Use progress-advance.

progress.scm

@@ -23,7 +23,7 @@
 ;; CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 ;;
 
-(declare (unit configuration))
+(declare (unit progress))
 
 (module
  progress
@@ -43,26 +43,31 @@
 
  ;; Prints current progress.
  (define (print-current-progress . args)
-   (display (sprintf "\r\x1b[K~A" (*current-progress*))))
+   (let ((cp (*current-progress*)))
+     (when cp
+       (display (sprintf "\r\x1b[K~A" cp)))))
 
  ;; Adds something to current progress and refreshes the display.
  (define (progress-advance str)
-   (*current-progress* (string-append (*current-progress*) (sprintf "~A" str)))
-   (print-current-progress))
+   (when (*current-progress*)
+     (*current-progress* (string-append (*current-progress*) (sprintf "~A" str)))
+     (print-current-progress)))
 
  ;; Runs given procedure within progress environment
- (define (run-with-progress pre-msg post-msg thunk)
-   (parameterize ((*current-progress* pre-msg))
+ (define (run-with-progress echo? pre-msg post-msg thunk)
+   (parameterize ((*current-progress* (if echo? pre-msg #f)))
      (print-current-progress)
-     (thunk)
-     (print-current-progress)
-     (print post-msg)))
+     (let ((result (thunk)))
+       (print-current-progress)
+       (when echo?
+	 (print post-msg))
+       result)))
 
  ;; Friendly syntax wrapper.
  (define-syntax with-progress
    (syntax-rules ()
-     ((_ pre post body ...)
-      (run-with-progress pre post (lambda () body ...)))))
+     ((_ echo? pre post body ...)
+      (run-with-progress echo? pre post (lambda () body ...)))))
 
  ;; If the program uses progress module, disable buffering
  (set-buffering-mode! (current-output-port) #:none)