exact timestamp for process 1, which ps shows only as Jun22:

ohm ~$ stat /proc/1
  File: `/proc/1'
  Size: 0               Blocks: 0          IO Block: 4096   directory
Device: 3h/3d   Inode: 65538       Links: 5
Access: (0555/dr-xr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2008-06-22 15:37:44.347627750 -0700
Modify: 2008-06-22 15:37:44.347627750 -0700
Change: 2008-06-22 15:37:44.347627750 -0700

In this way you can obtain the list of the ten oldest processes:

ps -elf | sort -r -k12 | head -n 10

Using ps is the right way. I've already done something similar before but don't have the source handy. Generally - ps has an option to tell it which fields to show and by which to sort. You can sort the output by running time, grep the process you want and then kill it.

HTH

In case anyone needs this in C, you can use readproc.h and libproc:

#include <proc/readproc.h>
#include <proc/sysinfo.h>

float
pid_age(pid_t pid)
{
        proc_t proc_info;
        int seconds_since_boot = uptime(0,0);
        if (!get_proc_stats(pid, &proc_info)) {
                return 0.0;
        }

        // readproc.h comment lies about what proc_t.start_time is. It's
        // actually expressed in Hertz ticks since boot

        int  seconds_since_1970 = time(NULL);
        int time_of_boot = seconds_since_1970 - seconds_since_boot;
        long  t = seconds_since_boot - (unsigned long)(proc_info.start_time / Hertz);

        int delta = t;
        float days = ((float) delta / (float)(60*60*24));
        return days;
}

My version of sincetime above by @Rafael S. Calsaverini :

#!/bin/bash
ps --no-headers -o etimes,args "$1"

This reverses the output fields: elapsed time first, full command including arguments second. This is preferred because the full command may contain spaces.