Designing and Managing Behavior Models - Using Trap Masks - Writing a Trigger Function - Functions for Use in Trigger Functions -
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Functions for Use in Trigger Functions

NerveCenter provides a number of functions (actually Perl subroutines) that facilitate the writing of trigger functions. The list below indicates what types of functions are available and where you can find detailed information about each function:

• Variable-binding functions. These functions enable you to determine the number of variable bindings in a trap's variable-binding list and to obtain information about each variable binding. For instance, you can retrieve the subobject and attribute associated with a variable-binding object and the value of a variable-binding object.

  For reference information about these functions, see the section Variable-Binding Functions.

• String-matching functions. These functions enable you to determine whether a string contains another string or a particular word. The functions are useful in conditions that test the value of a variable binding for a substring.

  For reference information about these functions, see the section String-Matching Functions.

• DefineTrigger(). This function enables you to create triggers which you can assign to variables and fire using FireTrigger() in NerveCenter Perl expressions.

  For reference information about this function, see the section DefineTrigger() Function.

• FireTrigger(). This function enables you to fire a trigger from your trigger function. You can specify the name, subobject, and node attributes of the trigger.

  For reference information about this function, see the section FireTrigger() Function.

• AssignPropertyGroup(). This function enables you to assign the node that sent a trap to a property group.

  For reference information about this function, see the section AssignPropertyGroup() Function.

• in(). This function enables you to determine whether one scalar value is in a set of scalar values.

  For reference information about this function, see the section in( ) Function.

Variable-Binding Functions

Before looking at the variable-binding functions, let's make sure that we're using the same terminology.

When a trap arrives, NerveCenter looks at the trap's variable bindings and, for each variable binding, it sees an object and a value.

Variable Binding

In this case, the object is the OID encoding of the object type (sysDescr) plus an instance, and the value is a string that describes the system.

When NerveCenter sees this variable binding, it stores the following information. The portion of the OID that corresponds to the system group is stored as the binding's base object, and the instance (0) is stored as the binding's instance. When concatenated, the base object and the instance form what NerveCenter calls a subobject.

Base Objects, Instances, and Subobjects

The variable sysDescr is stored as the binding's attribute.

Attributes

Finally, the value "Windows NT Workstation" is stored as the binding's value.

The variable-binding functions give you access to a binding's subobject, attribute, and value. There's also a function that returns the number of variable bindings in a trap or trigger.

Each of the variable-binding functions is explained below:

VbAttribute()

Syntax: VbAttribute(index)

Description: Returns the attribute from the variable binding with an index of index. The first variable binding has an index of 0.

VbNum()

Syntax: VbNum()

Description: Returns the number of variable bindings in the trap's variable-binding list.

VbObject()

Syntax: VbObject(index)

Description: Returns the subobject from the variable binding with an index of index. The first variable binding has an index of 0.

VbValue()

Syntax: VbValue(index)

Description: Returns the value from the variable binding with an index of index. The first variable binding has an index of 0.