-mode argument to Guile port open routines, except that it is
-restricted to one of @samp{"r"}, @samp{"w"}, or @samp{"r+"}. For
-compatibility @samp{"b"} (binary) may also be present, but we ignore
-it: memory ports are binary only. The default is @samp{"r"},
-read-only.
+mode argument to Guile port open routines, except that the @samp{"a"}
+and @samp{"l"} modes are not supported.
+@xref{File Ports,,, guile, GNU Guile Reference Manual}.
+The @samp{"b"} (binary) character may be present, but is ignored:
+memory ports are binary only. If @samp{"0"} is appended then
+the port is marked as unbuffered.
+The default is @samp{"r"}, read-only and buffered.