Empty
#! /bin/bash
read -p "type something: " str
if [ -z $str ]; then
echo "you didn't type anything"
#-z will pick up empty string or the string comes with space, using "$str" will ignore space, see below 2nd example
else
echo "$str"
fi
echo "Ignore space in between strings "
if [ -z "$str" ]; then
echo "you didn't type anything"
else
echo "$str"
fi