I am trying to validate user's input So input is a number not a string or null. using case I tried to do this
echo "input a number"
read num1
case $num1 in
"" |*[a-zA-Z]*)
echo "please inter a valid number"
esac
echo "input 2nd number"
read num2
let sum=$num1+$num2
echo "$num1 + $num2=$sum"
But it didn't quite work. It gives me the warning about the input though -- And is there away to validate both variables at the sametime?
Using bash you can use a regular expression to validate the number:
#! /bin/bash
while [ -z "$REPLY" ]; do
read -p "Enter a valid number: "
if ! [[ "$REPLY" =~ ^[0-9]+$ ]] ; then
echo Bad number: $REPLY
REPLY=
fi
done
echo A valid number: $REPLY
The program keeps reading input until the variable $REPLY is set by read. When the number is matched right against ^[0-9]+$ the loop is ended.
To check both variables at once, you can concatenate and check.
Here is the part that changes:
case $num1$num2 in
'' |*[!0-9]*)
echo "please enter a valid number"
exit
;;
You can also use exit to exit right after printing the error.
case
You can define a custom function for doing that.
# func def.
isInt() {
case ${1-} in '' | *[!0-9]* ) return 1 ;; esac
return 0
}
# now use it as:
if isInt "$num1"; then
echo "$num1 is a valid integer"
else
echo "$num1 is not an integer"
fi
Note that case uses wildcards and not regexes for it's job.