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From: Robert Klemme <shortcutter@googlemail.com>
Newsgroups: comp.lang.ruby
Subject: Re: editing file in ruby
Date: Sat, 21 Jul 2018 18:25:06 +0200
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On 21.07.2018 17:33, Mohan Mohta wrote:
> Hello
> I wrote a program but what beats me is the print works fine and gives me the expected output fir it does not write the same to the file
> 
> File.open("/tmp/grub.conf","r").each_line do |line|
>          file_boot=File.open("/tmp/bootfile","w")

You are not closing this file properly.

Here's how I'd do it

File.open '/tmp/bootfile', 'w' do |out|
   File.foreach '/tmp/grub.conf' do |line|
     if /^\s+kernel\b/ =~ line
       line.gsub! /transparent_hugepage=\w+/, ''
       line.sub! /\s+$/, ''
       line << ' transparent_hugepage=never'
     end

     out.puts line
   end
end

Cheers

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/