Question

So, I have a regexp that I have tested on Rubular and from the CLI (using the pry gem). This parses a custom Apache log format. When I feed input to it in pry, it works as expected (e.g. $~ is populated.) Rubular also reports correct matching and grouping for various lines of input. When run from the code below, no matches.

I have also tried messing with String.chomp! and the \n character, in case that was throwing off the match, but various permutations have no effect.

I’m sure it’s something a more experienced Rubyist could shed some light on.

Rubular link: http://www.rubular.com/r/fycHVYZdZz

Here is the relevant code, regex, and input — and thanks in advance:

log_regex = %r{
            (?<ip>(([0-9]{1,3}\.){3}[0-9]{1,3}))                                                                   
            \s-\s
            (?<src_ip>.*)
            -\s
            (?<date>\[.*\])
            \s
            (?<url>".+")
            \s
            (?<response>\d{3})
            \s
            (?<length>\d+)
            \s
            (?<referer>".+")
            \s
            (?<useragent>".*")
            \s(?<host>.*)?
            /ix
            }

logfile = ARGV[0]

def process_log(log_regex,logfile)
    IO.foreach(logfile, 'r') do |line|
        line.chomp!
        log_regex.match(line) do |m|
            puts m['ip']
        end
    end
end

process_log(log_regex,logfile)

Sample input:

209.123.123.123 - - [05/Jul/2012:11:02:01 -0700] "GET /url/mma/rss2.0.xml HTTP/1.1" 301 0 "-" "FeedBurner/1.0 (http://www.FeedBurner.com)" xml.somewhere.com

Answer 1

You probably want to take a close look at the definition of your regex. Your flags are inside the definition of the pattern, instead of following the closing of %r where they belong:

%r{
...
/ix
}

should be:

%r{
...
}ix

From IRB:

irb(main):001:0> %r{foo/ix}
/foo\/ix/
irb(main):002:0> %r{foo}ix
/foo/ix
irb(main):003:0> %r{^foo$}ix =~ 'foo'
0
irb(main):004:0> %r{^foo/ix$} =~ 'foo'
nil

Both PRY and IRB return the same results for the above tests.