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get-help Get-EventLog -full | more

[]square brackets for optional

<>angeled for required

[-LogName] <string> 

-Logname parameter is optional but the argument for it is required ( this works because it is a positional parameter if you scroll down in the help details you can see it is postion 1 for -Logname (this means that the first unbound parrameter will be used for this

Get-EventLog -newest 10 application

-newest 10 is a parameter and its argument and application is the first positional paramenter

[-ComputerName <string[]>]

this is an optional parameter but if you use it it has a required argument

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  Built in variables

$PSHOME

$_

$PWD

Objects

1. properties
2. methods
   
3. events

HashTables

$myhash= @{}
$myhash.gettype()
$myhash.FirstName = "Kevin"
$myhash.LastName = "Curran"
$myhash.FirstName + " " + $myhash.LastName 

use a hash table to display the output we want

@{Label="Handles";Expression={$_.HandleCount}

Get-Process | Where-Object {$_.handlecount -gt 200} | Sort-Object -Descending -Property handlecount | Format-Table id,processname,@{Label="Handles";Expression={$_.HandleCount}} -autosize

$ary = "Hello", "World!"

 join dilimited by space (` is used to escape the space)

[string]::join("` ",$ary)

join dilimited by comma

[string]::join(",",$ary)

$string= "Hello World!" 
$mat = [regex]::match($string,"o\sW")
$mat.Value

Common Parameters

Page 13 of Windows Powershell step by step book 

stop-process -name notepad* -whatif
stop-process -name notepad* -confirm