A simple .forward vacation enable/disable script

I got a little tired of manually enabling/disabling peoples vacation AutoReply. So I decided to knock out a simple bash script that does the enable/disable part, leaving me to simply make sure the actual response message was updated and just AT the script for whenever they wanted to leave/come back.

I used to move .forward to dotforward and back when enabling/disabling - so if you're wondering why I'm referencing files called 'dotforward' it's for backwards compatibility - plus I like the idea of setting up dotforward if the user doesn't have any .forward yet and leaving the rest up to the script.

#!/bin/bash

DATE=`date`
TMP_DATE=`date +%Y%m%d`
EMAIL_SUBJECT="AutoReply Status"
EMAIL_FROM="blah@blah.com"

USER="$1"
FORWARD="/home/$USER/.forward"
DOTFORWARD="/home/$USER/dotforward"
VACATION=$(which vacation)

if [ -z "$1" ]; then
echo "usage: $0 username"
exit
fi

echo "Doing the .forward thing with user: $USER"

if ! [ -e $FORWARD ]; then
echo "No .forward found, is there a dotforward?"
if [ -e $DOTFORWARD ]; then
echo "Found $DOTFORWARD, moving it to $FORWARD"
EMAIL_BODY="Hello $USER, I have enabled your AutoReply E-Mail as of $DATE"
mv $DOTFORWARD $FORWARD
echo "Moved $DOTFORWARD to $FORWARD"
fi
else
echo "Hmm, there's already a $FORWARD, I'll just add or remove the vacation reference..."
if [ -e $FORWARD ]; then
if grep "vacation" $FORWARD
then echo "Oooh I found a vacation reference in here! Let's DELETE it buwahaha"
sed -e "s!\"|$VACATION $USER\"!!g" $FORWARD > /tmp/$USER_forward-$TMP_DATE
mv /tmp/$USER_forward-$TMP_DATE $FORWARD
EMAIL_BODY="Hello $USER, I have disabled your AutoReply E-Mail as of $DATE"
else
echo "Didn't find any vacation reference, I'm adding one"
if ! grep "\\$USER," $FORWARD; then
echo "\\$USER," >> $FORWARD
fi
echo " \"|$VACATION $USER\"" >> $FORWARD
EMAIL_BODY="Hello $USER, I have enabled your AutoReply E-Mail as of $DATE"
fi
fi
fi

echo "$FORWARD now looks like:"
echo `cat $FORWARD`

echo "$EMAIL_BODY" | mail -s "$SUBJECT" $USER