I have a PowerShell script that checks that a certain directory is on the PATH (by looking through $env:path). It appears that $env:path is loaded and locally scoped by each application on startup, and that scope is passed on to any child applications. So... if someone opens Firefox, downloads my program, runs it, gets a message that they should change their path, fixes the problem, then runs the program again from the Firefox downloads window, they'll get the same message, unless they start my program from Explorer or restart Firefox.
Is there a way to reload $env:path in my PowerShell script so it'll get the current value, as if it were opened from Explorer?
If you were running outside the context of a browser I would tell you to use
[System.Environment]::SetEnvironmentVariable(string name, string value, EnvironmentVariableTarget target)
to change the Path variable for the user. That third parameter allows you to specify Process, User or Machine. If you specify either User or Machine the change is permanent and will appear in the env blocks of all programs that start after that. However, since you are running within the browser I don't think you would be able to do that.
If the user changes their path, that change will be available to future instances of the browser. Another option is to test (Get-Command) for the app you need in the path and if you can't find it, modify $env:Path yourself in the script each time it runs. That is, unless you don't know what the path should be.
Related
I'm working on a script that automatically installs software. One of the programs to be installed includes its own command line commands and sub-commands when installed.
The goal is to use the program's provided commands to perform an action after its installation.
But running the command right after the program's installation I'm greeted by:
" is not recognized as an internal or external command , operable program or batch file"
If I open a new Powershell or cmd window the command is available in that instance.
What is the easiest way to to grant the script access to the commands?
Bender the Greatest's helpful answer explains the problem and shows you how to modify the $env:PATH variable in-session by manually appending a new directory path.
While that is a pragmatic solution, it requires that you know the specific directory path of the recently installed program.
If you don't - or you just want a generic solution that doesn't require you to hard-code paths - you can refresh the value of $env:PATH (the PATH environment variable) from the registry, via the [Environment]::GetEnvironmentVariable() .NET API method:
$env:PATH = [Environment]::GetEnvironmentVariable('Path', 'Machine'),
[Environment]::GetEnvironmentVariable('Path', 'User') -join ';'
This updates $env:PATH in-session to the same value that future sessions will see.
Note how the machine-level value (list of directories) takes precedence over the user-level one, due to coming first in the composite value.
Note:
If you happen to have made in-session-only $env:PATH modifications before calling the above, these modifications are lost.
If applicable, this includes modifications made by your $PROFILE file.
Hypothetically, other processes could have made additional modifications to the persistent Path variable definitions as well since your session started, which the call above will pick up too (as will future sessions).
This is because the PATH environment variable gets updated, but existing processes don't see that update unless they specifically query the registry for the live value of the update the PATH environment variable, then update PATH within its own process. If you need to continue in the same process, the workaround is to add the installation location to the PATH variable yourself after the program has been installed:
Note: I don't recommend updating the live value from the registry instead of the below in most cases. Other processes can modify that value, not just your own. It can introduce unnecessary risk, whereas appending only what you know should have changed is a more pragmatic approach. In addition, it adds code complexity for a case that often doesn't need to be generalized to that point.
# This will update the PATH variable for the current process
$env:PATH += ";C:\Path\To\New\Program\Folder;"
I'm fairly new to the world of Powershell and currently I'm trying to push a Powershell script via Intune to the company devices (all Windows 10 21H2 machines) that will show the file extensions in File Explorer.
So far, I've found this:
Set-Itemproperty -path 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced' -Name 'HideFileExt' -value 0
The PS script is pushed via Intune to a test device and the monitor tells me the policy is applied successfuly but the file extensions are still not visible.
Is there something wrong with the line of code?
My original comment which helped:
The script works fine. I am positive that it is not applied successfully, despite Intune telling you it did. While it is not part of that question, I suppose you should check the user context in which the script is applied and if the eventvwr or any other possible source tells you why the script did not apply correctly. Also, after trying the script locally for myself, you need to refresh the explorer tab via f5 for the change to apply.
Solution was to set it as system/device rights, since it was indeed run as user context, hence solving the problem.
This was the solution:
"The script works fine. I am positive that it is not applied successfully, despite Intune telling you it did. While it is not part of that question, I suppose you should check the user context in which the script is applied and if the eventvwr or any other possible source tells you why the script did not apply correctly. Also, after trying the script locally for myself, you need to refresh the explorer tab via f5 for the change to apply" –
Bowshock
I have run into a couple cases where I am trying to use a command via command line, but the command is not recognized. I have narrowed it down to an issue with environment variables. In each case, the variable is present when I retrieve the variable with the underlying C# method, but not with the shorthand, $env:myVariable
For example, if I retrieve the variable like this, I will get a value.
[Environment]::GetEnvironmentVariable('ChocolateyInstall', 'Machine')
But, if I retrieve the variable like this, nothing is returned
$env:ChocolateyInstall
I then have to do something like this to to get my command to work.
$env:ChocolateyInstall = [Environment]::GetEnvironmentVariable('ChocolateyInstall', 'Machine')
I have not been able to find a good explanation as to why I have to do this. I've looked at this documentation, but nothing stands out to me. Ideally, I would like to install a CLI and then not have to deal with checking for and assigning environment variables for the command to work.
When opening a PowerShell session, all permanently stored environment variables1 will be loaded into the Environment drive (Env:) of this current session (source):
The Environment drive is a flat namespace containing the environment
variables specific to the current user's session.
The documentation you linked states:
When you change environment variables in PowerShell, the change
affects only the current session. This behavior resembles the behavior
of the Set command in the Windows Command Shell and the Setenv command
in UNIX-based environments. To change values in the Machine or User
scopes, you must use the methods of the System.Environment class.
So defining/changing an environment variable like this:
$env:ChocolateyInstall = [Environment]::GetEnvironmentVariable('ChocolateyInstall', 'Machine')
Will change it for the current session, thus being immediately effective, but will also only be valid for the current session.
The methods of [System.Environment] are more fine grained. There you can choose which environment variable scope to address. There are three scopes available:
Machine
User
Process
The Process scope is equivalent to the Environment drive and covers the environment variables available in your current session. The Machine and the User scope address the permanently stored environment variables1. You can get variables from a particular scope like this:
[Environment]::GetEnvironmentVariable('ChocolateyInstall', 'Machine')
And set them with:
[Environment]::SetEnvironmentVariable('ChocolateyInstall', 'any/path/to/somewhere', 'Machine')
If you want to have new variables from the Machine or User scope available in your current PowerShell session, you have to create a new one. But don't open a new PowerShell session from your current PowerShell session, as it will then inherit all environment variables from your current PowerShell session (source):
Environment variables, unlike other types of variables in PowerShell,
are inherited by child processes, such as local background jobs and
the sessions in which module members run. This makes environment
variables well suited to storing values that are needed in both parent
and child processes.
So, to address the problem you described, you most probably changed your permanently stored environment variables1, while already having an open PowerShell session. If so, you just need to open a new (really new, see above) session and you will be able to access your environment variables via the Environment drive. Just to be clear, opening a new session will even reload environment variables of the Machine scope. There is no reboot required.
1 That are the environment variables you see in the GUI when going to the System Control Panel, selecting Advanced System Settings and on the Advanced tab, clicking on Environment Variable. Those variables cover the User and the Machine scope.
Alternatively, you can open this GUI directly by executing:
rundll32 sysdm.cpl,EditEnvironmentVariables
When I call the following code:
Start-Process Firefox
Then the PowerShell opens the browser. I can do that with several other programs and it works. My question is: How does the PowerShell know which program to open if I type Firefox? I mean, Im not using a concrete Path or something ...
I though it has something to do with the environment variables ... But I cannot find any variable there which is called Firefox ... How can he know?
I traced two halves of it, but I can't make them meet in the middle.
Process Monitor shows it checks the PATHs, and eventually checks HKLM\Software\Microsoft\Windows\CurrentVersion\App Paths\firefox.exe so that's my answer to how it finds the install location, and then runs it.
That registry key is for Application Registration which says:
When the ShellExecuteEx function is called with the name of an executable file in its lpFile parameter, there are several places where the function looks for the file. We recommend registering your application in the App Paths registry subkey.
The file is sought in the following locations:
The current working directory.
The Windows directory only (no subdirectories are searched).
The Windows\System32 directory.
Directories listed in the PATH environment variable.
Recommended: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths
That implies PowerShell calls the Windows ShellExecuteEx function, which finds FireFox as a registered application, or it tries the same kind of searching itself internally.
Going the other way to try and confirm that, the Start-Process cmdlet has a parameter set called UseShellExecute. The 'Notes' of that help says:
This cmdlet is implemented by using the Start method of the System.Diagnostics.Process class. For more information about this method, see Process.Start Method
Trying to trace through the source code on GitHub:
Here is the PowerShell source code for Start-Process.
Here, at this line it tries to look up the $FilePath parameter with CommandDiscovery.LookupCommandInfo.
Here it checks else if (ParameterSetName.Equals("UseShellExecute"))
Then Here is the .Start() function which either starts it with ShellExecute or Process.Start()
OK, not sure if ShellExecute and ShellExecuteEx behave the same, but it could be PS calling Windows, which is doing the search for "FireFox".
That CommandSearcher.LookupCommandInfo comes in here and follows to TryNormalSearch() which is implemented here and immediately starts a CommandSearcher which has a state machine for the things it will search
SearchState.SearchingAliases
Functions
CmdLets
SearchingBuiltinScripts
StartSearchingForExternalCommands
PowerShellPathResolution
QualifiedFileSystemPath
and there I get lost. I can't follow it any further right now.
Either it shortcuts straight to Windows doing the lookup
Or the PowerShell CommandSearcher does the same search somehow
Or the PowerShell CommandSearcher in some way runs out of searching, and the whole thing falls back to asking Windows search.
The fact that Process Monitor only logs one query in each PATH folder for "firefox.*" and then goes to the registry key suggests it's not doing this one, or I'd expect many more lookups.
The fact that it logs one query for "get-firefox.*" in each PATH folder suggests it is PowerShell's command searcher doing the lookup and not Windows.
Hmm.
Using Process Monitor I was able to trace the PowerShell.
It first searches the $env:path variable, then the $profile variable.
In my case firefox wasn't found and then it searches through a whole lot in the Registry and somehow finds it.
It might have something to do with how firefox is installed on the system.
I'm having this weird situation :
My user's and system's PATH variable is different than the PATH in powershell.
When I do :
PS C:\$env:path
C:\Windows\System32\WindowsPowerShell\v1.0\;c:\oldpath
However this is not correct, it looks like it stuck on some old PATH variable of my system, so none of the udpates I've done on it didn't change this variable (I do restart after every change to test).
Why is this happening? Do I have to set a PATH variable just for powershell?
The change might be "delayed", so try one or more of these solutions:
Log off and on again;
Task Manager > Restart "Windows Explorer" (explorer.exe)
Restart your launcher app (launchy, SlickRun, etc)
Reboot
Explanation:
Powershell will inherit the environment of the process that launched it (which depends on how you launch it). This is usually the interactive shell (explorer.exe). When you modify the environment from computer properties, you modify the environment of explorer.exe, so if you launch powershell from explorer.exe, (for example from the start menu) you should see the new environment.
However, if you launch it from something else (say a cmd.exe shell that you already had opened), then you won't since that process was launched under the old environment.
In other words: be careful how you are launching things.
In my case, I installed an app that incorrectly added itself to the PATH by creating a powershell profile that would override $env:PATH and blow out the existing configuration every time I started powershell.
Check if you have profile at USER\Documents\WindowsPowerShell\Microsoft.PowerShell_profile.ps1 and if it's doing anything fishy like setting $env:PATH.