<PrereqDef> element

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The <PrereqDef> element that can later be used in a <Prereq> element.

Syntax

Parent element: <Catalog>

The following attribute is supported:
Table 1. Attribute
Attribute Required Type Description
name yes string Specifies the name of the property.
The following child elements are supported:
Table 2. Child elements
Child element Required Description
<Command> no Command
<Argument> no Command-line arguments
<Stdin> no Arguments that are supported by the <Stdin> element
<ErrMessage> no Message to print if prerequisite fails
Note: The <Command> element must be defined for each prerequisite: at the <ParameterDef> level, at the <CfgMethod> level, or in a <PrereqDef> element.

Usage

Prereq are commands that condition the run of the <Get>, <Set>, and <Discover> operations for parameters that use the <Get>, <Set>, or <Discover> operation. Parameters for which a prereq command fails (nonzero return code) are ignored, and the error message defined in the prerequisite is displayed.

The <PrereqDef> element defines a prerequisite. This prerequisites can later be associated with an operation of a parameter or a configuration method by using a <Prereq> element that has the same id attribute.

Example

The following example defines the nodeId prerequisite and assigns it to the netaddr and netaddr6 parameters:

<PrereqDef id="nodeId">
  <Command>[[ `/usr/bin/uname -f` = %p[nodeId] ]]</Command>
  <ErrMessage>Parameter cannot be applied to a different node</ErrMessage>
</PrereqDef>

<ParameterDef name="netaddr" type="string" targetClass="device" cfgmethod="attr">
  <Set type="permanent">
    <Prereq id="nodeId"/>
  </Set>
  <Property name="nodeId"/>
</ParameterDef>

<ParameterDef name="netaddr6" type="string" targetClass="device" cfgmethod="attr">
  <Set type="permanent">
    <Prereq id="nodeId"/>
  </Set>
  <Property name="nodeId"/>
</ParameterDef>

In this example, the test is executed only once, because the two parameters use the same <Command> element for their prerequisites, and the generated command line is the same for the two parameters.

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