> function clip { [ -t 0 ] && pbpaste || pbcopy }

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.

I'm not the OP, but I'll give it a go.

`[` 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`.

from `man test`:

   -t FD  file descriptor FD is opened on a terminal

FD 0 is stdin I'd guess. Pretty clever!

In light of the recent interest in fish shell, the equivalent in fish is:

  function clip
    if not tty >/dev/null
      pbcopy
    else
      pbpaste
    end
  end

Wow, that's really useful. For everyone who is as bad as me in bash, to actually use it put it like this in your bashrc:

function clip() { [ -t 0 ] && pbpaste || pbcopy }

I think you posted this because pasting the OP results in a syntax error. The problem is actually the list in the compound command needs to be terminated with a newline or semicolon. Both of the following are equivalent correct oneliners:

clip() { [ -t 0 ] && pbpaste || pbcopy;}

function clip { [ -t 0 ] && pbpaste || pbcopy;}