[[eql-function-ref]]
== EQL function reference
++++
<titleabbrev>Function reference</titleabbrev>
++++

experimental::[]

{es} supports the following EQL functions:

* <<eql-fn-between>>
* <<eql-fn-endswith>>
* <<eql-fn-length>>
* <<eql-fn-startswith>>
* <<eql-fn-substring>>
* <<eql-fn-wildcard>>

[discrete]
[[eql-fn-between]]
=== `between`

Extracts a substring that's between a provided `left` and `right` text in a
source string.

[%collapsible]
====
*Example*
[source,eql]
----
// file.path = "C:\\Windows\\System32\\cmd.exe"
between(file.path, "system32\\\\", ".exe")   // returns "cmd"
between(file.path, "workspace\\\\", ".exe")  // returns ""


// Greedy matching defaults to false.
between(file.path, "\\\\", "\\\\", false)  // returns "Windows"
// Sets greedy matching to true
between(file.path, "\\\\", "\\\\", true)  // returns "Windows\\System32"

// Case sensitivity defaults to false.
between(file.path, "system32\\\\", ".exe", false, false)  // returns "cmd"
// Sets case sensitivity to true
between(file.path, "system32\\\\", ".exe", false, true)   // returns ""
between(file.path, "System32\\\\", ".exe", false, true)   // returns "cmd"

// empty source string
between("", "system32\\\\", ".exe")          // returns ""
between("", "", "")                          // returns ""

// null handling
between(null, "system32\\\\", ".exe")                   // returns null
----

*Syntax*

[source,txt]
----
between(<source>, <left>, <right>[, <greedy_matching>, <case_sensitive>])
----

*Parameters*

`<source>`::
+
--
(Required, string or `null`)
Source string. Empty strings return an empty string (`""`), regardless of the
`<left>` or `<right>` parameters. If `null`, the function returns `null`.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field

Fields containing <<array,array values>> use the first array item only.
--

`<left>`::
+
--
(Required, string)
Text to the left of the substring to extract. This text should include
whitespace.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field

<<array,Array values>> are not supported.
--

`<right>`::
+
--
(Required, string)
Text to the right of the substring to extract. This text should include
whitespace.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field

<<array,Array values>> are not supported.
--

`<greedy_matching>`::
(Optional, boolean)
If `true`, match the longest possible substring, similar to `.*` in regular
expressions. If `false`, match the shortest possible substring, similar to `.*?`
in regular expressions. Defaults to `false`.

`<case_sensitive>`::
(Optional, boolean)
If `true`, matching is case-sensitive. Defaults to `false`.

*Returns:* string or `null`
====

[discrete]
[[eql-fn-endswith]]
=== `endsWith`

Returns `true` if a source string ends with a provided substring. Matching is
case insensitive.

[%collapsible]
====
*Example*
[source,eql]
----
endsWith("regsvr32.exe", ".exe")          // returns true
endsWith("regsvr32.exe", ".EXE")          // returns true
endsWith("regsvr32.exe", ".dll")          // returns false
endsWith("", "")                          // returns true

// file.name = "regsvr32.exe"
endsWith(file.name, ".exe")               // returns true
endsWith(file.name, ".dll")               // returns false

// file.extension = ".exe"
endsWith("regsvr32.exe", file.extension)  // returns true
endsWith("ntdll.dll", file.name)          // returns false

// file.name = [ "ntdll.dll", "regsvr32.exe" ]
endsWith(file.name, ".dll")               // returns true
endsWith(file.name, ".exe")               // returns false

// null handling
endsWith("regsvr32.exe", null)            // returns null
endsWith("", null)                        // returns null 
endsWith(null, ".exe")                    // returns null
endsWith(null, null)                      // returns null
----

*Syntax*

[source,txt]
----
endsWith(<source>, <substring>)
----

*Parameters*

`<source>`::
+
--
(Required, string or `null`)
Source string. If `null`, the function returns `null`.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field

Fields containing <<array,array values>> use the first array item only.
--

`<substring>`::
+
--
(Required, string or `null`)
Substring to search for. If `null`, the function returns `null`.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field
--

*Returns:* boolean or `null`
====

[discrete]
[[eql-fn-length]]
=== `length`

Returns the character length of a provided string, including whitespace and
punctuation.

[%collapsible]
====
*Example*
[source,eql]
----
length("explorer.exe")         // returns 12
length("start explorer.exe")   // returns 18
length("")                     // returns 0
length(null)                   // returns null

// process.name = "regsvr32.exe"
length(process.name)           // returns 12
----

*Syntax*
[source,txt]
----
length(<string>)
----

*Parameters*

`<string>`::
+
--
(Required, string or `null`)
String for which to return the character length. If `null`, the function returns
`null`. Empty strings return `0`.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field

<<array,Array values>> are not supported.
--

*Returns:* integer or `null`
====

[discrete]
[[eql-fn-startswith]]
=== `startsWith`

Returns `true` if a source string begins with a provided substring. Matching is
case insensitive.

[%collapsible]
====
*Example*
[source,eql]
----
startsWith("regsvr32.exe", "regsvr32")  // returns true
startsWith("regsvr32.exe", "RegSvr32")  // returns true
startsWith("regsvr32.exe", "explorer")  // returns false
startsWith("", "")                      // returns true

// process.name = "regsvr32.exe"
startsWith(process.name, "regsvr32")    // returns true
startsWith(process.name, "explorer")    // returns false

// process.name = "regsvr32"
startsWith("regsvr32.exe", process.name) // returns true
startsWith("explorer.exe", process.name) // returns false

// process.name = [ "explorer.exe", "regsvr32.exe" ]
startsWith(process.name, "explorer")    // returns true
startsWith(process.name, "regsvr32")    // returns false

// null handling
startsWith("regsvr32.exe", null)        // returns null
startsWith("", null)                    // returns null 
startsWith(null, "regsvr32")            // returns null
startsWith(null, null)                  // returns null
----

*Syntax*

[source,txt]
----
startsWith(<source>, <substring>)
----

*Parameters*

`<source>`::
+
--
(Required, string or `null`)
Source string. If `null`, the function returns `null`.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field

Fields containing <<array,array values>> use the first array item only.
--

`<substring>`::
+
--
(Required, string or `null`)
Substring to search for. If `null`, the function returns `null`.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field
--

*Returns:* boolean or `null`
====

[discrete]
[[eql-fn-substring]]
=== `substring`

Extracts a substring from a source string at provided start and end positions.

If no end position is provided, the function extracts the remaining string.

[%collapsible]
====
*Example*
[source,eql]
----
substring("start regsvr32.exe", 6)        // returns "regsvr32.exe"
substring("start regsvr32.exe", 0, 5)     // returns "start"
substring("start regsvr32.exe", 6, 14)    // returns "regsvr32"
substring("start regsvr32.exe", -4)       // returns ".exe"
substring("start regsvr32.exe", -4, -1)   // returns ".ex"
----

*Syntax*

[source,txt]
----
substring(<source>, <start_pos>[, <end_pos>])
----

*Parameters*

`<source>`::
(Required, string)
Source string.

`<start_pos>`::
+
--
(Required, integer)
Starting position for extraction.

If this position is higher than the `<end_pos>` position or the length of the
`<source>` string, the function returns an empty string.

Positions are zero-indexed. Negative offsets are supported.
--

`<end_pos>`::
(Optional, integer)
Exclusive end position for extraction. If this position is not provided, the
function returns the remaining string.
+
Positions are zero-indexed. Negative offsets are supported.

*Returns:* string
====

[discrete]
[[eql-fn-wildcard]]
=== `wildcard`
Returns `true` if a source string matches one or more provided wildcard
expressions.

[%collapsible]
====
*Example*
[source,eql]
----
// The two following expressions are equivalent.
process.name == "*regsvr32*" or process.name == "*explorer*"
wildcard(process.name, "*regsvr32*", "*explorer*")

// process.name = "regsvr32.exe"
wildcard(process.name, "*regsvr32*")                // returns true
wildcard(process.name, "*regsvr32*", "*explorer*")  // returns true
wildcard(process.name, "*explorer*")                // returns false
wildcard(process.name, "*explorer*", "*scrobj*")    // returns false

// empty strings
wildcard("", "*start*")                             // returns false
wildcard("", "*")                                   // returns true
wildcard("", "")                                    // returns true

// null handling
wildcard(null, "*regsvr32*")                        // returns null
wildcard(process.name, null)                        // returns null
----

*Syntax*

[source,txt]
----
wildcard(<source>, <wildcard_exp>[, ...])
----

*Parameters*

`<source>`::
+
--
(Required, string)
Source string. If `null`, the function returns `null`.

If using a field as the argument, this parameter supports only the following
field datatypes:

* <<keyword,`keyword`>>
* <<constant-keyword,`constant_keyword`>>
* <<text,`text`>> field with a <<keyword,`keyword`>> or
  <<constant-keyword,`constant_keyword`>> sub-field
--

`<wildcard_exp>`::
+
--
(Required{multi-arg}, string)
Wildcard expression used to match the source string. If `null`, the function
returns `null`. Fields are not supported as arguments.
-- 

*Returns:* boolean
====