Is there a command to refresh environment variables from the command prompt in Windows

Question

If I modify or add an environment variable I have to restart the command prompt   Is there a command I could execute that would do this without restarting CMD

User · Answer

Environment variables are kept in HKEY LOCAL MACHINE SYSTEM ControlSet Control Session Manager Environment   Many of the useful env vars  such as Path  are stored as REG SZ   There are several ways to access the registry including REGEDIT   REGEDIT  E  amp lt filename amp gt   HKEY LOCAL MACHINE SYSTEM ControlSet001 Control Session Manager Environment   The output starts with magic numbers   So to search it with the find command it needs to be typed and redirected  type  lt filename gt    findstr -c   Path    So  if you just want to refresh the path variable in your current command session with what s in system properties the following batch script works fine   RefreshPath cmd          echo off      REM This solution requests elevation in order to read from the registry       if exist  temp  env reg del  temp  env reg  q  f      REGEDIT  E  temp  env reg  HKEY LOCAL MACHINE SYSTEM ControlSet001 Control Session Manager Environment       if not exist  temp  env reg          echo  Unable to write registry to temp location         exit 1               SETLOCAL EnableDelayedExpansion      for  f  tokens 1 2  delims      i in   type  temp  env reg    findstr -c   Path      do          set upath    j        echo  upath         temp  newpath                ENDLOCAL       for  f  tokens      i in   temp  newpath  do set path   i

User · Answer

There is no straight way  as Kev said  In most cases  it is simpler to spawn another CMD box  More annoyingly  running programs are not aware of changes either  although IIRC there might be a broadcast message to watch to be notified of such change    It have been worse  in older versions of Windows  you had to log off then log back to take in account the changes

User · Answer

Calling this function has worked for me   VOID Win32ForceSettingsChange         DWORD dwReturnValue        SendMessageTimeout HWND BROADCAST  WM SETTINGCHANGE  0   LPARAM   Environment   SMTO ABORTIFHUNG  5000   amp dwReturnValue

User · Answer

Calling this function has worked for me   VOID Win32ForceSettingsChange         DWORD dwReturnValue        SendMessageTimeout HWND BROADCAST  WM SETTINGCHANGE  0   LPARAM   Environment   SMTO ABORTIFHUNG  5000   amp dwReturnValue

User · Answer

You can capture the system environment variables with a vbs script  but you need a bat script to actually change the current environment variables  so this is a combined solution   Create a file named resetvars vbs containing this code  and save it on the path     Set oShell   WScript CreateObject  WScript Shell   filename   oShell ExpandEnvironmentStrings   TEMP  resetvars bat   Set objFileSystem   CreateObject  Scripting fileSystemObject   Set oFile   objFileSystem CreateTextFile filename  TRUE   set oEnv oShell Environment  System   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next path   oEnv  PATH    set oEnv oShell Environment  User   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next  path   path  amp       amp  oEnv  PATH   oFile WriteLine  SET PATH    amp  path  oFile Close   create another file name resetvars bat containing this code  same location    echo off   dp0resetvars vbs call   TEMP  resetvars bat    When you want to refresh the environment variables  just run resetvars bat    Apologetics   The two main problems I had coming up with this solution were  a  I couldn t find a straightforward way to export environment variables from a vbs script back to the command prompt  and   b  the PATH environment variable is a concatenation of the user and the system PATH variables   I m not sure what the general rule is for conflicting variables between user and system  so I elected to make user override system  except in the PATH variable which is handled specifically   I use the weird vbs bat temporary bat mechanism to work around the problem of exporting variables from vbs   Note  this script does not delete variables   This can probably be improved   ADDED  If you need to export the environment from one cmd window to another  use this script  let s call it exportvars vbs    Set oShell   WScript CreateObject  WScript Shell   filename   oShell ExpandEnvironmentStrings   TEMP  resetvars bat   Set objFileSystem   CreateObject  Scripting fileSystemObject   Set oFile   objFileSystem CreateTextFile filename  TRUE   set oEnv oShell Environment  Process   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next oFile Close   Run exportvars vbs in the window you want to export from  then switch to the window you want to export to  and type     TEMP  resetvars bat

User · Answer

The best method I came up with was to just do a Registry query  Here is my example   In my example I did an install using a Batch file that added new environment variables  I needed to do things with this as soon as the install was complete  but was unable to spawn a new process with those new variables  I tested spawning another explorer window and called back to cmd exe and this worked but on Vista and Windows 7  Explorer only runs as a single instance and normally as the person logged in  This would fail with automation since I need my admin creds to do things regardless of running from local system or as an administrator on the box  The limitation to this is that it does not handle things like path  this only worked on simple enviroment variables  This allowed me to use a batch to get over to a directory  with spaces  and copy in files run  exes and etc  This was written today from may resources on stackoverflow com  Orginal Batch calls to new Batch   testenvget cmd SDROOT  or whatever the variable    ECHO OFF setlocal ENABLEEXTENSIONS set keyname HKLM System CurrentControlSet Control Session Manager Environment set value  1 SET ERRKEY 0  REG QUERY   KEYNAME    v   VALUE   2 gt NUL  FIND  I   VALUE   IF  ERRORLEVEL  EQU 0   ECHO The Registry Key Exists    ELSE   SET ERRKEY 1 Echo The Registry Key Does not Exist    Echo  ERRKEY  IF  ERRKEY  EQU 1 GOTO  ERROR  FOR  F  tokens 1-7    A IN   REG QUERY   KEYNAME    v   VALUE   2  gt NUL   FIND  I   VALUE     DO   ECHO   A ECHO   B ECHO   C ECHO   D ECHO   E ECHO   F ECHO   G SET ValueName   A SET ValueType   B SET C1   C SET C2   D SET C3   E SET C4   F SET C5   G    SET VALUE1  C1   C2   C3   C4   C5  echo The Value of  VALUE  is  C1   C2   C3   C4   C5  cd  d   VALUE1   pause REM   RUN Extra Commands here   GOTO  EOF   ERROR Echo The the Enviroment Variable does not exist  pause GOTO  EOF   Also there is another method that I came up with from various different ideas  Please see below  This basically will get the newest path variable from the registry however  this will cause a number of issues beacuse the registry query is going to give variables in itself  that means everywhere there is a variable this will not work  so to combat this issue I basically double up the path  Very nasty  The more perfered method would be to do      Set Path  Path  C  Program Files Software       Regardless here is the new batch file  please use caution    ECHO OFF SETLOCAL ENABLEEXTENSIONS set org  PATH  for  f  tokens 2     A in   REG QUERY  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   v Path   FIND  I  Path    DO   SET path   B   SET PATH  org   PATH  set path

User · Answer

If it concerns just one  or a few  specific vars you want to change  I think the easiest way is a workaround  just set in in your environment AND in your current console session   Set will put the var in your current session SetX will put the var in the environment  but NOT in your current session   I have this simple batch script to change my Maven from Java7 to Java8  which are both env  vars  The batch-folder is in my PATH var so I can always call  j8  and within my console and in the environment my JAVA HOME var gets changed   j8 bat    echo off set JAVA HOME  JAVA HOME 8  setx JAVA HOME   JAVA HOME 8     Till now I find this working best and easiest   You probably want this to be in one command  but it simply isn t there in Windows

User · Answer

I use this Powershell script to add to the PATH variable  With a little adjustment it can work in your case too I believe    REQUIRES -Version 3 0  if  -not   win32 nativemethods  -as  type            import sendmessagetimeout from win32     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  function global ADD-PATH        Cmdletbinding        param             parameter Mandatory  True  ValueFromPipeline  True  Position 0             string   Folder              See if a folder variable has been supplied      if    Folder -or  Folder -eq    -or  Folder -eq  null             throw  No Folder Supplied   ENV PATH Unchanged               Get the current search path from the environment keys in the registry       oldPath   Get-ItemProperty -Path  Registry  HKEY LOCAL MACHINE System CurrentControlSet Control Session Manager Environment  -Name PATH  Path        See if the new Folder is already in the path      if   oldPath   Select-String -SimpleMatch  Folder            return  Folder already within  ENV PATH                Set the New Path and add the   in front      newPath  oldPath      Folder     Set-ItemProperty -Path  Registry  HKEY LOCAL MACHINE System CurrentControlSet Control Session Manager Environment  -Name PATH -Value  newPath -ErrorAction Stop        Show our results back to the world     return  This is the new PATH content     newPath        notify all windows of environment block change      win32 nativemethods   SendMessageTimeout  HWND BROADCAST   WM SETTINGCHANGE   uintptr   Zero   Environment   2  5000   ref  result     function global REMOVE-PATH        Cmdletbinding        param             parameter Mandatory  True  ValueFromPipeline  True  Position 0            String   Folder              See if a folder variable has been supplied      if    Folder -or  Folder -eq    -or  Folder -eq  NULL             throw  No Folder Supplied   ENV PATH Unchanged               add a leading     if missing     if   Folder 0  -ne                 Folder          Folder               Get the Current Search Path from the environment keys in the registry      newPath   Get-ItemProperty -Path  Registry  HKEY LOCAL MACHINE System CurrentControlSet Control Session Manager Environment  -Name PATH  Path        Find the value to remove  replace it with  NULL  If it s not found  nothing will change and you get a message      if   newPath -match  regex   Escape  Folder               newPath  newPath -replace  regex   Escape  Folder   NULL        else            return  The folder you mentioned does not exist in the PATH environment                Update the Environment Path     Set-ItemProperty -Path  Registry  HKEY LOCAL MACHINE System CurrentControlSet Control Session Manager Environment  -Name PATH -Value  newPath -ErrorAction Stop        Show what we just did     return  This is the new PATH content     newPath        notify all windows of environment block change      win32 nativemethods   SendMessageTimeout  HWND BROADCAST   WM SETTINGCHANGE   uintptr   Zero   Environment   2  5000   ref  result        Use ADD-PATH or REMOVE-PATH accordingly    Anything to Add    Anything to Remove   REMOVE-PATH    installpath bin

User · Answer

Use  setx  and restart cmd prompt  There is a command line tool named  setx  for this job  It s for reading and writing env variables  The variables persist after the command window has been closed   It  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    Note  variables created or modified by this tool will be available in future command windows but not in the current CMD exe command window  So  you have to restart   If setx is missing     http   download microsoft com download win2000platform setx 1 00 0 1 nt5 en-us setx setup exe     Or modify the registry  MSDN says       To programmatically add or modify system environment variables  add   them to the   HKEY LOCAL MACHINE System CurrentControlSet Control Session   Manager Environment registry key  then broadcast a WM SETTINGCHANGE   message with lParam set to the string  Environment         This allows applications  such as the shell  to pick up your updates

User · Answer

The easiest way to add a variable to the path without rebooting for the current session is to open the command prompt and type    PATH  VARIABLE   path    and press enter    to check if your variable loaded  type   PATH   and press enter  However  the variable will only be a part of the path until you reboot

User · Answer

Here is what Chocolatey uses  https   github com chocolatey choco blob master src chocolatey resources redirects RefreshEnv cmd  echo off       RefreshEnv cmd       Batch file to read environment variables from registry and    set session variables to these values        With this batch file  there should be no need to reload command    environment every time you want environment changes to propagate    echo  quot RefreshEnv cmd only works from cmd exe  please install the Chocolatey Profile to take advantage of refreshenv from PowerShell quot  echo   set  p dummy  quot Refreshing environment variables from registry for cmd exe  Please wait    quot   goto main     Set one environment variable from registry key  SetFromReg      quot  WinDir  System32 Reg quot  QUERY  quot   1 quot   v  quot   2 quot   gt   quot  TEMP   envset tmp quot  2 gt NUL     for  f  quot usebackq skip 2 tokens 2   quot    A IN   quot  TEMP   envset tmp quot   do           echo set  quot   3   B quot            goto  EOF     Get a list of environment variables from registry  GetRegEnv      quot  WinDir  System32 Reg quot  QUERY  quot   1 quot   gt   quot  TEMP   envget tmp quot      for  f  quot usebackq skip 2 quot    A IN   quot  TEMP   envget tmp quot   do           if  I not  quot    A quot    quot Path quot                call  SetFromReg  quot   1 quot   quot    A quot   quot    A quot                      goto  EOF   main     echo  echo off  gt  quot  TEMP   env cmd quot          Slowly generating final file     call  GetRegEnv  quot HKLM System CurrentControlSet Control Session Manager Environment quot   gt  gt   quot  TEMP   env cmd quot      call  GetRegEnv  quot HKCU Environment quot  gt  gt  quot  TEMP   env cmd quot   gt  gt   quot  TEMP   env cmd quot          Special handling for PATH - mix both User and System     call  SetFromReg  quot HKLM System CurrentControlSet Control Session Manager Environment quot  Path Path HKLM  gt  gt   quot  TEMP   env cmd quot      call  SetFromReg  quot HKCU Environment quot  Path Path HKCU  gt  gt   quot  TEMP   env cmd quot          Caution  do not insert space-chars before  gt  gt  redirection sign     echo set  quot Path   Path HKLM     Path HKCU   quot   gt  gt   quot  TEMP   env cmd quot          Cleanup     del  f  q  quot  TEMP   envset tmp quot  2 gt nul     del  f  q  quot  TEMP   envget tmp quot  2 gt nul         capture user   architecture     SET  quot OriginalUserName  USERNAME  quot      SET  quot OriginalArchitecture  PROCESSOR ARCHITECTURE  quot          Set these variables     call  quot  TEMP   env cmd quot          Cleanup     del  f  q  quot  TEMP   env cmd quot  2 gt nul         reset user   architecture     SET  quot USERNAME  OriginalUserName  quot      SET  quot PROCESSOR ARCHITECTURE  OriginalArchitecture  quot       echo   set  p dummy  quot Finished  quot      echo

User · Answer

On Windows 7 8 10  you can install Chocolatey  which has a script for this built-in   After installing Chocolatey  just type refreshenv

User · Answer

The best method I came up with was to just do a Registry query  Here is my example   In my example I did an install using a Batch file that added new environment variables  I needed to do things with this as soon as the install was complete  but was unable to spawn a new process with those new variables  I tested spawning another explorer window and called back to cmd exe and this worked but on Vista and Windows 7  Explorer only runs as a single instance and normally as the person logged in  This would fail with automation since I need my admin creds to do things regardless of running from local system or as an administrator on the box  The limitation to this is that it does not handle things like path  this only worked on simple enviroment variables  This allowed me to use a batch to get over to a directory  with spaces  and copy in files run  exes and etc  This was written today from may resources on stackoverflow com  Orginal Batch calls to new Batch   testenvget cmd SDROOT  or whatever the variable    ECHO OFF setlocal ENABLEEXTENSIONS set keyname HKLM System CurrentControlSet Control Session Manager Environment set value  1 SET ERRKEY 0  REG QUERY   KEYNAME    v   VALUE   2 gt NUL  FIND  I   VALUE   IF  ERRORLEVEL  EQU 0   ECHO The Registry Key Exists    ELSE   SET ERRKEY 1 Echo The Registry Key Does not Exist    Echo  ERRKEY  IF  ERRKEY  EQU 1 GOTO  ERROR  FOR  F  tokens 1-7    A IN   REG QUERY   KEYNAME    v   VALUE   2  gt NUL   FIND  I   VALUE     DO   ECHO   A ECHO   B ECHO   C ECHO   D ECHO   E ECHO   F ECHO   G SET ValueName   A SET ValueType   B SET C1   C SET C2   D SET C3   E SET C4   F SET C5   G    SET VALUE1  C1   C2   C3   C4   C5  echo The Value of  VALUE  is  C1   C2   C3   C4   C5  cd  d   VALUE1   pause REM   RUN Extra Commands here   GOTO  EOF   ERROR Echo The the Enviroment Variable does not exist  pause GOTO  EOF   Also there is another method that I came up with from various different ideas  Please see below  This basically will get the newest path variable from the registry however  this will cause a number of issues beacuse the registry query is going to give variables in itself  that means everywhere there is a variable this will not work  so to combat this issue I basically double up the path  Very nasty  The more perfered method would be to do      Set Path  Path  C  Program Files Software       Regardless here is the new batch file  please use caution    ECHO OFF SETLOCAL ENABLEEXTENSIONS set org  PATH  for  f  tokens 2     A in   REG QUERY  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   v Path   FIND  I  Path    DO   SET path   B   SET PATH  org   PATH  set path

User · Answer

There is no straight way  as Kev said  In most cases  it is simpler to spawn another CMD box  More annoyingly  running programs are not aware of changes either  although IIRC there might be a broadcast message to watch to be notified of such change    It have been worse  in older versions of Windows  you had to log off then log back to take in account the changes

User · Answer

Try opening a new command prompt as an administrator  This worked for me on Windows 10   I know this is an old answer  but I had to share this because having to write a VBS script just for this is absurd

User · Answer

I came across this answer before eventually finding an easier solution    Simply restart explorer exe in Task Manager   I didn t test  but you may also need to reopen you command prompt   Credit to Timo Huovinen here  Node not recognized although successfully installed  if this helped you  please go give this man s comment credit

User · Answer

Try opening a new command prompt as an administrator  This worked for me on Windows 10   I know this is an old answer  but I had to share this because having to write a VBS script just for this is absurd

User · Answer

It is possible to do this by overwriting the Environment Table within a specified process itself   As a proof of concept I wrote this sample app  which just edited a single  known  environment variable in a cmd exe process   typedef DWORD    stdcall  NtQueryInformationProcessPtr  HANDLE  DWORD  PVOID  ULONG  PULONG    int   cdecl main int argc  char  argv          HMODULE hNtDll   GetModuleHandleA  ntdll dll        NtQueryInformationProcessPtr NtQueryInformationProcess    NtQueryInformationProcessPtr GetProcAddress hNtDll   NtQueryInformationProcess         int processId   atoi argv 1        printf  Target PID   u n   processId           open the process with read write access     HANDLE hProcess   OpenProcess PROCESS QUERY LIMITED INFORMATION   PROCESS VM READ   PROCESS VM WRITE   PROCESS VM OPERATION  0  processId       if hProcess    NULL                printf  Error opening process   u  n   GetLastError             return 0                find the location of the PEB     PROCESS BASIC INFORMATION pbi    0       NTSTATUS status   NtQueryInformationProcess hProcess  ProcessBasicInformation   amp pbi  sizeof pbi   NULL       if status    0                printf  Error ProcessBasicInformation  0x 8X  n   status             printf  PEB   p n   pbi PebBaseAddress           find the process parameters     char  processParamsOffset    char  pbi PebBaseAddress   0x20     hard coded offset for x64 apps     char  processParameters   NULL      if ReadProcessMemory hProcess  processParamsOffset   amp processParameters  sizeof processParameters   NULL                 printf  UserProcessParameters   p n   processParameters             else               printf  Error ReadProcessMemory   u  n   GetLastError                   find the address to the environment table     char  environmentOffset   processParameters   0x80     hard coded offset for x64 apps     char  environment   NULL      ReadProcessMemory hProcess  environmentOffset   amp environment  sizeof environment   NULL       printf  environment   p n   environment           copy the environment table into our own memory for scanning     wchar t  localEnvBlock   new wchar t 64 1024       ReadProcessMemory hProcess  environment  localEnvBlock  sizeof wchar t  64 1024  NULL           find the variable to edit     wchar t  found   NULL      wchar t  varOffset   localEnvBlock      while varOffset  lt  localEnvBlock   64 1024                if varOffset 0       0                            we reached the end             break                    if wcsncmp varOffset  L ENVTEST    8     0                        found   varOffset              break                    varOffset    wcslen varOffset  1                check to see if we found one     if found                size t offset    found - localEnvBlock    sizeof wchar t           printf  Offset   Iu n   offset               write a new version  if the size of the value changes then we have to rewrite the entire block          if  WriteProcessMemory hProcess  environment   offset  L ENVTEST def   12 sizeof wchar t   NULL                         printf  Error WriteProcessMemory   u  n   GetLastError                             cleanup     delete   localEnvBlock      CloseHandle hProcess        return 0      Sample output    gt set ENVTEST abc   gt cppTest exe 13796 Target PID  13796 PEB  000007FFFFFD3000 UserProcessParameters  00000000004B2F30 environment  000000000052E700 Offset  1528   gt set ENVTEST ENVTEST def   Notes  This approach would also be limited to security restrictions  If the target is run at higher elevation or a higher account  such as SYSTEM  then we wouldn t have permission to edit its memory   If you wanted to do this to a 32-bit app  the hard coded offsets above would change to 0x10 and 0x48 respectively  These offsets can be found by dumping out the  PEB and  RTL USER PROCESS PARAMETERS structs in a debugger  e g  in WinDbg dt  PEB and dt  RTL USER PROCESS PARAMETERS   To change the proof-of-concept into a what the OP needs  it would just enumerate the current system and user environment variables  such as documented by  tsadok s answer  and write the entire environment table into the target process  memory   Edit  The size of the environment block is also stored in the  RTL USER PROCESS PARAMETERS struct  but the memory is allocated on the process  heap  So from an external process we wouldn t have the ability to resize it and make it larger  I played around with using VirtualAllocEx to allocate additional memory in the target process for the environment storage  and was able to set and read an entirely new table  Unfortunately any attempt to modify the environment from normal means will crash and burn as the address no longer points to the heap  it will crash in RtlSizeHeap

User · Answer

Edit  this only works if the environment changes you re doing are as a result of running a batch file   If a batch file begins with SETLOCAL then it will always unravel back to your original environment on exit even if you forget to call ENDLOCAL before the batch exits  or if it aborts unexpectedly   Almost every batch file I write begins with SETLOCAL since in most cases I don t want the side-effects of environment changes to remain  In cases where I do want certain environment variable changes to propagate outside the batch file then my last ENDLOCAL looks like this   ENDLOCAL  amp      SET RESULT1  RESULT1    SET RESULT2  RESULT2

User · Answer

You can capture the system environment variables with a vbs script  but you need a bat script to actually change the current environment variables  so this is a combined solution   Create a file named resetvars vbs containing this code  and save it on the path     Set oShell   WScript CreateObject  WScript Shell   filename   oShell ExpandEnvironmentStrings   TEMP  resetvars bat   Set objFileSystem   CreateObject  Scripting fileSystemObject   Set oFile   objFileSystem CreateTextFile filename  TRUE   set oEnv oShell Environment  System   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next path   oEnv  PATH    set oEnv oShell Environment  User   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next  path   path  amp       amp  oEnv  PATH   oFile WriteLine  SET PATH    amp  path  oFile Close   create another file name resetvars bat containing this code  same location    echo off   dp0resetvars vbs call   TEMP  resetvars bat    When you want to refresh the environment variables  just run resetvars bat    Apologetics   The two main problems I had coming up with this solution were  a  I couldn t find a straightforward way to export environment variables from a vbs script back to the command prompt  and   b  the PATH environment variable is a concatenation of the user and the system PATH variables   I m not sure what the general rule is for conflicting variables between user and system  so I elected to make user override system  except in the PATH variable which is handled specifically   I use the weird vbs bat temporary bat mechanism to work around the problem of exporting variables from vbs   Note  this script does not delete variables   This can probably be improved   ADDED  If you need to export the environment from one cmd window to another  use this script  let s call it exportvars vbs    Set oShell   WScript CreateObject  WScript Shell   filename   oShell ExpandEnvironmentStrings   TEMP  resetvars bat   Set objFileSystem   CreateObject  Scripting fileSystemObject   Set oFile   objFileSystem CreateTextFile filename  TRUE   set oEnv oShell Environment  Process   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next oFile Close   Run exportvars vbs in the window you want to export from  then switch to the window you want to export to  and type     TEMP  resetvars bat

User · Answer

You can capture the system environment variables with a vbs script  but you need a bat script to actually change the current environment variables  so this is a combined solution   Create a file named resetvars vbs containing this code  and save it on the path     Set oShell   WScript CreateObject  WScript Shell   filename   oShell ExpandEnvironmentStrings   TEMP  resetvars bat   Set objFileSystem   CreateObject  Scripting fileSystemObject   Set oFile   objFileSystem CreateTextFile filename  TRUE   set oEnv oShell Environment  System   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next path   oEnv  PATH    set oEnv oShell Environment  User   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next  path   path  amp       amp  oEnv  PATH   oFile WriteLine  SET PATH    amp  path  oFile Close   create another file name resetvars bat containing this code  same location    echo off   dp0resetvars vbs call   TEMP  resetvars bat    When you want to refresh the environment variables  just run resetvars bat    Apologetics   The two main problems I had coming up with this solution were  a  I couldn t find a straightforward way to export environment variables from a vbs script back to the command prompt  and   b  the PATH environment variable is a concatenation of the user and the system PATH variables   I m not sure what the general rule is for conflicting variables between user and system  so I elected to make user override system  except in the PATH variable which is handled specifically   I use the weird vbs bat temporary bat mechanism to work around the problem of exporting variables from vbs   Note  this script does not delete variables   This can probably be improved   ADDED  If you need to export the environment from one cmd window to another  use this script  let s call it exportvars vbs    Set oShell   WScript CreateObject  WScript Shell   filename   oShell ExpandEnvironmentStrings   TEMP  resetvars bat   Set objFileSystem   CreateObject  Scripting fileSystemObject   Set oFile   objFileSystem CreateTextFile filename  TRUE   set oEnv oShell Environment  Process   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next oFile Close   Run exportvars vbs in the window you want to export from  then switch to the window you want to export to  and type     TEMP  resetvars bat

User · Answer

I liked the approach followed by chocolatey  as posted in anonymous coward s answer  since it is a pure batch approach  However  it leaves a temporary file and some temporary variables lying around  I made a cleaner version for myself   Make a file refreshEnv bat somewhere on your PATH  Refresh your console environment by executing refreshEnv    ECHO OFF REM Source found on https   github com DieterDePaepe windows-scripts REM Please share any improvements made   REM Code inspired by http   stackoverflow com questions 171588 is-there-a-command-to-refresh-environment-variables-from-the-command-prompt-in-w  IF   1        GOTO  help IF   1     help  GOTO  help IF   1    --help  GOTO  help IF   1      GOTO  main  ECHO Unknown command   1 EXIT  b 1    help ECHO Refresh the environment variables in the console  ECHO  ECHO   refreshEnv       Refresh all environment variables  ECHO   refreshEnv           Display this help  GOTO  EOF   main REM Because the environment variables may refer to other variables  we need a 2-step approach  REM One option is to use delayed variable evaluation  but this forces use of SETLOCAL and REM may pose problems for files with an     in the name  REM The option used here is to create a temporary batch file that will define all the variables   REM Check to make sure we don t overwrite an actual file  IF EXIST  TEMP    refreshEnvironment bat     ECHO Environment refresh failed    ECHO    ECHO This script uses a temporary file   TEMP    refreshEnvironment bat   which already exists  The script was aborted in order to prevent accidental data loss  Delete this file to enable this script    EXIT  b 1    REM Read the system environment variables from the registry  FOR  F  usebackq tokens 1 2   skip 2    I IN   REG QUERY  HKLM SYSTEM CurrentControlSet Control Session Manager Environment    DO     REM  I - gt  ignore casing  since PATH may also be called Path   IF  I NOT    I    PATH        ECHO SET   I   K gt  gt  TEMP    refreshEnvironment bat        REM Read the user environment variables from the registry  FOR  F  usebackq tokens 1 2   skip 2    I IN   REG QUERY HKCU Environment   DO     REM  I - gt  ignore casing  since PATH may also be called Path   IF  I NOT    I    PATH        ECHO SET   I   K gt  gt  TEMP    refreshEnvironment bat        REM PATH is a special variable  it is automatically merged based on the values in the REM system and user variables  REM Read the PATH variable from the system and user environment variables  FOR  F  usebackq tokens 1 2   skip 2    I IN   REG QUERY  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   v PATH   DO     ECHO SET PATH   K gt  gt  TEMP    refreshEnvironment bat   FOR  F  usebackq tokens 1 2   skip 2    I IN   REG QUERY HKCU Environment  v PATH   DO     ECHO SET PATH   PATH     K gt  gt  TEMP    refreshEnvironment bat    REM Load the variable definitions from our temporary file  CALL  TEMP    refreshEnvironment bat  REM Clean up after ourselves  DEL  Q  TEMP    refreshEnvironment bat  ECHO Environment successfully refreshed

User · Answer

By design there isn t a built in mechanism for Windows to propagate an environment variable add change remove to an already running cmd exe  either from another cmd exe or from  My Computer -  Properties - Advanced Settings -  Environment Variables    If you modify or add a new environment variable outside of the scope of an existing open command prompt you either need to restart the command prompt  or  manually add using SET in the existing command prompt    The latest accepted answer shows a partial work-around by manually refreshing all the environment variables in a script  The script handles the use case of changing environment variables globally in  My Computer   Environment Variables   but if an environment variable is changed in one cmd exe the script will not propagate it to another running cmd exe

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I use the following code in my batch scripts   if not defined MY ENV VAR       setx MY ENV VAR  VALUE   gt  nul     set MY ENV VAR VALUE   echo  MY ENV VAR    By using SET after SETX it is possible to use the  local  variable directly without restarting the command window  And on the next run  the enviroment variable will be used

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To solve this I have changed the environment variable using BOTH setx and set  and then restarted all instances of explorer exe  This way any process subsequently started will have the new environment variable   My batch script to do this   setx  M ENVVAR  NEWVALUE  set ENVVAR  NEWVALUE   taskkill  f  IM explorer exe start explorer exe  gt nul exit   The problem with this approach is that all explorer windows that are currently opened will be closed  which is probably a bad idea - But see the post by Kev to learn why this is necessary

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Thank you for posting this question which is quite interesting  even in 2019  Indeed  it is not easy to renew the shell cmd since it is a single instance as mentioned above   because renewing environment variables in windows allows to accomplish many automation tasks without having to manually restart the command line    For example  we use this to allow software to be deployed and configured on a large number of machines that we reinstall regularly  And I must admit that having to restart the command line during the deployment of our software would be very impractical and would require us to find workarounds that are not necessarily pleasant   Let s get to our problem  We proceed as follows    1 - We have a batch script that in turn calls a powershell script like this    file  task cmd     cmd  gt  powershell exe -executionpolicy unrestricted -File C  path here refresh ps1  2 - After this  the refresh ps1 script renews the environment variables using registry keys  GetValueNames    etc     Then  in the same powershell script  we just have to call the new environment variables available  For example  in a typical case  if we have just installed nodeJS before with cmd using silent commands  after the function has been called  we can directly call npm to install  in the same session  particular packages like follows     file  refresh ps1   function Update-Environment        locations    HKLM  SYSTEM CurrentControlSet Control Session  Manager Environment                     HKCU  Environment       locations   ForEach-Object            k   Get-Item             k GetValueNames     ForEach-Object                name                    value    k GetValue                  if   userLocation -and  name -ieq  PATH                      env Path       value                else                    Set-Item -Path Env   name -Value  value                                  userLocation    true         Update-Environment  Here we can use newly added environment variables like for example npm install    npm install -g create-react-app serve   Once the powershell script is over  the cmd script goes on with other tasks  Now  one thing to keep in mind is that after the task is completed  cmd has still no access to the new environment variables  even if the powershell script has updated those in its own session  Thats why we do all the needed tasks in the powershell script which can call the same commands as cmd of course

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I came across this answer before eventually finding an easier solution    Simply restart explorer exe in Task Manager   I didn t test  but you may also need to reopen you command prompt   Credit to Timo Huovinen here  Node not recognized although successfully installed  if this helped you  please go give this man s comment credit

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Edit  this only works if the environment changes you re doing are as a result of running a batch file   If a batch file begins with SETLOCAL then it will always unravel back to your original environment on exit even if you forget to call ENDLOCAL before the batch exits  or if it aborts unexpectedly   Almost every batch file I write begins with SETLOCAL since in most cases I don t want the side-effects of environment changes to remain  In cases where I do want certain environment variable changes to propagate outside the batch file then my last ENDLOCAL looks like this   ENDLOCAL  amp      SET RESULT1  RESULT1    SET RESULT2  RESULT2

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Thank you for posting this question which is quite interesting  even in 2019  Indeed  it is not easy to renew the shell cmd since it is a single instance as mentioned above   because renewing environment variables in windows allows to accomplish many automation tasks without having to manually restart the command line    For example  we use this to allow software to be deployed and configured on a large number of machines that we reinstall regularly  And I must admit that having to restart the command line during the deployment of our software would be very impractical and would require us to find workarounds that are not necessarily pleasant   Let s get to our problem  We proceed as follows    1 - We have a batch script that in turn calls a powershell script like this    file  task cmd     cmd  gt  powershell exe -executionpolicy unrestricted -File C  path here refresh ps1  2 - After this  the refresh ps1 script renews the environment variables using registry keys  GetValueNames    etc     Then  in the same powershell script  we just have to call the new environment variables available  For example  in a typical case  if we have just installed nodeJS before with cmd using silent commands  after the function has been called  we can directly call npm to install  in the same session  particular packages like follows     file  refresh ps1   function Update-Environment        locations    HKLM  SYSTEM CurrentControlSet Control Session  Manager Environment                     HKCU  Environment       locations   ForEach-Object            k   Get-Item             k GetValueNames     ForEach-Object                name                    value    k GetValue                  if   userLocation -and  name -ieq  PATH                      env Path       value                else                    Set-Item -Path Env   name -Value  value                                  userLocation    true         Update-Environment  Here we can use newly added environment variables like for example npm install    npm install -g create-react-app serve   Once the powershell script is over  the cmd script goes on with other tasks  Now  one thing to keep in mind is that after the task is completed  cmd has still no access to the new environment variables  even if the powershell script has updated those in its own session  Thats why we do all the needed tasks in the powershell script which can call the same commands as cmd of course

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The solution I ve been using for a few years now    echo off rem Refresh PATH from registry  setlocal set USR PATH  set SYS PATH  for  F  tokens 3  skip 2    P in    SystemRoot  system32 reg exe query  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   v PATH   do  set  SYS PATH   P   Q  for  F  tokens 3  skip 2    P in    SystemRoot  system32 reg exe query  HKCU Environment   v PATH   do  set  USR PATH   P   Q  if   SYS PATH  -1        set  SYS PATH  SYS PATH  0 -1   if   USR PATH  -1        set  USR PATH  USR PATH  0 -1   endlocal  amp  call set  PATH  SYS PATH   USR PATH   goto  EOF   Edit  Woops  here s the updated version

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This works on windows 7  SET PATH  PATH  C  CmdShortcuts  tested by typing echo  PATH  and it worked  fine  also set if you open a new cmd  no need for those pesky reboots any more

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The confusing thing might be that there are a few places to start the cmd from  In my case I ran cmd from windows explorer and the environment variables did not change while when starting cmd from the  run   windows key   r  the environment variables were changed   In my case I just had to kill the windows explorer process from the task manager and then restart it again from the task manager   Once I did this I had access to the new environment variable from a cmd that was spawned from windows explorer

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I liked the approach followed by chocolatey  as posted in anonymous coward s answer  since it is a pure batch approach  However  it leaves a temporary file and some temporary variables lying around  I made a cleaner version for myself   Make a file refreshEnv bat somewhere on your PATH  Refresh your console environment by executing refreshEnv    ECHO OFF REM Source found on https   github com DieterDePaepe windows-scripts REM Please share any improvements made   REM Code inspired by http   stackoverflow com questions 171588 is-there-a-command-to-refresh-environment-variables-from-the-command-prompt-in-w  IF   1        GOTO  help IF   1     help  GOTO  help IF   1    --help  GOTO  help IF   1      GOTO  main  ECHO Unknown command   1 EXIT  b 1    help ECHO Refresh the environment variables in the console  ECHO  ECHO   refreshEnv       Refresh all environment variables  ECHO   refreshEnv           Display this help  GOTO  EOF   main REM Because the environment variables may refer to other variables  we need a 2-step approach  REM One option is to use delayed variable evaluation  but this forces use of SETLOCAL and REM may pose problems for files with an     in the name  REM The option used here is to create a temporary batch file that will define all the variables   REM Check to make sure we don t overwrite an actual file  IF EXIST  TEMP    refreshEnvironment bat     ECHO Environment refresh failed    ECHO    ECHO This script uses a temporary file   TEMP    refreshEnvironment bat   which already exists  The script was aborted in order to prevent accidental data loss  Delete this file to enable this script    EXIT  b 1    REM Read the system environment variables from the registry  FOR  F  usebackq tokens 1 2   skip 2    I IN   REG QUERY  HKLM SYSTEM CurrentControlSet Control Session Manager Environment    DO     REM  I - gt  ignore casing  since PATH may also be called Path   IF  I NOT    I    PATH        ECHO SET   I   K gt  gt  TEMP    refreshEnvironment bat        REM Read the user environment variables from the registry  FOR  F  usebackq tokens 1 2   skip 2    I IN   REG QUERY HKCU Environment   DO     REM  I - gt  ignore casing  since PATH may also be called Path   IF  I NOT    I    PATH        ECHO SET   I   K gt  gt  TEMP    refreshEnvironment bat        REM PATH is a special variable  it is automatically merged based on the values in the REM system and user variables  REM Read the PATH variable from the system and user environment variables  FOR  F  usebackq tokens 1 2   skip 2    I IN   REG QUERY  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   v PATH   DO     ECHO SET PATH   K gt  gt  TEMP    refreshEnvironment bat   FOR  F  usebackq tokens 1 2   skip 2    I IN   REG QUERY HKCU Environment  v PATH   DO     ECHO SET PATH   PATH     K gt  gt  TEMP    refreshEnvironment bat    REM Load the variable definitions from our temporary file  CALL  TEMP    refreshEnvironment bat  REM Clean up after ourselves  DEL  Q  TEMP    refreshEnvironment bat  ECHO Environment successfully refreshed

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The solution I ve been using for a few years now    echo off rem Refresh PATH from registry  setlocal set USR PATH  set SYS PATH  for  F  tokens 3  skip 2    P in    SystemRoot  system32 reg exe query  HKLM SYSTEM CurrentControlSet Control Session Manager Environment   v PATH   do  set  SYS PATH   P   Q  for  F  tokens 3  skip 2    P in    SystemRoot  system32 reg exe query  HKCU Environment   v PATH   do  set  USR PATH   P   Q  if   SYS PATH  -1        set  SYS PATH  SYS PATH  0 -1   if   USR PATH  -1        set  USR PATH  USR PATH  0 -1   endlocal  amp  call set  PATH  SYS PATH   USR PATH   goto  EOF   Edit  Woops  here s the updated version

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There is no straight way  as Kev said  In most cases  it is simpler to spawn another CMD box  More annoyingly  running programs are not aware of changes either  although IIRC there might be a broadcast message to watch to be notified of such change    It have been worse  in older versions of Windows  you had to log off then log back to take in account the changes

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Restarting explorer did this for me  but only for new cmd terminals    The terminal I set the path could see the new Path variable already  in Windows 7    taskkill  f  im explorer exe  amp  amp  explorer exe

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I use this Powershell script to add to the PATH variable  With a little adjustment it can work in your case too I believe    REQUIRES -Version 3 0  if  -not   win32 nativemethods  -as  type            import sendmessagetimeout from win32     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  function global ADD-PATH        Cmdletbinding        param             parameter Mandatory  True  ValueFromPipeline  True  Position 0             string   Folder              See if a folder variable has been supplied      if    Folder -or  Folder -eq    -or  Folder -eq  null             throw  No Folder Supplied   ENV PATH Unchanged               Get the current search path from the environment keys in the registry       oldPath   Get-ItemProperty -Path  Registry  HKEY LOCAL MACHINE System CurrentControlSet Control Session Manager Environment  -Name PATH  Path        See if the new Folder is already in the path      if   oldPath   Select-String -SimpleMatch  Folder            return  Folder already within  ENV PATH                Set the New Path and add the   in front      newPath  oldPath      Folder     Set-ItemProperty -Path  Registry  HKEY LOCAL MACHINE System CurrentControlSet Control Session Manager Environment  -Name PATH -Value  newPath -ErrorAction Stop        Show our results back to the world     return  This is the new PATH content     newPath        notify all windows of environment block change      win32 nativemethods   SendMessageTimeout  HWND BROADCAST   WM SETTINGCHANGE   uintptr   Zero   Environment   2  5000   ref  result     function global REMOVE-PATH        Cmdletbinding        param             parameter Mandatory  True  ValueFromPipeline  True  Position 0            String   Folder              See if a folder variable has been supplied      if    Folder -or  Folder -eq    -or  Folder -eq  NULL             throw  No Folder Supplied   ENV PATH Unchanged               add a leading     if missing     if   Folder 0  -ne                 Folder          Folder               Get the Current Search Path from the environment keys in the registry      newPath   Get-ItemProperty -Path  Registry  HKEY LOCAL MACHINE System CurrentControlSet Control Session Manager Environment  -Name PATH  Path        Find the value to remove  replace it with  NULL  If it s not found  nothing will change and you get a message      if   newPath -match  regex   Escape  Folder               newPath  newPath -replace  regex   Escape  Folder   NULL        else            return  The folder you mentioned does not exist in the PATH environment                Update the Environment Path     Set-ItemProperty -Path  Registry  HKEY LOCAL MACHINE System CurrentControlSet Control Session Manager Environment  -Name PATH -Value  newPath -ErrorAction Stop        Show what we just did     return  This is the new PATH content     newPath        notify all windows of environment block change      win32 nativemethods   SendMessageTimeout  HWND BROADCAST   WM SETTINGCHANGE   uintptr   Zero   Environment   2  5000   ref  result        Use ADD-PATH or REMOVE-PATH accordingly    Anything to Add    Anything to Remove   REMOVE-PATH    installpath bin

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You can capture the system environment variables with a vbs script  but you need a bat script to actually change the current environment variables  so this is a combined solution   Create a file named resetvars vbs containing this code  and save it on the path     Set oShell   WScript CreateObject  WScript Shell   filename   oShell ExpandEnvironmentStrings   TEMP  resetvars bat   Set objFileSystem   CreateObject  Scripting fileSystemObject   Set oFile   objFileSystem CreateTextFile filename  TRUE   set oEnv oShell Environment  System   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next path   oEnv  PATH    set oEnv oShell Environment  User   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next  path   path  amp       amp  oEnv  PATH   oFile WriteLine  SET PATH    amp  path  oFile Close   create another file name resetvars bat containing this code  same location    echo off   dp0resetvars vbs call   TEMP  resetvars bat    When you want to refresh the environment variables  just run resetvars bat    Apologetics   The two main problems I had coming up with this solution were  a  I couldn t find a straightforward way to export environment variables from a vbs script back to the command prompt  and   b  the PATH environment variable is a concatenation of the user and the system PATH variables   I m not sure what the general rule is for conflicting variables between user and system  so I elected to make user override system  except in the PATH variable which is handled specifically   I use the weird vbs bat temporary bat mechanism to work around the problem of exporting variables from vbs   Note  this script does not delete variables   This can probably be improved   ADDED  If you need to export the environment from one cmd window to another  use this script  let s call it exportvars vbs    Set oShell   WScript CreateObject  WScript Shell   filename   oShell ExpandEnvironmentStrings   TEMP  resetvars bat   Set objFileSystem   CreateObject  Scripting fileSystemObject   Set oFile   objFileSystem CreateTextFile filename  TRUE   set oEnv oShell Environment  Process   for each sitem in oEnv      oFile WriteLine  SET    amp  sitem  next oFile Close   Run exportvars vbs in the window you want to export from  then switch to the window you want to export to  and type     TEMP  resetvars bat

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By design there isn t a built in mechanism for Windows to propagate an environment variable add change remove to an already running cmd exe  either from another cmd exe or from  My Computer -  Properties - Advanced Settings -  Environment Variables    If you modify or add a new environment variable outside of the scope of an existing open command prompt you either need to restart the command prompt  or  manually add using SET in the existing command prompt    The latest accepted answer shows a partial work-around by manually refreshing all the environment variables in a script  The script handles the use case of changing environment variables globally in  My Computer   Environment Variables   but if an environment variable is changed in one cmd exe the script will not propagate it to another running cmd exe

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There is no straight way  as Kev said  In most cases  it is simpler to spawn another CMD box  More annoyingly  running programs are not aware of changes either  although IIRC there might be a broadcast message to watch to be notified of such change    It have been worse  in older versions of Windows  you had to log off then log back to take in account the changes

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On Windows 7 8 10  you can install Chocolatey  which has a script for this built-in   After installing Chocolatey  just type refreshenv

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Here is what Chocolatey uses  https   github com chocolatey choco blob master src chocolatey resources redirects RefreshEnv cmd  echo off       RefreshEnv cmd       Batch file to read environment variables from registry and    set session variables to these values        With this batch file  there should be no need to reload command    environment every time you want environment changes to propagate    echo  quot RefreshEnv cmd only works from cmd exe  please install the Chocolatey Profile to take advantage of refreshenv from PowerShell quot  echo   set  p dummy  quot Refreshing environment variables from registry for cmd exe  Please wait    quot   goto main     Set one environment variable from registry key  SetFromReg      quot  WinDir  System32 Reg quot  QUERY  quot   1 quot   v  quot   2 quot   gt   quot  TEMP   envset tmp quot  2 gt NUL     for  f  quot usebackq skip 2 tokens 2   quot    A IN   quot  TEMP   envset tmp quot   do           echo set  quot   3   B quot            goto  EOF     Get a list of environment variables from registry  GetRegEnv      quot  WinDir  System32 Reg quot  QUERY  quot   1 quot   gt   quot  TEMP   envget tmp quot      for  f  quot usebackq skip 2 quot    A IN   quot  TEMP   envget tmp quot   do           if  I not  quot    A quot    quot Path quot                call  SetFromReg  quot   1 quot   quot    A quot   quot    A quot                      goto  EOF   main     echo  echo off  gt  quot  TEMP   env cmd quot          Slowly generating final file     call  GetRegEnv  quot HKLM System CurrentControlSet Control Session Manager Environment quot   gt  gt   quot  TEMP   env cmd quot      call  GetRegEnv  quot HKCU Environment quot  gt  gt  quot  TEMP   env cmd quot   gt  gt   quot  TEMP   env cmd quot          Special handling for PATH - mix both User and System     call  SetFromReg  quot HKLM System CurrentControlSet Control Session Manager Environment quot  Path Path HKLM  gt  gt   quot  TEMP   env cmd quot      call  SetFromReg  quot HKCU Environment quot  Path Path HKCU  gt  gt   quot  TEMP   env cmd quot          Caution  do not insert space-chars before  gt  gt  redirection sign     echo set  quot Path   Path HKLM     Path HKCU   quot   gt  gt   quot  TEMP   env cmd quot          Cleanup     del  f  q  quot  TEMP   envset tmp quot  2 gt nul     del  f  q  quot  TEMP   envget tmp quot  2 gt nul         capture user   architecture     SET  quot OriginalUserName  USERNAME  quot      SET  quot OriginalArchitecture  PROCESSOR ARCHITECTURE  quot          Set these variables     call  quot  TEMP   env cmd quot          Cleanup     del  f  q  quot  TEMP   env cmd quot  2 gt nul         reset user   architecture     SET  quot USERNAME  OriginalUserName  quot      SET  quot PROCESSOR ARCHITECTURE  OriginalArchitecture  quot       echo   set  p dummy  quot Finished  quot      echo

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It is possible to do this by overwriting the Environment Table within a specified process itself   As a proof of concept I wrote this sample app  which just edited a single  known  environment variable in a cmd exe process   typedef DWORD    stdcall  NtQueryInformationProcessPtr  HANDLE  DWORD  PVOID  ULONG  PULONG    int   cdecl main int argc  char  argv          HMODULE hNtDll   GetModuleHandleA  ntdll dll        NtQueryInformationProcessPtr NtQueryInformationProcess    NtQueryInformationProcessPtr GetProcAddress hNtDll   NtQueryInformationProcess         int processId   atoi argv 1        printf  Target PID   u n   processId           open the process with read write access     HANDLE hProcess   OpenProcess PROCESS QUERY LIMITED INFORMATION   PROCESS VM READ   PROCESS VM WRITE   PROCESS VM OPERATION  0  processId       if hProcess    NULL                printf  Error opening process   u  n   GetLastError             return 0                find the location of the PEB     PROCESS BASIC INFORMATION pbi    0       NTSTATUS status   NtQueryInformationProcess hProcess  ProcessBasicInformation   amp pbi  sizeof pbi   NULL       if status    0                printf  Error ProcessBasicInformation  0x 8X  n   status             printf  PEB   p n   pbi PebBaseAddress           find the process parameters     char  processParamsOffset    char  pbi PebBaseAddress   0x20     hard coded offset for x64 apps     char  processParameters   NULL      if ReadProcessMemory hProcess  processParamsOffset   amp processParameters  sizeof processParameters   NULL                 printf  UserProcessParameters   p n   processParameters             else               printf  Error ReadProcessMemory   u  n   GetLastError                   find the address to the environment table     char  environmentOffset   processParameters   0x80     hard coded offset for x64 apps     char  environment   NULL      ReadProcessMemory hProcess  environmentOffset   amp environment  sizeof environment   NULL       printf  environment   p n   environment           copy the environment table into our own memory for scanning     wchar t  localEnvBlock   new wchar t 64 1024       ReadProcessMemory hProcess  environment  localEnvBlock  sizeof wchar t  64 1024  NULL           find the variable to edit     wchar t  found   NULL      wchar t  varOffset   localEnvBlock      while varOffset  lt  localEnvBlock   64 1024                if varOffset 0       0                            we reached the end             break                    if wcsncmp varOffset  L ENVTEST    8     0                        found   varOffset              break                    varOffset    wcslen varOffset  1                check to see if we found one     if found                size t offset    found - localEnvBlock    sizeof wchar t           printf  Offset   Iu n   offset               write a new version  if the size of the value changes then we have to rewrite the entire block          if  WriteProcessMemory hProcess  environment   offset  L ENVTEST def   12 sizeof wchar t   NULL                         printf  Error WriteProcessMemory   u  n   GetLastError                             cleanup     delete   localEnvBlock      CloseHandle hProcess        return 0      Sample output    gt set ENVTEST abc   gt cppTest exe 13796 Target PID  13796 PEB  000007FFFFFD3000 UserProcessParameters  00000000004B2F30 environment  000000000052E700 Offset  1528   gt set ENVTEST ENVTEST def   Notes  This approach would also be limited to security restrictions  If the target is run at higher elevation or a higher account  such as SYSTEM  then we wouldn t have permission to edit its memory   If you wanted to do this to a 32-bit app  the hard coded offsets above would change to 0x10 and 0x48 respectively  These offsets can be found by dumping out the  PEB and  RTL USER PROCESS PARAMETERS structs in a debugger  e g  in WinDbg dt  PEB and dt  RTL USER PROCESS PARAMETERS   To change the proof-of-concept into a what the OP needs  it would just enumerate the current system and user environment variables  such as documented by  tsadok s answer  and write the entire environment table into the target process  memory   Edit  The size of the environment block is also stored in the  RTL USER PROCESS PARAMETERS struct  but the memory is allocated on the process  heap  So from an external process we wouldn t have the ability to resize it and make it larger  I played around with using VirtualAllocEx to allocate additional memory in the target process for the environment storage  and was able to set and read an entirely new table  Unfortunately any attempt to modify the environment from normal means will crash and burn as the address no longer points to the heap  it will crash in RtlSizeHeap

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If it concerns just one  or a few  specific vars you want to change  I think the easiest way is a workaround  just set in in your environment AND in your current console session   Set will put the var in your current session SetX will put the var in the environment  but NOT in your current session   I have this simple batch script to change my Maven from Java7 to Java8  which are both env  vars  The batch-folder is in my PATH var so I can always call  j8  and within my console and in the environment my JAVA HOME var gets changed   j8 bat    echo off set JAVA HOME  JAVA HOME 8  setx JAVA HOME   JAVA HOME 8     Till now I find this working best and easiest   You probably want this to be in one command  but it simply isn t there in Windows

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The easiest way to add a variable to the path without rebooting for the current session is to open the command prompt and type    PATH  VARIABLE   path    and press enter    to check if your variable loaded  type   PATH   and press enter  However  the variable will only be a part of the path until you reboot

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Use  setx  and restart cmd prompt  There is a command line tool named  setx  for this job  It s for reading and writing env variables  The variables persist after the command window has been closed   It  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    Note  variables created or modified by this tool will be available in future command windows but not in the current CMD exe command window  So  you have to restart   If setx is missing     http   download microsoft com download win2000platform setx 1 00 0 1 nt5 en-us setx setup exe     Or modify the registry  MSDN says       To programmatically add or modify system environment variables  add   them to the   HKEY LOCAL MACHINE System CurrentControlSet Control Session   Manager Environment registry key  then broadcast a WM SETTINGCHANGE   message with lParam set to the string  Environment         This allows applications  such as the shell  to pick up your updates

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The confusing thing might be that there are a few places to start the cmd from  In my case I ran cmd from windows explorer and the environment variables did not change while when starting cmd from the  run   windows key   r  the environment variables were changed   In my case I just had to kill the windows explorer process from the task manager and then restart it again from the task manager   Once I did this I had access to the new environment variable from a cmd that was spawned from windows explorer

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By design there isn t a built in mechanism for Windows to propagate an environment variable add change remove to an already running cmd exe  either from another cmd exe or from  My Computer -  Properties - Advanced Settings -  Environment Variables    If you modify or add a new environment variable outside of the scope of an existing open command prompt you either need to restart the command prompt  or  manually add using SET in the existing command prompt    The latest accepted answer shows a partial work-around by manually refreshing all the environment variables in a script  The script handles the use case of changing environment variables globally in  My Computer   Environment Variables   but if an environment variable is changed in one cmd exe the script will not propagate it to another running cmd exe

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To solve this I have changed the environment variable using BOTH setx and set  and then restarted all instances of explorer exe  This way any process subsequently started will have the new environment variable   My batch script to do this   setx  M ENVVAR  NEWVALUE  set ENVVAR  NEWVALUE   taskkill  f  IM explorer exe start explorer exe  gt nul exit   The problem with this approach is that all explorer windows that are currently opened will be closed  which is probably a bad idea - But see the post by Kev to learn why this is necessary

User · Answer

Restarting explorer did this for me  but only for new cmd terminals    The terminal I set the path could see the new Path variable already  in Windows 7    taskkill  f  im explorer exe  amp  amp  explorer exe

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I use the following code in my batch scripts   if not defined MY ENV VAR       setx MY ENV VAR  VALUE   gt  nul     set MY ENV VAR VALUE   echo  MY ENV VAR    By using SET after SETX it is possible to use the  local  variable directly without restarting the command window  And on the next run  the enviroment variable will be used

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Environment variables are kept in HKEY LOCAL MACHINE SYSTEM ControlSet Control Session Manager Environment   Many of the useful env vars  such as Path  are stored as REG SZ   There are several ways to access the registry including REGEDIT   REGEDIT  E  amp lt filename amp gt   HKEY LOCAL MACHINE SYSTEM ControlSet001 Control Session Manager Environment   The output starts with magic numbers   So to search it with the find command it needs to be typed and redirected  type  lt filename gt    findstr -c   Path    So  if you just want to refresh the path variable in your current command session with what s in system properties the following batch script works fine   RefreshPath cmd          echo off      REM This solution requests elevation in order to read from the registry       if exist  temp  env reg del  temp  env reg  q  f      REGEDIT  E  temp  env reg  HKEY LOCAL MACHINE SYSTEM ControlSet001 Control Session Manager Environment       if not exist  temp  env reg          echo  Unable to write registry to temp location         exit 1               SETLOCAL EnableDelayedExpansion      for  f  tokens 1 2  delims      i in   type  temp  env reg    findstr -c   Path      do          set upath    j        echo  upath         temp  newpath                ENDLOCAL       for  f  tokens      i in   temp  newpath  do set path   i

User · Answer

This works on windows 7  SET PATH  PATH  C  CmdShortcuts  tested by typing echo  PATH  and it worked  fine  also set if you open a new cmd  no need for those pesky reboots any more

User · Answer

By design there isn t a built in mechanism for Windows to propagate an environment variable add change remove to an already running cmd exe  either from another cmd exe or from  My Computer -  Properties - Advanced Settings -  Environment Variables    If you modify or add a new environment variable outside of the scope of an existing open command prompt you either need to restart the command prompt  or  manually add using SET in the existing command prompt    The latest accepted answer shows a partial work-around by manually refreshing all the environment variables in a script  The script handles the use case of changing environment variables globally in  My Computer   Environment Variables   but if an environment variable is changed in one cmd exe the script will not propagate it to another running cmd exe

[windows] Is there a command to refresh environment variables from the command prompt in Windows?

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