I have a code to find the area of a rectangle by giving the width and height.
echo -n "Enter width: "
read width
echo -n "Enter height:"
read height
echo "Area of rectangle $(echo "$height*$width" | bc) sqcm"
How can I make it so that only a number can be entered and, otherwise, an error display?
Since you are reading input twice, I would use a function to check it. This way you do not repeate code.
This checks whether input contains just digits and at least one. Otherwise, it keeps asking for the input:
myread () {
while : # infinite loop
do
read value
[[ $value =~ ^[0-9]+$ ]] && echo "$value" && return #return value if good input
done
}
echo -n "Enter width: "
width=$(myread) #call to the funcion and store in $width
echo -n "Enter height: "
height=$(myread) #call to the funcion and store in $height
echo "Area of rectangle $(echo "$height*$width" | bc) sqcm"
You could perhaps use grep to check but really bash (and shell in general) is a bad choice of language if you want these kinds of checks.
You can do some thing like thi
if [[ -n "$width" ]] ; then
nodigits="$(echo $width| sed 's/[[:digit:]]//g')"
if [[ ! -z $nodigits ]] ; then
print "Invalid number format! Only digits, no commas, spaces, etc."
fi
fi
Something like:
echo $width | grep -E -q '^[0-9]+$' || echo "numeral expected!"
