I.I need to validate if characters a-z are entered it will reprompt. Below is a snippet of my script
wh
While [true]
do
mainMenu # menu function
read $opt # read option from menu
if [ $opt -eq 0 ]; then
exit
elif [ $opt -gt 4 -o $choice -lt 1 ]; then
read $opt
elif [ $opt -eq [a-zA-Z]]; then # this line doesn't work need to validate
read $opt
else
break
fi
done