Animated shell output with Ruby

Question

I have implemented Game of Life.

What I cannot work out is how to print every iteration of the cell array in the shell. I want to make the output appear animated.

Here is my array print code

def print_board board
  wipe_screen
  board.each_with_index do |row,y|
    row.each_with_index do |cell,x|
      print cell == 1 ? '*' : ' '
    end
    print "\n"
  end
end

and here is the wipe_screen method:

def wipe_screen
  Board_Height.each do |_|
    # print "\r"
    # $stdout.write "\e[A\e[2K"
  end
end

You can see in the commented out bits what I have already tried.

How can I achieve animated output inside the shell?

EDIT:

Allow me to clarify with an example.

It simply prints out each iteration of the Game of Life cycle):

*  *     * * ** ** 
*** * **  * *  * **
** **** * *  **** * 
** *   **  * **  ** 
*   *  **  *  ***** 
*****  *  **** *   
*****  * * ** *   * 
* ** *** * **   ****
* **  * ** ***** * 
** *  *   * *****   
*            **  * 
**  ****     *** * 
   *** *     *** * 
   *  **     ***** 
      **     ***** 
      **       *   
       **      ****
        **    * * *
     ****   * *****
     *      ****   
*            **  * 
*   ****     *** * 
   *** *     *** * 
      **     ***** 
      **       *** 
      **       *** 
       ***     * **
       * *     ****
     *****  ** ****
     *      ****   
*            **  * 
    ****     *** * 
    ** *     *** * 
      **       *** 
      **       *** 
      **       *** 
       ***     * **
       * *       **
     *****  ***  **
     *      ****   
             **  * 
    ****     *** * 
    ** *       * * 
      **       *** 
      **       *** 
      **       *** 
       ***     ** *
       * *        *
     *****  ****  *
     *      ****

Whereas what I want is:

*  *     * * ** ** 
*** * **  * *  * **
** **** * *  **** * 
** *   **  * **  ** 
*   *  **  *  ***** 
*****  *  **** *   
*****  * * ** *   * 
* ** *** * **   ****
* **  * ** ***** * 
** *  *   * *****

Then, as it iterates over the game of life cycle, replaced by:

  *      ****   
          **  * 
  ****     *** * 
  ** *       * * 
   **       *** 
   **       *** 
   **       *** 
    ***     ** *
    * *        *
  *****  ****  *
  *      ****

EDIT:

game of life gist

how about one of those ways? http://stackoverflow.com/questions/3170553/how-can-i-clear-the-terminal-in-ruby — Sergio Tulentsev, Feb 12 '16 at 11:48
just tried them, none of them work. they just print out a massive gap on the in the shell and then the next iteration rather than printing out the next iteration over the previous print array — Thermatix, Feb 12 '16 at 11:56
Ok, then curses will help you: http://ablogaboutcode.com/2013/04/01/overwriting-console-output-using-curses-in-ruby/ — Sergio Tulentsev, Feb 12 '16 at 12:19
Could you post your complete runnable code somewhere (gist.github.com, for example) so that we can see if it works on our machines? (keywords: complete and runnable) — Sergio Tulentsev, Feb 12 '16 at 12:22
BTW, have you tried _all_ of them? There are many ways in that post. — Sergio Tulentsev, Feb 12 '16 at 12:23
I did, they either did nothing or print a giant gap without actually clearing the previously printed array. — Thermatix, Feb 12 '16 at 12:24
yeah, none of them work. Try that curses thing, though. It's the industry standard for printing to terminal in arbitrary positions. — Sergio Tulentsev, Feb 12 '16 at 12:29
Is that really the only way? It feels like using a bazooka to swat a fly. — Thermatix, Feb 12 '16 at 12:32
@Thermatix you are using `"\e[A\e[2K"`, correct control sequence is `"\e[A\e[2J"` as in the linked answer... — Sven Koschnicke, Feb 12 '16 at 12:36
@Thermatix: it's the only working way to overwrite multiple lines that I know of. Posted a comment to your gist. — Sergio Tulentsev, Feb 12 '16 at 12:50

score 3 · Accepted Answer · answered Feb 12 '16 at 12:51

3

For an animated look, do not wipe the screen, but return the cursor to the home position. At least in bash and tcsh, you may achieve that with

print "\033[0;0H]"

Then continue and overwrite the updated cell contents. Use STDOUT.flush at the end of the page to empty the output buffer.

answered Feb 12 '16 at 12:51

bogl

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That's fairly close to what I want, how does it work? specifically,how to make it below the input line? – Thermatix Feb 12 '16 at 12:55
This is not a Ruby issue, but shell specific. Have a look at Cursor movement in the shell documentation, e.g.: http://www.tldp.org/HOWTO/Bash-Prompt-HOWTO/x361.html . – bogl Feb 12 '16 at 12:59
Just fairly close? You can move the cursor to any location. Just replace 0;0 with your coordinates. – bogl Feb 12 '16 at 12:59

Animated shell output with Ruby

1 Answers1