It’s a little difficult to show, so you might have to use your imagination. There are several ways to cue it; in my test runs, this:
./watchfile.sh test.txt cat test.txt
was enough to refresh the screen with my edits, when I saved test.txt back to disk from another terminal window.
That’s not the only way to use watchfile.sh, and the help flags will give you ideas on other methods. For example, you can monitor the output of a second command, and when that changes, execute a third command.
I like watchfile.sh a lot better than either fsniper or entr. fsniper was a bit more complex, and in the end, didn’t quite work. entr, on the other hand, worked fine, but expected to receive updates through a pipe, which is a tiny bit clunky.
But watchfile.sh is very straightforward and very flexible, and does what it promises. And I like that the task is reduced to an easily dissected script, rather than complex code.
So my advice, if you have to pick one of the three, is to go with watchfile.sh. Unless of course, you have another method you prefer. 😉