That's great! Would you please explain why that works? Are there any cases you know of where that doesn't work as expected?
Edit: btw you need a semicolon after pbcopy to make that function valid on one line.
`[` is a Bash built-in command also known as `test`. The `-t` parameter tells it to test if a file descriptor is open for `0`, which is also known as `STDIN`.
So if you're piping something into `STDIN` it will do `pbcopy`. If not -- it will do `pbpaste`.
-t FD file descriptor FD is opened on a terminal