Keep it simple on command line

      case KEY_ENTER:
        strings[char_cursor]=0;
        args[base]="IO_Return");
        args[base+1]=strings+line_cursor;
        IO_Return(argc,args);
        line_cursor=char_cursor+1;
        char_cursor=line_cursors;
        write(flush_fd,strings+line_cursor,char_cursor);
        break;

 When IO Manager command line sees the enter key, it calls the installed return and write to the scroll device. Scroll handled by flush, chained to xchars. IO has no clue, flush had no clue, xchars no clue.