Table of Contents
Fundamentals of Parameters
Mandatory Parameters (Required)
How do I know that this parameter is a named and mandatory parameter? I’m good in reading the help. Type
Get-Help Stop-Process -Parameter NameIn the first time when you ran the Get-Help command. PowerShell requires you to update the help database. Type Y then hit enter to update the database.
PS C:\> Get-Help Stop-Process -Parameter Name
Do you want to run Update-Help?
The Update-Help cmdlet downloads the most current Help files for Windows PowerShell modules, and installs them on your computer. For
more information about the Update-Help cmdlet, see https:/go.microsoft.com/fwlink/?LinkId=210614.
[Y] Yes [N] No [S] Suspend [?] Help (default is "Y"): YAs we can see, this parameter is required and named. What does this actually mean?
- Required: means that this parameter is mandatory. So, you have to specify the name of the process.
- Named: signifies that you have to type the parameter name and the argument. Everything else leads to an error message.
PS C:\> Get-Help Stop-Process -Parameter Name
-Name <System.String[]>
Specifies the process names of the processes to stop. You can type multiple process names,
separated by commas, or use wildcardcharacters.
Required? true
Position? named
Default value None
Accept pipeline input? True (ByPropertyName)
Accept wildcard characters? truePositional Parameters
Which brings me to the next example. Most of PowerShell parameters are not mandatory, nor named. Some of them are positional parameters. Let’s take a look to this second example that shows the parameter LogName of the Get-EventLog cmdlet.
PS C:\> Get-Help Get-Eventlog -Parameter LogName
-LogName <string>
Required? true
Position? 0
Accept pipeline input? false
Parameter set name LogName
Aliases LN
Dynamic? falseCrazy thing. It’s required but it’s position is not named, but 0. This means that you have to specify the LogName, but you can do it without the parameter name. The first argument that is given will be automatically bound to this parameter.. Let’s give it a try. PowerShell is asking me for the LogName, because LogName is a mandatory parameter. (Required? true)
PS C:\> Get-EventLog
cmdlet Get-EventLog at command pipeline position 1
Supply values for the following parameters:
LogName:There are 3 main types of Windows Event Logs: System, Application and Security. What happens if I enter one of the three without the parameter name? It works because the parameter is not named.
PS C:\> Get-EventLog System | select -First 5
Index Time EntryType Source InstanceID Message
----- ---- --------- ------ ---------- -------
430353 Aug 20 10:38 Warning Netwtw10 2147489710 6062 - Lso was triggered
430352 Aug 20 10:38 Information Netwtw10 1073748827 7003 - Roam Complete
430351 Aug 20 10:38 Information Netwtw10 1073748845 7021 - Connection telemetry fields and analysis...
430350 Aug 20 09:50 Information Microsoft-Windows... 12 Process C:\Windows\System32\WUDFHost.exe (proce...
430349 Aug 20 09:50 Information Microsoft-Windows... 566 The description for Event ID '566' in Source 'M...Switched Parameters
What if a Parameter does not require an argument? I mean parameters without any input, but with default values. They are called switched parameters. Let’s say you want to show what will happen if you restart your computer. (We’ve already done this before). The parameter for this is WhatIf.
PS C:\> Get-Help Restart-Computer -Parameter WhatIf
-WhatIf
Required? false
Position? Named
Accept pipeline input? false
Parameter set name (All)
Aliases wi
Dynamic? false
PS C:\> Get-Help Restart-Computer -Parameter ComputerName
-ComputerName <string[]>
Required? false
Position? 0
Accept pipeline input? true (ByValue, ByPropertyName)
Parameter set name (All)
Aliases CN, __SERVER, Server, IPAddress
Dynamic? falseNow let’s compare the WhatIf parameter with another parameter which calls for an argument, for example a string. Note the highlight. Unlike WhatIf, ComputerName requires a string.
WhatIf requires no input. ComputerName calls for an HostName. This means that you can run the WhatIf parameter without any input. Look at this:
PS C:\> Restart-Computer -WhatIf
What if: Performing operation "Enable the Local shutdown access rights and restart the computer."
on target "localhost (DESKTOP-B2TOHJT)".But we encounter problems when we try to restart a remote computer without specifying it’s name.
PS C:\> Restart-Computer -ComputerName
Restart-Computer : Missing an argument for parameter 'ComputerName'.
Specify a parameter of type 'System.String[]' andtry again.
At line:1 char:18
+ Restart-Computer -ComputerName
+ ~~~~~~~~~~~~~
+ CategoryInfo : InvalidArgument: (:) [Restart-Computer], ParameterBindingException
+ FullyQualifiedErrorId : MissingArgument,Microsoft.PowerShell.Commands.RestartComputerCommandIt’s not possible to cover all topics of parameters in a single blog post. You can start exploring all parameters by using the following command:
PS C:\> Get-Help Get-Eventlog -Parameter *
-After <datetime>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases None
Dynamic? false
-AsBaseObject
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases None
Dynamic? false
-AsString
Required? false
Position? Named
Accept pipeline input? false
Parameter set name List
Aliases None
Dynamic? false
-Before <datetime>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases None
Dynamic? false
-ComputerName <string[]>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name (All)
Aliases Cn
Dynamic? false
-EntryType <string[]>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases ET
Dynamic? false
-Index <int[]>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases None
Dynamic? false
-InstanceId <long[]>
Required? false
Position? 1
Accept pipeline input? false
Parameter set name LogName
Aliases None
Dynamic? false
-List
Required? false
Position? Named
Accept pipeline input? false
Parameter set name List
Aliases None
Dynamic? false
-LogName <string>
Required? true
Position? 0
Accept pipeline input? false
Parameter set name LogName
Aliases LN
Dynamic? false
-Message <string>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases MSG
Dynamic? false
-Newest <int>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases None
Dynamic? false
-Source <string[]>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases ABO
Dynamic? false
-UserName <string[]>
Required? false
Position? Named
Accept pipeline input? false
Parameter set name LogName
Aliases None
Dynamic? false
Some useful parameter examples to play with
At the end I would like to provide some useful examples you can play with. Don’t worry if the commands seems very complex to you. It’s ok. We haven’t done some things yet. They’re just for playing.
Retrieve the newest 5 Event Log Errors from the System Log:
PS C:\> Get-EventLog -LogName System -Newest 5 -EntryType Error | Format-Table Time,EntryType,Message -AutoSize -Wrap
Time EntryType Message
---- --------- -------
Error The mutual authentication between the local Bluetooth adapter and a device with Bluetooth adapter
address (b4:ee:25:89:6d:23) failed.
Error Miniport Microsoft Wi-Fi Direct Virtual Adapter #2, {6a0b0f63-385e-4dd0-be0f-b0bcc0314f87}, had event 74
Error Miniport Microsoft Wi-Fi Direct Virtual Adapter #2, {6a0b0f63-385e-4dd0-be0f-b0bcc0314f87}, had event 74
Error Miniport Microsoft Wi-Fi Direct Virtual Adapter #2, {6a0b0f63-385e-4dd0-be0f-b0bcc0314f87}, had event 74
Error Miniport Microsoft Wi-Fi Direct Virtual Adapter #2, {6a0b0f63-385e-4dd0-be0f-b0bcc0314f87}, had event 74Get the Filename of a Windows Process
PS C:\> Get-Process notepad -FileVersionInfo
ProductVersion FileVersion FileName
-------------- ----------- --------
11.2306.15.0 11.2306.15.0 C:\Program Files\WindowsApps\Microsoft.WindowsNotepad_11.2306.15.0_x64__8wekyb3d8bShow all *.txt files in C:\Temp
Get-ChildItem -Filter *.txt -Path C:\temp
