Logstash grok built-in Regular Expressions and logstashgrok built-in
Reference: https://github.com/elastic/logstash/blob/v1.4.2/patterns/grok-patterns
USERNAME [a-zA-Z0-9._-]+USER %{USERNAME}INT (?:[+-]?(?:[0-9]+))BASE10NUM (?<![0-9.+-])(?>[+-]?(?:(?:[0-9]+(?:\.[0-9]+)?)|(?:\.[0-9]+)))NUMBER (?:%{BASE10NUM})BASE16NUM (?<![0-9A-Fa-f])(?:[+-]?(?:0x)?(?:[0-9A-Fa-f]+))BASE16FLOAT \b(?<![0-9A-Fa-f.])(?:[+-]?(?:0x)?(?:(?:[0-9A-Fa-f]+(?:\.[0-9A-Fa-f]*)?)|(?:\.[0-9A-Fa-f]+)))\bPOSINT \b(?:[1-9][0-9]*)\bNONNEGINT \b(?:[0-9]+)\bWORD \b\w+\bNOTSPACE \S+SPACE \s*DATA .*?GREEDYDATA .*QUOTEDSTRING (?>(?<!\\)(?>"(?>\\.|[^\\"]+)+"|""|(?>'(?>\\.|[^\\']+)+')|''|(?>`(?>\\.|[^\\`]+)+`)|``))UUID [A-Fa-f0-9]{8}-(?:[A-Fa-f0-9]{4}-){3}[A-Fa-f0-9]{12}# NetworkingMAC (?:%{CISCOMAC}|%{WINDOWSMAC}|%{COMMONMAC})CISCOMAC (?:(?:[A-Fa-f0-9]{4}\.){2}[A-Fa-f0-9]{4})WINDOWSMAC (?:(?:[A-Fa-f0-9]{2}-){5}[A-Fa-f0-9]{2})COMMONMAC (?:(?:[A-Fa-f0-9]{2}:){5}[A-Fa-f0-9]{2})IPV6 ((([0-9A-Fa-f]{1,4}:){7}([0-9A-Fa-f]{1,4}|:))|(([0-9A-Fa-f]{1,4}:){6}(:[0-9A-Fa-f]{1,4}|((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){5}(((:[0-9A-Fa-f]{1,4}){1,2})|:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3})|:))|(([0-9A-Fa-f]{1,4}:){4}(((:[0-9A-Fa-f]{1,4}){1,3})|((:[0-9A-Fa-f]{1,4})?:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){3}(((:[0-9A-Fa-f]{1,4}){1,4})|((:[0-9A-Fa-f]{1,4}){0,2}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){2}(((:[0-9A-Fa-f]{1,4}){1,5})|((:[0-9A-Fa-f]{1,4}){0,3}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(([0-9A-Fa-f]{1,4}:){1}(((:[0-9A-Fa-f]{1,4}){1,6})|((:[0-9A-Fa-f]{1,4}){0,4}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:))|(:(((:[0-9A-Fa-f]{1,4}){1,7})|((:[0-9A-Fa-f]{1,4}){0,5}:((25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)(\.(25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)){3}))|:)))(%.+)?IPV4 (?<![0-9])(?:(?:25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{1,2})[.](?:25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{1,2})[.](?:25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{1,2})[.](?:25[0-5]|2[0-4][0-9]|[0-1]?[0-9]{1,2}))(?![0-9])IP (?:%{IPV6}|%{IPV4})HOSTNAME \b(?:[0-9A-Za-z][0-9A-Za-z-]{0,62})(?:\.(?:[0-9A-Za-z][0-9A-Za-z-]{0,62}))*(\.?|\b)HOST %{HOSTNAME}IPORHOST (?:%{HOSTNAME}|%{IP})HOSTPORT %{IPORHOST}:%{POSINT}# pathsPATH (?:%{UNIXPATH}|%{WINPATH})UNIXPATH (?>/(?>[\w_%!$@:.,-]+|\\.)*)+TTY (?:/dev/(pts|tty([pq])?)(\w+)?/?(?:[0-9]+))WINPATH (?>[A-Za-z]+:|\\)(?:\\[^\\?*]*)+URIPROTO [A-Za-z]+(\+[A-Za-z+]+)?URIHOST %{IPORHOST}(?::%{POSINT:port})?# uripath comes loosely from RFC1738, but mostly from what Firefox# doesn't turn into %XXURIPATH (?:/[A-Za-z0-9$.+!*'(){},~:;=@#%_\-]*)+#URIPARAM \?(?:[A-Za-z0-9]+(?:=(?:[^&]*))?(?:&(?:[A-Za-z0-9]+(?:=(?:[^&]*))?)?)*)?URIPARAM \?[A-Za-z0-9$.+!*'|(){},~@#%&/=:;_?\-\[\]]*URIPATHPARAM %{URIPATH}(?:%{URIPARAM})?URI %{URIPROTO}://(?:%{USER}(?::[^@]*)?@)?(?:%{URIHOST})?(?:%{URIPATHPARAM})?# Months: January, Feb, 3, 03, 12, DecemberMONTH \b(?:Jan(?:uary)?|Feb(?:ruary)?|Mar(?:ch)?|Apr(?:il)?|May|Jun(?:e)?|Jul(?:y)?|Aug(?:ust)?|Sep(?:tember)?|Oct(?:ober)?|Nov(?:ember)?|Dec(?:ember)?)\bMONTHNUM (?:0?[1-9]|1[0-2])MONTHNUM2 (?:0[1-9]|1[0-2])MONTHDAY (?:(?:0[1-9])|(?:[12][0-9])|(?:3[01])|[1-9])# Days: Monday, Tue, Thu, etc...DAY (?:Mon(?:day)?|Tue(?:sday)?|Wed(?:nesday)?|Thu(?:rsday)?|Fri(?:day)?|Sat(?:urday)?|Sun(?:day)?)# Years?YEAR (?>\d\d){1,2}HOUR (?:2[0123]|[01]?[0-9])MINUTE (?:[0-5][0-9])# '60' is a leap second in most time standards and thus is valid.SECOND (?:(?:[0-5]?[0-9]|60)(?:[:.,][0-9]+)?)TIME (?!<[0-9])%{HOUR}:%{MINUTE}(?::%{SECOND})(?![0-9])# datestamp is YYYY/MM/DD-HH:MM:SS.UUUU (or something like it)DATE_US %{MONTHNUM}[/-]%{MONTHDAY}[/-]%{YEAR}DATE_EU %{MONTHDAY}[./-]%{MONTHNUM}[./-]%{YEAR}ISO8601_TIMEZONE (?:Z|[+-]%{HOUR}(?::?%{MINUTE}))ISO8601_SECOND (?:%{SECOND}|60)TIMESTAMP_ISO8601 %{YEAR}-%{MONTHNUM}-%{MONTHDAY}[T ]%{HOUR}:?%{MINUTE}(?::?%{SECOND})?%{ISO8601_TIMEZONE}?DATE %{DATE_US}|%{DATE_EU}DATESTAMP %{DATE}[- ]%{TIME}TZ (?:[PMCE][SD]T|UTC)DATESTAMP_RFC822 %{DAY} %{MONTH} %{MONTHDAY} %{YEAR} %{TIME} %{TZ}DATESTAMP_RFC2822 %{DAY}, %{MONTHDAY} %{MONTH} %{YEAR} %{TIME} %{ISO8601_TIMEZONE}DATESTAMP_OTHER %{DAY} %{MONTH} %{MONTHDAY} %{TIME} %{TZ} %{YEAR}DATESTAMP_EVENTLOG %{YEAR}%{MONTHNUM2}%{MONTHDAY}%{HOUR}%{MINUTE}%{SECOND}# Syslog Dates: Month Day HH:MM:SSSYSLOGTIMESTAMP %{MONTH} +%{MONTHDAY} %{TIME}PROG (?:[\w._/%-]+)SYSLOGPROG %{PROG:program}(?:\[%{POSINT:pid}\])?SYSLOGHOST %{IPORHOST}SYSLOGFACILITY <%{NONNEGINT:facility}.%{NONNEGINT:priority}>HTTPDATE %{MONTHDAY}/%{MONTH}/%{YEAR}:%{TIME} %{INT}# ShortcutsQS %{QUOTEDSTRING}# Log formatsSYSLOGBASE %{SYSLOGTIMESTAMP:timestamp} (?:%{SYSLOGFACILITY} )?%{SYSLOGHOST:logsource} %{SYSLOGPROG}:COMMONAPACHELOG %{IPORHOST:clientip} %{USER:ident} %{USER:auth} \[%{HTTPDATE:timestamp}\] "(?:%{WORD:verb} %{NOTSPACE:request}(?: HTTP/%{NUMBER:httpversion})?|%{DATA:rawrequest})" %{NUMBER:response} (?:%{NUMBER:bytes}|-)COMBINEDAPACHELOG %{COMMONAPACHELOG} %{QS:referrer} %{QS:agent}# Log LevelsLOGLEVEL ([Aa]lert|ALERT|[Tt]race|TRACE|[Dd]ebug|DEBUG|[Nn]otice|NOTICE|[Ii]nfo|INFO|[Ww]arn?(?:ing)?|WARN?(?:ING)?|[Ee]rr?(?:or)?|ERR?(?:OR)?|[Cc]rit?(?:ical)?|CRIT?(?:ICAL)?|[Ff]atal|FATAL|[Ss]evere|SEVERE|EMERG(?:ENCY)?|[Ee]merg(?:ency)?)