When you run a command or a script that runs for a long time, it may be helpful to have all its output prefixed with a timestamp. For example we want to change this:
foo
bar
baz
to this:
[2020-12-13 12:20:38] foo
[2020-12-13 12:21:32] bar
[2020-12-13 12:22:20] baz
Here's how you can do it.