bash环境，只能输入10-99
#!/bin/bash
while true; do
read -p "Enter a number between 10 and 99 as sn: " number
[[ $number =~ ^[0-9]+$ ]] || { echo "error, please enter a valid number"; continue; }
if ((number >= 10 && number <= 99)); then
echo "##############"
echo "ok, valid number"
echo $number
break
else
echo "number out of range, try again"
fi
done
sh环境，只能输入10-99
#!/bin/sh
while true; do
read -p "Enter a number between 10 and 99 as sn: " number
expr $number + 1 &> /dev/null
if [ $? -ne 0 ];then
echo "error, please enter a valid number!"
continue
fi
if [[ $number -ge 10 && $number -le 99 ]]; then
echo "##############"
echo "ok, valid number"
echo "$number
break
else
echo "number out of range, try again"
fi
done
