---
title: "PSADT v4 Built-in Variables"
id: "psadt-variables"
psadt_target: "4.1.7"
last_updated: "2025-12-07"
verified_by: "maintainer"
source_ref: "ReferenceKnowledge/V4Assets/PSAppDeployToolkit"
tags: ["psadt", "variables", "session", "environment", "v4.1.7"]
---
# PSADT v4.1.7 Built-in Variables
PSADT v4.1.7 provides variables through the `$adtSession` object and environment variables that become available after opening a session.
## Session Object ($adtSession)
In v4.1.7, you define `$adtSession` as a hashtable, then it becomes the session object after `Open-ADTSession`.
### Session Variables (v4.1.7)
```powershell
# Initial hashtable definition
$adtSession = @{
# Application info
AppVendor = 'Microsoft'
AppName = 'Office 365'
AppVersion = '16.0'
AppArch = 'x64'
AppLang = 'EN'
AppRevision = '01'
# Exit codes
AppSuccessExitCodes = @(0)
AppRebootExitCodes = @(1641, 3010)
# Processes to close (used in Install/Uninstall/Repair)
AppProcessesToClose = @(
@{ Name = 'winword'; Description = 'Microsoft Word' },
@{ Name = 'excel'; Description = 'Microsoft Excel' }
)
# Admin requirement
RequireAdmin = $true
# UI titles (optional overrides)
InstallName = ''
InstallTitle = ''
# Script metadata
AppScriptVersion = '1.0.0'
AppScriptDate = '2025-01-01'
AppScriptAuthor = 'IT Admin'
# Script info (auto-populated)
DeployAppScriptFriendlyName = $MyInvocation.MyCommand.Name
DeployAppScriptParameters = $PSBoundParameters
DeployAppScriptVersion = '4.1.7'
}
# After Open-ADTSession, these become session properties:
$iadtParams = Get-ADTBoundParametersAndDefaultValues -Invocation $MyInvocation
$adtSession = Remove-ADTHashtableNullOrEmptyValues -Hashtable $adtSession
$adtSession = Open-ADTSession @adtSession @iadtParams -PassThru
```
### Session Properties (After Open-ADTSession)
```powershell
# Application information
$adtSession.AppVendor # Application vendor
$adtSession.AppName # Application name
$adtSession.AppVersion # Application version
$adtSession.InstallName # Full install name (Vendor AppName AppVersion)
$adtSession.InstallTitle # Display title for UI
# Deployment info
$adtSession.DeploymentType # Install, Uninstall, or Repair
$adtSession.DeployMode # Auto, Interactive, NonInteractive, Silent
$adtSession.InstallPhase # Current phase (Pre-Install, Install, Post-Install, etc.)
# Directories
$adtSession.DirFiles # Files/ directory path
$adtSession.DirSupportFiles # SupportFiles/ directory path
$adtSession.ScriptDirectory # Script root directory
# Logging
$adtSession.LogName # Log file name
$adtSession.LogTempFolder # Temporary log folder (when CompressLogs enabled)
# State
$adtSession.IsAdmin # Running with admin rights
$adtSession.IsSystemAccount # Running as SYSTEM
$adtSession.RunAsActiveUser # Username when running as SYSTEM
# Zero-Config MSI (when AppName is empty)
$adtSession.UseDefaultMsi # Boolean: Using zero-config mode
$adtSession.DefaultMsiFile # Detected MSI file path
$adtSession.DefaultMstFile # Detected MST transform path
$adtSession.DefaultMspFiles # Array of detected MSP files
```
## Environment Variables
Environment variables become available after `Open-ADTSession` (or after calling `Export-ADTEnvironmentTableToSessionState`).
### System Information
```powershell
$envComputerName # Computer name
$envComputerNameFQDN # Fully qualified domain name
$envUserName # Current username
$envUserDomain # User's domain
$envOSName # OS name (e.g., "Microsoft Windows 11 Pro")
$envOSVersion # OS version object
$envOSVersionMajor # Major version (10 for Win10/11)
$envOSVersionMinor # Minor version
$envOSVersionBuild # Build number (e.g., 22631)
$envOSArchitecture # 32-bit or 64-bit
```
### Architecture Detection
```powershell
$Is64Bit # Boolean: 64-bit OS
$Is64BitProcess # Boolean: 64-bit PowerShell process
$envProcessorArchitecture # x86, AMD64, or ARM64
```
### Common Paths
```powershell
# System paths
$envSystemRoot # Windows directory (C:\Windows)
$envProgramFiles # Program Files (64-bit on 64-bit OS)
$envProgramFilesX86 # Program Files (x86)
$envCommonProgramFiles # Common Files
$envCommonProgramFilesX86 # Common Files (x86)
$envProgramData # C:\ProgramData
$envTemp # System temp directory
$envWinDir # Windows directory
# User paths
$envUserProfile # User profile (C:\Users\username)
$envAppData # Roaming AppData
$envLocalAppData # Local AppData
$envUserDesktop # User's Desktop
$envUserDocuments # User's Documents
# Public paths
$envPublic # C:\Users\Public
$envCommonDesktop # Public Desktop (shortcuts for all users)
$envCommonStartMenuPrograms # All Users Start Menu\Programs
$envCommonStartMenu # All Users Start Menu
$envCommonStartup # All Users Startup folder
```
### Registry Paths
```powershell
# Pre-formatted registry paths
$regKeyLMSoftware # HKLM:\SOFTWARE
$regKeyLMSoftwareWow6432Node # HKLM:\SOFTWARE\WOW6432Node (on 64-bit)
$regKeyCUSoftware # HKCU:\SOFTWARE
```
## Usage Examples
### Architecture-Aware Installation
```powershell
# Select installer based on architecture
if ($Is64Bit) {
$installerFile = 'setup_x64.exe'
} else {
$installerFile = 'setup_x86.exe'
}
Start-ADTProcess -FilePath $installerFile -ArgumentList '/S'
```
### Deploy Mode Handling
```powershell
# Different behavior based on deploy mode
if ($adtSession.DeployMode -ne 'Silent') {
Show-ADTInstallationPrompt -Message 'Installation complete!' -ButtonRightText 'OK' -Icon Information -NoWait
}
```
### Windows Version Checks
```powershell
# Windows 11 detection (build 22000+)
if ($envOSVersionBuild -ge 22000) {
Write-ADTLogEntry 'Running on Windows 11'
# Apply Windows 11 specific settings
}
# Windows 10 feature update check
if ($envOSVersionBuild -ge 19041) {
# Windows 10 2004 or later
}
```
### Context-Aware File Paths
```powershell
# Determine config location based on context
if ($adtSession.IsSystemAccount) {
# Machine-wide config
$configPath = "$envProgramData\MyApp\config.xml"
} else {
# Per-user config
$configPath = "$envLocalAppData\MyApp\config.xml"
}
# Use session directory properties
$installer = Join-Path $adtSession.DirFiles 'setup.exe'
$supportFile = Join-Path $adtSession.DirSupportFiles 'settings.reg'
```
### Creating Shortcuts
```powershell
# Desktop shortcut for all users
New-ADTShortcut -Path "$envCommonDesktop\MyApp.lnk" -TargetPath "$envProgramFiles\MyApp\myapp.exe"
# Start menu shortcut
New-ADTShortcut -Path "$envCommonStartMenuPrograms\MyApp\MyApp.lnk" -TargetPath "$envProgramFiles\MyApp\myapp.exe"
```
### Logging Context Information
```powershell
# Log deployment context at start (good practice)
Write-ADTLogEntry -Message "=== Deployment Context ==="
Write-ADTLogEntry -Message "Computer: $envComputerName"
Write-ADTLogEntry -Message "OS: $envOSName (Build $envOSVersionBuild)"
Write-ADTLogEntry -Message "Architecture: $envOSArchitecture"
Write-ADTLogEntry -Message "User: $envUserName"
Write-ADTLogEntry -Message "IsAdmin: $($adtSession.IsAdmin)"
Write-ADTLogEntry -Message "IsSystem: $($adtSession.IsSystemAccount)"
Write-ADTLogEntry -Message "DeployMode: $($adtSession.DeployMode)"
Write-ADTLogEntry -Message "DeploymentType: $($adtSession.DeploymentType)"
```
## Best Practices
1. **Use `$adtSession.DirFiles`** instead of hardcoding `"$PSScriptRoot\Files"`
2. **Check architecture** before selecting x86 vs x64 installers
3. **Use environment variables** for system paths rather than hardcoding
4. **Log context** at deployment start for troubleshooting
5. **Handle both SYSTEM and user context** appropriately
6. **Use `AppProcessesToClose`** (v4.1) instead of repeating process lists
7. **Set `RequireAdmin`** (v4.1) in session instead of config file
