Delete first two lines of file with ruby - ruby

Question

My script reads in large text files and grabs the first page with a regex. I need to remove the first two lines of each first page or change the regex to match 1 line after the ==Page 1== string. I include the entire script here because I've been asked to in past questions and because I'm new to ruby and don't always know how integrate snippets as answers:
#!/usr/bin/env ruby -wKU
require 'fileutils'
source = File.open('list.txt')
source.readlines.each do |line|
line.strip!
if File.exists? line
file = File.open(line)
end
text = (File.read(line))
match = text.match(/==Page 1(.*)==Page 2==/m)
puts match
end

Answer 1

Now, when You have updated your question, I had to delete a big part of so good answer :-)
I guess the main point of your problem was that you wanted to use match[1] instead of match. The object returned by Regexp.match method (MatchData) can be treated like an array, which holds the whole matched string as the first element, and each subquery in the following elements. So, in your case the variable match (and match[0]) is the whole matched string (together with '==Page..==' marks), but you wanted just the first subexpression which is hidden in match[1].
Now about other, minor problems I sense in your code. Please, don't be offended in case you already know what I say, but maybe others will profit from the warnings.
The first part of your code (if File.exists? line) was checking whether the file exists, but your code just opened the file (without closing it!) and still was trying to open the file few lines later.
You may use this line instead:
next unless File.exists? line
The second thing is that the program should be prepared to handle the situation when the file has no page marks, so it does not match the pattern. (The variable match would then be nil)
The third suggestion is that a little more complicated pattern might be used. The current one (/==Page 1==(.*)==Page 2==/m) would return the page content with the End-Of-Line mark as the first character. If you use this pattern:
/==Page 1==\s*\n(.*)==Page 2==/m
then the subexpression will not contain the white spaces placed in the same line as the '==Page 1==` text. And if you use this pattern:
/==Page 1==\s*\n(.*\n)==Page 2==/m
then you will be sure that the '==Page 2==' mark starts from the beginning of the line.
And the fourth issue is that very often programmers (sometimes including me, of course) tend to forget about closing the file after they opened it. In your case you have opened the 'source' file, but in the code there was no source.close statement after the loop. The most secure way of handling files is by passing a block to the File.open method, so You might use the following form of the first lines of your program:
File.open('list.txt') do |source|
source.readlines.each do |line|
...but in this case it would be cleaner to write just:
File.readlines('list.txt').each do |line|
Taking it all together, the code might look like this (I changed the variable line to fname for better code readability):
#!/usr/bin/env ruby -wKU
require 'fileutils'
File.readlines('list.txt').each do |fname|
fname.strip!
next unless File.exists? fname
text = File.read(fname)
if match = text.match(/==Page 1==\s*\n(.*\n)==Page 2==/m)
# The whole 'page' (String):
puts match[1].inspect
# The 'page' without the first two lines:
# (in case you really wanted to delete lines):
puts match[1].split("\n")[2..-1].inspect
else
# What to do if the file does not match the pattern?
raise "The file #{fname} does NOT include the page separators."
end
end