# Grep

The *Grep Filter* plugin allows to match or exclude specific records based in regular expression patterns.

## Configuration Parameters

The plugin supports the following configuration parameters:

| Key     | Value Format | Description                                                 |
| ------- | ------------ | ----------------------------------------------------------- |
| Regex   | FIELD REGEX  | Keep records which field matches the regular expression.    |
| Exclude | FIELD REGEX  | Exclude records which field matches the regular expression. |

## Getting Started

In order to start filtering records, you can run the filter from the command line or through the configuration file. The following example assumes that you have a file called *lines.txt* with the following content

```
aaa
aab
bbb
ccc
ddd
eee
fff
ggg
```

### Command Line

> Note: using the command line mode need special attention to quote the regular expressions properly. It's suggested to use a configuration file.

The following command will load the *tail* plugin and read the content of *lines.txt* file. Then the *grep* filter will apply a regular expression rule over the *log* field (created by tail plugin) and only *pass* the records which field value starts with *aa*:

```
$ bin/fluent-bit -i tail -p 'path=lines.txt' -F grep -p 'regex=log aa' -m '*' -o stdout
```

### Configuration File

```python
[INPUT]
    Name   tail
    Path   lines.txt

[FILTER]
    Name   grep
    Match  *
    Regex  log aa

[OUTPUT]
    Name   stdout
    Match  *
```

The filter allows to use multiple rules which are applied in order, you can have many *Regex* and *Exclude* entries as required.


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# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.fluentbit.io/manual/1.0/filter/grep.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.