Mastering Windows PowerShell Scripting - Second Edition

PowerShell uses a tick as a multipurpose escaped character.

A tick may be used as a line continuation character. Consider the following example:

'one' -replace 'o', 't' ` 
      -replace 'n', 'w' ` 
      -replace 'e', 'o' 

When using a tick to split a long statement across several lines, the tick must be the last character (it cannot be followed by a space or any other character).

A tick is used to construct several characters that can be used in strings:

The tab character, for example, may be included in a string:

PS> Write-Host "First`tSecond" 
First Second  

Alternatively, the bell sound may be played in the PowerShell console (but not ISE):

Write-Host "`a"

ISE is a rich editing environment that includes IntelliSense, built-in help, syntax checking, debugging, and so on.

Additional features are available for ISE from the following add-on tools website:

http://social.technet.microsoft.com/wiki/contents/articles/2969.windows-powershell-ise-add-on-tools.aspx

If you are developing code for use on production systems, I strongly recommend adding PS Script Analyzer. PS Script Analyzer will highlight areas of your code that do not conform to its rule set; for example, using an alias instead of a command name would be highlighted.

Community and commercial add-ons can greatly extend the functionality of ISE to simplify day-to-day use.

In PowerShell 5, the distribution model for ISE is in the process of changing. Until version 5, ISE was released as a part of the Windows Management Framework (WMF). New features were introduced with each version of WMF, but the time between the versions was long.

ISE Preview may be installed from the PowerShell gallery using the following command:

Install-Module -Name PowerShellISE-Preview

Once installed, the update-module command may be used to bring ISE up to par with the published version.

ISE Preview can coexist with the version of ISE installed by the WMF package.

ISE may be started from the start menu; however, running the powershell_ise command (from the Run dialog, cmd, or the search box) is sufficient. In PowerShell, the simpler ise command is aliased to powershell_ise.exe.

If the preview version from the PowerShell gallery is being used, the following command will start that version of ISE:

Start-ISEPreview 

This first preview version differs a little from the version of ISE shipping with WMF 5. If the distribution model is successful, the PowerShell team hopes to release a new version of ISE every month, with each release fixing bugs and/or adding new features.

VS Code does not come with the native PowerShell support. It must be added. Once VS Code is installed, open it, and select the EXTENSIONS button on the left-hand side.

Type PowerShell in the search dialog box, and install the PowerShell language support:

After installation, the extension provides Syntax highlighting, testing using PowerShell Script Analyzer, debugging, and so on.

Unlike ISE, the console (or terminal, as it is named) in VS Code must be configured. By default, the terminal in code uses cmd.exe.

The following process is used to make the terminal use PowerShell:

"terminal.integrated.shell.windows": "C:\\Windows\\sysnative\\WindowsPowerShell\\v1.0\\powershell.exe" 

Visual Studio Code comes with integrated support for Git version control. Git is a distributed version control system; each developer has a copy of the same repository.

Setting up a repository is simple, as follows:

Subsequent changes to files may be inspected before committing again:

Windows editors, including ISE, tend to use a carriage return followed by linefeed (\r\n or `r`n) at the end of each line. Linux editors use linefeed only (\n or `n).

Line endings are less important if the only thing reading the file is PowerShell (on any platform). However, if a script is set to executable on Linux, a sha-bang must be included and the line-ending character used must be linefeed only.

For example, a created as follows named test.ps1 must use \n to end lines:

#!/usr/bin/env powershell 
Get-Process

The first line is the sha-bang and lets Linux know which parser to use when executing the shell script.

Once created, chmod may be used to make the script executable outside of PowerShell:

chmod +x test.ps1

After being made executable, the script may be executed from bash with the full path or a relative path:

./test.ps1

Windows editors, including ISE, tend to save files using what is commonly known as ANSI encoding; this is more correctly known as Windows-1252.

As Windows-1252 is a Microsoft native format, it may be more appropriate to save files in a universally accepted format such as UTF8.

Testing shows that PowerShell on Linux is forgiving about path separators; that is, Microsoft Windows uses the backslash (\), where Linux uses a forward slash (/).

If anything outside of PowerShell (including native commands) is to be used, a correct separator should be chosen.

The Join-Path command will merge path elements using the correct separator for each platform. Manual path construction (based on merging strings) should be avoided.

The following function uses the System.Net.NetworkInformation namespace to discover IPv4 address information. This allows us to return the same thing whether it is run on Windows or Linux.

If it were Windows only, we might have used WMI or the Get-NetIPConfiguration command. Creating something to work on both operating systems is more challenging:

function Get-IPConfig { 
    [System.Net.NetworkInformation.NetworkInterface]::GetAllNetworkInterfaces() | ForEach-Object { 
        $ipProperties = $_.GetIPProperties() 
             
        $addresses = $ipProperties.UnicastAddresses | 
            Where-Object { 
                $_.Address.AddressFamily -eq 'InterNetwork' 
            } | ForEach-Object { 
                "$($_.Address) $($_.IPv4Mask)" 
            } 
 
        $gateway = $ipProperties.GatewayAddresses.Address | 
            Where-Object { 
                $_.AddressFamily -eq 'InterNetwork' -and  
                $_ -ne '0.0.0.0' 
            } 
 
        [PSCustomObject]@{ 
            Name      = $_.Name 
            Id        = $_.Id 
            Addresses = $addresses 
            Gateway   = $gateway 
        } 
    } | Where-Object { $_.Addresses } 
} 
Get-IPConfig