Variables

Enumerate

Get-Variable	Displays current variables
gci variable:	Same as above
Get-ChildItem env:	List all Environment Variables
set	Lists all environment variables in the Command Prompt.
echo %VARIABLE_NAME%	Shows the value of a specific environment variable in the Command Prompt.
$env:VARIABLE_NAME	Retrieves the value of a specific environment variable in PowerShell.
printenv	Windows Subsystem for Linux (WSL) environment.

Modify

Get-Variable	Names are displayed without the preceding <$>
Clear-Variable -Name MyVariable	Delete the value of a Variable
Remove-Variable -Name MyVariable	Delete the Variable
$MyVariable = 1, 2, 3	Creates the MyVariable with 1,2,3
$Processes = Get-Process	Creates a Variable with the results of Get-Process
$Today = (Get-Date).DateTime	Creates a combined Date/Time variable from the results of Get-Date
Set-Item -Path Env:/A -Value 1	Sets environment variable 'A' to '1'

Automatic Variables

$$	Last token in the last line received by the session.
$?	Execution status of the last operation.
$^	First token in the last line received by the session.
$_	Contains the current object in the pipeline object.
$ARGS	Array of the undeclared parameters and/or parameter values passed to a function, script, or script block.
$ERROR	An array of error objects that represent the most recent errors.
$FALSE	Represent FALSE in commands and scripts instead of using the string "false".
$FOREACH	Enumerator (not the resulting values) of a ForEach loop.
$HOME	Full path of the user’s home directory.
$LASTEXITCODE	Exit code of the last Windows-based program that was run.
$MATCHES	Works with the -match and -notmatch operators.
$NULL	Automatic variable that contains a NULL or empty value.
$PID	Process identifier (PID) of the process hosting the current PowerShell session.
$PROFILE	Full path of the PowerShell profile for the current user and the current host application.
$PSVERSIONTABLE	Read-only hash table displaying details about the version of PowerShell running in the current session.
$TRUE	Used to represent TRUE in commands and scripts.

Registry Locations

Environment variables in Windows are stored in the registry in two primary locations:

System Variables:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment

This key contains environment variables that are set system-wide and affect all users on the system.

User Variables:

HKEY_CURRENT_USER\Environment

This key stores environment variables that are specific to the currently logged-in user.

When you set or modify environment variables via system settings or using tools like setx, the changes are reflected in these registry locations.