system:You will be provided with log, output the grok that can match the log .Grok is a pattern matching tool that is used to parse and extract data from unstructured log files. It is a part of the ELK stack (Elasticsearch, Logstash, and Kibana) and is used to identify and extract structured data from logs. In the context of matching log files, Grok is used to create custom patterns that can match specific log file formats and extract relevant information from them. Logs typically contain multiple fields, such as timestamp, IP address, user ID, request NAME_1, request NAME_2, response code, etc. These fields can be segmented based on specific delimiters or matched using regular expressions
####
here is an example：
``
2022-01-01 12:34:56 192.168.1.1 USER1234 GET /api/v1/users/1 200
`
the grok could generate in following step:
1.split the log into 6 parts timestamp:{2022-01-01 12:34:56},ip:{192.168.1.1},user_id:{USER1234},http_NAME_1:{GET},request_NAME_2:{/api/v1/users/1},http_status:{200}
2.write  matched grok for each part 
timestamp:%{TIMESTAMP_ISO8601:timestamp} ;
ip:%{IP:ip};
user_id:%{WORD:user_id} ;
http_NAME_1:%{WORD:http_NAME_1};
request_NAME_2:%{URIPATHPARAM:request_NAME_2} ;
http_status: %{NUMBER:http_status}
3.combine all part grok the complete grok will be 
`
%{TIMESTAMP_ISO8601:timestamp} %{IP:ip} %{WORD:user_id} %{WORD:http_NAME_1} %{URIPATHPARAM:request_NAME_2} %{NUMBER:http_status}
``
This grok expression means: match a timestamp, an IP address, a user ID, an HTTP NAME_1, a request NAME_2, and a List of HTTP status codes from the log, and name them timestamp, ip, and user respectively_ ID, HTTP_ NAME_1, request_ NAME_2 and HTTP_ Status“

more exampes:
{input: "2021-09-15T09:23:17.123+00:00 I NETWORK  [listener] connection accepted from 192.168.0.100:54321 #123456 (1 connection now open)"
output:"%{TIMESTAMP_ISO8601:timestamp} %{WORD:severity} %{WORD:component} %{DATA:context} %{GREEDYDATA:message}"

input:"51948:M 25 May 2023 09:48:12.761 * Background saving terminated with success"
output:"%{INT:pid}:%{DATA:loglevel} %{MONTHDAY} %{MONTH} %{YEAR} %{TIME} %{GREEDYDATA:message}"

input:"19382:C 23 Mar 16:20:54.107 * RDB: 0 MB of memory used by copy-on-write"
output:"%{NUMBER:pid}:%{WORD:role_char}\s%{REDISTIMESTAMP:timestamp}\s[#*]\s%{GREEDYDATA:message}"
}

###
user:ouput grok of the log "2021-07-05 23:55:02,814 [myid:5] - INFO [main:QuorumPeerMain@132] - Starting quorum peer"
output: