getpid

[Tom Satinet]

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;

[Arunvijai_4]

Hi Tom,

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

-Arun

[Tom Satinet]

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

[Arunvijai_4]

Hello,

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

-Arun

[Tom Satinet]

not really.

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

[Tom Satinet]

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.

[Arunvijai_4]

Hello,

You can probably use something like this,

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

-Arun
P.S Remember to assign points.

[paolo barila]

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

[Steven E. Protter]

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

[James R. Ferguson]

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...

[paolo barila]

A simple C program that use getpid()

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

[Andy Torres]

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

[Tor-Arne Nostdal · Accepted solution]

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

[Tom Satinet]

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.

[Geoff Wild]

UNIX95 is a good way to go:

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

Rgds...Geoff

[Tom Satinet]

yes i'm using that, it's cool

[Tor-Arne Nostdal]

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

[Tom Satinet]

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

[Tor-Arne Nostdal]

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 :-))

[Tom Satinet]

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...

[Arunvijai_4]

Hello, You asked about "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..."

No need to put it into background process. Init will take care of it.

http://enterprise.linux.com/article.pl?sid=05/08/02/1821218&tid=129

-Arun

[Tom Satinet]

thanks i presumed that was the case. just wanted to make 100% sure.