not getting right output,getting error "not recognised $age"
 

clear
echo -n "enter ur birth year "
read byear
cyear='date | tr -s ''| cut -d "" -f 6'

age='expr $cyear - $byear'

echo "ur $age"

Is there a reason you don't just use:
And for the math you do not need expr either:
Of course depending on the month and day this is only an approximation.

thanks grail