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▶️ Powershell

These notes are from Mastering PowerShell Scripting - Fourth Edition, by Chris Dent.

Discovery, Basics

Update-Help to get the latest docs.

Get-help Get-Process gets you help about the Get-Process command.

Very cool, you can also add a -Examples to specifically see a bunch of examples :)

Get-Command shows all available commands, and you can use a regex like this to filter the output:

Get-Command Get-*ip*

Get-Alias prints all the aliases, as always use regexes to filter, e.g. Get-Alias s*. Some linux equivalents:

Copy-Item -> cp
Get-ChildItem -> ls
Get-Content -> cat
Get-Location -> pwd
Remove-Item -> rm
Write-Output -> cat

Exercise

Create an empty file, pipe some content to it and display the result.

new-item helloworld.txt
add-content "this is like echo > " .\helloworld.txt    # this is wrong
get-help Add-Content -examples
add-content -value "this is like echo > " -path .\helloworld.txt # this is correct
get-content .\helloworld.txt

Common parameters

Almost all commands support commonparameters like these:

  • Debug
  • ErrorAction: what to do on non-terminating errors, e.g. ignore, enquire, continue, stop
  • ErrorVariable: variable that stores all stderr
  • InformationAction, InformationVariable, OutBuffer, OutVariable: similar to above
  • Verbose
  • Confirm: prompt before executing
  • PassThru: return the same object back, e.g. Start-Process notepad -PassThru

More in Get-Help about_CommonParameters

Providers

Specialized interfaces to a service or dataset, e.g. Alias, Environment, Filesystem, Function, Variable, Registry, Certificate, WSMan.

More in Get-Help about_Providers and Get-Help about_<ProviderName>_Provider.

To see all content in a provider, do this: get-childitem environment::

Splatting

Sort-of like using a dict to store the cmd and args.

$splat = @{
Name = 'explorer'
}

Get-process @splat

Useful for readability, breaking long lines into smaller chunks. And for setting a conditional parameter in the dictionary and invoking the command with it.