Ok, so you've had nix (home-manager) working fine. Then Apple tells you it's time to update.
Ok. Reboot. Oops. It has now broken your Nix setup. Here's some stuff to work through. YMMV.
Note: This is what worked for me, who was just using nix + home-manager. The upgrade that I last did that caused all these issues was 12.3.X > 12.4
Type crontab -l to see your cron jobs. Type crontab -e to edit them. You have to use Vim apparently.
Add a line like this:
0,30 * * * * /Users/YOURNAME/Documents/scripts/stretch.sh
That is on every 0th and 30th minute of the hour. Make sure all the separators in there are tabs!
DIR=$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )
Is a useful one-liner which will give you the full directory name of the script no matter where it is being called from
These will work as long as the last component of the path used to find the script is not a symlink (directory links are OK). If you want to also resolve any links to the script itself, you need a multi-line solution:
SOURCE="${BASH_SOURCE[0]}"
while [ -h "$SOURCE" ]; do # resolve $SOURCE until the file is no longer a symlink