I need to write a script in the Bash shell that asks for users to input number. The script needs to check to see if a non number was entered. Please help.

I don't do much bash. However, try this:

echo "Enter a number:"
read NUM
if [ "$(expr $NUM + 0 2> /dev/null)" = "$NUM" ]
then
echo "It's a Number"
else
echo "It's not a Number"
fi

Here is a better way to do it (it avoids external calls to expr and echo), but it doesn't work in bash (perhaps someone can explain why) but works fine in ksh:

#!/bin/ksh

print "Enter a number:"

read NUM

case $NUM in

+([0-9]) ) print "It's a number"
;;
*) print "It's not a number"
;;
esac

Jerry:

In the bash shell, for a script like yours to work, the extended pattern matching has to be turned on. Place the following line in your script, and it works fine with bash:

shopt -s extglob

BTW, my take on this handles a sign:

shopt -s extglob

i=-99
function is_integer {
[[ $1 = ?([+-])+([0-9]) ]]
}
is_integer $i && echo "yes" || echo "no"

Regards,

Nails