Question

Hi just getting into Ruby, and I am trying to learn some basic file reading commands, and I haven’t found any solid sources yet.

I am trying to go through certain lines from that file, til the end of the file.

So in the file where it says FILE_SOURCES I want to read all the sources til end of file, and place them in a file.

I found printing the whole file, and replacing words in the file, but I just want to read certain parts in the file.

Answer 1

I would do it like this (assuming you can read the entire file into memory):

source_lines = IO.readlines('source_file.txt')
start_line   = source_lines.index{ |line| line =~ /SOURCE_LINE/ } + 1
File.open( 'other_file.txt', 'w' ) do |f|
  f << source_lines[ start_line..-1 ].join( "\n" )
end

Relevant methods:

• IO.readlines to read the lines into an array
• Array#index to find the index of the first line matching a regular expression
• File.open to create a new file on disk (and automatically close it when done)
• Array#[] to get the subset of lines from the index to the end

If you can’t read the entire file into memory, then I’d do a simpler variation on @tadman’s state-based one:

started = false
File.open( 'other_file.txt', 'w' ) do |output|
  IO.foreach( 'source_file.txt' ) do |line|
    if started then
      output << line
    elsif line =~ /FILE_SOURCES/
      started = true
    end
  end
end

Welcome to Ruby!