Bash scripting, how to remove trailing substring, case insensitive?

I am modifying a script that reads in a user email. It is very simple, too simple.

echo -n "Please enter your example.com email address: "
read email
email=${email%%@example.com} # removes trailing @example.com from email
echo "email is $email"

This works, but only for lower case开发者_运维百科 @example.com. How could I modify this to remove the trailing @example.com, case insensitive?

If you have bash 4:

email=${email,,}
email=${email%%@example.com}

Otherwise, perhaps just use tr:

email=$(echo "${email}" | tr "A-Z" "a-z")
email=${email%%@example.com}

Update:

If you are just wanting to strip the host (any host) then perhaps this is really what you want:

email=${email%%@*}

For Bash 3.2 and greater:

shopt -s nocasematch
email='JoHnDoE@eXaMpLe.CoM'
pattern='^(.*)@example.com$'
[[ $email =~ $pattern ]]
email=${BASH_REMATCH[1]}    # result: JoHnDoE

How about using sed?

email="$(sed 's|@example\.com$||i' <<<"$email")"

Note the 'i' flag in the sed substitution command which requests case-insensitive matching.

Here's yet another (though a bit lengthy) take on it:

email='JoHnDoE@eXaMpLe.CoM'
email=${email%%@[Ee][Xx][Aa][Mm][Pp][Ll][Ee].[Cc][Oo][Mm]}
echo "email is $email"

echo -n "Please enter your example.com email address: "
read _email
_email=$(echo $_email | awk 'BEGIN{ FS="@" }  {print $1}')
echo $_email

and for transfer email to lower case you can use declare, such as

declare -l email=$email

Use case insensitive matching to a regular expression:

echo -n "Please enter your example.com email address: "
read email
shopt -s nocasematch # Makes comparisons case insensitive
if [[ $email =~ example.com$ ]]; then
    domain=${BASH_REMATCH[0]}
    echo "email is ${email%%@$domain}"
fi

Alternatively, you can cut off a string based on its length (which only makes sense if you know that the user entered the domain correctly):

echo -n "Please enter your example.com email address: "
read email
domain=example.com
email_length=${#email}
domain_length=${#domain}
name_length=$(($email_length-$domain_length-1))
email=${email:0:$name_length} # removes trailing @example.com from email
echo "email is $email"