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Version: v4.21

grok

Parses a string using a grok-pattern, backed by regular expressions.

Synopsis​

grok <input_pattern> [--pattern-definitions <additional_patterns>]
     [--include-unnamed] [--indexed-captures]
     [--merge] [--schema <schema>] [--selector <fieldname[:prefix]>]
     [--schema-only] [--raw] [--unnest-separator <separator>]

Description​

grok uses a regular expression based parser similar to the Logstash grok plugin in Elasticsearch. Tenzir ships with the same built-in patterns as Elasticsearch, found here.

In short, <input_pattern> consists of replacement fields, that look like %{SYNTAX[:SEMANTIC[:CONVERSION]]}. SYNTAX is a reference to a pattern, either built-in or user-defined through --pattern-defintions. SEMANTIC is an identifier that names the field in the parsed record. CONVERSION is either infer (default), string (default with --raw), int, or float.

The supported regular expression syntax is the only supported by Boost.Regex, which is effectively Perl-compatible.

<input_pattern>​

The grok pattern used for matching. Must match the input in its entirety.

Common Options (Parser)​

The grok parser supports the common schema inference options.

--include-unnamed​

By default, only fields that were given a name with SEMANTIC, or with the regular expression named capture syntax (?<name>...) are included in the resulting record.

With --include-unnamed, replacement fields without a SEMANTIC are included in the output, using their SYNTAX value as the record field name.

--indexed-captures​

All subexpression captures are included in the output, with the SEMANTIC used as the field name if possible, and the capture index otherwise.

--pattern-definitions <additional_patterns>​

<additional_patterns> can contain a user-defined newline-delimited list of patterns, where a line starts with the pattern name, followed by a space, and the grok-pattern for that pattern. For example, the built-in pattern INT is defined as follows:

INT (?:[+-]?(?:[0-9]+))

Examples​

Parse a fictional HTTP request log:

# Example input:
# 55.3.244.1 GET /index.html 15824 0.043
grok "%{IP:client} %{WORD:method} %{URIPATHPARAM:request} %{NUMBER:bytes} %{NUMBER:duration}"