topic Re: getpid in Operating System - HP-UX

getpid

Tom Satinet — Tue, 07 Feb 2006 05:51:16 GMT

Hello,

I've created a script that monitors a process that runs in on our sever. I have also created a script in /etc/rc.config.d/ and /sbin/init.d to start this script at boot time. however i want to create a file that contains the PID of this script. From within the script i want to divert the process id to a file so my init script knows which process to kill. I know getpid does this but i am not sure how to use it.... can someone help?

also is this alright? do i need to background it??

PATH=/sbin:/usr/sbin:/usr/bin
export PATH

if [ -r /etc/rc.config.d/ecommalert ]
then
. /etc/rc.config.d/ecommalert
fi

case "$1" in

"start") if [ "$ECOMMSTART" -ne 0 ]
then
/ops/scripts/ecommalert&
exit 0
fi
exit 2 ;;

"stop") if [ "$ECOMMSTART" -ne 0 ]
then
/ops/scripts/ecommstop
exit 0
fi
exit 2 ;;
*)
echo "usage: $0 {start|stop}"
exit 1
;;
esac

exit 0;

Re: getpid

Arunvijai_4 — Tue, 07 Feb 2006 06:02:45 GMT

Hi Tom,

You can take a look at, /sbin/init.d/template
to write your own startup script.

-Arun

Re: getpid

Tom Satinet — Tue, 07 Feb 2006 06:04:43 GMT

thanks, but i'm more concerned with get the PID of the script. thanks:-)

Re: getpid

Arunvijai_4 — Tue, 07 Feb 2006 06:07:43 GMT

Hello,

For PID, you can take a look at Secure shell's startup script /sbin/init.d/secsh. It should help you.

-Arun

Re: getpid

Tom Satinet — Tue, 07 Feb 2006 06:11:55 GMT

not really.

that the sshd writes the PID to a file. this script just cats it and assigns that to a variable.

Re: getpid

Tom Satinet — Tue, 07 Feb 2006 06:16:31 GMT

sorry, maybe i was not clear.

from within the script (not the init.d or rc.config.d) that actually monitors the process. Say its called 'ecommalert'. I want 'ecommalert' to get its own PID and send that to a file.

ecommalert will be started at run level 3.

Re: getpid

Arunvijai_4 — Tue, 07 Feb 2006 06:21:44 GMT

Hello,

You can probably use something like this,

echo "ecomalert PID is $$" >ecom.pid

-Arun
P.S Remember to assign points.

Re: getpid

paolo barila — Tue, 07 Feb 2006 06:22:09 GMT

Hi,

You can't use getpid() from a shell script,
it should be the process (written in a language like C) that call that function and writes its PID in a file.

From shell you can only do somenthing like:

# ps -efx | grep

Pablo

Re: getpid

Steven E. Protter — Tue, 07 Feb 2006 06:30:10 GMT

Shalom,

You may find some Linux code useful in this regard.

/usr/local/cluster/cluster.mon &
RETVAL=$?
echo
[ $RETVAL = 0 ] && touch /var/lock/subsys/cluster.mon
return $RETVAL
}

thats from a clsuter monitor script. It creates a lock file by PID.

SEP

Re: getpid

James R. Ferguson — Tue, 07 Feb 2006 07:20:57 GMT

Hi Tom:

The following shell variables are directly available to you:

?? -> the process number of the current shell

?! -> the process number of the last background command

Does this help?

Regards!

...JRF...

Re: getpid

paolo barila — Tue, 07 Feb 2006 07:27:47 GMT

A simple C program that use getpid()

#include
main()
{
printf("Salve mondo!\n");
printf("PID= %d\n", getpid());
}

Re: getpid

Andy Torres — Tue, 07 Feb 2006 09:16:37 GMT

Not sure if this will help, but by using the basename of the script you can get the PID and pass it to a file, like in this example, used to get the PID of the scopeux process:

UNIX95= ps -C scopeux -o pid= > scopeux.pid

Re: getpid

Tor-Arne Nostdal — Wed, 08 Feb 2006 11:53:47 GMT

Hi Tom.
Do you want to stop the ecommalert or the process this script is monitoring (or both)?

If ecommalert is a script, you could simply add a line which echo the PID to a file during startup.

example:
echo "$$" >/ops/scripts/ecommalert.pid

As others have mentioned it is not that simple if the ecommalert is a binary.

Another approach could be to use a killproc function.
You could have a look in /sbin/init.d/nfs.client to see how it is used, and how to define the function.

This use a unique string input on the process you want to kill, rather than the PID itself.

Example
You would be writing:
killproc ecommalert
Instead of writing:
kill `cat /ops/scripts/ecommalert.pid`

The killproc function will use ps to find and grep the correct process, then kill it.

======= some hint/tips =======
If you use a PID-file you can check if the process is alive with this command:
#sh-posix syntax
kill -0 `cat /ops/scripts/ecommalert.pid` || {
print "Warning: No such process"
rm -f /ops/scripts/ecommalert.pid
}

In the /sbin/init.d/nfs.client you should notice these three functions.
killproc : "nice kill"
killbiod : identical, but "sure kill" (-9)
findproc : returning the PID for a named process

To test this I suggest you copy the functions into a new script which you can do some testing with.
Then change the kill $pid to echo "kill $pid"
Then you can safely try it out and see that the correct PID's are used.

Last hint:
If you have many functions which is useful for many purposes you can define these in separate files.
example:
/ops/scripts/Functions/killproc
/ops/scripts/Functions/findproc
containing the function(s) from nfs.client
When you want to use functions in /ops/scripts/Functions you simply set the environment variable FPATH
(export FPATH=/ops/scripts/Functions)
- and then they're ready for use.
can be used both in scripts as well as from command-line.

To see functions defined: typeset -f

Best regards
Tor-Arne

Re: getpid

Tom Satinet — Wed, 08 Feb 2006 12:00:08 GMT

Hey thanks! :-)

this is very useful to me.

I am just using a shell script now, before i learn C. but i am very interesting in process control.

I'll go away and do some testing :-)

Thanks for your time.

Re: getpid

Geoff Wild — Wed, 08 Feb 2006 12:14:02 GMT

UNIX95 is a good way to go:

MYPID="$(UNIX95= ps -C $MYPROC -o pid=)"

Rgds...Geoff

Re: getpid

Tom Satinet — Wed, 08 Feb 2006 12:15:31 GMT

yes i'm using that, it's cool

Re: getpid

Tor-Arne Nostdal — Wed, 08 Feb 2006 12:16:28 GMT

When something is useful we appreaciate assigned points ;-))

Re: getpid

Tom Satinet — Wed, 08 Feb 2006 12:17:49 GMT

as you will see i have assigned 100% of points so far. impatience eh! ok ok......

Re: getpid

Tor-Arne Nostdal — Wed, 08 Feb 2006 12:36:02 GMT

he, he...
The points are encouraging activity, though most sysadmins is willing to help out and share knowledge even if it doesn't "pay off". It's almost as built into the spinal cord :-))

Re: getpid

Tom Satinet — Thu, 09 Feb 2006 04:42:23 GMT

one question i have - if i run a script from an init script, do i need to background it (&), or can i just run it?

bearing in mind the script runs for ever...