Command line to remove an environment variable from the OS level configuration

Question

Windows has the setx command   Description      Creates or modifies environment variables in the user or system     environment    So you can set a variable like this   setx FOOBAR 1   And you can clear the value like this   setx FOOBAR      However  the variable does not get removed  It stays in the registry     So how would you actually remove the variable

User · Answer

setx FOOBAR      just causes the value of FOOBAR to be a null string   Although  it shows with the set command with the    so maybe double-quotes is the string    I used   set FOOBAR    and then FOOBAR was no longer listed in the set command   Log-off was not required    Windows nbsp 7 32 bit  using the command prompt  non-administrator is what I used   Not cmd or Windows   R  which might be different    BTW  I did not see the variable I created anywhere in the registry after I created it  I m using RegEdit not as administrator

User · Answer

You can also create a small VBScript script   Set env   CreateObject  WScript Shell   Environment  System   If env WScript Arguments 0    lt  gt  vbNullString Then env Remove WScript Arguments 0    Then call it like  windir  System32 cscript exe   Nologo  script name vbs  FOOBAR   The disadvantage is you need an extra script  but it does not require a reboot

User · Answer

To remove the variable from the current command session without removing it permanently  use the regular built-in set command - just put nothing after the equals sign   set FOOBAR   To confirm  run set with no arguments and check the current environment  The variable should be missing from the list entirely      Note  this will only remove the variable from the current environment - it will not persist the change to the registry  When a new command process is started  the variable will be back

User · Answer

I agree with CupawnTae   SET is not useful for changes to the master environment   FYI  System variables are in HKLM SYSTEM CurrentControlSet Control Session Manager Environment  a good deal longer than user vars    The full command for a system var named FOOBAR therefore is   REG delete  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   F  V FOOBAR    Note the quotes required to handle the space    It is too bad the setx command doesn t support a delete syntax      PS  Use responsibly - If you kill your path variable  don t blame me

User · Answer

The command in DougWare s answer did not work  but this did   reg delete  HKEY LOCAL MACHINE SYSTEM CurrentControlSet Control Session Manager Environment   v FOOBAR  f   The shortcut HKLM can be used for HKEY LOCAL MACHINE

User · Answer

To remove the variable from the current environment  not permanently    set FOOBAR    To permanently remove the variable from the user environment  which is the default place setx puts it    REG delete HKCU Environment  F  V FOOBAR   If the variable is set in the system environment  e g  if you originally set it with setx  M   as an administrator run   REG delete  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   F  V FOOBAR   Note  The REG commands above won t affect any existing processes  and some new processes that are forked from existing processes   so if it s important for the change to take effect immediately  the easiest and surest thing to do is log out and back in or reboot  If this isn t an option or you want to dig deeper  some of the other answers here have some great suggestions that may suit your use case

User · Answer

From PowerShell you can use the  NET  System Environment   SetEnvironmentVariable   method    To remove a user environment variable named FOO    Environment   SetEnvironmentVariable  FOO    null   User      Note that  null is used to better signal the intent to remove the  variable  though technically it is effectively the same as passing    in this case    To remove a system  machine-level  environment variable named FOO - requires elevation  must be run as administrator     Environment   SetEnvironmentVariable  FOO    null   Machine      Aside from faster execution  the advantage over the reg exe-based method is that other applications are notified of the change  via a WM SETTINGCHANGE message  though not all applications listen to that message

User · Answer

Delete Without Rebooting  The OP s question indeed has been answered extensively  including how to avoid rebooting through powershell  vbscript  or you name it   However  if you need to stick to cmd commands only and don t have the luxury of being able to call powershell or vbscript  you could use the following approach   rem remove from current cmd instance   SET FOOBAR  rem remove from the registry if it s a user variable   REG delete HKCU Environment  F  V FOOBAR rem remove from the registry if it s a system variable   REG delete  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   F  V FOOBAR rem tell Explorer exe to reload the environment from the registry   SETX DUMMY    rem remove the dummy   REG delete HKCU Environment  F  V DUMMY   So the magic here is that by using  setx  to assign something to a variable you don t need  in my example DUMMY   you force Explorer exe to reread the variables from the registry  without needing powershell  You then clean up that dummy  and even though that one will stay in Explorer s environment for a little while longer  it will probably not harm anyone   Or if after deleting variables you need to set new ones  then you don t even need any dummy  Just using SETX to set the new variables will automatically clear the ones you just removed from any new cmd tasks that might get started   Background information  I just used this approach successfully to replace a set of user variables by system variables of the same name on all of the computers at my job  by modifying an existing cmd script  There are too many computers to do it manually  nor was it practical to copy extra powershell or vbscripts to all of them  The reason I urgently needed to replace user with system variables was that user variables get synchronized in roaming profiles  didn t think about that   so multiple machines using the same windows login but needing different values  got mixed up

User · Answer

This has been covered quite a bit  but there s a crucial piece of information that s missing  Hopefully  I can help to clear up how this works and give some relief to weary travellers   -   Delete From Current Process  Obviously  everyone knows that you just do this to delete an environment variable from your current process   set FOO    Persistent Delete  There are two sets of environment variables  system-wide and user   Delete User Environment Variable   reg delete  HKCU Environment   v FOO  f   Delete System-Wide Environment Variable   REG delete  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   F  V FOO   Apply Value Without Rebooting  Here s the magic information that s missing  You re wondering why after you do this  when you launch a new command window  the environment variable is still there  The reason is because explorer exe has not updated its environment  When one process launches another  the new process inherits the environment from the process that launched it   There are two ways to fix this without rebooting  The most brute-force way is to kill your explorer exe process and start it again  You can do that from Task Manager  I don t recommend this method  however   The other way is by telling explorer exe that the environment has changed and that it should reread it  This is done by broadcasting a Windows message  WM SETTINGCHANGE   This can be accomplished with a simple PowerShell  script  You could easily write one to do this  but I found one in Update Window Settings After Scripted Changes   if  -not   win32 nativemethods  -as  type          add-type -Namespace Win32 -Name NativeMethods -MemberDefinition             DllImport  user32 dll   SetLastError   true  CharSet   CharSet Auto           public static extern IntPtr SendMessageTimeout              IntPtr hWnd  uint Msg  UIntPtr wParam  string lParam              uint fuFlags  uint uTimeout  out UIntPtr lpdwResult                  HWND BROADCAST    intptr 0xffff   WM SETTINGCHANGE   0x1a   result    uintptr   zero   win32 nativemethods   SendMessageTimeout  HWND BROADCAST   WM SETTINGCHANGE  uintptr   Zero   Environment   2  5000   ref  result     Summary  So to delete a user environment variable named  FOO  and have the change reflected in processes you launch afterwards  do the following    Save the PowerShell script to a file  we ll call it updateenv ps1   Do this from the command line  reg delete  HKCU Environment   v FOO  f Run updateenv ps1  Close and reopen your command prompt  and you ll see that the environment variable is no longer defined    Note  you ll probably have to update your PowerShell settings to allow you to run this script  but I ll leave that as a Google-fu exercise for you

[windows] Command line to remove an environment variable from the OS level configuration

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