Grafana Agent FlowConfiguration languageExpressionsOperators

Operators

River uses a set of operators that most should be familiar with. All operations follow the standard PEMDAS rule for operator precedence.

Arithmetic operators

OperatorDescription
+Adds two numbers.
-Subtracts two numbers.
*Multiplies two numbers.
/Divides two numbers.
%Computes the remainder after dividing two numbers.
^Raises the number to the specified power.

The + operator can also be used for string concatenation.

Comparison operators

OperatorDescription
==true when two values are equal.
!=true when two values are not equal.
<true when the left value is less than the right value.
<=true when the left value is less than or equal to the right value.
>true when the left value is greater than the right value.
>=true when the left value is greater or equal to the right value.

The equality operators == and != can be applied to any operands.

On the other hand, for the ordering operators < <= > and >= the two operands must both be orderable and of the same type. The result of the comparisons are defined as follows:

  • Boolean values are equal if they are either both true or both false.
  • Numerical (integer and floating-point) values are orderable, in the usual way.
  • String values are orderable lexically byte-wise.
  • Objects are equal if all their fields are equal.
  • Array values are equal if their corresponding elements are equal.

Logical operators

OperatorDescription
&&true when the both left and right value are true.
||true when the either left or right value are true.
!Negates a boolean value.

Logical operators apply to boolean values and yield a boolean result.

Assignment operator

River uses = as its assignment operator.

An assignment statement may only assign a single value. In assignments, each value must be assignable to the attribute or object key to which it is being assigned.

  • The null value can be assigned to any attribute.
  • Numerical, string, boolean, array, function, capsule and object types are assignable to attributes of the corresponding type.
  • Numbers can be assigned to string attributes with an implicit conversion.
  • Strings can be assigned to numerical attributes, provided that they represent a number.
  • Blocks are not assignable.

Brackets

BracketsDescription
{ }Defines blocks and objects.
( )Groups and prioritizes expressions.
[ ]Defines arrays.

In the following example we can see the use of curly braces and square brackets to define an object and an array.

obj = { app = "agent", namespace = "dev" }
arr = [1, true, 7 * (1+1), 3]

Access operators

OperatorDescription
[ ]Access a member of an array or object.
.Access a named member of an object or an exported field of a component.

River’s access operators support accessing of arbitrarily nested values. Square brackets can be used to access zero-indexed array indices as well as object fields by enclosing the field name in double quotes. The dot operator can be used to access both object fields (without double quotes) and component exports.

obj["app"]
arr[1]

obj.app
local.file.token.content