From: Daniel Berger <Daniel.Berger@...>
Date: 2005-07-15T03:59:45+09:00
Subject: Re: Help: very simple script problem

Tristan Knowles wrote:
> Just another quick question regarding flow control.
> 
> What variable can I refer to, and what method do I use
> to create a while loop so that only x amount of lines
> are shown at once from a file?
> 
> This is how I have been approaching it, its obviously
> not working, and I'm still not up to speed at working
> out how to use methods based on the online reference
> details only.
> 
> =====
> if File.exists? Log_File
>   lines = File.open(Log_File).readlines
>   lines.each_with_index do |line, index|
>      index % 2 == 0 ? color = "#dddddd" :
>  color="#cccccc"
> 
> 	while index <= 50
> 
> 	    puts "<tr bgcolor=\"#{color}\">\n 
>  <td>#{index}</td>\n  <td>#{line}</td>"    
> 	    puts "</tr>"
>       
>        end
> 
>    end
> =====
> 
> 
> Am I even approaching this the correct way?  Or should
> this be handled once step before with a grep
> statement?

Your code looks fine as is, although I wonder if 50 is a constant number 
you can rely on.  But, here's some more info for you:

If you only want 1 line per iteration, then your best bet is to use 
IO.foreach.  If you only want to slurp X number of lines into a 
variable, then just keep in mind that IO.readlines returns an array. 
So, you can use a range as the index and do:

# No need to use the File class, btw
lines = IO.readlines(Log_File)[0..49]

Just keep in mind that, even though you're only selecting 50 lines, the 
entire file has been slurped into memory.

Regards,

Dan