Windows how to set env var

Introduction

Environment variables are key-value pairs a system uses to set up a software environment. The environment variables also play a crucial role in certain installations, such as installing Java on your PC or Raspberry Pi.

In this tutorial, we will cover different ways you can set, list, and unset environment variables in Windows 10.

Prerequisites

• A system running Windows 10
• User account with admin privileges
• Access to the Command Prompt or Windows PowerShell

Check Current Environment Variables

The method for checking current environment variables depends on whether you are using the Command Prompt or Windows PowerShell:

List All Environment Variables

In the Command Prompt, use the following command to list all environment variables:

set

If you are using Windows PowerShell, list all the environment variables with:

Get-ChildItem Env:

Check A Specific Environment Variable

Both the Command Prompt and PowerShell use the echo command to list specific environment variables.

The Command prompt uses the following syntax:

echo %[variable_name]%

In Windows PowerShell, use:

echo $Env:[variable_name]

Here, [variable_name] is the name of the environment variable you want to check.

Follow the steps to set environment variables using the Windows GUI:

1. Press Windows + R to open the Windows Run prompt.

2. Type in sysdm.cpl and click OK.

3. Open the Advanced tab and click on the Environment Variables button in the System Properties window.

4. The Environment Variables window is divided into two sections. The sections display user-specific and system-wide environment variables. To add a variable, click the New… button under the appropriate section.

5. Enter the variable name and value in the New User Variable prompt and click OK.

Set Environment Variable in Windows via Command Prompt

Use the setx command to set a new user-specific environment variable via the Command Prompt:

setx [variable_name] "[variable_value]"

Where:

• [variable_name]: The name of the environment variable you want to set.
• [variable_value]: The value you want to assign to the new environment variable.

For instance:

setx Test_variable "Variable value"

To add a system-wide environment variable, open the Command Prompt as administrator and use:

setx [variable_name] "[variable_value]" /M

Unset Environment Variables

There are two ways to unset environment variables in Windows:

Unset Environment Variables in Windows via GUI

To unset an environment variable using the GUI, follow the steps in the section on setting environment variables via GUI to reach the Environment Variables window.

In this window:

1. Locate the variable you want to unset in the appropriate section.

2. Click the variable to highlight it.

3. Click the Delete button to unset it.

Unset Environment Variables in Windows via Registry

When you add an environment variable in Windows, the key-value pair is saved in the registry. The default registry folders for environment variables are:

• user-specific variables: HKEY_CURRENT_USEREnvironment
• system-wide variables: HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment

Using the reg command allows you to review and unset environment variables directly in the registry.

Use the following command to list all user-specific environment variables:

reg query HKEY_CURRENT_USEREnvironment

List all the system environment variables with:

reg query "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment"

If you want to list a specific variable, use:

reg query HKEY_CURRENT_USEREnvironment /v [variable_name]

or

reg query "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment" /v [variable_name]

Where:

• /v: Declares the intent to list a specific variable.
• [variable_name]: The name of the environment variable you want to list.

Use the following command to unset an environment variable in the registry:

reg delete HKEY_CURRENT_USEREnvironment /v [variable_name] /f

or

reg delete "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment" /v [variable_name] /f

Run the setx command again to propagate the environment variables and confirm the changes to the registry.

setx [variable_name] trash

Conclusion

After following this guide, you should know how to set user-specific and system-wide environment variables in Windows 10.

Looking for this tutorial for a different OS? Check out our guides on How to Set Environment Variables in Linux and How to Set Environment Variables in MacOS.

Environment variables are not often seen directly when using Windows. However there are cases, especially when using the command line, that setting and updating environment variables is a necessity. In this series we talk about the various approaches we can take to set them. In this article we look at how to interface with environment variables using the Command Prompt and Windows PowerShell. We also note where in the registry the environment variables are set, if you needed to access them in such a fashion.

Print environment variables

You can use environment variables in the values of other environment variables. It is then helpful to be able to see what environment variables are set already. This is how you do it:

Command Prompt

List all environment variables

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ALLUSERSPROFILE=C:ProgramData
APPDATA=C:UsersuserAppDataRoaming
.
.
.
windir=C:Windows

Print a particular environment variable:

Windows PowerShell

List all environment variables

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Name                           Value
----                           -----
ALLUSERSPROFILE                C:ProgramData
APPDATA                        C:UsersuserAppDataRoaming
.
.
.
windir                         C:Windows

Print a particular environment variable:

Set Environment Variables

To set persistent environment variables at the command line, we will use setx.exe. It became part of Windows as of Vista/Windows Server 2008. Prior to that, it was part of the Windows Resource Kit. If you need the Windows Resource Kit, see Resources at the bottom of the page.

setx.exe does not set the environment variable in the current command prompt, but it will be available in subsequent command prompts.

User Variables

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setx EC2_CERT "%USERPROFILE%awscert.pem"

Open a new command prompt.

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C:Usersuserawscert.pem

System Variables

To edit the system variables, you’ll need an administrative command prompt. See HowTo: Open an Administrator Command Prompt in Windows to see how.

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setx EC2_HOME "%APPDATA%awsec2-api-tools" /M

Warning This method is recommended for experienced users only.

The location of the user variables in the registry is: HKEY_CURRENT_USEREnvironment. The location of the system variables in the registry is: HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment.

When setting environment variables through the registry, they will not recognized immediately. One option is to log out and back in again. However, we can avoid logging out if we send a WM_SETTINGCHANGE message, which is just another line when doing this programatically, however if doing this on the command line it is not as straightforward.

One way is to get this message issued is to open the environment variables in the GUI, like we do in HowTo: Set an Environment Variable in Windows — GUI; we do not need to change anything, just open the Environment Variables window where we can see the environment variables, then hit OK.

Another way to get the message issued is to use setx, this allows everything to be done on the command line, however requires setting at least one environment variable with setx.

Printing Environment Variables

With Windows XP, the reg tool allows for accessing the registry from the command line. We can use this to look at the environment variables. This will work the same way in the command prompt or in powershell. This technique will also show the unexpanded environment variables, unlike the approaches shown for the command prompt and for powershell.

First we’ll show the user variables:

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reg query HKEY_CURRENT_USEREnvironment

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HKEY_CURRENT_USEREnvironment
    TEMP    REG_EXPAND_SZ    %USERPROFILE%AppDataLocalTemp
    TMP    REG_EXPAND_SZ    %USERPROFILE%AppDataLocalTemp

We can show a specific environment variable by adding /v then the name, in this case we’ll do TEMP:

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reg query HKEY_CURRENT_USEREnvironment /v TEMP

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HKEY_CURRENT_USEREnvironment
    TEMP    REG_EXPAND_SZ    %USERPROFILE%AppDataLocalTemp

Now we’ll list the system environment variables:

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reg query "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment"

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HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment
    ComSpec    REG_EXPAND_SZ    %SystemRoot%system32cmd.exe
    FP_NO_HOST_CHECK    REG_SZ    NO
    NUMBER_OF_PROCESSORS    REG_SZ    8
    OS    REG_SZ    Windows_NT
    Path    REG_EXPAND_SZ    C:ProgramDataOracleJavajavapath;C:WINDOWSsystem32;C:WINDOWS;C:WINDOWSSystem32Wbem;C:WINDOWSSystem32WindowsPowerShellv1.0;%SystemRoot%system32;%SystemRoot%;%SystemRoot%System32Wbem;%SYSTEMROOT%System32WindowsPowerShellv1.0
    PATHEXT    REG_SZ    .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
    PROCESSOR_ARCHITECTURE    REG_SZ    AMD64
    PROCESSOR_IDENTIFIER    REG_SZ    Intel64 Family 6 Model 60 Stepping 3, GenuineIntel
    PROCESSOR_LEVEL    REG_SZ    6
    PROCESSOR_REVISION    REG_SZ    3c03
    PSModulePath    REG_EXPAND_SZ    %SystemRoot%system32WindowsPowerShellv1.0Modules;C:Program FilesIntel
    TEMP    REG_EXPAND_SZ    %SystemRoot%TEMP
    TMP    REG_EXPAND_SZ    %SystemRoot%TEMP
    USERNAME    REG_SZ    SYSTEM
    windir    REG_EXPAND_SZ    %SystemRoot%

And same as with the user variables we can query a specific variable.

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reg query "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment" /v PATH

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HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment
    PATH    REG_EXPAND_SZ    C:ProgramDataOracleJavajavapath;C:WINDOWSsystem32;C:WINDOWS;C:WINDOWSSystem32Wbem;C:WINDOWSSystem32WindowsPowerShellv1.0;%SystemRoot%system32;%SystemRoot%;%SystemRoot%System32Wbem;%SYSTEMROOT%System32WindowsPowerShellv1.0

Unsetting a Variable

When setting environment variables on the command line, setx should be used because then the environment variables will be propagated appropriately. However one notable thing setx doesn’t do is unset environment variables. The reg tool can take care of that, however another setx command should be run afterwards to propagate the environment variables.

The layout for deleting a user variable is: reg delete HKEY_CURRENT_USEREnvironment /v variable_name /f. If /f had been left off, we would have been prompted: Delete the registry value EXAMPLE (Yes/No)?. For this example we’ll delete the user variable USER_EXAMPLE:

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reg delete HKEY_CURRENT_USEREnvironment /v USER_EXAMPLE /f

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The operation completed successfully.

Deleting a system variable requires administrator privileges. See HowTo: Open an Administrator Command Prompt in Windows to see how to do this.

The layout for deleting a system variable is: reg delete "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment" /v variable_name /f. For this example we’ll delete the system variable SYSTEM_EXAMPLE:

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reg delete "HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlSession ManagerEnvironment" /v SYSTEM_EXAMPLE /f

If this was run as a normal user you’ll get:

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ERROR: Access is denied.

But run in an administrator shell will give us:

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The operation completed successfully.

Finally we’ll have to run a setx command to propagate the environment variables. If there were other variables to set, we could just do that now. However if we were just interested in unsetting variables, we will need to have one variable left behind. In this case we’ll set a user variable named throwaway with a value of trash

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SUCCESS: Specified value was saved.

Resources

• Windows XP Service Pack 2 Support Tools
• Windows Server 2003 Resource Kit Tools
• Reg — Edit Registry | Windows CMD | SS64.com
• Reg — Microsoft TechNet
• Registry Value Types (Windows) — Microsoft Windows Dev Center
• How to propagate environment variables to the system — Microsoft Support
• WM_SETTINGCHANGE message (Windows) — Microsoft Windows Dev Center
• Environment Variables (Windows) — Microsoft Windows Dev Center

Windows Server 2003 Resource Kit Tools will also work with Windows XP and Windows XP SP1; use Windows XP Service Pack 2 Support Tools with Windows XP SP2. Neither download is supported on 64-bit version.

Parts in this series

• HowTo: Set an Environment Variable in Windows

• HowTo: Set an Environment Variable in Windows — GUI

• HowTo: Set an Environment Variable in Windows — Command Line and Registry

Introduction

In Windows, you sometimes need to modify environment variables.
There are environment variables like %APPDATA% and %PROGRAMFILES%
which contain useful paths, and others that contain things like
your username (%USERNAME%). An important one that you may
want to modify is %PATH%. In this guide we will look at
how to set, check, update, and unset environment variables
using the GUI and the command prompt.

Note that environment variables are case-insentive and that
there are system-wide environment variables
and user-specific environment variables.

Using GUI

You can edit the environment through the Windows settings
You can get to the GUI a few ways:

1. Press Windows key and search for «environment» and click Edit the system environment variables from the Control Panel.
2. Press Windows key+R to directly run: SystemPropertiesAdvanced.exe

Once in the System Properties panel, click the «Environment Variables…» button in the bottom-right.
From the GUI, you can edit the user variables on the top and the system variables on the bottom.

After setting an environment variable using this GUI method,
you will need to restart your applications for it to take effect.

Using command prompt

Use set and setx to manipulate environment variables from the command line.
Get help with set /? and setx /?. Let’s look at what each one does.

Check an environment variable

Check all environment variables with set:

set

Check a specific variable like this:

set X

You can print out an environment variable like this:

echo %X%

Set environment variable for a single session

To set an environment variable just for the current command prompt, use set.

set X=something

Permanently set environment variable

To permanently set an environment variable that will persist across
command prompts and through restart, use setx. Get help with setx /?.

setx X 123

By default, this is a user environment variable, not a system one.
To set a system environment variable, add the /M flag (will require admin prompt).

A common scenario is the need to update your PATH.
In this situation you want to add to the existing variable.
You can do that by referencing the original value like this:

setx PATH "%PATH%;C:optbin"

Unset environment variable

To unset an environment variable, set to to an empty string.

set X=

or

setx X ""

Conclusion

After reading this, you should know how to set environment variables in Windows
permanently or for a single session using the GUI or the command prompt.