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PowerShell Scripting

PowerShell is a task-based command-line shell and scripting language built on .NET. PowerShell helps system administrators and power-users rapidly automate task that manage operating systems (Linux, macOS, and Windows) and processes.

PowerShell offers more benefits compared to Bash for power-users, some of which include:

  • First of all PowerShell is being told to compatible for Windows, Linux, and macOS.
  • PowerShell also offer backward compatibility for Windows PowerShell. PowerShell also supports the windows commands like cd.
  • PowerShell 7 is a next-generation version of PowerShell 5.1 and 6.0 that offer. It offers more features and one notable feature is auto completion which makes scripting easier and faster.

Useful Resources and Reads:

PowerShell Tutorial​

PowerShell 7 can be launched using pwsh command.

PowerShell Profiles​

PowerShell profiles offer a way to store configuration settings for the current user or for all users on the system. To list all available profiles, run the following command:

$Profile | Select-Object *

It would print something like this:

AllUsersAllHosts       : C:\Program Files\PowerShell\7\profile.ps1
AllUsersCurrentHost    : C:\Program Files\PowerShell\7\Microsoft.PowerShell_profile.ps1
CurrentUserAllHosts    : C:\Users\<username>\Documents\PowerShell\profile.ps1
CurrentUserCurrentHost : C:\Users\<username>\Documents\PowerShell\Microsoft.PowerShell_profile.ps1
Length                 : 81

PowerShell profiles can be edited using the profile.ps1 file.

tip

My CurrentUserCurrentHost profile is customized as below to include my name in the prompt.

  • Call $Profile | Select-Object * to list all available profiles. Get the path of the CurrentUserCurrentHost profile and open it in code using code <profile path>.
  • Alternatively, call the following command code $Profile.CurrentUserCurrentHost to directly open the profile.

Open Current User Current Host PS Profile

code $Profile.CurrentUserCurrentHost

Customize the PS Launch Pre-Operation. Adding the below context to the file will print the statement whenever a PS is launched from CurrentUserCurrentHost.

Write-Host "Welcome to <Name>" -ForegroundColor Green PowerShell!"

Useful PowerShell Commands​

  • Plain text
Write-Host "Hello World"
  • Write Error to the console
Write-Error "This is an error message"
  • Print warning to the console, Similar to echo in Bash.
Write-Warning "This is a warning message"

Create a new file​

New-Item -Path "path/to/file.txt" -ItemType File

The command can also be simplified to

New-Item "path/to/file.txt"

Delete a file​

Remove-Item -Path "path/to/file.txt"

The command can also be simplified to

Remove-Item "path/to/file.txt"

Move a file​

Move-Item -Path "path/to/file.txt" -Destination "path/to/new/file.txt"

The command can also be simplified to

Move-Item "path/to/file.txt" "path/to/new/file.txt"

Parameters​

Reference​

Inputs​

  • Parameters should be defined on top of the file.
  • Parameters can be prefixed with data type and assigned default values.
  • You can get help on the parameters by calling Get-Help command on the powershell script.
Param(
    [Parameter(Mandatory, HelpMessage = "Name of the Executor", Position=0)]
    [string]$Name,

    [Parameter(HelpMessage = "Age of the Executor", Position=1)]
    [ValidateRange(1, 120)]
    [int]$Age,

    [Parameter(HelpMessage = "Favorite Color of the Executor", Position=2)]
    [ValidateSet("Red", "Green", "Blue")]
    [string]$FavoriteColor = "Blue",

    [Parameter(HelpMessage = "Optional Parameter", Position=3)]
    [switch]$Flag
)
  • Some common parameter types are listed above: string, int and switch (boolean).
  • Parameters can be used in the script by using $ParameterName variable.
  • $ sign can be escaped by prefixing it with backtick.
  • Parameters can be passed to the script using .\script.ps1 -Name "John" -Age 30 -FavoriteColor "Red"
  • Parameters can be made optional by assigning default values to them.
  • Validation can be added for the parameters. Couple of examples are listed above including ValidateRange which validates the input against a range of values and ValidateSet which validates the input against a set of values.
  • When the switch parameter is uncalled the default value is false.
tip

Compressing a folder using powershell

Compress-Archive -Path .\folder -CompressionLevel Fastest -DestinationPath .\folder.zip

Flow Control​

If-Else​

Powershell provides if, elseif and else keywords.

if ($Flag) {
    Write-Host "Flag is true"
} else {
    Write-Host "Flag is false"
}
tip

Useful keywords in if-else statements

  • -eq - Equal
  • -ne - Not Equal
  • -gt - Greater Than
  • -ge - Greater Than or Equal
  • -lt - Less Than
  • -le - Less Than or Equal
  • -and - Logical And
  • -or - Logical Or
  • -not - Logical Not