topic Re: while read line iteration cause variable value reset? in Operating System - HP-UX

while read line iteration cause variable value reset?

RoyP — Wed, 14 Apr 2010 14:21:55 GMT

Hi There.

First, I apologize. Used to be on HP-UX, but now Linux, but this is the best forum I've known for this sort of thing...

I've got a small script that basically checks if a process from a given process list is using more then a given MAXCPU utilization... the case being an email should be sent out. This is what I have. It seems like the $MailIt variable is reset on each iteration. As if the pipe / readline cause a new subshell to spawn? If that were the case, I already tried doing an export of the variable at first. Didn't help...

#!/bin/bash

MAXCPU=0
MailIt=0

(ps aux | grep f60webmx) | \
while read line
do
cpu=`echo $line | awk '{print $3}'`

#if [ ${cpu} -gt ${MAXCPU} ]; then
if awk 'BEGIN{if(0+'$cpu'>'$MAXCPU'+0)exit 0;exit 1}'; then
echo "GOT A HIT!!!"
MailIt=1
else
echo "no hit..."
fi
done

echo "MailIt = $MailIt"

Exit

The output I get is something like:

no hit...
no hit...
GOT A HIT!!!
no hit...
no hit...
GOT A HIT!!!
GOT A HIT!!!
no hit...
no hit...
no hit...
MailIt = 0

Any ideas??

Mny thanks. Pat

Re: while read line iteration cause variable value reset?

James R. Ferguson — Wed, 14 Apr 2010 15:28:03 GMT

Hi Pat:

> It seems like the $MailIt variable is reset on each iteration.

You never reset 'Mailit' to zero. Once set to one it says as one.

Regards!

...JRF...

Re: while read line iteration cause variable value reset?

RoyP — Wed, 14 Apr 2010 16:03:40 GMT

Hi James.

That's exactly my troubles: I DON'T reset MailIt to 0. But why is it that at the end, it comes out as 0 ?

I wish I had an hpux box to test this on... I don't It works as expected on Tru64, but not on Linux.

Can someone try the same little script (replacing the process Im looking for) on hpux?

I simply don't get it...

Re: while read line iteration cause variable value reset?

James R. Ferguson — Wed, 14 Apr 2010 16:13:25 GMT

Hi (again) Pat:

OK, I see. See Duncan's comments here:

http://forums.itrc.hp.com/service/forums/questionanswer.do?threadId=1265374

Regards!

...JRF...

Re: while read line iteration cause variable value reset?

James R. Ferguson — Wed, 14 Apr 2010 16:39:25 GMT

Hi Pat:

I don't run the bash shell on my HP-UX servers, but I did look at this further in a LINUX instance. Consider:

#!/bin/bash
echo "pass-1"
V=0
cat /etc/hosts|while read LINE
do
(( V=V+1 ))
echo "${V} = ${LINE}"
done
echo ${V}

echo "pass-2"
V=0
while read LINE
do
(( V=V+1 ))
echo "${V} = ${LINE}"
done < /etc/hosts
echo ${V}
exit

...Thus, to rectify your problem you could do:

# cat ./newway
!/bin/bash
MYFILE=/tmp/stuff
trap 'rm ${MYFILE}' EXIT
MAXCPU=0
MailIt=0
ps aux | grep root > ${MYFILE}
while read line
do
cpu=`echo $line | awk '{print $3}'`

#if [ ${cpu} -gt ${MAXCPU} ]; then
if awk 'BEGIN{if(0+'$cpu'>'$MAXCPU'+0)exit 0;exit 1}'; then
echo "GOT A HIT!!!"
MailIt=1
else
echo "no hit..."
fi
done < ${MYFILE}
echo "MailIt = $MailIt"
exit

Regards!

...JRF...

Re: while read line iteration cause variable value reset?

RoyP — Wed, 14 Apr 2010 17:55:02 GMT

James, of course! Just put it all in a tmp file, removing the need of a pipe! I had thought about it, but did not know how to have the while loop process it without the use of pipe. I didn't know about the "done < /foo.txt" part!

Thanks so much.

Pat

Re: while read line iteration cause variable value reset?

RoyP — Wed, 14 Apr 2010 17:55:54 GMT

Closed as per James's solution.