Bash script to monitor the Alamo Drafthouse calendar for changes

mp.sh

# Usage: Run script with watch to repeat this check every N seconds `watch -n 20 ./mp.sh`
# On macos: `brew install jq watch`
# Example Used for Master Pancake CYOP tickets that often go on sale and then sell out quickly. 

rm mp*.json

# Download the Alamo Drafthouse calendar for Austin
curl -s https://feeds.drafthouse.com/adcService/showtimes.svc/calendar/0002/ > mp.json
# Hacky jq query to pull out the Ritz location's events for the desired week/day combinations
cat mp.json | jq .Calendar.Cinemas[0].Months[0].Weeks[2].Days[4] >> mp-res.json
cat mp.json | jq .Calendar.Cinemas[0].Months[0].Weeks[2].Days[5] >> mp-res.json

# See if there is a difference between the current and previous results
DIFF=$(diff mp-res.json mp-res.old)
if [ "$DIFF" != "" ]
then
  echo 'Something changed.'
  osascript -e 'display notification "Alamo day check has a change." sound name "Frog" with title "Master Pancake"'
else
  cp mp-res.json mp-res.old
fi

Instead of assuming that mp-res.old exists test for it. if [ -f mp-res.old ]; then echo "Yup"; fi

If you wanted to always run the diff command, even when mp-res.old does not exist you could compare mp-res.json against itself when you detected that mp-res.old didn't exist.

You don't need to pipe mp.json into jq, just use the command-line interface provided.

jq .Calendar.Cinemas[0].Months[0].Weeks[2].Days[4] mp.json >> mp-res.json
jq .Calendar.Cinemas[0].Months[0].Weeks[2].Days[5] mp.json >> mp-res.json

Furthermore, if you overwrote instead of appended the output from the first command you could drop the rm mp*.json step.

jq .Calendar.Cinemas[0].Months[0].Weeks[2].Days[4] mp.json > mp-res.json
jq .Calendar.Cinemas[0].Months[0].Weeks[2].Days[5] mp.json >> mp-res.json

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I'm not that familiar with scripting on OSX. Your use of osascript is cool! I didn't know how to do that.