How to escape square bracket in Logstash Grok filter?

Elastic Stack Logstash
7

I did a quick test and came up with this.

Input data (assuming the \t is a tab in the input file)

pjanzen@logstash1:~$ cat /home/pjanzen/input.txt
	[05/Feb/2018:10:39:47 +0000]
pjanzen@logstash1:~$


input {
  file {
    path => "/home/pjanzen/input.txt"
    sincedb_path => "/dev/null"
    start_position => "beginning"
  }
}

filter {
  grok {
    match => { "message" => "\t\[%{GREEDYDATA:timestamp}\]\t" }
  }
}

output {
  stdout { codec => rubydebug }
}

The result is this.

pjanzen@logstash1:~$ sudo /usr/share/logstash/bin/logstash --path.settings=/etc/logstash -f /home/pjanzen/test.conf
Sending Logstash's logs to /opt/logstash/logs which is now configured via log4j2.properties
{
          "path" => "/home/pjanzen/input.txt",
    "@timestamp" => 2018-03-13T13:06:30.315Z,
      "@version" => "1",
          "host" => "logstash1",
       "message" => "\t[05/Feb/2018:10:39:47 +0000]\t",
     "timestamp" => "05/Feb/2018:10:39:47 +0000"
}

I hope this helps.