Environment variables in PowerShell

Introduction

Environment variables store information that programs and scripts can use to work properly. They help scripts know about the system or user settings without hardcoding values.

You want to get the current user's home folder path in a script.

You need to check or set the system's PATH to run programs.

You want to store a secret key or configuration that your script can access.

You want to make your script work on different computers without changing code.

You want to temporarily change a setting for a program run by your script.

Syntax

PowerShell

Get-ChildItem Env:\
$env:VARIABLE_NAME = "value"
$env:VARIABLE_NAME

Use Get-ChildItem Env:\ to list all environment variables.

Use $env:VARIABLE_NAME to read or set an environment variable.

Examples

Lists all environment variables available in the current session.

PowerShell

Get-ChildItem Env:\

Shows the current user's name stored in the environment variable USERNAME.

PowerShell

$env:USERNAME

Sets a new environment variable MY_VAR to 'Hello' and prints it.

PowerShell

$env:MY_VAR = "Hello"
Write-Output $env:MY_VAR

Sample Program

This script sets a new environment variable GREETING, prints it, and then shows the current user and home path from existing environment variables.

PowerShell

$env:GREETING = "Hello, PowerShell!"
Write-Output "The greeting is: $env:GREETING"

# List a few important environment variables
Write-Output "User: $env:USERNAME"
Write-Output "Home Path: $env:HOMEPATH"

Important Notes

Environment variables set in a script only last for that session unless saved permanently.

Use $env:VARIABLE_NAME = $null to remove an environment variable in the current session.

Be careful not to overwrite important system environment variables.

Summary

Environment variables store system or user information accessible to scripts.

Use $env:VARIABLE_NAME to read or write environment variables in PowerShell.

They help make scripts flexible and adaptable to different environments.

Practice

1. What is the correct way to access the environment variable PATH in PowerShell?

easy

A. Use PATH$

B. Use get-env PATH

C. Use env(PATH)

D. Use $env:PATH

Solution

1. Step 1: Understand PowerShell environment variable syntax

   PowerShell uses $env:VARIABLE_NAME to access environment variables.

2. Step 2: Apply syntax to PATH variable

   To get the PATH variable, write $env:PATH.

3. Final Answer:

   Use $env:PATH -> Option D

4. Quick Check:

   Environment variable access = $env:VARIABLE [OK]

Hint: Remember: environment variables use $env: prefix in PowerShell [OK]

Common Mistakes:

• Using incorrect syntax like get-env or env()
• Forgetting the $env: prefix
• Trying to access variables without colon

2. Which of the following is the correct syntax to set an environment variable named MY_VAR to the value hello in PowerShell?

easy

A. set-env MY_VAR hello

B. $env:MY_VAR = 'hello'

C. env MY_VAR = hello

D. set $env:MY_VAR hello

Solution

1. Step 1: Recall how to assign environment variables in PowerShell

   PowerShell assigns environment variables by setting $env:VariableName to a value.

2. Step 2: Apply assignment to MY_VAR

   Use $env:MY_VAR = 'hello' to set the variable.

3. Final Answer:

   $env:MY_VAR = 'hello' -> Option B

4. Quick Check:

   Set env var = $env:VAR = value [OK]

Hint: Set env vars with $env:VAR = 'value' syntax [OK]

Common Mistakes:

• Using set-env which is not a PowerShell cmdlet
• Missing quotes around string values
• Trying to assign without $env: prefix

3. What will be the output of the following PowerShell commands?

$env:GREETING = 'Hello'
Write-Output "$env:GREETING, World!"

medium

A. Hello, World!

B. $env:GREETING, World!

C. GREETING, World!

D. Error: Variable not found

Solution

1. Step 1: Assign environment variable GREETING

   The command $env:GREETING = 'Hello' sets the environment variable GREETING to 'Hello'.

2. Step 2: Output the string with variable expansion

   The command Write-Output "$env:GREETING, World!" expands $env:GREETING to 'Hello', so the output is 'Hello, World!'.

3. Final Answer:

   Hello, World! -> Option A

4. Quick Check:

   Variable expands correctly = Hello, World! [OK]

Hint: Variables inside double quotes expand automatically in PowerShell [OK]

Common Mistakes:

• Expecting literal $env:GREETING instead of expansion
• Using single quotes which prevent expansion
• Assuming environment variables are not accessible in strings

4. You run this script but get an error:

Write-Output $envMY_VAR

What is the error and how to fix it?

medium

A. Environment variables cannot be used in Write-Output

B. Variable name is case sensitive; use $env:my_var

C. Missing colon after env; fix by using $env:MY_VAR

D. Use double quotes around variable: "$envMY_VAR"

Solution

1. Step 1: Identify syntax error in variable name

   The variable $envMY_VAR is invalid because environment variables require a colon after env, like $env:MY_VAR.

2. Step 2: Correct the syntax

   Fix the script by changing to Write-Output $env:MY_VAR to properly access the environment variable.

3. Final Answer:

   Missing colon after env; fix by using $env:MY_VAR -> Option C

4. Quick Check:

   Env vars need colon after env = $env:VAR [OK]

Hint: Always use colon after env to access variables: $env:VAR [OK]

Common Mistakes:

• Omitting colon after env
• Assuming variable names are case sensitive
• Trying to quote variable name instead of fixing syntax

5. You want to temporarily add a folder C:\Tools to the PATH environment variable for your current PowerShell session only. Which command correctly does this?

hard

A. $env:PATH = $env:PATH + ';C:\Tools'

B. setx PATH "$env:PATH;C:\Tools"

C. New-Item -Path Env:PATH -Value 'C:\Tools'

D. $env:PATH += 'C:\Tools'

Solution

1. Step 1: Understand session vs persistent environment variables

   Modifying $env:PATH directly changes it only for the current session.

2. Step 2: Append new folder to existing PATH

   Use $env:PATH = $env:PATH + ';C:\Tools' to add the folder, separating with a semicolon.

3. Final Answer:

   $env:PATH = $env:PATH + ';C:\Tools' -> Option A

4. Quick Check:

   Append with $env:PATH = $env:PATH + ';new_path' [OK]

Hint: Append with $env:PATH = $env:PATH + ';new_folder' for session only [OK]

Common Mistakes:

• Using setx which changes persistent variables, not session
• Using += without semicolon separator
• Overwriting PATH without appending