######################## # operation functions ######################## function addition { a=`expr $1 + $2` echo "$1 + $2 = $a" return $a } function subtraction { a=`expr $1 - $2` echo "$1 - $2 = $a" return $a } function multiplication { a=`expr $1 \* $2` echo "$1 * $2 = $a" return $a } function division { a=`expr $1 / $2` echo "$1 / $2 = $a" return $a }