From: Morton Goldberg <m_goldberg@...>
Date: 2007-07-10T14:24:18+09:00
Subject: Re: Trying to get dynamic output in console

On Jul 10, 2007, at 12:45 AM, Nobuyoshi Nakada wrote:

> Hi,
>
> At Tue, 10 Jul 2007 03:21:07 +0900,
> Morton Goldberg wrote in [ruby-talk:258465]:
>> 0.step(100, 10) do |i|
>       printf("\rProgress: %3.2d%%", i)
>>     $stdout.flush
>>     sleep(1)
>> end
>> puts
>
> The backslash before % is meaningless and just ignored.  You
> need two %'s to print one %.

You are of course right: the backslash before the percent should be  
another percent. But in this case doubling the percent also turns out  
to be unnecessary. The following works (in Ruby 1.8.2) although one  
would think that it wouldn't:

<code>
0.step(100, 10) do |i|
    printf((i < 100 ? "\rProgress:  %02d%" : "\rProgress: %3d%"), i)
    $stdout.flush
    sleep(1)
end
puts
</code>

It seems to work because the single percent occurs at the end of the  
format string. Is this a minor bug in printf? Is it behavior  
inherited from C?

Regards, Morton