Help with if statement

Shell Programming and Scripting
1

I have a useradd bash script which requests the user enter an e-mail address for the user being created. This is so the user receives his username/password in an e-mail when his/her account is created.

Currently this part of the code is very simple:

echo Enter the users e-mail address
read ADDRESS

What i'm finding is that sometimes when the operators run the script they are entereing blank information. How can I put a if statement in place that enforces they enter an e-mail address format.

I tried the following code but it doesn't work. The idea was to at least verify they are using the @ symbol.

string=@
if [[ $string != "@" ]] ; then
echo You have entered an invalid e-mail address!
exit 1
else
do something
2

It does not really reply to the question, but you can use this bit of code if you want to check for a mail address

#!/bin/bash

read -p'Enter Email address : ' ADDRESS

if ! echo "$ADDRESS" | grep -E '^[[:alnum:]]+@[[:alnum:]]+\.[[:alnum:]]+$' > /dev/null; then
	echo 'You have entered an invalid e-mail address!'
	exit 1
fi

#continue here.
3 
string=@
if [[ $string != *@* ]] ; then
echo You have entered an invalid e-mail address!
exit 1
else
do something
4

I was able to get what I wanted using the following regex

                echo Setting up e-mail notification!
                echo Please take the time to ensure you are entering the correct e-mail information.
                echo Enter the users e-mail address
                read ADDRESS
                if [[ "$ADDRESS" =~ "^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,4}$" ]] ; then
                getmail
                else
                echo You entered an invalid e-mail address!!!
                cleanup
                exit 1
                fi
5

Just remember that regexes are a BASH-only feature, and only very modern versions of BASH at that. Take your script anywhere else and it won't work.

6

Or a recent ksh93