How do I read a gzip file line by line?

Question

I have a gzip file and currently I read it like this:

infile = open("file.log.gz")
gz = Zlib::GzipReader.new(infile)
output = gz.read
puts result

I think this converts the file to a string, but I would like to read it line by line.

What I want to accomplish is that the file has some warning messages with some garbage, I want to grep those warning messages and then write them to another file. But, some warning messages are repeated so I have to make sure that i only grep them once. Hence line by line reading would help me.

Answer 1

You should be able to simply loop over the gzip reader like you do with regular streams (according to the docs)

infile = open("file.log.gz")
gz = Zlib::GzipReader.new(infile)
gz.each_line do |line|
  puts line
end

Answer 2

Try this:

infile = open("file.log.gz")
gz = Zlib::GzipReader.new(infile)
while output = gz.gets
  puts output
end