[Powershell Examples] #PowerShell #Examples

Format-Relative.ps1

<#
.SYNOPSIS
    Diffrent methods for displaying relative path
#>

# Existing Path
$PWD | Resolve-Path -Relative

# Replace String
$Path -replace [regex]::Escape((Get-Location).Path), '.'

Get-ImageData.ps1

<#
.SYNOPSIS
    Get image information
#>

Add-Type -AssemblyName System.Drawing
$Image = [System.Drawing.Image]::FromFile('.\path\to\img.png')
$Image.size

Get-LastAccess.ps1

<#
.SYNOPSIS
    Retreive a timestamp of when an item was accessed.
#>

Write-Host "`nThe " + "$" + "HOME Directory was last accessed at: " + $(Get-Item $HOME).LastAccessTime

Get-ModuleCount.ps1

<#
.SYNOPSIS
	Measure the amount of loaded modules.
#>
Write-Host "Number of modules loaded = " + (Get-Module).Count

Hide-Item.ps1

<#
.SYNOPSIS
    Change item attributes, i.e. 'Hidden'
.NOTES
    ! For files/folders that are already hidden, Force paramater is REQUIRED!
    Otherwise Get-Item/Get-ChildItem cannot access the item.
#>

$Path = "your_path_here"

# For a single file, you can change the attributes property, like this:
$Item = Get-Item -Path:$Path -Force
$Item.Attributes = "Hidden"

# To hide everything within a folder, you can use Get-ChildItem, like this:
Get-ChildItem -Path:$Path -Recurse -Force | ForEach-Object { $_.Attributes = "Hidden" }

Invoke-BSOD.ps1

<#
.SYNOPSIS
    Invokes a Blue Screen of Death from remote script; w/o admin privileges.
.LINK
    Source: https://github.com/peewpw/Invoke-BSOD
#>

# Quick One-liner
Invoke-Expression((New-Object Net.Webclient).DownloadString('https://raw.githubusercontent.com/peewpw/Invoke-BSOD/master/Invoke-BSOD.ps1')); Invoke-BSOD

# Seperated
$URI = 'https://raw.githubusercontent.com/peewpw/Invoke-BSOD/master/Invoke-BSOD.ps1'
Invoke-Expression((New-Object Net.Webclient).DownloadString($URI))
Invoke-BSOD

Measure-Filesize.ps1

<#
.SYNOPSIS
    Determine human readable filesize
.LINK
    https://stackoverflow.com/questions/24616806/powershell-display-files-size-as-kb-mb-or-gb
#>

# !IMPORTANT: Get-Help command wont work if script starts with function.
# This is required for example scripts to generate markdown description from Synopsis.
Write-Host "`n" (Get-Help $PSCommandPath).Synopsis

function DisplayInBytes($Value) {
    $Index = 0
    $Suffix = "B", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"
    while ($Value -gt 1kb) {
        $Value = $Value / 1kb
        $Index++
    }
    "{0:N1} {1}" -f $Value, $Suffix[$Index]
}

# Invocation context, only execute if NOT sourced
if ($MyInvocation.InvocationName -eq '.') {
    Write-Host "This script is not designed to be sourced" -ForegroundColor Red
    return
}

# Execute Example
Write-Host "Directory Information" -ForegroundColor Magenta
$Files = Get-ChildItem -Recurse
$Bytes = ($Files | Measure-Object -Property Length -Sum).Sum
$Hash = [ordered]@{
    Filecount  = $Files.Count
    WorkingDir = $PWD
}
$Hash | Format-Table -HideTableHeaders

Write-Host "Static Measurements" -ForegroundColor Magenta
$Hash = [ordered]@{
    Bytes     = $Bytes
    Kilobytes = ("{0} KB" -f ($Bytes / 1KB))
    Megabytes = ("{0} MB" -f ($Bytes / 1MB))
    Gigabytes = ("{0} GB" -f ($Bytes / 1GB))
    Terabytes = ("{0} TB" -f ($Bytes / 1TB))
}
$Hash | Format-Table -HideTableHeaders

Write-Host "Dynamic Measurements" -ForegroundColor Magenta
$Hash = [ordered]@{
    Bytes     = $Bytes
    Truncated = $(DisplayInBytes $Bytes)
}
$Hash | Format-Table -HideTableHeaders

Select-GridView.ps1

<#
.SYNOPSIS
    GUI listview of symbolic links, selection opens path in explorer.
#>

$ReparsePoints = Get-ChildItem -Path $ENV:USERPROFILE -Recurse -Depth 4 |
Where-Object { $_.Attributes -match "ReparsePoint" }
$Selection = $ReparsePoints | Out-GridView -PassThru -Title "Symbolic Links"
if ( $Null -ne $Selection) { Invoke-Item $Selection }

Show-AnsiColorGradient.ps1

<#
.SYNOPSIS
    Display a color gradient in the terminal. Just for fun.
.LINK
    https://www.reddit.com/r/PowerShell/comments/b06gtw/til_that_powershell_can_do_colors/
#>

# !IMPORTANT: Get-Help command wont work if script starts with function.
# This is required for example scripts to generate markdown description from Synopsis.
Write-Host "`n" (Get-Help $PSCommandPath).Synopsis

function Show-AnsiColorGradient {
    # ANSI escape character
    $ansi_escape = [char]27
    try {
        for ($r = 0; $r -le 255; $r += 16) {
            for ($g = 0; $g -le 255; $g += 8) {
                Write-Host "" # Separate
                for ($b = 0; $b -le 255; $b += 4) {
                    $ansi_command = "$ansi_escape[48;2;{0};{1};{2}m" -f $r, $g, $b
                    $text = " "
                    $ansi_terminate = "$ansi_escape[0m"
                    $out = $ansi_command + $text + $ansi_terminate
                    Write-Host -NoNewline $out
                }
            }
            break
        }
    }
    finally {
        Write-Host "" # Separate
    }
}

Show-Confirmation.ps1

<#
.SYNOPSIS
    Prompt user for [y/n] confirmation.
.NOTES
    * Consider:
    If a cmdlet supports the -confirm parameter, it can be forced to prompt before any action.
    I just like version #1 because it's concise.
#>

# Version #1
$Message = "Are you sure you wish to commit this action?"
while ( -not ( ($Choice = (Read-Host $Message)) -match "y|n")) { $Message = "Please specify [y/n]" }
if ($Choice -notmatch "[yY]") { break }

# Version #2
$Caption = "Confirm"
$Message = "Are You Sure?"
$Yes = New-Object System.Management.Automation.Host.Choicedescription "&Yes", "Help"
$No = New-Object System.Management.Automation.Host.Choicedescription "&No", "Help"
$Choices = [System.Management.Automation.Host.Choicedescription[]]($Yes, $No)
$Answer = $Host.Ui.Promptforchoice($Caption, $Message, $Choices, 0)

Switch ($Answer) {
    0 { "You Entered 0"; Break }
    1 { "You Entered 1"; Break }
}

Show-MessageBox.ps1

<#
.SYNOPSIS
    Make a GUI Message Box visible to the user
.EXAMPLE
    * Windows Forms:
    Add-Type -AssemblyName System.Windows.Forms
    [System.Windows.Forms.MessageBox]::Show('Hello')
.LINK
    https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.messagebox
.EXAMPLE
    * PresentationFramework:
    Add-Type -AssemblyName PresentationFramework
    [System.Windows.MessageBox]::Show('Hello')
.LINK
    https://docs.microsoft.com/en-us/dotnet/api/system.windows.messagebox
#>

# MessageBox Dialog
$Title = 'MessageBox Example'
$Message = 'What action do you wish to take?'
$ButtonType = 'YesNoCancel'
$MessageIcon = 'Error'

Add-Type -AssemblyName PresentationFramework
$MsgBox = [System.Windows.MessageBox]::Show($Message, $Title, $ButtonType, $MessageIcon)

switch ($MsgBox) {
    'Yes' { Write-Output "You clicked 'Yes'" }
    'No' { Write-Output "You clicked 'No'" }
    'Cancel' { Write-Output "You clicked 'Cancel'" }
}

Test-AppendPerformance.ps1

<#
.SYNOPSIS
    Comparing the performance of two serperate appending methods
.DESCRIPTION
    PowerShell, arrays are of a fixed size.
    This means that each time you use the '+=' in the background you are creating a brand new array,
    containing the old contents plus the newly appended item.
    This is computationally expensive! It would be better to use [Collections.Generic.List]
.LINK
    Reference: https://theposhwolf.com/howtos/PS-Plus-Equals-Dangers/
#>

# Set the number of loop iterations
$Iterations = 10000

# Powershell version information
Write-Host "`nPS $($PSVersionTable.PSEdition) $($PSVersionTable.PSVersion.ToString())`n"

$Measurement_01 = Measure-Command {
    $Array = @()
    1..$Iterations | ForEach-Object { $Array += "$_" }
}
# Example #1 -- Standard Array
Write-Host "'Array +='`t: " -NoNewline
Write-Host "Milliseconds: $($Measurement_01.TotalMilliseconds)"

# Example #2 -- Generic List
$Measurement_02 = Measure-Command {
    $List = [System.Collections.Generic.List[string]]::new()
    1..$Iterations | ForEach-Object { $null = $List.Add("$_") }
}
Write-Host "'List.Add()'`t: " -NoNewline
Write-Host "Milliseconds: $($Measurement_02.TotalMilliseconds)"

# Compute difference
Write-Host "'Complete'`t: " -NoNewline
Write-Host "Milliseconds: $($Measurement_02.TotalMilliseconds + $Measurement_01.TotalMilliseconds)"

Test-Interrupt.ps1

<#
.SYNOPSIS
    Continue script action after interuption.
.DESCRIPTION
    Using 'try : finally' blocks to continue some action,
    even if the user stops the script preemptively.
.NOTES
    Additionally,
    the stationary loop counter showed me that when calculating the length of an integer,
    you can convert it to a string.
#>

Try {
    $counter = 0
    Write-Host "`nThis script will not stop on its own" -fore yellow
    Write-Host "Press 'Ctrl+C' to stop the current script...`n"
    Write-Host "Loop: " -NoNewline
    While ($True) {
        # Runs ad infinitum
        Write-Host ("$counter" + ("`b" * $counter.tostring().length)) -NoNewline
        Start-Sleep 1
        $counter++
    }
}
Finally {
    Write-Host "`nScript has been terminated." -fore red; ""
}

Test-Invocation.ps1

<#
.SYNOPSIS
    Check script invocation method
.DESCRIPTION
    Verify the invocation method of the current script.
    Allowing for similar functionality to python's if __name == '__main__':
    A script function can be sourced without running the payload.
    Or executed as a standalone script.
#>

# Checking Command Origin
# Runspace if script is executed
# Internal if script is imported
if ($MyInvocation.CommandOrigin -eq 'Runspace') { Write-Host "Runspace" }
if ($MyInvocation.CommandOrigin -eq 'Internal') { Write-Host "Internal" }

# Alternatively, more information about how the script was started
If ($MyInvocation.InvocationName -eq '&') {
    "Called using operator: '$($MyInvocation.InvocationName)'"
}
ElseIf ($MyInvocation.InvocationName -eq '.') {
    "Dot sourced: '$($MyInvocation.InvocationName)'"
}
ElseIf ((Resolve-Path -Path $MyInvocation.InvocationName).ProviderPath -eq $MyInvocation.MyCommand.Path) {
    "Called using path: '$($MyInvocation.InvocationName)'"
}

Test-Pipeline.ps1

<#
.SYNOPSIS
    Does something with paths supplied via pipeline.
.PARAMETER Path
    Specifies a path to one or more locations. Wildcards are permitted.w
    The default location is the current directory (.).
.LINK
    https://stackoverflow.com/questions/30893839/create-powershell-parameter-default-value-is-current-directory
#>

# !IMPORTANT: Get-Help command wont work if script starts with function.
# This is required for example scripts to generate markdown description from Synopsis.
Write-Host "`n" (Get-Help $PSCommandPath).Synopsis

Function Test-Pipeline {
    [CmdletBinding()]
    param(
        [Parameter(
            Mandatory = $False,
            ValueFromPipeline = $True,
            ValueFromPipelineByPropertyName = $True
        )]
        [PSDefaultValue(Help = 'Description for default value.')]
        [SupportsWildcards()]
        [String[]]$Path = '.'
    )

    BEGIN { Write-Host "Script Begin!" }
    PROCESS {
        $Path | ForEach-Object {
            $Item = Get-Item $_
            Write-Host "Item: $Item"
        }
    }
    END { Write-Host "Script End!" }
}

Test-ProgressBar.ps1

<#
.SYNOPSIS
    Display & update progress bar
.DESCRIPTION
    For this we will be counting for 1 minute; the Start-Sleep function is 1 second
    By looping through each second and calculating the percent complete we can update the progess bar.
#>

# !IMPORTANT: Get-Help command wont work if script starts with function.
# This is required for example scripts to generate markdown description from Synopsis.
Write-Host "`n" (Get-Help $PSCommandPath).Synopsis

function Test-ProgressBar {
    Write-Host -fore Cyan "Let's just take a minute to relax..."
    For ($i = 0; $i -le 60; $i++) {
        Write-Progress -Activity "I'll count. $i second[s]" -PercentComplete ($i / 60 * 100)
        Start-Sleep 1
    }
}

Test-WhatIf.ps1

<#
.SYNOPSIS
    Example function for '-WhatIf' parameter support.
#>

# !IMPORTANT: Get-Help command wont work if script starts with function.
# This is required for example scripts to generate markdown description from Synopsis.
Write-Host "`n" (Get-Help $PSCommandPath).Synopsis

Function Test-WhatIf {
    [CmdletBinding(SupportsShouldProcess)]
    Param([String]$Objects)

    ForEach ($item in $Objects) {
        If ($PSCmdlet.ShouldProcess("$item", "Action")) {
            "Action: -> $item" # This will only run without '-WhatIf'
        }
    }
}

# Invocation context, only execute if NOT sourced
if ($MyInvocation.InvocationName -ne '.') {
    Test-WhatIf "ITEM" -WhatIf
}

Write-HostCenter.ps1

<#
.SYNOPSIS
    Display text in the center of the terminal window.
.DESCRIPTION
    * Bonus Example: Selection Menu
    A function that calculates the center of the console by character columns to display some text,
    This is mostly a stylistic function. It doesn't fair very well when the console window is resized.
#>

# !IMPORTANT: Get-Help command wont work if script starts with function.
# This is required for example scripts to generate markdown description from Synopsis.
Write-Host "`n" (Get-Help $PSCommandPath).Synopsis

function Write-HostCenter {
    Param($Message)
    Write-Host ("{0}{1}" -f (' ' * (([Math]::Max(0, $Host.UI.RawUI.BufferSize.Width / 2) - [Math]::Floor($Message.Length / 2)))), $Message)
}

function Show-Menu {
    Param ([string]$Title = 'My Menu')
    Clear-Host
    Write-HostCenter "================ $Title ================"

    Write-HostCenter "1: Press '1' for this option."
    Write-HostCenter "2: Press '2' for this option."
    Write-HostCenter "3: Press '3' for this option."
    Write-HostCenter "Q: Press 'Q' to quit."

}

Do {
    Show-Menu
    $input = Read-Host "Please make a selection"
    Switch ($input) {
        '1' { 'You chose option #1' }
        '2' { 'You chose option #2' }
        '3' { 'You chose option #3' }
        'q' { Return }
    }
    Pause
}
Until ($input -eq 'q')
Clear-Host