Ubuntu – How to grep logs based on timestamp

If you are just looking for a word you can use a for loop.

STRING="upgrade this if you can"
for x in $STRING; do
   echo $x
   if [ "$x" = 'upgrade' ]; then
       echo found
       y=$x
       break
   fi
done 
echo $y

If upgrade is always in the same position you could try array assignment.

declare -a z
z=($STRING)
echo ${z[0]}

Those warnings are directed to the stderr stream, as opposed to the standard out file descriptor. You can silence the stderr output by adding 2>/dev/null to the end of your command.