For a pattern operation, the <_> placeholder can be replaced by any valid index or wildcard character that can be used to access an element of an array or a table. The $IfTable variable is a table that contains information about the network interfaces of a device1. The InstanceID attribute is a unique identifier for each interface2.
To access the InstanceID of a specific interface, the pattern operation can use the following syntax:
$IfTable[<index>].InstanceID
where <index> is either:
* A numeric index that corresponds to the position of the interface in the table, such as 3 for the third interface.
* A dot (.) followed by a key-value pair that matches a specific attribute and value of the interface, such as
[.Name=eth0] for the interface with the name eth0.
* An asterisk () that represents a wildcard that matches any interface in the table, such as [] for all interfaces.
References:
* 1: IfTable - Product Documentation: San Diego - ServiceNow
* 2: InstanceID - Product Documentation: San Diego - ServiceNow