One of the cool features about PowerShell is its support for POSIX style patterns in many of the pre-installed cmdlets. For example the following command will get all items under the C root that have the second, third and forth characters “rog”:
Outputs:
Directory: C:\
Mode LastWriteTime Length Name
---- ------------- ------ ----
d-r-- 6/7/2012 11:30 PM Program Files
d-r-- 6/26/2012 1:50 PM Program Files (x86)
The following table shows a reference of the supported POSIX style matching patterns:
| Wildcard character | Description | Example | Matches | Does not match |
| * | Matches zero or more characters, starting at the specified position | a* | A, ag, Apple | |
| ? | Matches any character at the specified position | ?n | An, in, on | ran |
| [ ] | Matches a range of characters | [a-l]ook | book, cook, look | took |
| [ ] | Matches the specified characters | [bc]ook | book, cook | look |
So how would one go about adding support for these types of patterns in a script CMDLET? In order to do this you’ll need to work with two .NET types:
First define your options (Compile, CultureInvariant, IgnoreCase or None). Then use New-Object to create a WildcardPattern instance using the pattern you want to match against as the first argument and the WildcardOptions object as the second argument.
Here is a an example function:
