Watching for hash changes

[musjj]

While waiting for #571 to be merged, are there any alternative solutions for watching for file hash changes?

I tried exporting shell functions and calling it from watchexec, but the problem is that global variables (that stores the previous hash) are not retained between calls. Are there any better ways of doing this?

[passcod]

You can use the JSON event stream mode and a second watchexec instance triggered on signals, or store global state in a file, or use xattrs to store per-file hashes, etc.

[musjj]

I ended up using signals instead:

callback() {
  echo hello world
}

trap callback USR1 USR2
watchexec -- kill -USR1 $$ &
trap "kill $!" EXIT
until wait; do
  :
done

watchexec will send a signal to the script itself every time it is triggered. The nice thing here is that you can keep state (e.g. global variables) inbetween runs.