rails reading lines of file before upload with paperclip

I am trying to upload a file in rails (using paperclip), and I want to process some of the file data before letting paperclip send it off to s3 storage. In my controller, I just grab the file parameter (which does give me a file) and then I try to read the lines into an array

csv_file = params[:activity][:data]

array = IO.readlines(csv_file.path)

The problem is, I'm only getting the last line of the file. I tried using .rewind, but 开发者_如何学JAVAstill get just the last line.

I dislike readlines and I always use regular expressions. Try this. End of line - \n

Handy block structure to ensure that the file handle is closed:

File.open(csv_file.path) do |f|
  a = f.readlines
  process a...
end

Reading a whole file into memory might not be a good idea depending on the size of the files.