Functions¶

Function calls keep the core language for EQL simple but easily extendable. Functions are used to perform math, string manipulation or more sophisticated expressions to be expressed.

add(x, y)¶: Returns x + y

Changed in version 0.8: Added + operator directly.

arrayContains(some_array, value[, ...])¶

Check if value is a member of the array some_array.

Changed in version 0.7: Support for additional arguments.

// {my_array: ["value1", "value2", "value3"]}

arrayContains(my_array, "value2")           // returns true
arrayContains(my_array, "value4")           // returns false
arrayContains(my_array, "value3", "value4)  // returns true

arrayCount(array, variable, expression)¶

Count the number of matches in an array to an expression.

New in version 0.7.

// {my_array: [{user: "root", props: [{level: 1}, {level: 2}]},
//             {user: "guest", props: [{level: 1}]}]

arrayCount(my_array, item, item.user == "root")                           // returns 1
arrayCount(my_array, item, item.props[0].level == 1)                      // returns 2
arrayCount(my_array, item, item.props[1].level == 4)                      // returns 0
arrayCount(my_array, item, arrayCount(item.props, p, p.level == 2) == 1)  // returns 1

arraySearch(array, variable, expression)¶

Check if any member in the array matches an expression. Unlike arrayContains(), this can search over nested structures in arrays, and supports searching over arrays within arrays.

// {my_array: [{user: "root", props: [{level: 1}, {level: 2}]},
//             {user: "guest", props: [{level: 1}]}]

arraySearch(my_array, item, item.user == "root")                       // returns true
arraySearch(my_array, item, item.props[0].level == 1)                  // returns true
arraySearch(my_array, item, item.props[1].level == 4)                  // returns false
arraySearch(my_array, item, arraySearch(item.props, p, p.level == 2))  // returns true

between(source, left, right[, greedy=false, case_sensitive=false])¶

Extracts a substring from source that’s also between left and right.

Parameters:	greedy – Matches the longest string when set, similar to `.` vs `.?`. case_sensitive – Match case when searching for `left` and right`.

between("welcome to event query language", " ", " ")            // returns "to"
between("welcome to event query language", " ", " ", true)      // returns "to event query"

cidrMatch(ip_address, cidr_block[, ...])¶

Returns true if the source address matches any of the provided CIDR blocks.

Changed in version 0.8.

// ip_address = "192.168.152.12"
cidrMatch(ip_address, "10.0.0.0/8", "192.168.0.0/16")     // returns true

concat(...)¶

Returns a concatenated string of all the input arguments.

concat("Process ", process_name, " executed with pid ", pid)

divide(m, n)¶: Return m / n

Changed in version 0.8: Added / operator directly.

endsWith(x, y)¶: Checks if the string x ends with the substring y.

indexOf(source, substring[, start=0])¶

Find the first position (zero-indexed) of a string where a substring is found. If start is provided, then this will find the first occurrence at or after the start position.

indexOf("some-subdomain.another-subdomain.com", ".")     // returns 14
indexOf("some-subdomain.another-subdomain.com", ".", 14) // returns 14
indexOf("some-subdomain.another-subdomain.com", ".", 15) // returns 32

length(s)¶: Returns the length of a string. Non-string values return 0.

match(source, pattern[, ...])¶

Checks if multiple regular expressions are matched against a source string.

match("event query language", ?"[a-z]+ [a-z]+ [a-z]")   // returns true

modulo(m, n): Performs the modulo operator and returns the remainder of m / n.

Changed in version 0.8: Added % operator directly.

multiply(x, y)¶: Returns x * y

Changed in version 0.8: Added * operator directly.

number(s[, base=10])¶

Parameters:	base (number) – The base of a number.

Returns a number constructed from the string s.

number("1337")                  // returns 1337
number("0xdeadbeef", 16)        // 3735928559

startsWith(x, y)¶: Checks if the string x starts with the string y.

string(val)¶: Returns the string representation of the value val.

stringContains(a, b)¶: Returns true if b is a substring of a

substring(source[, start, end])¶

Extracts a substring between from another string between start and end. Like other EQL functions, start and end are zero-indexed positions in the string. Behavior is similar to Python’s string slicing (source[start:end]), and negative offsets are supported.

substring("event query language", 0, 5)                     // returns "event"
substring("event query language", 0, length("event"))       // returns "event"
substring("event query language", 6, 11)                    // returns "query"
substring("event query language", -8)                       // returns "language"
substring("event query language", -length("language"))      // returns "language"
substring("event query language", -5, -1))                  // returns "guag"

subtract(x, y)¶: Returns x - y

wildcard(value, wildcard[, ...])¶

Compare a value to a list of wildcards. Returns true if any of them match. For example, the following two expressions are equivalent.

command_line == "* create *" or command_line == "* config *" or command_line == "* start *"

wildcard(command_line, "* create *", "* config *", "* start *")

Methods¶

Calling functions with values returned from other functions can often be difficult to read for complex expressions. EQL also provides an alternative method syntax that flows more naturally from left to right.

For instance, the expression:

length(between(command_line, "-enc ", " ")) > 500

is equivalent to the method syntax:

command_line:between(command_line, "-enc ", " "):length() > 500