Progressive Perl for Windows: Using WMI to Request Data About Disk Drives

Step 4
The last step is to use the Win32::OLE->in() function to enumerate the class instances. This function returns an array that contains each class instance found in the COM collection object. You might recall that you imported the in() function in Step 1. Because you imported the function at that time, you can simply refer to the function as in() in this step.

You pass the in() function the collection of instances ($DriveCollection), as Listing 1 shows. With each iteration of the foreach loop, the $Drive variable contains a COM-based instance of the Win32_DiskDrive class. In this case, you're just enumerating the drives, but you can query properties and call methods on $Drive as you would any other COM object.

These four steps provide a script with disk-drive information from a remote machine. Let's now look at a real-world example of how you can use the Win32_DiskDrive class in a script.

A Practical Example
Listing 2 contains a real-world script called WDiskDrives.pl. The Win32_DiskDrive class doesn't contain any writable properties or methods. Thus, WDiskDrives.pl explores the target machine's disk drives by querying 7 of the class's 48 properties:

• Capabilities (returns a list of the drive's capabilities)
  
  
• InterfaceType (returns the type of interface the drive uses, such as SCSI or IDE)
  
  
• MediaType (returns the type of media that the drive uses)
  
  
• Model (returns the drive's model number)
  
  
• Name (returns the OS's physical path to the drive)
  
  
• Partitions (returns the number of partitions on the drive)
  
  
• Size (returns the drive's size in bytes)

Let's begin exploring WDiskDrives.pl by finding the four steps just discussed. In Listing 2, callouts A, B, C, and D highlight the code for Steps 1, 2, 3, and 4, respectively. . . .