23 May 16 14:35, you wrote to me:

 ac>> Years ago I wrote a sh script to download a web page, compare it to
 ac>> a local copy using diff and email me any changes. The script runs
 ac>> twice a day as a cron job.

 BR> Cool, dig it up and post!

Here you go...

#!/bin/sh

#  webmonitor.sh
#
#  Monitor web pages for changes and email the diffs.

WGETOPT="--cache=off --no-check-certificate"
ELINKSOPT="-no-references -no-numbering -dump-width 75"
DIFFOPT="-uw"
BINDIR="/usr/local/bin"
WORKDIR="$HOME/bin/cron/webmonitor"
MAILTO=$USER

# Pretend we're Firefox instead of Wget.

#USERAGENT="Mozilla/5.0 (X11; Linux i686; rv:7.0) Gecko/20100101
Firefox/7.0"
#USERAGENT="Mozilla/5.0 (X11; Linux x86_64; rv:10.0) Gecko/20100101
Firefox/10.0"
#USERAGENT="Mozilla/5.0 (Windows NT 6.1; WOW64; rv:30.0)
Gecko/20100101 Firefox/25.0"
USERAGENT="Mozilla/5.0 (X11; Linux x86_64; rv:10.0) Gecko/20100101
Firefox/40.0"

# Check that Wget and ELinks are installed.

require_util()
{
  if [ ! -f $BINDIR/$1 ]; then
    echo "$0: $1 is missing!"
    exit 1
  fi
}

require_util "wget"
require_util "elinks"

# Get command-line args.

URL=$1
CACHEFILE=$2

# We require two args, otherwise complain.

if [ $# -ne 2 ]; then
  echo "Usage: $0  "
  exit 1
fi

# Chdir to our working directory, or die trying.

cd "$WORKDIR"

if [ $? -ne 0 ]; then
  echo "$0: Unable to change to working directory: $WORKDIR"
  exit 1
fi

# Yoink the web page we want.

wget -U "$USERAGENT" $WGETOPT -O $CACHEFILE.new "$URL"

# Bail out if Wget failed. This ensures we don't overwrite our old cache.

if [ $? -ne 0 ]; then
  echo "$0: Error retrieving $URL"
  exit 1
fi

# If we don't already have a cached copy from before the Wget then this
# is probably our first run, and we don't have much to do except copy
# the new file to the old cache.

if [ ! -f $CACHEFILE.cache ]; then
  mv $CACHEFILE.new $CACHEFILE.cache
  exit 0
fi

# We have a cached page and a new page, so run both through ELinks.

elinks -dump $ELINKSOPT $CACHEFILE.cache > $CACHEFILE.cache.dump
elinks -dump $ELINKSOPT $CACHEFILE.new > $CACHEFILE.new.dump

# We want the dumpfiles to have the same timestamp as their source files.
# This is useful as diff will show the timestamps of both files in the
# header of the output.

touch -r $CACHEFILE.cache $CACHEFILE.cache.dump
touch -r $CACHEFILE.new $CACHEFILE.new.dump

# Compare and enjoy.

diff $DIFFOPT $CACHEFILE.cache.dump $CACHEFILE.new.dump > $CACHEFILE.dump.diff

# If any changes were detected, send e-mail with the diff as the text.

if [ $? -ne 0 ]; then
  cat $CACHEFILE.dump.diff | mail -s "[webmonitor] Changed: $URL" $MAILTO
fi

# Clean up any temp files, and make the newly downloaded web page
# become our cached page.

rm -f $CACHEFILE.cache.dump $CACHEFILE.new.dump $CACHEFILE.dump.diff
mv $CACHEFILE.new $CACHEFILE.cache

--- GoldED+/BSD 1.1.5-b20160201