how can I complete this?

Question

the question is:

use a script to take two numbers as arguments and output their sum using (i) bc, (ii) expr. include error-checking to test whether two arguments were entered.

My answer:

echo " The first number is"
read a
echo " The second number is"
read b
c=`echo "scale=2; $a + $b"|bc`
echo _____________________________________________
echo " The sum of two numbers using bc:$c "
echo
d=`expr $a + $b`
echo " The sum of two numbers using expr:$d "
echo _____________________________________________

I can't include the error checking in this program. how can i do it? please help!

Answer 1

Get the numbers from arguments $1 and $2 , not by prompting for input.

Check the number of arguments using $# .

if [ $# -ne 2 ]
then
    echo "Usage: $0 number1 number2" >&2 # write error message to stderr
    exit 1
fi
a=$1
b=$2
# rest of your script goes here