OpenSearch/docs/reference/eql/functions.asciidoc

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[[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-indexof>>
* <<eql-fn-length>>
* <<eql-fn-startswith>>
* <<eql-fn-string>>
* <<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-indexof]]
=== `indexOf`
Returns the first position of a provided substring in a source string.
If an optional start position is provided, this function returns the first
occurrence of the substring at or after the start position.
[%collapsible]
====
*Example*
[source,eql]
----
// url.domain = "subdomain.example.com"
indexOf(url.domain, ".") // returns 9
indexOf(url.domain, ".", 9) // returns 9
indexOf(url.domain, ".", 10) // returns 17
indexOf(url.domain, ".", -6) // returns 9
// empty strings
indexOf("", "") // returns 0
indexOf(url.domain, "") // returns 0
indexOf(url.domain, "", 9) // returns 9
indexOf(url.domain, "", 10) // returns 10
indexOf(url.domain, "", -6) // returns 0
// missing substrings
indexOf(url.domain, "z") // returns null
indexOf(url.domain, "z", 9) // returns null
// start position is higher than string length
indexOf(url.domain, ".", 30) // returns null
// null handling
indexOf(null, ".", 9) // returns null
indexOf(url.domain, null, 9) // returns null
indexOf(url.domain, ".", null) // returns null
----
*Syntax*
[source,txt]
----
indexOf(<source>, <substring>[, <start_pos>])
----
*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
--
`<substring>`::
+
--
(Required, string or `null`)
Substring to search for.
If this argument is `null` or the `<source>` string does not contain this
substring, the function returns `null`.
If the `<start_pos>` is positive, empty strings (`""`) return the `<start_pos>`.
Otherwise, 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
--
`<start_pos>`::
+
--
(Optional, integer or `null`)
Starting position for matching. The function will not return positions before
this one. Defaults to `0`.
Positions are zero-indexed. Negative offsets are treated as `0`.
If this argument is `null` or higher than the length of the `<source>` string,
the function returns `null`.
If using a field as the argument, this parameter supports only the following
<<number,numeric>> field datatypes:
* `long`
* `integer`
* `short`
* `byte`
--
*Returns:* integer 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-string]]
=== `string`
Converts a value to a string.
[%collapsible]
====
*Example*
[source,eql]
----
string(42) // returns "42"
string(42.5) // returns "42.5"
string("regsvr32.exe") // returns "regsvr32.exe"
string(true) // returns "true"
// null handling
string(null) // returns null
----
*Syntax*
[source,txt]
----
string(<value>)
----
*Parameters*
`<value>`::
(Required)
Value to convert to a string. If `null`, the function returns `null`.
+
If using a field as the argument, this parameter does not support the
<<text,`text`>> field datatype.
*Returns:* string 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
====