How to permanently set environment variables in C #
I am using the following code to get and set environment variables.
public static string Get( string name, bool ExpandVariables=true ) {
if ( ExpandVariables ) {
return System.Environment.GetEnvironmentVariable( name );
} else {
return (string)Microsoft.Win32.Registry.LocalMachine.OpenSubKey( @"SYSTEM\CurrentControlSet\Control\Session Manager\Environment\" ).GetValue( name, "", Microsoft.Win32.RegistryValueOptions.DoNotExpandEnvironmentNames );
}
}
public static void Set( string name, string value ) {
System.Environment.SetEnvironmentVariable( name, value );
}
The problem I am facing is even when the program is running as administrator, the environment variable is only kept as long as the program is running. I confirmed this by running Get on a variable set in a previous instance.
Usage example above
Set("OPENSSL_CONF", @"c:\openssl\openssl.cfg");
And to retrieve
MessageBox.Show( Get("OPENSSL_CONF") );
As long as the program is running, after use, the Set
value is returned with help Get
without any problem. The problem is that the environment variable is not persistent (set on the system).
It also never appears in the extended properties.
Thanks in advance.
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While the program is running, after using Set, the value is returned using Get without any problems. The problem is the environment variable is not persistent (set on the system).
This is because there is an overload SetEnvironmentVariable
that you are using in process variables. From the docs :
Calling this method is equivalent to calling the SetEnvironmentVariable (String, String, EnvironmentVariableTarget) overload with the EnvironmentVariableTarget.Process value for the target argument.
You need to use overload by specifying EnvironmentVariableTarget.Machine
:
public static void Set(string name, string value)
{
Environment.SetEnvironmentVariable(name, value, EnvironmentVariableTarget.Machine);
}
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According to MSDN, the method you are using just changes the variable for the runtime of the process.
Try the overload described here: https://msdn.microsoft.com/library/96xafkes%28v=vs.110%29.aspx
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Here's an example that constantly updates the User PATH variable by programmatically editing the registry:
// Admin Permission not-required:
// HKCU\Environment\Path
// Admin Permission required:
// HKLM\SYSTEM\CurrentControlSet\Control
// \Session Manager\Environment\Path
public static void UserPathAppend(string path, int verbose=1) {
string oldpath = UserPathGet();
List<string> newpathlist = oldpath.Split(';').ToList();
newpathlist.Add(path);
string newpath = String.Join(";", newpathlist.ToArray());
UserPathSet(newpath);
UpdateEnvPath();
if (verbose!=0) {
System.Windows.MessageBox.Show(
"PATH APPEND:\n\n"
+ path + "\n\n"
+ "OLD HKCU PATH:\n\n"
+ oldpath + "\n\n"
+ "NEW HKCU PATH:\n\n"
+ newpath + "\n\n"
+ "REGISTRY KEY MODIFIED:\n\n"
+ "HKCU\\Environment\\Path\n\n"
+ "NOTE:\n\n"
+ "'Command Path' is a concat of 'HKLM Path' & 'HKCU Path'.\n",
"Updated Current User Path Environment Variable"
);
}
}
public static void UserPathPrepend(string path, int verbose=1) {
string oldpath = UserPathGet();
List<string> newpathlist = oldpath.Split(';').ToList();
newpathlist.Insert(0, path);
string newpath = String.Join(";", newpathlist.ToArray());
UserPathSet(newpath);
UpdateEnvPath();
if (verbose != 0) {
System.Windows.MessageBox.Show(
"PATH PREPEND:\n\n"
+ path + "\n\n"
+ "OLD HKCU PATH:\n\n"
+ oldpath + "\n\n"
+ "NEW HKCU PATH:\n\n"
+ newpath + "\n\n"
+ "REGISTRY KEY MODIFIED:\n\n"
+ "HKCU\\Environment\\Path\n\n"
+ "NOTE:\n\n"
+ "'Command Path' is a concat of 'HKLM Path' & 'HKCU Path'.\n",
"Updated Current User Path Environment Variable"
);
}
}
public static string UserPathGet()
{
// Reads Registry Path "HKCU\Environment\Path"
string subKey = "Environment";
Microsoft.Win32.RegistryKey sk = Microsoft.Win32.Registry.CurrentUser.OpenSubKey(subKey);
if (sk == null)
return null;
else
return sk.GetValue("Path").ToString();
}
public static void UserPathSet(string newpath)
{
// Writes Registry Path "HKCU\Environment\Path"
string subKey = "Environment";
Microsoft.Win32.RegistryKey sk1 = Microsoft.Win32.Registry.CurrentUser.CreateSubKey(subKey);
sk1.SetValue("Path", newpath);
}
//===========================================================
// Private: This part required if you don't want to logout
// and login again to see Path Variable update
//===========================================================
[DllImport("user32.dll", SetLastError = true, CharSet = CharSet.Auto)]
private static extern IntPtr SendMessageTimeout(IntPtr hWnd,
uint Msg, UIntPtr wParam, string lParam,
SendMessageTimeoutFlags fuFlags,
uint uTimeout, out UIntPtr lpdwResult);
private enum SendMessageTimeoutFlags : uint
{
SMTO_NORMAL = 0x0, SMTO_BLOCK = 0x1,
SMTO_ABORTIFHUNG = 0x2, SMTO_NOTIMEOUTIFNOTHUNG = 0x8
}
private static void UpdateEnvPath() {
// SEE: https://support.microsoft.com/en-us/help/104011/how-to-propagate-environment-variables-to-the-system
// Need to send WM_SETTINGCHANGE Message to
// propagage changes to Path env from registry
IntPtr HWND_BROADCAST = (IntPtr)0xffff;
const UInt32 WM_SETTINGCHANGE = 0x001A;
UIntPtr result;
IntPtr settingResult
= SendMessageTimeout(HWND_BROADCAST,
WM_SETTINGCHANGE, (UIntPtr)0,
"Environment",
SendMessageTimeoutFlags.SMTO_ABORTIFHUNG,
5000, out result);
}
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