$ctime{$PID} = (stat "/proc/$PID/stat")[10];
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This gives you the creation time of the process in seconds since the start of the epoch. While there can be concerns about portability across different OSes, you specified linux, and you wouldn't want to use /proc if you wanted to port this anywhere else anyway ...

(Yes, I know, it's technically the time since the file was last changed, but the stat file is special that way.)

++

Awesome! That's exactly what I was looking for!

Going with your original idea, I came up with this:

open my $pstat, "<", "/proc/$ARGV[0]/stat" or die "$!";
chomp(my $stat_line = <$procstat>);
close $pstat;

my $time_offset = (split / /, $stat_line)[21];
$time_offset = int $time_offset / 100;

my $btime;
open my $stat, "<", "/proc/stat" or die "$!";
while (<$stat>) {
  if (/^btime (\d*)/) {
    $btime = $1;
    last;
  }
}
close $stat;

my $start_time = $time_offset + $btime;
my $length = time - $start_time;
print $length;
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FYI, a jiffy is the time for one tick of the system interrupt timer, which happens to be 100Hz on my computer. That means this code is not portable. It would be if I knew a way to get the interrupt period at run time.

++

Nice!

Maybe /proc/cpuinfo? Non-portable, I know.

The only place I know of that makes that information available is actually in /proc/config.gz. So, theoretically, you could get the timer frequency with zgrep CONFIG_HZ= /proc/config.gz, but it really doesn't seem like the best way of doing this.

$ perl -le'print "".localtime($^T)'
Mon Jul 27 12:16:06 2009

$ perl -le'print "".localtime($^T)'
Mon Jul 27 12:16:07 2009

$ perl -le'print "".localtime($^T)'
Mon Jul 27 12:16:08 2009

$ perl -le'print "".localtime($^T)'
Mon Jul 27 12:16:09 2009
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Update: Oops! Nevermind. You want to know how long *another* process has been running.

In this case, the trick would work if the rsync command was run from a Perl script. Moreover, alarm could also be used to set a timeout (this has saved my day several times).

You might try just keeping track of PID and procname between calls to your monitor. Using 'ps -ex | grep 'name1|name2|...' should give you what you want with either a POSIX or BSD ps(pid will always be first field). If the same PID/procname shows up twice in a row, kill it off. Just a thought...

fnord

I've had the output of ps change on me in a distro version update. But, actually, you're probably right, I wasn't using a POSIX or BSD output format. That would stabilize it.

And yes, /proc isn't portable. It might be a little bit portable. I know it's optional on OpenBSD, for instance.

Looking for the same process name twice won't help. I want to know the age. I think I'll add an example to the OP.

Good point about POSIX or BSD ps output.

--Pileofrogs

Sorry, I should have been clearer. Let's say you run the monitor in cron every 10 minutes:
• try to open /tmp/monitor_info
• if non-existent, generate pid/procname list, write to /tmp/monitor_info and exit
• read file data into array/hash
• generate pid/procname list using aforementioned ps command
• compare lists. If same pair shows up in both, kill it (it's been running longer than 10 minutes).
• write new list to /tmp/monitor_info
Adjust cron interval to be a time comfortable to ensuring that process is broken. It is a little more complicated if you have processes that have different 'comfort intervals', but you could simply include a count to each line in /tmp/monitor_info to manage this.

This script is short and easy. Does that make sense?

fnord

Great link! Thanks!