Advanced Windows PowerShell Scripting Video Training

Advanced Windows PowerShell Scripting Video Training
Advanced Windows PowerShell Scripting Video Training

Tuesday, January 12, 2016

Reading and Resolving PowerShell Errors - Part 9

This is part 9 of my series of the most common PowerShell errors that are made in my PowerShell classes.  I will be posting one a day to help you understand why an error occurred and what the error’s meaning is.

Today’s error:  Get-CimInstance : A positional parameter cannot be found that accepts argument '='.

Here is our starting code:
Get-CimInstance -ClassName Win32_LogicalDisk -Filter DeviceID = 'C:'

And here is the full error:
Get-CimInstance : A positional parameter cannot be found that accepts argument '='.
At line:1 char:1
+ Get-CimInstance -ClassName Win32_LogicalDisk -Filter DeviceID = 3
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [Get-CimInstance], ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,Microsoft.Management.Infrastructure.CimCmdlets.GetCimInstanceComman
   d

Resolution:
Use the parameter correctly.  In this situation, I found several of my students making assumptions about how to use the –Filter parameter.  When you are about to use a parameter for the first time, read both the help file information for that parameter and also look at the examples to see how to use it.
PS C:\> Get-Help Get-CimInstance -Parameter Filter

-Filter
    Specifies a where clause to use as a filter. Specify the clause in either the WQL or the CQL query language.
   
    Note: Do not include the where keyword in the value of the parameter.
   
    Required?                    false
    Position?                    named
    Default value               
    Accept pipeline input?       True (ByPropertyName)
    Accept wildcard characters?  false

Example 4: Get instances of a class filtered by using a class name and a filter expression
   
    PS C:\>Get-CimInstance -ClassName Win32_Process -Filter "Name like 'p%'"
   
   
    This command retrieves all the CIM instances that start with the letter p of a class named Win32_Process using the Filter
    parameter.

Here is the correct code.  We only needed to add “” to the filter.
Get-CimInstance -ClassName Win32_LogicalDisk -Filter "DeviceID = 'C:'"
DeviceID DriveType ProviderName VolumeName Size         FreeSpace
-------- --------- ------------ ---------- ----         ---------
C:       3                      OS         116280782848 2190163968



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