Determine last line in Ruby

Question

I'm wondering how I can determine when I am on the last line of a file that I reading in. My code looks like

File.open(file_name).each do |line|
    if(someway_to_determine_last_line)
end

I noticed that there is a file.eof? method, but how would I call the method as the file is being read? Thanks!

Answer 1

If you're iterating the file with each, then the last line will be passed to the block after the end-of-file is reached, because the last line is, by definition, the line ending with EOF.

So just call file.eof? in the block.

If you'd like to determine if it's the last non-empty line in the file, you'd have to implement some kind of readahead.

Answer 2

Depending on what you need to do with this "last non-empty line", you might be able to do something like this:

last_line = nil
File.open(file_name).each do |line|
    last_line = line if(!line.chomp.empty?)
    # Do all sorts of other things
end
if(last_line)
    # Do things with the last non-empty line.
end