Takes an expression — source —
and sets the field defined by
as to the result of the
source expression.
Can be used to manipulate fields whose names are not statically known, but computed at runtime.
The function can be used to read fields whose exact name might not be known, by getting the value of a dynamically-named field. This happens when the field name is computed from an expression, so the function works by evaluating this expression as input.
It can also be used to manipulate fields whose names contain a space or
- like in:
deltaTime:= now() - getField("time-in-ms")getField() Examples
Get the Value of a Field Stored in Another Field
Query
result := getField("foo")Introduction
Given an event with the following fields:
|------------------|
| foo | bar |
| bar | 123 |
| foo | quux |
|------------------|
Do a "direct" lookup where the result is set to the value that
is stored in that field, by quoting the string — it takes
expressions as input (similar to eval() and
test() functions):
Step-by-Step
Starting with the source repository events.
- logscale
result := getField("foo")The result is set to the value that is stored in field foo
Event Result set.
Summary and Results
| bar | foo | result |
|---|---|---|
| 123 | bar | bar |
| <no value> | quux | quux |
In the same event, using the same query that does not quote the string:
result := getField(foo)
will get the value of the field which name is stored at
foo, so 123
is stored as the result:
| bar | foo | result |
|---|---|---|
| 123 | bar | 123 |
| <no value> | quux | <no value> |
(no result is output for
foo=quux as
quux does not exist).
Take Field Names as Parameters
Query
| test(getField(?foo)==?bar)Introduction
Use the function to take a field name as a parameter.
Given an event with the following fields:
|----------------------|
| hello | world |
|----------------------|Test if a field exists on an event with a specific value where both the field and the value are given as parameters. This query:
Step-by-Step
Starting with the source repository events.
- logscale
| test(getField(?foo)==?bar)Tests if the field given by the parameter
?foo (hello)is equal to the value given by the parameter?bar (world). Event Result set.
Summary and Results
| hello |
|---|
| world |
Get the Last Element of an Array
Query
| index := array:length("foo[]")-1
| fieldName := format("foo[%s]", field=[index])
| result := getField(fieldName)Introduction
Given an event with an array for field foo[x]:
foo['a','b','c','d']
Looks up the value of the field which is part of an array of
elements, using getField() in combination
with expressions: first build the string with the field, then
perform getField() in that string to get
the result.
Step-by-Step
Starting with the source repository events.
- logscale
| index := array:length("foo[]")-1Sets the index as the last element of the array (in this case,
[6]) - logscale
| fieldName := format("foo[%s]", field=[index])Takes the field index and builds the string foo[6] using
format() - logscale
| result := getField(fieldName)Provides the value of the field whose name is foo[6]
Event Result set.
Summary and Results
The output is displayed as follows, where the last column shows the value of fieldName column (which is foo[3]) as the result:
| @timestamp | @rawstring | @timestamp.nanos | fieldName | foo[0] | foo[1] | foo[2] | foo[3] | index | result |
|---|---|---|---|---|---|---|---|---|---|
| 2024-03-01T08:43:12 | {"foo": ["a","b","c","d"]} | 0 | foo[3] | a | b | c | d | 3 | d |
Find the First Values in a List of Fields
Find the first values of a list of fields to normalize data using the coalesce() function
Query
coalesce([host, server, host[0].name, "example.com"])Introduction
The coalesce() function accepts a list of
fields and returns the first value that is not null or empty.
Using coalesce() returns the first matching
value across the selection of supplied fields. In this example,
coalesce() is used to normalize data from
different sources — the fields have the same meaning but
different names in the input data.
Example incoming data might look like this:
| host='' |
| server='crowdstrike.com' |
| host[0].name='crowdstrike.com' |
| machine='clienta' |
Step-by-Step
Starting with the source repository events.
- logscale
coalesce([host, server, host[0].name, "example.com"])Finds the values of the first three fields host, server, host[0].name and the value of a string
"example.com"and returns the results in a new field named __coalesce. Notice that the query uses a string literal as the last expression, which serves as a default value, because its value is not null. The first three expressions, on the other hand, are field names.In this example, the field names are simple and do not contain unsupported characters. If the field names contain unsupported characters, for example a space or an operator like ‘-', then the field cannot be quoted in Falcon LogScale, as it would be interpreted as string literals, in these situations, the
getField()must be used together with thecoalesce()function:coalesce([getField("host-name"), getField("server name"), "example.com"]) Event Result set.
Summary and Results
The query is used to normalize data from different sources by
finding the first value of a list of fields that are defined.
The coalesce() function is useful if, for
example, you want to easily pick the first non-null value from
the list of prioritized fields and save it as a new field, or if
you want to be able to use default (string) value or an
expression instead of field name as an argument.
Sample output from the incoming example data:
| _coalesce | host | server | host[0].name | machine |
|---|---|---|---|---|
| crowdstrike.com | <no value> | crowdstrike.com |