Windows Env Variable Mgmt

Windows Environment Variable Management

Managing PATH and environment variables on Windows.

Scopes

Reading

# Process scope (current session)
$env:PATH
$env:DOCKER_HOST

# User scope
[Environment]::GetEnvironmentVariable('PATH', 'User')
[Environment]::GetEnvironmentVariable('DOCKER_HOST', 'User')

# Machine scope
[Environment]::GetEnvironmentVariable('PATH', 'Machine')

# All scopes with fallback
[Environment]::GetEnvironmentVariable('PATH', 'User')
[Environment]::GetEnvironmentVariable('PATH', 'Machine')
$env:PATH  # combines User + Machine

Writing

# Process scope (temporary, current session only)
$env:MY_VAR = "value"

# User scope (persistent)
[Environment]::SetEnvironmentVariable('MY_VAR', 'value', 'User')

# Machine scope (persistent, needs admin)
[Environment]::SetEnvironmentVariable('MY_VAR', 'value', 'Machine')

# Delete
[Environment]::SetEnvironmentVariable('MY_VAR', $null, 'User')

PATH Manipulation

# Add to User PATH (idempotent)
$scope = 'User'
$path = [Environment]::GetEnvironmentVariable('PATH', $scope)
$newEntry = "C:\MyApp\bin"
if ($path -split ';' -notcontains $newEntry) {
    $path = $newEntry + ';' + $path
    [Environment]::SetEnvironmentVariable('PATH', $path, $scope)
}

# Remove Docker from PATH
$path = [Environment]::GetEnvironmentVariable('PATH', 'User')
$newPath = ($path -split ';' | Where-Object { $_ -notmatch '(?i)docker' }) -join ';'
[Environment]::SetEnvironmentVariable('PATH', $newPath, 'User')

Docker Env Vars to Remove

$dockerVars = @('DOCKER_HOST','DOCKER_CERT_PATH','DOCKER_TLS_VERIFY',
                'DOCKER_CONFIG','DOCKER_CONTEXT','DOCKER_API_VERSION')
foreach ($ev in $dockerVars) {
    [Environment]::SetEnvironmentVariable($ev, $null, 'User')
    [Environment]::SetEnvironmentVariable($ev, $null, 'Machine')
}

Broadcast Change (Notify Windows)

# After changing environment, notify running apps
$HWND_BROADCAST = 0xFFFF
$WM_SETTINGCHANGE = 0x001A
[User32.SendMessage]::SendMessage($HWND_BROADCAST, $WM_SETTINGCHANGE, 0, 'Environment')

Pitfalls

• Machine scope requires admin -- use try/catch
• PATH is cached per process -- new processes pick up changes
• $env:PATH only shows Process scope (User+Machine combined at logon)
• String length limit -- PATH has ~2048 char limit in older Windows
• %VARIABLE% in PATH entries are expanded; set with REG_EXPAND_SZ type
• [Environment]::SetEnvironmentVariable with Machine scope auto-broadcasts