By default SLIME does not change
friends outside of the REPL. If you have any other threads which
write-string, etc. that output will be seen
only in the
*inferior-lisp* buffer or on the terminal, more
often than not this is inconvenient. So, if you want code such as this:
(run-in-new-thread (lambda () (write-line "In some random thread.~%" *standard-output*)))
to send its output to SLIME's repl buffer, as opposed to
swank:*globally-redirect-io* to T.
Note that the value of this variable is only checked when swank
accepts the connection so you should set it via
~/.swank.lisp. Otherwise you will need to call
swank::globally-redirect-io-to-connection yourself, but you
shouldn't do that unless you know what you're doing.