Master PowerShell Scripting with Functions, Modules, and Real-World Fixes

Introduction

PowerShell isn’t just a scripting language. Whether you’re a sysadmin, DevOps engineer, or automation enthusiast, knowing how to write reusable code using functions, organize your scripts into modules, and troubleshoot effectively will save hours of repetitive work.

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PowerShell Functions: Reusable Brilliance

Functions let you encapsulate logic for reuse across scripts.

Basic Function Example:

function Get-SystemInfo {

    Write-Output "Computer Name: $env:COMPUTERNAME"

    Write-Output "OS Version: $(Get-CimInstance Win32_OperatingSystem).Version"

    Write-Output "Logged In User: $env:USERNAME"

}

<strong># Call the function</strong>

Get-SystemInfo

Function with Parameters:

powershell

CopyEdit

function Get-ServiceStatus {

    param (

        [string]$ServiceName

    )

    Get-Service -Name $ServiceName | Select-Object Name, Status

}

function Get-SystemInfo {

Write-Output "Computer Name: $env:COMPUTERNAME"

Write-Output "OS Version: $(Get-CimInstance Win32_OperatingSystem).Version"

Write-Output "Logged In User: $env:USERNAME"

}

# Call the function

Get-SystemInfo

Function with Parameters:

powershell

CopyEdit

function Get-ServiceStatus {

param (

[string]$ServiceName

)

Get-Service -Name $ServiceName | Select-Object Name, Status

}

# Usage

Get-ServiceStatus -ServiceName 'wuauserv'

1	Get-ServiceStatus -ServiceName 'wuauserv'

Creating PowerShell Modules: Organize Like a Pro

Modules help structure your scripts and functions into reusable components.

Step 1: Create a .psm1 File

# File: MyTools.psm1

function Get-DiskSpace {

    Get-PSDrive -PSProvider 'FileSystem' |

        Select-Object Name, Used, Free

}




function Restart-SafeService {

    param([string]$ServiceName)

    Restart-Service -Name $ServiceName -Force

}

# File: MyTools.psm1

function Get-DiskSpace {

Get-PSDrive -PSProvider 'FileSystem' |

Select-Object Name, Used, Free

}

function Restart-SafeService {

param([string]$ServiceName)

Restart-Service -Name $ServiceName -Force

}

Step 2: Import the Module

# Save the file, then:

Import-Module "C:\Path\To\MyTools.psm1"

1	Import-Module "C:\Path\To\MyTools.psm1"

# Use the functions

<strong>Get-DiskSpace</strong>

<strong>Restart-SafeService -ServiceName 'Spooler'</strong>

Get-DiskSpace

Restart-SafeService -ServiceName 'Spooler'

You can also create a module manifest (.psd1) for advanced features like versioning and dependency management.

Troubleshooting PowerShell Scripts: Common Pitfalls

Troubleshooting PowerShell Scripts: Common Pitfalls

Use -Verbose and -Debug

function Test-Network {

    [CmdletBinding()]

    param([string]$Host)

    Write-Verbose "Pinging $Host..."

    Test-Connection $Host -Count 2

}

function Test-Network {

[CmdletBinding()]

param([string]$Host)

Write-Verbose "Pinging $Host..."

Test-Connection $Host -Count 2

}

Test-Network -Host “google.com” -Verbose

$Error and Try/Catch for Error Handling

try {

    Get-Item "C:\nonexistent.txt"

} catch {

    Write-Error "File not found: $_"

}

try {

Get-Item "C:\nonexistent.txt"

} catch {

Write-Error "File not found: $_"

}

Check Execution Policy

Scripts not running? Check:

Get-ExecutionPolicy

Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy RemoteSigned

Get-ExecutionPolicy

Set-ExecutionPolicy -Scope CurrentUser -ExecutionPolicy RemoteSigned

Some More Examples :

Function for Recursive Directory Search with Error Handling

This function searches for files within a directory and subdirectories, with error handling for inaccessible paths.

function Search-DirectoryFiles {

    param (

        [string]$DirectoryPath,

        [string]$FileType = "*.*"

    )




    if (-not (Test-Path $DirectoryPath)) {

        Write-Error "The directory path '$DirectoryPath' does not exist."

        return

    }

    try {

        $files = Get-ChildItem -Path $DirectoryPath -Recurse -Filter $FileType -ErrorAction Stop

        return $files

    } catch {

        Write-Error "Error accessing directory '$DirectoryPath'."

    }

}

function Search-DirectoryFiles {

param (

[string]$DirectoryPath,

[string]$FileType = "*.*"

)

if (-not (Test-Path $DirectoryPath)) {

Write-Error "The directory path '$DirectoryPath' does not exist."

return

}

try {

$files = Get-ChildItem -Path $DirectoryPath -Recurse -Filter $FileType -ErrorAction Stop

return $files

} catch {

Write-Error "Error accessing directory '$DirectoryPath'."

}

Usage:

Search-DirectoryFiles -DirectoryPath "C:\Logs" -FileType "*.log"

1	Search-DirectoryFiles -DirectoryPath "C:\Logs" -FileType "*.log"

This function allows searching recursively and includes error handling for invalid or inaccessible directories.

PowerShell Module for Disk Space Monitoring (with Exported Data)

This module defines functions for monitoring disk space and exporting the data to a CSV file.

# DiskSpaceModule.psm1

function Get-DiskSpace {

    $drives = Get-PSDrive -PSProvider FileSystem

    $diskSpaceInfo = $drives | Select-Object Name, @{Name="UsedGB"; Expression={[math]::Round($_.Used / 1GB, 2)}}, @{Name="FreeGB"; Expression={[math]::Round($_.Free / 1GB, 2)}}, @{Name="TotalGB"; Expression={[math]::Round($_.Used / 1GB, 2) + [math]::Round($_.Free / 1GB, 2)}}

    return $diskSpaceInfo

}

function Export-DiskSpaceReport {

    param (

        [string]$FilePath = "C:\disk_space_report.csv"

    )

    $diskSpace = Get-DiskSpace

    $diskSpace | Export-Csv -Path $FilePath -NoTypeInformation

    Write-Output "Disk space report exported to $FilePath"

}

# DiskSpaceModule.psm1

function Get-DiskSpace {

$drives = Get-PSDrive -PSProvider FileSystem

$diskSpaceInfo = $drives | Select-Object Name, @{Name="UsedGB"; Expression={[math]::Round($_.Used / 1GB, 2)}}, @{Name="FreeGB"; Expression={[math]::Round($_.Free / 1GB, 2)}}, @{Name="TotalGB"; Expression={[math]::Round($_.Used / 1GB, 2) + [math]::Round($_.Free / 1GB, 2)}}

return $diskSpaceInfo

}

function Export-DiskSpaceReport {

param (

[string]$FilePath = "C:\disk_space_report.csv"

)

$diskSpace = Get-DiskSpace

$diskSpace | Export-Csv -Path $FilePath -NoTypeInformation

Write-Output "Disk space report exported to $FilePath"

}

Usage:

Import-Module "C:\Path\To\DiskSpaceModule.psm1"

Export-DiskSpaceReport -FilePath "C:\Reports\disk_report.csv"

Import-Module "C:\Path\To\DiskSpaceModule.psm1"

Export-DiskSpaceReport -FilePath "C:\Reports\disk_report.csv"

This module allows you to monitor and export disk space usage into a CSV for later analysis.

PowerShell Module for User Management (with Creation and Deletion)

This module provides user management functions for creating and deleting users with validation checks.

# UserManagement.psm1

function New-User {

    param (

        [string]$Username,

        [string]$Password

    )




    if (Get-LocalUser -Name $Username -ErrorAction SilentlyContinue) {

        Write-Error "User $Username already exists."

        return

    }

    New-LocalUser -Name $Username -Password (ConvertTo-SecureString -AsPlainText $Password -Force) -FullName "$Username User"

    Write-Output "User $Username created successfully."

}

function Remove-User {

    param (

        [string]$Username

    )

    if (-not (Get-LocalUser -Name $Username -ErrorAction SilentlyContinue)) {

        Write-Error "User $Username does not exist."

        return

    }

    Remove-LocalUser -Name $Username

    Write-Output "User $Username removed successfully."

}

# UserManagement.psm1

function New-User {

param (

[string]$Username,

[string]$Password

)

if (Get-LocalUser -Name $Username -ErrorAction SilentlyContinue) {

Write-Error "User $Username already exists."

return

}

New-LocalUser -Name $Username -Password (ConvertTo-SecureString -AsPlainText $Password -Force) -FullName "$Username User"

Write-Output "User $Username created successfully."

}

function Remove-User {

param (

[string]$Username

)

if (-not (Get-LocalUser -Name $Username -ErrorAction SilentlyContinue)) {

Write-Error "User $Username does not exist."

return

}

Remove-LocalUser -Name $Username

Write-Output "User $Username removed successfully."

}

Usage:

Import-Module "C:\Path\To\UserManagement.psm1"

New-User -Username "NewUser" -Password "SecureP@ss123"

Remove-User -Username "OldUser"

Import-Module "C:\Path\To\UserManagement.psm1"

New-User -Username "NewUser" -Password "SecureP@ss123"

Remove-User -Username "OldUser"

This module manages user accounts by providing functions for both creating and removing users, with built-in validation to check if the user exists or not.

Conclusion

PowerShell scripting becomes truly powerful when you learn to structure your code with functions and modules, and master troubleshooting techniques.

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