Table of Contents
6 Expression macros
Overview
Expression macros are useful for formula calculations. They are calculated by expanding all macros inside and evaluating the resulting expression.
Expression macros have a special syntax:
The syntax in EXPRESSION is the same as in trigger expressions (see usage limitations below).
{HOST.HOST<1-9>} and {ITEM.KEY<1-9>} macros are supported inside expression macros.
Usage
In the following locations:
- graph names
- map element labels
- map shape labels
- map link labels
only a single function, from the following set: avg, last, max, min, is allowed as an expression macro, e.g.:
Expressions such as {?last(/host/item1)/last(/host/item2)}, {?count(/host/item1,5m)} and {?last(/host/item1)*10} are incorrect in these locations.
However, in:
- trigger event names
- trigger-based notifications and commands
- problem update notifications and commands
complex expressions are allowed, e.g.:
When using expression macros in templates please do not specify the template name but rather use {HOST.HOST<N>}, because template names are not substituted with hosts during linkage. You can also omit host reference altogether for the first host, e.g. {?avg(//item1,1h)}
See also:
- Supported macros for a list of supported locations of the expression macro
- Example of using an expression macro in the event name