From: Brian Candler <B.Candler@...>
Date: 2007-02-23T20:01:03+09:00
Subject: Re: File.open with line =~ /.../

On Fri, Feb 23, 2007 at 04:36:05PM +0900, Rebhan, Gilbert wrote:
> 
> Hi,
> 
> i have a txtfile like that =
> 
> bla1
> foo=red
> 
> bla2
> foo=green
> 
> bla3
> foo=yellow
> 
> and i want to get i.e. bla1 and the corresponding value of foo
> 
> i tried with 
> 
> File.open("Y:/test/sample.txt", "r").each do |line|
>   puts $1<<' : '<< $3 if line =~ /(\w+)\s+(\w+=)(\w+)/
> end
> 
> but somehow the regex doesn't work ?!
> whereas it works in the QuickRex Plugin for Eclipse
> 
> Any ideas ?

It's because you're only searching within each line individually, whereas
your regexp matches ( word, space, word=word ) in one go. Using 'each' it
will be invoked first with "bla1\n" and then with "foo=red\n", neither of
which matches by itself.

If it's a small file then just slurp it in all in one go:

ans = File.open("sample.txt").read.scan(/(\w+)\s+(\w+=)(\w+)/)
p ans

Your regexp works, but personally I would add some anchors, i.e.

ans = File.open("sample.txt").read.scan(/^(\w+)\s+(\w+=)(\w+)$/)
p ans

If you want to avoid reading the whole file in, there are more complex
solutions, e.g.

require 'enumerator'
ans = File.open("sample.txt").each_cons(2) do |line1, line2|
  next unless line1 =~ /^(\w+)$/
  cat = $1
  next unless line2 =~ /^(\w+)=(\w+)$/
  puts "#{cat}: #{$1} => #{$2}"
end

HTH,

Brian.