Basics of Writing PowerShell Scripts

Mohammad Gufran Jahangir August 7, 2025 0

🧩 1. What is PowerShell?

A task automation and configuration management tool.
Used by IT admins, SREs, and cloud engineers for managing Windows, Azure, and more.
Works with cmdlets (built-in functions), scripts, REST APIs, and .NET objects.

🛠️ 2. Basic Structure of a PowerShell Script

# My first script
Write-Host "Hello, world!"

Save as myscript.ps1 and run it in PowerShell.

🧱 3. Core Building Blocks

✅ Variables

$name = "Gufran"
$age = 30

✅ Strings

Write-Host "Hello, $name"

✅ Arrays & Loops

$servers = @("server1", "server2")
foreach ($s in $servers) {
    Write-Host "Pinging $s"
}

✅ If Conditions

if ($age -gt 18) {
    Write-Host "Adult"
} else {
    Write-Host "Minor"
}

🧰 4. Functions

function Say-Hello {
    param([string]$name)
    Write-Host "Hello, $name!"
}

Say-Hello -name "Rahul"

📦 5. Parameters and Script Arguments

param(
  [string]$UserName,
  [int]$Age
)

Write-Host "Name: $UserName, Age: $Age"

Run as:

.\myscript.ps1 -UserName "Rahul" -Age 30

🧪 6. Error Handling

try {
    Get-Item "C:\nonexistent.txt"
}
catch {
    Write-Host "Error occurred: $($_.Exception.Message)"
}

📁 7. File Operations

# Read
$content = Get-Content "file.txt"

# Write
Set-Content "file.txt" "New content"

# Append
Add-Content "file.txt" "Additional line"

🌐 8. Calling REST APIs

$token = "Bearer YOUR_TOKEN"
Invoke-RestMethod -Uri "https://api.example.com" -Headers @{Authorization = $token}

🔧 9. Useful Cmdlets for Admins

Cmdlet	Use
`Get-Service`	View Windows services
`Restart-Service`	Restart a service
`Get-Process`	View processes
`Start-Process`	Launch an app
`Test-Connection`	Ping
`Get-EventLog`	Read event logs
`Get-AzSqlDatabase`	Azure SQL info
`Start-Sleep -Seconds 5`	Pause execution

🧾 10. Commenting Code

# Single-line comment

<#
Multi-line
comment
#>

📦 11. Modules and Importing

Import-Module Az.Accounts

Install if not present:

Install-Module Az -AllowClobber -Scope CurrentUser

⚙️ 12. Running Scripts

Run the script:

.\yourscript.ps1

Allow script execution (once):

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

🛡️ 13. Best Practices

Always use parameter validation:

[Parameter(Mandatory)]
[ValidateNotNullOrEmpty()]
[string]$ServerName

Use try/catch for all critical tasks
Comment your code
Use logging and output clearly
Avoid hardcoding secrets (use Key Vault or variables)

🔄 14. Practical Script Example for Admins

param(
  [string]$ServerName
)

if (Test-Connection -ComputerName $ServerName -Count 1 -Quiet) {
    Write-Host "$ServerName is reachable"
} else {
    Write-Host "$ServerName is not reachable"
}

🧠 Want to Practice?

Try writing these:

A script to stop and start a Windows service
A script to read a list of servers from CSV and ping them
A script to monitor disk space and send alert if low

Category:

powershell