Cross-Platform PowerShell

PowerShell 7 runs on Windows, Linux, and macOS — but scripts only work everywhere if you write them that way.

Detecting the platform

# illustrative
if ($IsWindows) { 'Windows' }
elseif ($IsLinux) { 'Linux' }
elseif ($IsMacOS) { 'macOS' }
$PSVersionTable.OS

$IsWindows, $IsLinux, and $IsMacOS exist in PowerShell 6+. (In Windows PowerShell 5.1 they're undefined — treat $null as Windows.)

Paths

$base = Join-Path $PSScriptRoot 'data'
$file = Join-Path 'data' 'reports' 'summary.csv'
[System.IO.Path]::GetFileName($file)
[System.IO.Path]::DirectorySeparatorChar -in '\', '/'
[System.IO.Path]::GetTempPath().Length -gt 0

summary.csv
True
True

• Build paths with Join-Path or [IO.Path], never by gluing strings with \.
• Use $HOME and [IO.Path]::GetTempPath() instead of C:\Users\... or $env:TEMP, which doesn't exist on Linux.
• Linux and macOS file systems are case-sensitive: Report.csv and report.csv are different files.

Things that differ

• Aliases — on Linux and macOS, ls, cp, mv, rm, cat, and sort are not aliases; they run the native commands, which output text instead of objects. Use full cmdlet names.
• Windows-only modules — ActiveDirectory, services (Get-Service is limited), the registry, CIM/WMI, and scheduled tasks don't exist elsewhere.
• Line endings — Set-Content writes the platform's line ending; Git can convert them. Keep scripts as LF or CRLF consistently.
• Native commands — output from grep or systemctl is text; parse it, or look for a JSON output option (--output json) and pipe it to ConvertFrom-Json.

Test cross-platform code in CI on all three systems (see the CI/CD lesson).