Forum: Ruby Retrieving PID running time

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phil (Guest)
on 2005-12-08 16:35
(Received via mailing list)
People,

I have found how to get PIDs etc but how can I find the running time of
a particular PID without messing around with a system call to ps etc

Thanks,

Phil.
--
Philip R.

Pricom Pty Limited  (ACN 003 252 275  ABN 91 003 252 275)
GPO Box 3411
Sydney NSW      2001
Australia
Mobile:  +61:(0)411-185-652
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joevandyk (Guest)
on 2005-12-08 17:04
(Received via mailing list)
On 12/8/05, Philip R. <removed_email_address@domain.invalid> wrote:
> People,
>
> I have found how to get PIDs etc but how can I find the running time of
> a particular PID without messing around with a system call to ps etc

That information should be in /proc/<pid>/stat.  Look at the man page
for proc for more details.
phil (Guest)
on 2005-12-08 17:17
(Received via mailing list)
On Fri, 2005-12-09 at 00:03 +0900, Joe Van D. wrote:
> On 12/8/05, Philip R. <removed_email_address@domain.invalid> wrote:
> > People,
> >
> > I have found how to get PIDs etc but how can I find the running time of
> > a particular PID without messing around with a system call to ps etc
>
> That information should be in /proc/<pid>/stat.  Look at the man page
> for proc for more details.

Yes, but what I want (in Ruby) is something like:

ptime = Process.pid.time

How can I do that?

Thanks,

Phil.
--
Philip R.

Pricom Pty Limited  (ACN 003 252 275  ABN 91 003 252 275)
GPO Box 3411
Sydney NSW      2001
Australia
Mobile:  +61:(0)411-185-652
Fax:     +61:(0)2-8221-9599
E-mail:  removed_email_address@domain.invalid
gwtmp01 (Guest)
on 2005-12-08 17:58
(Received via mailing list)
On Dec 8, 2005, at 10:14 AM, Philip R. wrote:
> Yes, but what I want (in Ruby) is something like:
>
> ptime = Process.pid.time
>
> How can I do that?

This sort of thing is very platform specific.  I'm assuming
a unix/linux/macosx environment.  I can't answer for Windows.

For your own process you can use Process::times, which
probably ends up calling getrusage(), a kernel system
call.  See the Ruby doc for Process::times, and your system
docs for getrusage.

For the general problem of finding the information for
an arbitrary process it becomes more difficult.  Some unix
systems make that sort of information available via the
/proc file system.  Some make it available via the sysctl
system calls.

In either case, I don't think there is a standard Ruby library
for parsing /proc or for extracting sysctl values.  You would
have to role your own.

Another hurdle is /proc and sysctl often restrict access to
programs with root privileges.   So you would have to create
a setuid root ruby script to be able to read /proc or sysctl
information directly.

So if you want to get the information for an arbitrary process,
I think the quick and dirty solution is to capture the output of
ps and parse it yourself.  You can use

   text = `ps -l -p1234`

to get the data and then string juggling to extract the time info.
Daniel.Berger (Guest)
on 2005-12-08 18:11
(Received via mailing list)
removed_email_address@domain.invalid wrote:
> This sort of thing is very platform specific.  I'm assuming
> /proc file system.  Some make it available via the sysctl
> system calls.
>
> In either case, I don't think there is a standard Ruby library
> for parsing /proc or for extracting sysctl values.  You would
> have to role your own.

<snip>

It's not in the standard library, but there is sys-proctable, available
on the RAA.

Regards,

Dan
joevandyk (Guest)
on 2005-12-08 19:46
(Received via mailing list)
On 12/8/05, removed_email_address@domain.invalid 
<removed_email_address@domain.invalid> wrote:
>
> For your own process you can use Process::times, which
> probably ends up calling getrusage(), a kernel system
> call.  See the Ruby doc for Process::times, and your system
> docs for getrusage.

I thought Process::times just returned the system and user cpu time,
not the total real time since the application was started.
joevandyk (Guest)
on 2005-12-08 19:50
(Received via mailing list)
On 12/8/05, Philip R. <removed_email_address@domain.invalid> wrote:
> Yes, but what I want (in Ruby) is something like:
>
> ptime = Process.pid.time

untested:

class Process
  def meth_missing pid, *args
    get_process_info(pid)[args.first]
  end

  def get_process_info pid
    # parse /proc/<pid>/stat, put values you want into some struct and
return it
  end
end
gwtmp01 (Guest)
on 2005-12-08 20:02
(Received via mailing list)
On Dec 8, 2005, at 12:44 PM, Joe Van D. wrote:
>
> I thought Process::times just returned the system and user cpu time,
> not the total real time since the application was started.


I assumed the OP was looking for the system/user time not the clock
time.

In any case I think you'd have to go through /proc, sysctl, or
parse the output of ps to get the starting time of a process.

I only have quick access to Mac OSX where the start time is available
via the 'lstart' keyword using ps:

$ps -p3357 -o lstart
STARTED
Thu Dec  8 00:58:42 2005
$
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