This format specification is a subset of mod_log_config of Apache.

http://httpd.apache.org/docs/mod/mod_log_config.html#formats

Source Code

# File webrick/accesslog.rb, line 25
def setup_params(config, req, res)
  params = Hash.new("")
  params["a"] = req.peeraddr[3]
  params["b"] = res.sent_size
  params["e"] = ENV
  params["f"] = res.filename || ""
  params["h"] = req.peeraddr[2]
  params["i"] = req
  params["l"] = "-"
  params["m"] = req.request_method
  params["n"] = req.attributes
  params["o"] = res
  params["p"] = req.port
  params["q"] = req.query_string
  params["r"] = req.request_line.sub(/\x0d?\x0a\z/o, '')
  params["s"] = res.status       # won't support "%>s"
  params["t"] = req.request_time
  params["T"] = Time.now - req.request_time
  params["u"] = req.user || "-"
  params["U"] = req.unparsed_uri
  params["v"] = config[:ServerName]
  params
end