Final answer:
The standard URI specification does not define a wildcard character for numbers. In regular expressions, '\d' is used to match any digit from 0 to 9, which can be used in programming for URI manipulations.
Step-by-step explanation:
When coding a Uniform Resource Identifier (URI), the character used as a wildcard to match any number is not defined by the standard URI specification itself. In the context of regular expressions, often used for pattern matching within strings, the wildcard character for matching a single digit is '\d' which represents any digit from 0 to 9.
However, this is not a part of the URI standard but could be used in programming when processing or parsing URIs to match any number within them.
For more sophisticated URI manipulations, such as those involving wildcards, you would typically use a combination of programming logic and regular expressions.