From: Chris <chris@...>
Date: 2002-05-06T11:53:33+09:00
Subject: Re: newbie Q: how to strip blank lines from file?

In article <YmlB8.26235$GG6.2378585@news3.calgary.shaw.ca>,
 Stewart Midwinter <stewart@NOWHERE_midwinter.ca> wrote:

> Well, I've spent a few days reading about Ruby, and want to try my first 
> project: a little utility that will read a file that has too many blank 
> lines in it, and strip out all of those blank line (could contain spaces or 
> tabs).
> 
> As I tackles this, I realise that I need to have a good manual in front of 
> me, because I'm not getting anywhere. I am definitely confused at this 
> point, since this problem could be solved in one or two lines, I believe. 
> Does anyone more experienced have any suggestions?  I looked in 
> rubycookbook.org and couldn't find anything there either.
> 
> Thanks!
> 
> here's my attempt so far, which seems to go into an infinite loop.
> 
> ---
> # IO.foreach("snip.txt") { |line| puts line }
> arr = IO.readlines("snip.txt")
> puts "I read in " + arr.length.to_s + "lines from file."
> def blank (s)    # looking for blank lines to chop
>    (s =~ /\S/) != nil
> end
> i = 0
> while i < arr.length do
>  if blank(arr[i]) == nil then arr[i] = nil
> IO.printf("snip.out")
> end
> # file.close("snip.out")
> end
> ---

The reason for your infinite loop is that in your while loop, you never 
increment i.

IO.readlines("snip.txt").collect { |x|
   x.strip unless x.strip == ""
}

Iterators are your friend.  :-)