Windows Environment Variables - Legacy

Windows Environment Variables

Environment variables are mainly used within batch files, they can be created, modified and deleted for a session using theSET command. To make permanent changes, use SETX 

Variables can be displayed using either SET or ECHO.

Variables have a percent sign on both sides: %ThisIsAVariable%
The variable name can include spaces, punctuation and mixed case: %_Another Ex.ample%
(This is unlike Parameter variables which only have one % sign and are always one character long: %A )

 

Standard (built-in) Environment Variables

VariableVolatile
(Read-Only)Default value in Windows 7/10/2008 (assuming the system drive is C: )

ALLUSERSPROFILE C:\ProgramData

APPDATA C:\Users\{username}\AppData\Roaming

CDYThe current directory (string).

ClientNameYTerminal servers only - the ComputerName of a remote host.

CMDEXTVERSIONYThe current Command Processor Extensions version number. (NT = "1", Win2000+ = "2".)

CMDCMDLINEYThe original command line that invoked the Command Processor.

CommonProgramFiles C:\Program Files\Common Files

COMMONPROGRAMFILES(x86) C:\Program Files (x86)\Common Files

COMPUTERNAME {computername}

COMSPEC C:\Windows\System32\cmd.exe or if running a 32 bit WOW - C:\Windows\SysWOW64\cmd.exe

DATEYThe current date using same region specific format as DATE.

ERRORLEVELYThe current ERRORLEVEL value, automatically set when a program exits.

FPS_BROWSER_APP_PROFILE_STRING
FPS_BROWSER_USER_PROFILE_STRING

 Internet Explorer
Default
These are undocumented variables for the Edge browser in Windows 10.

HighestNumaNodeNumberY (hidden)The highest NUMA node number on this computer.

HOMEDRIVEYC:

HOMEPATHY\Users\{username}

LOCALAPPDATA C:\Users\{username}\AppData\Local

LOGONSERVER \\{domain_logon_server}

NUMBER_OF_PROCESSORSYThe Number of processors running on the machine.

OSYOperating system on the user's workstation.

PATHUser and
SystemC:\Windows\System32\;C:\Windows\;C:\Windows\System32\Wbem;{plus program paths}

PATHEXT
.COM; .EXE; .BAT; .CMD; .VBS; .VBE; .JS ; .WSF; .WSH; .MSC
The syntax is like the PATH variable - semicolon separators.

PROCESSOR_ARCHITECTUREYAMD64/IA64/x86 This doesn't tell you the architecture of the processor but only of the current process, so it returns "x86" for a 32 bit WOW process running on 64 bit Windows. See detecting OS 32/64 bit

PROCESSOR_ARCHITEW6432 =%ProgramFiles% (only available on 64 bit systems)

PROCESSOR_IDENTIFIERYProcessor ID of the user's workstation.

PROCESSOR_LEVELYProcessor level of the user's workstation.

PROCESSOR_REVISIONYProcessor version of the user's workstation.

ProgramW6432 =%PROCESSOR_ARCHITECTURE% (only available on 64 bit systems)

ProgramData C:\ProgramData

ProgramFiles C:\Program Files

ProgramFiles(x86) 1 C:\Program Files (x86)

PROMPT Code for current command prompt format,usually $P$G
C:>

PSModulePath %SystemRoot%\system32\WindowsPowerShell\v1.0\Modules\

Public C:\Users\Public

RANDOMYA random integer number, anything from 0 to 32,767 (inclusive).

%SessionName% Terminal servers only - for a terminal server session, SessionName is a combination of the connection name, followed by #SessionNumber. For a console session, SessionName returns "Console".

SYSTEMDRIVE C:

SYSTEMROOT By default, Windows is installed to C:\Windows but there's no guarantee of that, Windows can be installed to a different folder, or a different drive letter.
systemroot is a read-only system variable that will resolve to the correct location.
NT 4.0, Windows 2000 and Windows NT 3.1 default to C:\WINNT

TEMP and TMPUser VariableC:\Users\{Username}\AppData\Local\Temp
Under XP this was \{username}\Local Settings\Temp

TIMEYThe current time using same format as TIME.

UserDnsDomainY
User VariableSet if a user is a logged on to a domain and returns the fully qualified DNS domain that the currently logged on user's account belongs to.

USERDOMAIN {userdomain}

USERDOMAIN_roamingprofile The user domain for RDS or standard roaming profile paths. Windows 8/10/2012 (or Windows 7/2008 with Q2664408)

USERNAME {username}

USERPROFILE %SystemDrive%\Users\{username}
This is equivalent to the $HOME environment variable in Unix/Linux

WINDIR

%WinDir% pre-dates Windows NT and seems to be superseded by %SystemRoot%
Set by default as windir=%SystemRoot%
%windir% is a regular variable and can be changed, which makes it less robust than %systemroot%

1 Only on 64 bit systems, is used to store 32 bit programs.

Unless stated otherwise, all the variables above are System variables

Environment variables are stored in the registry:

User Variables: HKEY_CURRENT_USER\Environment
System Variables: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment

By default, files stored under Local Settings do not roam with a roaming profile.

Dynamic environment variables are read-only and are computed each time the variable is expanded. When all variables are listed with SET, these will not appear in the list. Do not attempt to directly SET a dynamic variable.  

Undocumented Dynamic variables (read only)

%__APPDIR__%   The directory path to the current application .exe, terminated with a trailing backslash. (Global) - discuss
%__CD__%   The current directory, terminated with a trailing backslash. (Global)
%=C:%   The current directory of the C: drive.
%=D:%   The current directory of the D: drive if drive D: has been accessed in the current CMD session.
%DPATH%   Related to the (deprecated) DPATH command.
%=ExitCode%   The hex value of the last return code set by EXIT /B
%=ExitCodeAscii%   The ASCII value of the last return code set by EXIT /B if greater than 32.
%FIRMWARE_TYPE% The boot type of the system: Legacy ,UEFI,Not implemented ,Unknown Windows 8/2012.
%KEYS%   Related to the (deprecated) KEYS command.

Undocumented Dynamic variables (read/write)

%__COMPAT_LAYER%   Set the ExecutionLevel to either RunAsInvoker (asInvoker), RunAsHighest(highestAvailable) orRunAsAdmin(requireAdministrator) for more see elevation and Q286705 / Application Compatibility Toolkit for other Compatibility Layers (colours,themes etc).

Pass variables between batch scripts

There are several ways to pass values between batch files, or between a batch file and the command line, see the CALL andSETLOCAL pages for full details.

A child process by default inherits a copy of all environment variables from its parent, this makes environment variables unsuitable for storing secret information such as API keys or user passwords, especially in rare occasions like crashes where a crash log will often include the full OS environment at the time of the crash. PowerShell/Get-Credential is a more secure approach.

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