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?
This question is related to
windows
cmd
environment-variables
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 > 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.
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.
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 > 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.
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 & (
SET RESULT1=%RESULT1%
SET RESULT2=%RESULT2%
)
I use the following code in my batch scripts:
if not defined MY_ENV_VAR (
setx MY_ENV_VAR "VALUE" > 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.
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:
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.
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 & call set "PATH=%SYS_PATH%;%USR_PATH%"
goto :EOF
Edit: Woops, here's the updated version.
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, &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, &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, &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 < 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:
>set ENVTEST=abc
>cppTest.exe 13796
Target PID: 13796
PEB: 000007FFFFFD3000
UserProcessParameters: 00000000004B2F30
environment: 000000000052E700
Offset: 1528
>set ENVTEST
ENVTEST=def
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).
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).
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%"
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 && explorer.exe
I use the following code in my batch scripts:
if not defined MY_ENV_VAR (
setx MY_ENV_VAR "VALUE" > 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.
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...
Calling this function has worked for me:
VOID Win32ForceSettingsChange()
{
DWORD dwReturnValue;
::SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0, (LPARAM) "Environment", SMTO_ABORTIFHUNG, 5000, &dwReturnValue);
}
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.
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).
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 <filename> "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 <filename> | 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
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.
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 && explorer.exe
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
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...
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.
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).
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:
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.
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...
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.
On Windows 7/8/10, you can install Chocolatey, which has a script for this built-in.
After installing Chocolatey, just type refreshenv.
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 "RefreshEnv.cmd only works from cmd.exe, please install the Chocolatey Profile to take advantage of refreshenv from PowerShell"
echo | set /p dummy="Refreshing environment variables from registry for cmd.exe. Please wait..."
goto main
:: Set one environment variable from registry key
:SetFromReg
"%WinDir%\System32\Reg" QUERY "%~1" /v "%~2" > "%TEMP%\_envset.tmp" 2>NUL
for /f "usebackq skip=2 tokens=2,*" %%A IN ("%TEMP%\_envset.tmp") do (
echo/set "%~3=%%B"
)
goto :EOF
:: Get a list of environment variables from registry
:GetRegEnv
"%WinDir%\System32\Reg" QUERY "%~1" > "%TEMP%\_envget.tmp"
for /f "usebackq skip=2" %%A IN ("%TEMP%\_envget.tmp") do (
if /I not "%%~A"=="Path" (
call :SetFromReg "%~1" "%%~A" "%%~A"
)
)
goto :EOF
:main
echo/@echo off >"%TEMP%\_env.cmd"
:: Slowly generating final file
call :GetRegEnv "HKLM\System\CurrentControlSet\Control\Session Manager\Environment" >> "%TEMP%\_env.cmd"
call :GetRegEnv "HKCU\Environment">>"%TEMP%\_env.cmd" >> "%TEMP%\_env.cmd"
:: Special handling for PATH - mix both User and System
call :SetFromReg "HKLM\System\CurrentControlSet\Control\Session Manager\Environment" Path Path_HKLM >> "%TEMP%\_env.cmd"
call :SetFromReg "HKCU\Environment" Path Path_HKCU >> "%TEMP%\_env.cmd"
:: Caution: do not insert space-chars before >> redirection sign
echo/set "Path=%%Path_HKLM%%;%%Path_HKCU%%" >> "%TEMP%\_env.cmd"
:: Cleanup
del /f /q "%TEMP%\_envset.tmp" 2>nul
del /f /q "%TEMP%\_envget.tmp" 2>nul
:: capture user / architecture
SET "OriginalUserName=%USERNAME%"
SET "OriginalArchitecture=%PROCESSOR_ARCHITECTURE%"
:: Set these variables
call "%TEMP%\_env.cmd"
:: Cleanup
del /f /q "%TEMP%\_env.cmd" 2>nul
:: reset user / architecture
SET "USERNAME=%OriginalUserName%"
SET "PROCESSOR_ARCHITECTURE=%OriginalArchitecture%"
echo | set /p dummy="Finished."
echo .
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%"
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.
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 >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
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 & call set "PATH=%SYS_PATH%;%USR_PATH%"
goto :EOF
Edit: Woops, here's the updated version.
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 -> ignore casing, since PATH may also be called Path
IF /I NOT [%%I]==[PATH] (
ECHO SET %%I=%%K>>%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 -> ignore casing, since PATH may also be called Path
IF /I NOT [%%I]==[PATH] (
ECHO SET %%I=%%K>>%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>>%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>>%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.
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 :)
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.
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.
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 -> ignore casing, since PATH may also be called Path
IF /I NOT [%%I]==[PATH] (
ECHO SET %%I=%%K>>%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 -> ignore casing, since PATH may also be called Path
IF /I NOT [%%I]==[PATH] (
ECHO SET %%I=%%K>>%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>>%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>>%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.
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).
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
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...
On Windows 7/8/10, you can install Chocolatey, which has a script for this built-in.
After installing Chocolatey, just type refreshenv.
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 :)
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 >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
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>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^>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
Calling this function has worked for me:
VOID Win32ForceSettingsChange()
{
DWORD dwReturnValue;
::SendMessageTimeout(HWND_BROADCAST, WM_SETTINGCHANGE, 0, (LPARAM) "Environment", SMTO_ABORTIFHUNG, 5000, &dwReturnValue);
}
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, &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, &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, &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 < 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:
>set ENVTEST=abc
>cppTest.exe 13796
Target PID: 13796
PEB: 000007FFFFFD3000
UserProcessParameters: 00000000004B2F30
environment: 000000000052E700
Offset: 1528
>set ENVTEST
ENVTEST=def
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).
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>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^>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
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 "RefreshEnv.cmd only works from cmd.exe, please install the Chocolatey Profile to take advantage of refreshenv from PowerShell"
echo | set /p dummy="Refreshing environment variables from registry for cmd.exe. Please wait..."
goto main
:: Set one environment variable from registry key
:SetFromReg
"%WinDir%\System32\Reg" QUERY "%~1" /v "%~2" > "%TEMP%\_envset.tmp" 2>NUL
for /f "usebackq skip=2 tokens=2,*" %%A IN ("%TEMP%\_envset.tmp") do (
echo/set "%~3=%%B"
)
goto :EOF
:: Get a list of environment variables from registry
:GetRegEnv
"%WinDir%\System32\Reg" QUERY "%~1" > "%TEMP%\_envget.tmp"
for /f "usebackq skip=2" %%A IN ("%TEMP%\_envget.tmp") do (
if /I not "%%~A"=="Path" (
call :SetFromReg "%~1" "%%~A" "%%~A"
)
)
goto :EOF
:main
echo/@echo off >"%TEMP%\_env.cmd"
:: Slowly generating final file
call :GetRegEnv "HKLM\System\CurrentControlSet\Control\Session Manager\Environment" >> "%TEMP%\_env.cmd"
call :GetRegEnv "HKCU\Environment">>"%TEMP%\_env.cmd" >> "%TEMP%\_env.cmd"
:: Special handling for PATH - mix both User and System
call :SetFromReg "HKLM\System\CurrentControlSet\Control\Session Manager\Environment" Path Path_HKLM >> "%TEMP%\_env.cmd"
call :SetFromReg "HKCU\Environment" Path Path_HKCU >> "%TEMP%\_env.cmd"
:: Caution: do not insert space-chars before >> redirection sign
echo/set "Path=%%Path_HKLM%%;%%Path_HKCU%%" >> "%TEMP%\_env.cmd"
:: Cleanup
del /f /q "%TEMP%\_envset.tmp" 2>nul
del /f /q "%TEMP%\_envget.tmp" 2>nul
:: capture user / architecture
SET "OriginalUserName=%USERNAME%"
SET "OriginalArchitecture=%PROCESSOR_ARCHITECTURE%"
:: Set these variables
call "%TEMP%\_env.cmd"
:: Cleanup
del /f /q "%TEMP%\_env.cmd" 2>nul
:: reset user / architecture
SET "USERNAME=%OriginalUserName%"
SET "PROCESSOR_ARCHITECTURE=%OriginalArchitecture%"
echo | set /p dummy="Finished."
echo .
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 & (
SET RESULT1=%RESULT1%
SET RESULT2=%RESULT2%
)
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...
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 <filename> "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 <filename> | 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
Source: Stackoverflow.com