Very simple bash code to alert me about Dow Jones index being higher or lower than yesterday by a set threshold:

#!/bin/bash
# you may schedule a cron job to run it after 4PM Eastern Time, e.g.
# 1 16 * * 1-5 /path_to_this_script &> /tmp/somename.log
# If your timezone is not EDT (where New York is), change 16:01 accordingly. 
# It's good practice to redirect stdout/stderr; see Sec. 2 of http://yong321.freeshell.org/computer/CronJobs.html

ALRT=100 # set threshold
cd /path_to_the_dir # better do this if scheduled in cron
PV=$(<dj.txt)
cp dj.txt djp.txt
wget -qO- http://google.com/finance | perl -nle 'print $1 if /YMlKec">([^<]+)/' | head -1 | sed 's/,//;s/\...//' > dj.txt
CR=$(<dj.txt)
if (( CR-PV>ALRT )); then
 echo "Current Dow Jones index is higher than yesterday by $((CR-PV))" | mail -s ck_dj_alert yong321@yahoo.com anotheruser@example.com
 # echo "CR is higher by $((CR-PV))"
elif (( PV-CR>ALRT )); then
 echo "Current Dow Jones index is lower than yesterday by $((PV-CR))" | mail -s ck_dj_alert yong321@yahoo.com anotheruser@example.com
 # echo "PV is higher by $((PV-CR))"
fi

It's been running since 2021. I just added another email. Due to minimal public info fetched, it's hardly considered web scraping. Or it is, but I'm sure it's allowed.
(Posted to https://www.linkedin.com/feed/update/urn:li:activity:7358351624798461952/ in Aug 2025)