cat replacement in ruby

cat.rb

#!/usr/bin/ruby
#by Lampros Chaidas
#cat replacement in ruby - if the -n switch is provided the lines start with a number

#check if the -n option is given to prepend each line with a line number
if ARGV.include? "-n"
        @lines=true
        ARGV.delete("-n")
end

#checks if the file exists and returns true/false
def file_exists? (filename)
        File.exist?(filename)
end

#line counter - we set it outside the loop so it doesn't reset to 0 for every file we add
@i = 0

def print_file (filename)
        #using the foreach here so we don't read the entire file in memory, instead we go line-by-line
        File.foreach(filename) do |line|
                @i = @i + 1
                #prepends line with the line number
                if @lines==true then line = "    #{@i} #{line}" end
                #puts a space in front of numbers less than 0 to make output even
                if @i < 10 then line.sub!("#{@i}"," #{@i}") end
                puts "#{line}"
        end
end

#loops through the files in the ARGV list
ARGV.each do |item|
        #if the file doesn't exist, skip
        next if file_exists?(item)==false
        #print the contents of the file
        print_file item
end