Variables are used in discovery patterns to store and manipulate data that is collected or calculated during the discovery process. There are three kinds of variables used in discovery patterns12:
* CI attributes: These are variables that correspond to the attributes of the configuration item (CI) type that the pattern is discovering. For example, name, serial_number, manufacturer, etc. CI attributes are used to populate the CI record in the CMDB with the information gathered by the pattern.
* Temporary: These are variables that are created and used within the pattern, but are not stored in the CMDB. For example, $result, $output, $user_var, etc. Temporary variables are used to store and manipulate data such as the output of a command, the value of a parameter, or the result of a calculation.
* Global: These are variables that are defined in the global scope and can be accessed by any pattern. For example, $mid, $target, $ip_address, etc. Global variables are used to store and access data that is common to all patterns, such as the MID Server, the target device, or the IP address.
References:
* 1: ServiceNow Discovery Documentation, Pattern Variables section
* 2: ServiceNow Discovery Overview, page 11