这些脚本是幂等的(可以运行多次)。 它们更新Windows路径和当前/未来的Powershell会话:

永久添加路径

    $targetDir="c:\bin"
    $oldPath = [System.Environment]::GetEnvironmentVariable("Path","Machine")
    $oldPathArray=($oldPath) -split ';'
    if(-Not($oldPathArray -Contains "$targetDir")) {
        write-host "Adding $targetDir to Machine Path"
        $newPath = "$oldPath;$targetDir" -replace ';+', ';'
        [System.Environment]::SetEnvironmentVariable("Path",$newPath,"Machine")
        $env:Path = [System.Environment]::GetEnvironmentVariable("Path","User"),[System.Environment]::GetEnvironmentVariable("Path","Machine") -join ";"
    }
    write-host "Windows paths:"
    ($env:Path).Replace(';',"`n")

永久删除路径

    $targetDir="c:\bin"
    $oldPath = [System.Environment]::GetEnvironmentVariable("Path","Machine")
    $oldPathArray=($oldPath) -split ';'
    if($oldPathArray -Contains "$targetDir") {
        write-host "Removing $targetDir from Machine path"
        $newPathArray = $oldPathArray | Where-Object { $_ –ne "$targetDir" }
        $newPath = $newPathArray -join ";"
        [System.Environment]::SetEnvironmentVariable("Path",$newPath,"Machine")
        $env:Path = [System.Environment]::GetEnvironmentVariable("Path","User"),[System.Environment]::GetEnvironmentVariable("Path","Machine") -join ";"
    }
    write-host "Windows paths:"
    ($env:Path).Replace(';',"`n")

正如Jonathan Leaders在这里提到的，运行提升的命令/脚本来改变“machine”的环境变量是很重要的，但是运行一些提升的命令并不一定要用社区扩展来完成，所以我想在某种程度上修改和扩展JeanT的回答，即使脚本本身没有运行提升，也可以改变机器变量:

function Set-Path ([string]$newPath, [bool]$permanent=$false, [bool]$forMachine=$false )
{
    $Env:Path += ";$newPath"

    $scope = if ($forMachine) { 'Machine' } else { 'User' }

    if ($permanent)
    {
        $command = "[Environment]::SetEnvironmentVariable('PATH', $env:Path, $scope)"
        Start-Process -FilePath powershell.exe -ArgumentList "-noprofile -command $Command" -Verb runas
    }

}

这些脚本是幂等的(可以运行多次)。 它们更新Windows路径和当前/未来的Powershell会话:

永久添加路径

    $targetDir="c:\bin"
    $oldPath = [System.Environment]::GetEnvironmentVariable("Path","Machine")
    $oldPathArray=($oldPath) -split ';'
    if(-Not($oldPathArray -Contains "$targetDir")) {
        write-host "Adding $targetDir to Machine Path"
        $newPath = "$oldPath;$targetDir" -replace ';+', ';'
        [System.Environment]::SetEnvironmentVariable("Path",$newPath,"Machine")
        $env:Path = [System.Environment]::GetEnvironmentVariable("Path","User"),[System.Environment]::GetEnvironmentVariable("Path","Machine") -join ";"
    }
    write-host "Windows paths:"
    ($env:Path).Replace(';',"`n")

永久删除路径

    $targetDir="c:\bin"
    $oldPath = [System.Environment]::GetEnvironmentVariable("Path","Machine")
    $oldPathArray=($oldPath) -split ';'
    if($oldPathArray -Contains "$targetDir") {
        write-host "Removing $targetDir from Machine path"
        $newPathArray = $oldPathArray | Where-Object { $_ –ne "$targetDir" }
        $newPath = $newPathArray -join ";"
        [System.Environment]::SetEnvironmentVariable("Path",$newPath,"Machine")
        $env:Path = [System.Environment]::GetEnvironmentVariable("Path","User"),[System.Environment]::GetEnvironmentVariable("Path","Machine") -join ";"
    }
    write-host "Windows paths:"
    ($env:Path).Replace(';',"`n")

所有建议永久更改的答案都有相同的问题:它们破坏了路径注册表值。

SetEnvironmentVariable将REG_EXPAND_SZ值%SystemRoot%\system32转换为c:\ windows \system32的REG_SZ值。

路径中的任何其他变量也会丢失。使用%myNewPath%添加新的将不再工作。

这里有一个脚本Set-PathVariable。我用来解决这个问题的ps1:

 [CmdletBinding(SupportsShouldProcess=$true)]
 param(
     [parameter(Mandatory=$true)]
     [string]$NewLocation)

 Begin
 {

 #requires –runasadministrator

     $regPath = "SYSTEM\CurrentControlSet\Control\Session Manager\Environment"
     $hklm = [Microsoft.Win32.Registry]::LocalMachine

     Function GetOldPath()
     {
         $regKey = $hklm.OpenSubKey($regPath, $FALSE)
         $envpath = $regKey.GetValue("Path", "", [Microsoft.Win32.RegistryValueOptions]::DoNotExpandEnvironmentNames)
         return $envPath
     }
 }

 Process
 {
     # Win32API error codes
     $ERROR_SUCCESS = 0
     $ERROR_DUP_NAME = 34
     $ERROR_INVALID_DATA = 13

     $NewLocation = $NewLocation.Trim();

     If ($NewLocation -eq "" -or $NewLocation -eq $null)
     {
         Exit $ERROR_INVALID_DATA
     }

     [string]$oldPath = GetOldPath
     Write-Verbose "Old Path: $oldPath"

     # Check whether the new location is already in the path
     $parts = $oldPath.split(";")
     If ($parts -contains $NewLocation)
     {
         Write-Warning "The new location is already in the path"
         Exit $ERROR_DUP_NAME
     }

     # Build the new path, make sure we don't have double semicolons
     $newPath = $oldPath + ";" + $NewLocation
     $newPath = $newPath -replace ";;",""

     if ($pscmdlet.ShouldProcess("%Path%", "Add $NewLocation")){

         # Add to the current session
         $env:path += ";$NewLocation"

         # Save into registry
         $regKey = $hklm.OpenSubKey($regPath, $True)
         $regKey.SetValue("Path", $newPath, [Microsoft.Win32.RegistryValueKind]::ExpandString)
         Write-Output "The operation completed successfully."
     }

     Exit $ERROR_SUCCESS
 }

我在一篇博文中更详细地解释了这个问题。

在@ali Darabi的回答中编辑注册表键对我来说是最好的，但是 当我没有Powershell的权限时。所以我直接在regedit里编辑。

我想在这个回答中进一步展开这个主题。

重新启动Powershell也不足以传播更改。我必须打开任务管理器并重新启动explorer.exe以触发注册表的重新加载。

导航注册表可能相当乏味，所以为了保持用户友好的体验，你可以从Powershell执行这个:

REG ADD "HKCU\Software\Microsoft\Windows\CurrentVersion\Applets\Regedit" /v "LastKey" /d "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\Environment" /f; regedit

它将最后打开的窗口设置为某个注册表路径，这样当您下次打开regedit时，它将以适当的键打开。

警告:在PowerShell提示符中执行$env:path >> a.out保存现有路径的副本，以防出现错误。

PowerShell提示符:

setx PATH "$env:path;\the\directory\to\add" -m

然后你应该看到文本:

SUCCESS: Specified value was saved.

重新启动会话，变量就可用了。Setx也可以用来设置任意变量。输入setx /?在文档提示符处。