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Powershell Statements/Cmdlets



Powershell statements are "commands" to the powershell console.
The purpose of the statements is to tell the powershell what to do.
Command to get powershell version

Execute below command to know powershell version
ps>$host.version

Major Minor Build Revision
----- ----- ----- --------
2 0 -1 -1

Note: You can identify version at the top powershell window.

Aliasing in PowerShell allows for the use of commands we become accustomed to. Windows users can utilize commands like dir, move, type, cls, etc… PowerShell also provides a set of aliases for Linux; ls, pwd, mv, man, cat, etc… PowerShell Aliases are provided for the purpose of allowing new users the ability to quickly interact with the shell. An alias is an alternative name assigned to a cmdlet. For example, "dir" is an alias for "Get-ChildItem." This tutorial presents two types of aliases:

* Built-in Aliases - Predefined alternative names for Windows, Unix, and PowerShell cmdlets.

* User-defined Aliases - Custom alternative names created by the user.

Launch your PowerShell Console and let’s get started.

Built-In PowerShell Aliases

As previously described, built-in aliases are predefined. Use the following cmdlet to get a list of PowerShell Aliases:

Get-Alias <enter>

Get-Alias
Image 3.1

While browsing through the list, notice that there are multiple Aliases for the "Get-ChildItem" cmdlet. Windows "dir" command, Unix "ls" command, and a PowerShell alias "gci" command. No matter which alias you have chosen to use, typing any one of the aliases will result in the running of the "Get-ChildItem" cmdlet. Let’s test this out, type the following:

dir <enter>
ls <enter>
gci <enter>
Get-ChildItem <enter>

Get-ChildItem cmdlet
Image 3.2

Listed in Image 3.2, we can verify that each command resulted in the same output. In essence, we just ran "Get-ChildItem" four times. There is really not much more to built-in aliases. They exist to assist you while working in the shell, until you become more familiar with the cmdlets. User-Defined aliases require a little more attention.

User-Defined PowerShell Aliases

Set-Alias alias command - Simple syntax, not much to it. Let’s say I want to create a User-Defined alias for the "Get-Service" cmdlet:

Set-Alias gs Get-Service <enter>

Test your new Alias:

gs <enter>

User Defined Alias

Image 3.3

That was easy, so why does a user-defined alias need a little more attention? User-defined aliases only last while the PowerShell session is active. As soon a you quit the session, your alias is gone forever. Close your PowerShell session and re-launch PowerShell. Attempt to use the "gs" alias, you will receive the following error: "The term ‘gs’ is not recognized as a cmdlet, function, operable program, or script file. Verify the term and try again." O.k. - Recognize the term by creating the alias again:

Set-Alias gs Get-Service

So, we have created a User-defined PowerShell alias and don’t want to lose it when we quit the session, what do we do? There are two options to explore:

  • Import/Export the PowerShell alias.
  • User-defined Aliases using PowerShell Profiles.

Import/Export User-Defined PowerShell Aliases

The purpose of Importing and Exporting is to make user-defined aliases available to multiple machines. Say you wrote a script that uses custom aliases. If you attempted to run your script on another machine, it would fail. The remote PowerShell session is not aware of the custom aliases you have created. Unless, you export the aliases to a text file in which the remote computer could import.

Go ahead and export the "gs" alias using the "Export-Alias" cmdlet:

Export-Alias -Path Aliases.txt <enter>

Since I am running from my home directory "C:\MyScripts" the Aliases.txt file will be created there. Use the "-Path" parameter to set the desired location. One option is to save the export file to a UNC path so that it is available from a network share. Open "Aliases.txt" in notepad:

PS C:\MyScripts>notepad Aliases.txt <enter>

Do you notice anything odd about the text file?

Export-Alias cmdlet

Export-Alias

Image 3.4

Not only did it export the "gs" user-defined alias we created, it exported ALL PowerShell aliases. Is this an issue? If we attempt to import the Aliases.txt file, PowerShell will report an error for each alias that already exists. Import the Aliases.txt file using the "Import-Alias" cmdlet:

Import-Alias -Path Aliases.txt <enter>

Alias Import Error
Image 3.5

That looks ugly… but, if the alias does not exist, it will get imported. There is actually a better way to do this. The example above was shown to make you aware of a potential problem when you are importing and exporting aliases. By using the -Name parameter, you can export only the aliases you choose. So with our "gs" alias let’s attempt the following:

Export-Alias -Path Alias.txt -Name gs <enter>
notepad Alias.txt <enter>

Alias Export with Name Paramter
Image 3.6

That looks much better… What do you think would happen if you attempted to import this file? If your PowerShell Session is still active, you should get the import error because the "gs" alias still exists in the current session. Exit your PowerShell session and re-launch PowerShell.

Let’s import the Alias.txt file:

Import-Alias -Path Alias.txt <enter>
gs <enter>

Import-Alias gs
Image 3.7

No error reported when importing the Alias.txt file and entering the "gs" alias provides us with the output expected.

Importing and Exporting allows for the use of user-defined aliases on local and multiple systems. What if you just wanted to use custom aliases on your local system and don’t want to be burdened with importing a file each time you launch PowerShell? PowerShell profiles allow you to customize the PowerShell environment at launch time. The last section of this tutorial introduces the PowerShell profile. We are only going to discuss profiles as it pertains to user-defined aliases. With Profiles, there are many options to customize your PowerShell environment, which will be covered in this series.

User-Defined Aliases using PowerShell Profiles

What is a PowerShell Profile? In simplest terms, a profile is a script that runs at session startup. The location of the Profile is stored in the $Profile variable, which by default is "My Documents\WindowsPowerShell\Microsoft.PowerShell_profile.ps1″
To verify the location of your profile type:

$Profile <enter>

Profile Variable
Image 3.8

In image 3.8 you can see the path to my profile, which happens to be were "My Documents" are stored. As already mentioned, the profile is a script which is denoted by the ".ps1″ extension. All PowerShell scripts are identified by this extension. Since the profile is a PowerShell script we will need to edit it. You can use any PowerShell editor, in this tutorial I will be using Notepad. Before editing the file we need to check the PowerShell execution policy.

When PowerShell is first installed the default execution policy is "Restricted." This means PowerShell will not run scripts or configuration files. Here is a list of policy levels:

  • Restricted - We know what this means.

* AllSigned - All scripts and configuration files must be signed by a trusted publisher.

* RemoteSigned - All scripts and configuration files downloaded from the Internet must be signed by a trusted publisher.

* Unrestricted - All scripts and configuration files will run. Scripts downloaded from the Internet will prompt for permission before running.

Use the "Get-ExecutionPolicy" cmdlet to verify policy level:

Get-ExecutionPolicy <enter>

What is your policy set at? By definition, since the profile is a script file, the execution policy should be set to anything other than "Restricted." For this exercise you will set your policy to "Unrestricted." Here is how to set that policy:

Set-ExecutionPolicy Unrestricted <enter>

Now that the policy is set to run scripts, let’s create a profile by following the steps below:

Step 1. Verify existence of a profile.

test-path $Profile <enter>

If the result = False. No profile exists (continue to step2).
If the result = True. Profile exists (skip steps 2 & 3). Unless you want to create a new profile, which will delete the current profile.

Step 2. Create a new profile.

New-Item -Path $Profile -ItemType file -Force <enter>

Step 3. Verify new profile was created.

Repeat step 1. Result should equal "True."

Let’s open our new profile in notepad:

notepad $Profile <enter>

PowerShell Profile Notepad
Image 3.9

Isn’t that great! We have a blank page! The important thing to note: We have a script file called "Microsoft.PowerShell_profile.ps1″

This script file will be called using the $Profile variable each time a PowerShell session is launched. What goes into the script file will be up to you, how you decide to configure your PowerShell environment. For now, let’s have our profile load our custom user-defined PowerShell alias. Edit and Save the profile as shown below:

PowerShell Profile Saved
Image 3.10

After you have saved the profile, close notepad, and exit the PowerShell session.

Launch a new PowerShell session and verify that your custom alias is functional:

gs <enter>

Viola! your profile has loaded successfully and your alias is working. Use "Get-Alias" cmdlet to verify the existence of your new alias:

Get-Alias <enter>

-or- a more refined search:

Get-Alias -Name gs <enter>

Hope you enjoyed the Tutorial on PowerShell Aliases, we covered a lot. Built-in aliases, user-defined aliases, importing aliases, exporting aliases, a small preview into profiles, and PowerShell script files.