Script to check if the Dropbox agent download redirect URL changes from an expected value

dropbox_redirectURL_check.sh

#!/bin/bash

# This script looks at the headers for a URL to download the Dropbox desktop app to determine the redirect URL to the actual
# download from Dropbox's CDN. It then compares this to an expected URL and logs when they do not match.
#
# There seems to be an issue where the redirect will randomly change to point at an unexpected (beta) build instead of the 
# expected stable build.

## Vars
# URL with redirect the check for change
checkURL='https://www.dropbox.com/download?plat=mac&full=1'
# The expected URL to the redirected to for the stable build. This will change over time, current as of 8/2/24.
knownCorrectRedirectURL="https://edge.dropboxstatic.com/dbx-releng/client/Dropbox%20204.4.5420.dmg"
# Interval between checks
sleepIntervalSeconds=20
# Paths to log to
logHome="$HOME/Desktop/Dropbox_issue" # Folder the logs will live in
logPath="$logHome/dropbox_redirect_log.txt" # log containing all output
problemLogPath="$logHome/bad_redirect_log.txt" # log containing the bad redirect events

## Functions
# Logging function to write to console and main log file
logme () {
	local input="$1"
	echo "$(date '+%Y-%m-%d_%H:%M:%S_%Z') :: $input" | tee -a "$logPath"
}

## Main
# Setup
mkdir -p "$logHome"

# Loop indefinitely 
while true; do
	# clear previous value and check for the redirect URL
	thisCheck=''
	thisCheck="$(curl -Is "$checkURL" | grep 'location' | awk -F ': ' '{print $NF}' | tr -d '\n\t\r ')"
	
	# Determine if we got a good or bad redirect
	if [[ -z "$thisCheck" ]]; then
		logme "Couldn't determine redirect URL."
	elif [[ "$thisCheck" != "$knownCorrectRedirectURL" ]]; then
		logme "Redirect URL mismatch. Currently redirecting to: $thisCheck" | tee -a "$problemLogPath"
	else
		logme "Expected redirect URL was returned."
	fi
	
	# Wait and run again
	sleep "$sleepIntervalSeconds"
done