How can I update the PATH variable permanently from the Windows command line?

Question

If I execute set PATH=%PATH%;C:\\Something\\bin from the command line (cmd.exe) and then execute echo %PATH%, I see this string added to the PATH. If I close and open the command line, that new string is not in PATH.

How can I update PATH permanently from the command line for all processes in the future, not just for the current process?

I don't want to do this by going to System Properties → Advanced → Environment variables and update PATH there.

This command must be executed from a Java application (please see my other question).

• Austen Holmes: Using powershell, it's fairly straightfoward stackoverflow.com/questions/714877/…. Using cmd, I'm not sure. You may have to modify the registry or pull in a .net assembly somehow.
• vale4674: As I said, I have to do this from within java application. I thought just to execute some cmd command useng java's Runtime.getRuntime().exec("my command");
• Dave Jarvis: Does this answer your question? Adding a directory to the PATH environment variable in Windows
• Karl Knechtel: This does not become a Java question simply because OP wanted to execute the command from within a Java application. It's purely OS-level functionality; and "how do I execute a DOS command from Java?" is a separate and orthogonal question (i.e., running the command from Java doesn't depend on what the command is, and figuring out the command doesn't depend on the fact that it will be executed programmatically, nor on what language would be used).
• Melanie Shebel: Add to PATH > youtu.be/rWVaxSWvxUQ then close the console window and reopen it. Does that answer your question?

Answer 1

You can use:

setx PATH "%PATH%;C:\\Something\\bin"

However, setx will truncate the stored string to 1024 bytes, potentially corrupting the PATH.

/M will change the PATH in HKEY_LOCAL_MACHINE instead of HKEY_CURRENT_USER. In other words, a system variable, instead of the user's. For example:

SETX /M PATH "%PATH%;C:\your path with spaces"

You have to keep in mind, the new PATH is not visible in your current cmd.exe.

But if you look in the registry or on a new cmd.exe with "set p" you can see the new value.

• Corey Ogburn: Is there a way to use setx to change the machine's path instead of the user's path?
• panny: From here you can tell it might be possible to set a variable not only for the currently logged in user but for the machine by using /m at the end of the command, on windows xp and 7. I haven't tried it though.
• Nam G VU: I got the error when running setx command "Default option is not allowed more than '2' time" How to bypass it?
• beresfordt: @KilgoreCod comments: I caution against using the command: On many (most?) installations these days the PATH variable will be lengthy - setx will truncate the stored string to 1024 bytes, potentially corrupting the PATH (see the discussion here superuser.com/q/812754).
• Laurence: I try to echo out the path it's already over 1200bytes. any other way instead of setx?

Answer 2

The documentation on how to do this can be found on MSDN. The key extract is this:

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.

Note that your application will need elevated admin rights in order to be able to modify this key.

You indicate in the comments that you would be happy to modify just the per-user environment. Do this by editing the values in HKEY_CURRENT_USER\Environment. As before, make sure that you broadcast a WM_SETTINGCHANGE message.

You should be able to do this from your Java application easily enough using the JNI registry classes.

• David Heffernan: Yes, using the JNI registry classes. A bigger issue is that your app probably doesn't run elevated. Do you know how to make it do that? If you only want a small portion of your app to run elevated (i.e. just to do this change) then the simplest solution is a very simple C++ app to do the job, marked with the app manifest, and then executed as a separate process which provokes the UAC dialog.
• kichik: You can also edit HKEY_CURRENT_USER\Environment to avoid elevation requirement.
• vale4674: @David Heffernan Yes only this thing has to run elevated. So your suggestion is to write C++ application and execute it from my java application? Can you provide me some example code or link on how to do this?
• kichik: Yep. Just like David said. Only you don't elevation. I should also mention this will modify the environment for the current user only.
• David Heffernan: You need to separate this into a separate process so that you only force a UAC dialog when modifying system PATH. It just needs a simple C++ app with a few registry reads and writes, followed by a SendMessage. Set the requestedExecutionLevel to requireAdministrator in the app manifest.

Answer 3

I caution against using the command

setx PATH "%PATH%;C:\Something\bin"

to modify the PATH variable because of a "feature" of its implementation. On many (most?) installations these days the variable will be lengthy - setx will truncate the stored string to 1024 bytes, potentially corrupting the PATH (see the discussion here).

• Mofi: ATTENTION: Do not use this command line! It is a NO GO - NEVER EVER using setx with %PATH% to modify persistent stored user or system environment variable PATH. That results always in a PATH corruption by duplicating folder paths, replacing environment variable references by their expanded forms and perhaps a truncation of existing PATH variable with folder path to add not added at all. For more details see: What is the best practice for adding a directory to the PATH environment variable on Windows?

Answer 4

This Python-script[*] does exactly that:

"""
Show/Modify/Append registry env-vars (ie `PATH`) and notify Windows-applications to pickup changes.
First attempts to show/modify HKEY_LOCAL_MACHINE (all users), and
if not accessible due to admin-rights missing, fails-back
to HKEY_CURRENT_USER.
Write and Delete operations do not proceed to user-tree if all-users succeed.
Syntax:
 {prog} : Print all env-vars.
 {prog} VARNAME : Print value for VARNAME.
 {prog} VARNAME VALUE : Set VALUE for VARNAME.
 {prog} +VARNAME VALUE : Append VALUE in VARNAME delimeted with ';' (i.e. used for `PATH`).
 {prog} -VARNAME : Delete env-var value.
Note that the current command-window will not be affected,
changes would apply only for new command-windows.
"""
import winreg
import os, sys, win32gui, win32con
def reg_key(tree, path, varname):
 return '%s\%s:%s' % (tree, path, varname)
def reg_entry(tree, path, varname, value):
 return '%s=%s' % (reg_key(tree, path, varname), value)
def query_value(key, varname):
 value, type_id = winreg.QueryValueEx(key, varname)
 return value
def yield_all_entries(tree, path, key):
 i = 0
 while True:
 try:
 n,v,t = winreg.EnumValue(key, i)
 yield reg_entry(tree, path, n, v)
 i += 1
 except OSError:
 break ## Expected, this is how iteration ends.
def notify_windows(action, tree, path, varname, value):
 win32gui.SendMessage(win32con.HWND_BROADCAST, win32con.WM_SETTINGCHANGE, 0, 'Environment')
 print("---%s %s" % (action, reg_entry(tree, path, varname, value)), file=sys.stderr)
def manage_registry_env_vars(varname=None, value=None):
 reg_keys = [
 ('HKEY_LOCAL_MACHINE', r'SYSTEM\CurrentControlSet\Control\Session Manager\Environment'),
 ('HKEY_CURRENT_USER', r'Environment'),
 ]
 for (tree_name, path) in reg_keys:
 tree = eval('winreg.%s'%tree_name)
 try:
 with winreg.ConnectRegistry(None, tree) as reg:
 with winreg.OpenKey(reg, path, 0, winreg.KEY_ALL_ACCESS) as key:
 if not varname:
 for regent in yield_all_entries(tree_name, path, key):
 print(regent)
 else:
 if not value:
 if varname.startswith('-'):
 varname = varname[1:]
 value = query_value(key, varname)
 winreg.DeleteValue(key, varname)
 notify_windows("Deleted", tree_name, path, varname, value)
 break ## Don't propagate into user-tree.
 else:
 value = query_value(key, varname)
 print(reg_entry(tree_name, path, varname, value))
 else:
 if varname.startswith('+'):
 varname = varname[1:]
 value = query_value(key, varname) + ';' + value
 winreg.SetValueEx(key, varname, 0, winreg.REG_EXPAND_SZ, value)
 notify_windows("Updated", tree_name, path, varname, value)
 break ## Don't propagate into user-tree.
 except PermissionError as ex:
 print("!!!Cannot access %s due to: %s" %
 (reg_key(tree_name, path, varname), ex), file=sys.stderr)
 except FileNotFoundError as ex:
 print("!!!Cannot find %s due to: %s" %
 (reg_key(tree_name, path, varname), ex), file=sys.stderr)
if __name__=='__main__':
 args = sys.argv
 argc = len(args)
 if argc > 3:
 print(__doc__.format(prog=args[0]), file=sys.stderr)
 sys.exit()
 manage_registry_env_vars(*args[1:])

Below are some usage examples, assuming it has been saved in a file called setenv.py somewhere in your current path.

Note that in these examples I didn't have administrator rights, so the changes affected only my local user's registry tree:

> REM ## Print all environment variables
> setenv.py
!!!Cannot access HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment:PATH due to: [WinError 5] Access is denied
HKEY_CURRENT_USER\Environment:PATH=...
...
> REM ## Query environment variable:
> setenv.py PATH C:\foo
!!!Cannot access HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment:PATH due to: [WinError 5] Access is denied
!!!Cannot find HKEY_CURRENT_USER\Environment:PATH due to: [WinError 2] The system cannot find the file specified
> REM ## Set env-var:
> setenv.py PATH C:\foo
!!!Cannot access HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment:PATH due to: [WinError 5] Access is denied
---Set HKEY_CURRENT_USER\Environment:PATH=C:\foo
> REM ## Append environment variable:
> setenv.py +PATH D:\Bar
!!!Cannot access HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment:PATH due to: [WinError 5] Access is denied
---Set HKEY_CURRENT_USER\Environment:PATH=C:\foo;D:\Bar
> REM ## Delete environment variable:
> setenv.py -PATH
!!!Cannot access HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment:PATH due to: [WinError 5] Access is denied
---Deleted HKEY_CURRENT_USER\Environment:PATH

[*] Adapted from: http://code.activestate.com/recipes/416087-persistent-environment-variables-on-windows/

Answer 5

For reference purpose, for anyone searching how to change the path via code, I am quoting a useful post by a Delphi programmer from the forum post Registry PATH change/update without restart

TonHu (Programmer) 22 Oct 03 17:57 I found where I read the original posting, it's here: http://news.jrsoftware.org/news/innosetup.isx/msg02129....

The excerpt of what you would need is this:

You must specify the string "Environment" in LParam. In Delphi you'd do it this way:

 SendMessage(HWND_BROADCAST, WM_SETTINGCHANGE, 0, Integer(PChar('Environment')));

It was suggested by Jordan Russell, http://www.jrsoftware.org, the author of (a.o.) InnoSetup, ("Inno Setup is a free installer for Windows programs. First introduced in 1997, Inno Setup today rivals and even surpasses many commercial installers in feature set and stability.") (I just would like more people to use InnoSetup)

• David Heffernan: You have to modify the registry. Also, the cast to Integer is poor. Cast to LPARAM instead for 64 bit compatibility.
• user6307369: Here is example github.com/gilligan/snesdev/blob/1253994/tools/cc65-2.13.2/…

Answer 6

In a corporate network, where the user has only limited access and uses portable applications, there are these command line tricks:

1. Query the user environment variables: reg query "HKEY_CURRENT_USER\Environment". Use "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" for LOCAL_MACHINE.
2. Add a new user environment variable: reg add "HKEY_CURRENT_USER\Environment" /v shared_directory /d "c:\shared" /t REG_SZ. Use REG_EXPAND_SZ for paths containing other %% variables.
3. Delete an existing environment variable: reg delete "HKEY_CURRENT_USER\Environment" /v shared_directory.

Answer 7

This script Modify system PATH -- GUI includes all the necessary Windows API calls which can be refactored for your needs. It is actually an AutoHotkey GUI to change the System PATH easily. Needs to be run as an Administrator.

• jwzumwalt: Great script. I use HotKey but don't know how or what I need to do to add the script to it. Can you offer help, offer a link, or explain what needs to be done?