A script for checking when websites have changed and notifying via email

delta.sh

#!/bin/bash

CHANGED=()
abs=/abs/path/to/script/
# if we're calling from cronjob, use absolute path
if [ "$abs" == $(pwd) ]; then
    pref=
else
    pref=$abs
fi

sites=$pref
sites+="sites.txt"
while read url; do
    file=$pref
    file+="."`echo $url | md5sum | cut -f1 -d" "`
    if [ ! -f $file ]; then
        last=
    else
        last=$(cat $file)
    fi
    wget $url -O $file
    current=$(cat $file)
    if [ "$last" != "$current" ]; then
        CHANGED+=($url)
    fi
done < $sites

if [ ${#CHANGED[@]} -gt 0 ]; then
    # We need to send an email out
    efile=$pref
    efile+="emails.txt"
    emails=$(sed 's/#.*$//g' < "$efile")  # remove comments
    emails=$(echo $emails | tr ' ' ',')  # Make comma separated list

    msg="The following websites have changed since yesterday. You should check them out.\n"
    for i in "${CHANGED[@]}"; do
        msg+="$i \n"
    done
    msg+="Thanks,\nHades"
    echo -e $msg | mail -s "Class Updates" user -b $emails -- -F"Class Update Bot" -ffrom@email.com
fi