Reload the path in PowerShell

If I have an instance of PowerShell ISE running and I install something that modifies the PATH or I modify it in any way outside of PowerShell then I need to restart PowerShell for it to see the updated PATH variable.

Is there a way to reload the path from within PowerShell without restarting it?

Just to bring Rob's comment to light:

$env:Path = [System.Environment]::GetEnvironmentVariable("Path","Machine") + ";" + [System.Environment]::GetEnvironmentVariable("Path","User") 

Try getting the machine path and assigning it to the session's path.

$env:Path = [System.Environment]::GetEnvironmentVariable("Path","Machine")

Easiest way, use Chocolatey (freeware). It works for both CMD and PowerShell. Then you will be able to reload PATH (with variable expansion) with a simple command:

refreshenv

Installation from cmd (requires administrator rights):

@"%SystemRoot%\System32\WindowsPowerShell\v1.0\powershell.exe" -NoProfile -InputFormat None -ExecutionPolicy Bypass -Command "iex ((New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1'))" && SET "PATH=%PATH%;%ALLUSERSPROFILE%\chocolatey\bin"

Example usage:

> SET JAVA_HOME=c:/java/jdk6
> SET PATH=%JAVA_HOME%/bin
> ECHO %PATH%
c:/java/jdk6/bin

> SET JAVA_HOME=c:/java/jdk8
> refreshenv
Refreshing environment variables from registry for cmd.exe. Please wait...Finished..
> echo %PATH%
c:/java/jdk8/bin

Based on mpen's answer, here is a PowerShell function:

function refresh-path {
    $env:Path = [System.Environment]::GetEnvironmentVariable("Path","Machine") +
                ";" +
                [System.Environment]::GetEnvironmentVariable("Path","User")
}

Then just call refresh-path.

Just to add to other answers, you can make sure you don't add superfluous joins by filtering in case the user has an empty path.

$env:Path=(
    [System.Environment]::GetEnvironmentVariable("Path","Machine"),
    [System.Environment]::GetEnvironmentVariable("Path","User")
) -match '.' -join ';'

Or, more usefully, if you're running a script that adds to a different or multiple environment variables, use a function to reset them all

function resetEnv {
    Set-Item `
        -Path (('Env:', $args[0]) -join '') `
        -Value ((
            [System.Environment]::GetEnvironmentVariable($args[0], "Machine"),
            [System.Environment]::GetEnvironmentVariable($args[0], "User")
        ) -match '.' -join ';')
}
resetEnv Path
resetEnv AppPath

If your path contains environment variables that weren't defined at the start of the session, you'll want to expand those too:

$env:Path = [System.Environment]::ExpandEnvironmentVariables([System.Environment]::GetEnvironmentVariable("Path","Machine") + ";" + [System.Environment]::GetEnvironmentVariable("Path","User"))

For me this was useful after installing NVM which defines and adds %NVM_HOME% to the path.

To take this to its logical conclusion you could use this recursive function to expand instead:

function Expand-EnvironmentVariablesRecursively($unexpanded) {
    $previous = ''
    $expanded = $unexpanded
    while($previous -ne $expanded) {
        $previous = $expanded
        $expanded = [System.Environment]::ExpandEnvironmentVariables($previous)
    }
    return $expanded
}

And then use:

$env:Path = Expand-EnvironmentVariablesRecursively([System.Environment]::GetEnvironmentVariable("Path","Machine") + ";" + [System.Environment]::GetEnvironmentVariable("Path","User"))

I've opened an issue to add this solution into refreshenv from Chocolatey.