Environment variables in Windows

Overview

The environment variables are a set of dynamic values used during the running processes. They are introduced in first time in Linux OS but they are used in Windows OSs since 30 and more years old.

The following reading explains how to manage the environment variables either through the User Interface or through the prompt.

Manage the environment variables via User Interface

As a first step you open the "System Properties" windows but there are some differences depending on the operating system version, in detail the change takes place between Windows 7 and Windows 8. 

In Windows 8 and Windows 10:

• From the Desktop, right-click the very bottom left corner of the screen to get the Power User Task Menu.
• From the Power User Task Menu, click System.

In Windows 2000, Windows XP, Windows Vista and Windows 7

• From the Desktop, right-click the Computer icon and select Properties. If you don't have a Computer icon on your desktop, click the Start button, right-click the Computer option in the Start menu, and select Properties.

Click the Advanced System Settings link in the left column (valid for all operation system versions).

Then click the Environment Variables button near the bottom of that tab. The windows below manages (add, edit and delete) the "User Variables" and the "System Variables".

Example 1

If you want add a new system variable then click on "New...." button under System variables (as shows the picture):

After the click, will be showed the following window:

You can put the name and the value of new System Variable. Finally click on "OK" button. The System Variable is created.

Example 2

If you want edit an user variable, for example "TEMP" then select it and  click on "Edit..." button under User Variables (as shows the picture):

After the click, will be showed the following window: 

Edit the value and click on "OK" button. 

Manage the environment variables via Prompt

The environment variables in Windows are denoted with percent signs (%) surrounding the name:

 %VAR%

The echo of a variable you can use the commands as below:

 set %VAR%

or

 echo %VAR%

To create or edit a variable, you can use:

 set VAR=value

To append a value to a variable already created:

 set APPEND=value2

 set VAR=%VAR%;%APPEND%

 echo %VAR%
 value;value2

Environment variables set in this way are available for (the rest of) the duration of the Command Prompt process in which they are set, and are available to processes that are started after the variables were set. After the closed of Command Prompt the variables are not present.

Manage permanently  the environment variables

The setx command prompt [1] creates or modifies environment variables in the user or system environment, without requiring programming or scripting. The Setx command also retrieves the values of registry keys and writes them to text files. 

The setx is available in Windows Vista, Windows Server 2008, Windows Server 2012, Windows 8.

The official syntax [2] is:

 setx [/s <Computer> [/u [<Domain>\]<User name> [/p [<Password>]]]] <Variable> <Value> [/m]
 setx [/s <Computer> [/u [<Domain>\]<User name> [/p [<Password>]]]] [<Variable>] /k <Path> [/m]
 setx [/s <Computer> [/u [<Domain>\]<User name> [/p [<Password>]]]] /f <FileName> {[<Variable>] {/a <X>,<Y> | /r <X>,<Y> "<String>"} [/m] | /x} [/d <Delimiters>]

Some examples:

To set the MYVAR environment variable in the local environment to the value ValueA:

 set MYVAR valueA

To set the MYVAR environment variable in the system environment to the value Value A:

 set MYVAR "value A" /m

To set the MYPATH environment variable in the local environment to use the search path defined in the PATH environment variable:

 setx MYPATH %PATH%

To set the MYPATH environment variable in the local environment to use the search path defined in the PATH environment variable after replacing ~ with %:

 setx MYPATH ~PATH~

Internal link

May be of interest to you:

[1] Environment variables in Linux

External links

For more detail see the Windows documentation:
[1] https://technet.microsoft.com/en-us/library/cc755104(v=ws.11).aspx
[2] https://technet.microsoft.com/en-us/library/cc771080(v=ws.11).aspx