Linux redirection question

Question

What does the following do on Linux?

cat <> FIFO |

Where FIFO is a FIFO created in the current directory.

Answer 1

in bash the redirection operator <> causes a file to be opened for both reading and writing (on file descriptor 0 by default, although you can specify another).

see the bash manual page on redirections, section 3.6.10

Answer 2

You can't both read and write onto the same pipe.