When connecting via M-x slime-connect SLIME does
not change *standard-output* and friends outside of the
REPL. If you have any other threads which call format,
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
*inferior-lisp*, set swank:*globally-redirect-io* to T
in ~/.swank.lisp
But when started using M-x slime the streams are redirected by default.