About substitution parameters

You can use substitution parameters in configuration templates, rules, and other areas to support reusability. 

• • Substitution parameters syntax
  • Pod substitution parameters
  • Container substitution parameters
  • Example parameter substitution
  • Example Linux script execution
  • Example Windows script execution
  • Substitution parameters applicability

Substitution parameters syntax

The following table defines the substitution parameters that are available in BMC Network Automation:

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Pod substitution parameters

All pod-related substitution parameters have the basic form ${pod.parameter}. The string indicated by parameter can contain multiple components. See Pod substitution parameter syntax in the BMC Cloud Lifecycle Management on-line technical documentation.

Container substitution parameters

All container-related substitution parameters have the basic form ${container.parameter}. The string indicated by parameter can contain multiple components. See Container substitution parameter syntax in the BMC Cloud Lifecycle Management on-line technical documentation.

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Example parameter substitution

Examples are based on Cisco IOS CLI:

Below are two examples of very simple scripts and how to use ${exec} to execute the scripts. ${exec} programs or script must be located in the BCAN_DATA/endorsed directory.

Both scripts (Microsoft Windows and Linux version) return the value my_value.

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Example Linux script execution

• Create the BCAN_DATA/endorsed/my_script.sh with the following lines:

  #!/bin/sh
  echo my_value
  
• Invoke my_script.sh by using a ${exec} expression:
  
  ${exec my_script.sh}

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Example Windows script execution

• Create the BCAN_DATA/endorsed/my_script.bat file with the following lines:

  @echo off
  echo my_value
• Copy cmd.exe into the endorsed directory:
  
  copy C:\windows\system32\cmd.exe BCAN_DATA\endorsed
  
  
• Invoke my_script.bat by using a ${exec} expression:
  
  ${exec cmd.exe /c my_script.bat}

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Substitution parameters applicability

Substitution parameters can be used by the following components:

Footnotes:

1. BMC Network Automation allows 10 layers of nesting for template substitution parameters in templates.
2. BMC Network Automation allows 1 layer of nesting for the following substitution parameter and component combinations:
   • Internal Function substitution parameters in Internal Functions.
   • Internal Function substitution parameters in External Programs.
   • External Programs substitution parameters in Internal Functions.
   • External Programs substitution parameters in External Programs.

Be cautious when using internal function or external program substitution parameters in CAP queries because they impact the performance of Snapshot and Refresh Device Status span actions.

Some factory installed templates (syslog) and rules reference global substitution parameters. Ensure you create and assign values to these global substitution parameters before using the factory installed templates and rules.

When referring to a Multi Select Menu type of dynamic field, the system replaces the substitution parameter with all values of the dynamic field in sorted order. Be cautious about referring to such dynamic fields because such a list of values might be invalid in context. For example, if you are editing a template, a device might not accept a comma-separated list of values in its command line. Follow these guidelines when referring to such a dynamic field:

• If the text is inside something that carries a regular expression (such as the subject pattern in a rule), the system separates the values with the | (or) operation. For example: valueA|valueB|valueC. You must include parentheses around the substitution parameter in order for the or operation to have an effect. For example: (${device.myValueList}) is the correct way to refer to a Multi Select Menu dynamic field in a rule. Thus, referring to a Multi Select Menu dynamic field in a regular expression means you are searching for a match on one of its values.
• If the text is inside a non-regular expression (such as the subject line in a rule), the multiple values are separated by a comma and a space. For example: valueA, valueB, valueC.

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