# parse_cef

Parses a string as a CEF message

```tql
parse_cef(input:string, [schema=string, selector=string, schema_only=bool,
          raw=bool, unflatten_separator=string]) -> record
```

## Description

The `parse_cef` function parses a string as a CEF message

### `input: string`

The string to parse.

### `raw = bool (optional)`

Use only the raw types that are native to the parsed format. Fields that have a type specified in the chosen `schema` will still be parsed according to the schema.

### `schema = string (optional)`

Provide the name of a schema to be used by the parser.

If a schema with a matching name is installed, the result will always have all fields from that schema.

* Fields that are specified in the schema, but did not appear in the input will be null.
* Fields that appear in the input, but not in the schema will also be kept. Use `schema_only=true` to reject fields that are not in the schema.

If the given schema does not exist, this option instead assigns the output schema name only.

The `schema` option is incompatible with the `selector` option.

### `selector = string (optional)`

Designates a field value as schema name with an optional dot-separated prefix.

The string is parsed as `<fieldname>[:<prefix>]`. The `prefix` is optional and will be prepended to the field value to generate the schema name.

For example, the Suricata EVE JSON format includes a field `event_type` that contains the event type. Setting the selector to `event_type:suricata` causes an event with the value `flow` for the field `event_type` to map onto the schema `suricata.flow`.

The `selector` option is incompatible with the `schema` option.

### `schema_only = bool (optional)`

When working with an existing schema, this option will ensure that the output schema has *only* the fields from that schema.

If the schema name is obtained via a `selector` and it does not exist, this has no effect.

This option requires either `schema` or `selector` to be set.

### `unflatten_separator = string (optional)`

A delimiter that, if present in keys, causes values to be treated as values of nested records.

A popular example of this is the [Zeek JSON](https://preview.docs.tenzir.com/375/375/reference/operators/read_zeek_json.md) format. It includes the fields `id.orig_h`, `id.orig_p`, `id.resp_h`, and `id.resp_p` at the top-level. The data is best modeled as an `id` record with four nested fields `orig_h`, `orig_p`, `resp_h`, and `resp_p`.

Without an unflatten separator, the data looks like this:

Without unflattening

```json
{
  "id.orig_h": "1.1.1.1",
  "id.orig_p": 10,
  "id.resp_h": "1.1.1.2",
  "id.resp_p": 5
}
```

With the unflatten separator set to `.`, Tenzir reads the events like this:

With 'unflatten'

```json
{
  "id": {
    "orig_h": "1.1.1.1",
    "orig_p": 10,
    "resp_h": "1.1.1.2",
    "resp_p": 5
  }
}
```

### Duplicate Keys

If the parser encounters a duplicate key in an event, it will transparently upgrade the field to be a list of values instead.

For a simple example, consider this JSON file:

Duplicate Keys

```json
{"key": 7}
{"key": 0.0, "key": 1}
{"key": 42}
```

```tql
{key: 7}
{key: [0.0, 1.0]}
{key: 42}
```

If the values are of different type, conversions to a common type will be attempted, such as to a common number type. Ultimately values will be stringified if they do not share a common type:

Type Conflict

```json
{"key": 0.0, "key": "1.1.1.1", "key": "example.com"}
```

```tql
{key: ["0", "1.1.1.1", "example.com"]}
```

## Examples

```tql
from { x: "CEF:0|Cynet|Cynet 360|4.5.4.22139|0|Memory Pattern - Cobalt Strike Beacon ReflectiveLoader|8|key=value" }
y = x.parse_cef()
```

```tql
{
  cef_version: 0,
  device_vendor: "Cynet",
  device_product: "Cynet 360",
  device_version: "4.5.4.22139",
  signature_id: "0",
  name: "Memory Pattern - Cobalt Strike Beacon ReflectiveLoader",
  severity: "8",
  extension: {
    key: "value"
  }
}
```

## See Also

* [`print_cef`](https://preview.docs.tenzir.com/375/375/reference/functions/print_cef.md)
* [`read_cef`](https://preview.docs.tenzir.com/375/375/reference/operators/read_cef.md)
* [`read_syslog`](https://preview.docs.tenzir.com/375/375/reference/operators/read_syslog.md)
* [Parse string fields](https://preview.docs.tenzir.com/375/375/guides/parsing/parse-string-fields.md)
* [Syslog](https://preview.docs.tenzir.com/375/375/integrations/syslog.md)