Environment Variables

 

SHORT DESCRIPTION

How to access Windows environment variables in Windows PowerShell

 

LONG DESCRIPTION

Environment variables store information about the operating system environment. This information includes details such as the operating system path, the number of processors used by the operating system, and the location of temporary folders.

 

The environment variables store data that is used by the operating system and other programs. For example, the "windir" environment variable contains the location of the Windows installation directory. Programs can query the value of this variable to determine where Windows operating system files are located.

 

WINDOWS POWERSHELL ENVIRONMENT PROVIDER

The Windows PowerShell environment provider lets you access Windows environment variable in Windows PowerShell in a Windows PowerShell drive, Env:, that looks much like a file system drive.

 

For example, to go to the Windows PowerShell Env: drive, type:

 

 

Then, to display the contents of the Windows PowerShell Env: drive, type:

 

 

You can view the environment variables in the Windows PowerShell Env: drive from any other Windows PowerShell drive, and you can go into the Windows PowerShell Env: drive to view and change the environment

variables.

 

ENVIRONMENT VARIABLE OBJECTS

In Windows PowerShell, each environment variable is represented by an object that is an instance of the System.Collections.DictionaryEntry class.

     

In each DictionaryEntry object, the name of the environment variable is the dictionary key and the value of the variable is the dictionary value.

 

To display an environment variable in Windows PowerShell, get an object that represents the variable and then display the values of the object properties. When you change an environment variable in Windows PowerShell, use the methods associated with the DictionaryEntry object.

 

To display the properties and methods of the object that represents an environment variable in Windows PowerShell, use the Get-Member cmdlet. For example, to display the methods and properties of all of the objects in the Windows PowerShell Env: drive, type:

 

 

DISPLAYING ENVIRONMENT VARIABLES

You can use the Windows PowerShell Item cmdlets (*-Item) to display and change the values of environment variables. Because environment variables do not have child items, the output of Get-Item and Get-Childitem is the same.

 

When referring to an environment variable, type the "Env:" drive name and then the name of the variable. For example, to display the value of the COMPUTERNAME environment variable, type:

 

 

To display the values of all environment variables, type:

 

 

By default, Windows PowerShell displays the environment variables in the order that it retrieves them. To sort the list of environment variables by variable name, pipe the output of a Get-Childitem command to the Sort-Object cmdlet. For example, from any Windows PowerShell drive, type:

 

 

You can also go into the Windows PowerShell Env: drive by using the Set-Location cmdlet.

 

 

When you are in the Windows PowerShell Env: drive, you can omit the "Env:" drive name from the path. For example, to display all of the environment variables, type:

 

 

To display the value of the COMPUTERNAME variable from within the Windows PowerShell Env: drive, type:

 

 

You can also display and change the values of environment variables without using a cmdlet by using the expression parser in Windows PowerShell. To display the value of an environment variable, use the follow syntax:

 

 

For example, to display the value of the Windir environment variable, at the Windows PowerShell command prompt, type:

 

 

In this syntax, the dollar sign ($) indicates a variable and the drive name, "env:" indicates an environment variable.

 

CHANGING ENVIRONMENT VARIABLES

When you change environment variables in Windows PowerShell, the change affects only the current session, much like using the Set command in Windows and the Setenv command in Unix. To make the changes permanent, you have to change them in the registry.

 

You must also have permission to change the values of the variables. If you try to change a value without sufficient permission, the command fails and Windows PowerShell displays an error.

 

You can change the values of variables without using a cmdlet by using the following syntax:

 

 

For example, to append ";c:\ps-test" to the value of the Path environment variable, use the following syntax:

 

 

You can also use the Item cmdlets, such as Set-Item, Remove-Item, and Copy-Item to change the values of environment variables. For example, to use the Set-Item cmdlet to append ";c:\ps-test: to the value of the Path environment variable, use the following syntax:

 

     

In this command, the value is enclosed in parentheses so that it is interpreted as a unit.

 

SEE ALSO

For information about the Windows PowerShell environment provider, type: