Why can’t watch run my shell function?

You can export the function and explicitly tell `watch` to use Bash:

```bash
export -f what-changed
watch bash -c what-changed
```

The important part is `bash -c`; plain `watch what-changed` uses `sh`, which generally does not import or understand exported Bash functions. This also needs to be done in the same shell where the function was defined.

A shell function exists only inside the current shell process. `watch` starts another process and normally runs the command through `/bin/sh`, so it cannot see functions, aliases, or other definitions that only exist in your interactive Bash session. Keeping the command in an executable script is the simplest and most portable solution.

If you want to pass the complete pipeline directly to `watch`, quote the entire command so the pipeline is interpreted by the shell started by `watch`:

```bash
watch "find -not ( -path './snap/firefox/common' -prune ) -not ( -path './.cache' -prune ) -type f -mmin -1 -printf '%C+ %p\n' | sort -n | tail -10"
```

However, with formatting strings and nested quotes, a small script is usually easier to read and less error-prone.

Another option is to avoid `watch` and run the command in a loop:

```bash
while true; do
clear
what-changed
sleep 5
done
```

That runs in the current shell, so the function is available, and it is easy to adjust the delay or add other commands. You can also use `while date; do` if displaying the current time is useful.