Fluentd Regexp patterns

expression /^(?<host>[^ ]*) [^ ]* (?<user>[^ ]*) \[(?<time>[^\]]*)\] "(?<method>\S+)(?: +(?<path>[^ ]*) +\S*)?" (?<code>[^ ]*) (?<size>[^ ]*)(?: "(?<referer>[^\"]*)" "(?<agent>[^\"]*)")?$/
time_format %d/%b/%Y:%H:%M:%S %z

192.168.0.1 - - [28/Feb/2013:12:00:00 +0900] "GET / HTTP/1.1" 200 777 "-" "Opera/12.0"

time:
1362020400 (28/Feb/2013:12:00:00 +0900)

record:
{
  "user"   : nil,
  "method" : "GET",
  "code"   : 200,
  "size"   : 777,
  "host"   : "192.168.0.1",
  "path"   : "/",
  "referer": nil,
  "agent"  : "Opera/12.0"
}