OpenSearch/docs/reference/eql/syntax.asciidoc

[role="xpack"]
[testenv="basic"]
[[eql-syntax]]
== EQL syntax reference
++++
<titleabbrev>Syntax reference</titleabbrev>
++++

experimental::[]

[IMPORTANT]
====
{es} supports a subset of EQL syntax.
====

[discrete]
[[eql-basic-syntax]]
=== Basic syntax

EQL queries require an event category and a matching condition. The `where`
keyword connects them.

[source,eql]
----
event_category where condition
----

For example, the following EQL query matches `process` events with a
`process.name` field value of `svchost.exe`:

[source,eql]
----
process where process.name == "svchost.exe"
----

[discrete]
[[eql-syntax-event-categories]]
==== Event categories

In {es}, an event category is a valid, indexed value of the
<<eql-required-fields,event category field>>. You can set the event category
field using the `event_category_field` parameter of the EQL search API.

[discrete]
[[eql-syntax-match-any-event-category]]
===== Match any event category

To match events of any category, use the `any` keyword. You can also use the
`any` keyword to search for documents without a event category field.

For example, the following EQL query matches any documents with a
`network.protocol` field value of `http`:

[source,eql]
----
any where network.protocol == "http"
----

[discrete]
[[eql-syntax-conditions]]
==== Conditions

A condition consists of one or more criteria an event must match.
You can specify and combine these criteria using the following operators:

[discrete]
[[eql-syntax-comparison-operators]]
===== Comparison operators

[source,eql]
----
<   <=   ==   !=   >=   >
----

.*Definitions*
[%collapsible]
====
`<` (less than)::
Returns `true` if the value to the left of the operator is less than the value
to the right. Otherwise returns `false`.

`<=` (less than or equal) ::
Returns `true` if the value to the left of the operator is less than or equal to
the value to the right. Otherwise returns `false`.

`==` (equal)::
Returns `true` if the values to the left and right of the operator are equal.
Otherwise returns `false`.

`!=` (not equal)::
Returns `true` if the values to the left and right of the operator are not
equal. Otherwise returns `false`.

`>=` (greater than or equal) ::
Returns `true` if the value to the left of the operator is greater than or equal
to the value to the right. Otherwise returns `false`.

`>` (greater than)::
Returns `true` if the value to the left of the operator is greater than the
value to the right. Otherwise returns `false`.
====

[discrete]
[[eql-syntax-logical-operators]]
===== Logical operators

[source,eql]
----
and  or  not
----

.*Definitions*
[%collapsible]
====
`and`::
Returns `true` only if the condition to the left and right _both_ return `true`.
Otherwise returns `false.

`or`::
Returns `true` if one of the conditions to the left or right `true`.
Otherwise returns `false.

`not`::
Returns `true` if the condition to the right is `false`.
====

[discrete]
[[eql-syntax-lookup-operators]]
===== Lookup operators

[source,eql]
----
user.name in ("Administrator", "SYSTEM", "NETWORK SERVICE")
user.name not in ("Administrator", "SYSTEM", "NETWORK SERVICE")
----

.*Definitions*
[%collapsible]
====
`in`::
Returns `true` if the value is contained in the provided list.

`not in`::
Returns `true` if the value is not contained in the provided list.
====

[discrete]
[[eql-syntax-math-operators]]
===== Math operators

[source,eql]
----
+  -  *  /  %
----

.*Definitions*
[%collapsible]
====
`+` (add)::
Adds the values to the left and right of the operator.

`-` (Subtract)::
Subtracts the value to the right of the operator from the value to the left.

`*` (Subtract)::
Multiplies the values to the left and right of the operator.

`/` (Divide)::
Divides the value to the left of the operator by the value to the right.

`%` (modulo)::
Divides the value to the left of the operator by the value to the right. Returns only the remainder.
====

[discrete]
[[eql-syntax-strings]]
==== Strings

Strings are enclosed with double quotes (`"`) or single quotes (`'`).

[source,eql]
----
"hello world"
"hello world with 'substring'"
----

[discrete]
[[eql-syntax-wildcards]]
===== Wildcards

You can use the wildcard operator (`*`) within a string to match specific
patterns. You can use wildcards with the `==` (equal) or `!=` (not equal)
operators:

[source,eql]
----
field == "example*wildcard"
field != "example*wildcard"
----

[discrete]
[[eql-syntax-match-any-condition]]
===== Match any condition

To match events solely on event category, use the `where true` condition.

For example, the following EQL query matches any `file` events:

[source,eql]
----
file where true
----

To match any event, you can combine the `any` keyword with the `where true`
condition:

[source,eql]
----
any where true
----

[discrete]
[[eql-syntax-escaped-characters]]
===== Escaped characters

When used within a string, special characters, such as a carriage return or
double quote (`"`), must be escaped with a preceding backslash (`\`).

[source,eql]
----
"example \t of \n escaped \r characters"
----

.*Escape sequences*
[%collapsible]
====
[options="header"]
|====
| Escape sequence | Literal character
|`\n`             | A newline (linefeed) character
|`\r`             | A carriage return character
|`\t`             | A tab character
|`\\`             | A backslash (`\`) character
|`\"`             | A double quote (`"`) character
|`\'`             | A single quote (`'`) character
|====
====

[discrete]
[[eql-syntax-raw-strings]]
===== Raw strings

Raw strings are preceded by a question mark (`?`) and treat backslashes (`\`) as
literal characters.

[source,eql]
----
?"String with a literal 'blackslash' \ character included"
----

You can escape single quotes (`'`) and double quotes (`"`) with a backslash, but
the backslash remains in the resulting string.

[source,eql]
----
?"\""
----

[NOTE]
====
Raw strings cannot contain only a single backslash. Additionally, raw strings
cannot end in an odd number of backslashes.
====

[discrete]
[[eql-syntax-non-alpha-field-names]]
==== Non-alphanumeric field names

Field names containing non-alphanumeric characters, such as underscores (`_`),
dots (`.`), hyphens (`-`), or spaces, must be escaped using backticks (+++`+++).

[source,eql]
----
`my_field`
`my.field`
`my-field`
`my field`
----

[discrete]
[[eql-functions]]
=== Functions

{es} supports several of EQL's built-in functions. You can use these functions
to convert data types, perform math, manipulate strings, and more.

For a list of supported functions, see <<eql-function-ref>>.

[TIP]
====
Using functions in EQL queries can result in slower search speeds. If you
often use functions to transform indexed data, you can speed up search by making
these changes during indexing instead. However, that often means slower index
speeds.

.*Example*
[%collapsible]
=====
An index contains the `file.path` field. `file.path` contains the full path to a
file, including the file extension.

When running EQL searches, users often use the `endsWith` function with the
`file.path` field to match file extensions:

[source,eql]
----
file where endsWith(file.path,".exe") or endsWith(file.path,".dll")
----

While this works, it can be repetitive to write and can slow search speeds. To
speed up search, you can do the following instead:

. <<indices-put-mapping,Add a new field>>, `file.extension`, to the index. The
  `file.extension` field will contain only the file extension from the
  `file.path` field.
. Use an <<ingest,ingest pipeline>> containing the <<grok-processor,`grok`>>
  processor or another preprocessor tool to extract the file extension from the
  `file.path` field before indexing.
. Index the extracted file extension to the `file.extension` field.

These changes may slow indexing but allow for faster searches. Users
can use the `file.extension` field instead of multiple `endsWith` function
calls:

[source,eql]
----
file where file.extension in ("exe", "dll")
----
=====

We recommend testing and benchmarking any indexing changes before deploying them
in production. See <<tune-for-indexing-speed>> and <<tune-for-search-speed>>.
====