Disable *COMPILE-VERBOSE* and *LOAD-VERBOSE* for --script

Scripts using COMPILE or LOAD, either directly or through third party systems,
pollute the standard output with messages unrelated to the script itself.

This is undesirable (to quote a comment in toplevel.lisp, "scripts don't need
to be stylish or fast, but silence is usually a desirable quality") and can
cause bugs when the output of a script is processed through a UNIX pipe by a
program expecting to get output and not verbose diagnostic messages.

Problem originally signaled by Hraban Luyat <hraban@0brg.net>.

doc/manual/start-stop.texinfo

@@ -338,6 +338,11 @@ broken pipe) on either standard input, standard output, or standard
 error, the script silently exits with code 0. This allows e.g. safely
 piping output from SBCL to @code{head -n1} or similar.
 
+Additionally, the option sets @code{*compile-verbose*} and
+@code{*load-verbose*} to @code{nil} while loading the file to avoid
+potentially verbose diagnostic messages printed on the standard
+output.
+
 @end table
 
 @node Initialization Files

src/code/toplevel.lisp

@@ -381,7 +381,13 @@ any non-negative real number."
                    (*debug-io* (make-two-way-stream *stdin* *stderr*))
                    (*standard-input* *stdin*)
                    (*standard-output* *stdout*)
-                   (*error-output* *stderr*))
+                   (*error-output* *stderr*)
+                   ;; Compile/load messages from the language implementation
+                   ;; are not really what one would expect from a script. And
+                   ;; these messages are printed on stdout interfere when
+                   ;; scripts are used as part as a UNIX pipeline.
+                   (*compile-verbose* nil)
+                   (*load-verbose* nil))
                (load stream :verbose nil :print nil)))))
     (handling-end-of-the-world
       (if (eq t script)

tests/script.test.sh

@@ -26,6 +26,10 @@ echo '(exit :code 7)' > $tmpscript
 run_sbcl --script $tmpscript
 check_status_maybe_lose "--script exit status from EXIT" $? 7 "(status good)"
 
+echo '(when (and (null *load-verbose*) (null *compile-verbose*)) (exit :code 7))' > $tmpscript
+run_sbcl --script $tmpscript
+check_status_maybe_lose "--script verbosity" $? 7 "(silent)"
+
 echo '(error "oops")' > $tmpscript
 run_sbcl --script $tmpscript 1> $tmpout 2> $tmperr
 check_status_maybe_lose "--script exit status from ERROR" $? 1 "(error implies 1)"