Monitor for iowait in linux

Hi,

I need monitor iowait in my server, but it always returns 0

Monitor Name Disk I/O
Protocol CLI
Command top b n 1|grep 'Cpu(s)'|awk -F ' ' '{print $10}'| cut -d '.' -f1
Monitor value 0
Units %

When I run the command in linux, its returns the right value

# top b n 1|grep 'Cpu(s)'|awk -F ' ' '{print $10}'| cut -d '.' -f1
2

This is my configuration

<CATEGORY ID="DiskIO" command="top b n 1|grep 'Cpu(s)'|awk -F ' ' '{print $10}'| cut -d '.' -f1" parseAll="false" description="Utilization on the disk I/O.">

<ENTITY ID="DiskIO" applyThresholdOver="curValue" threshold="Th6" storeHistory="true" units="%" storeValue="curValue" comparePreValue="false">
<PARSE line="1" token="1" name="curValue"/>
</ENTITY>
</CATEGORY>

thanks