Powershell Powershell Powershell
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To create a new variable, use an assignment statement to assign a value to the variable.
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$MyVariable = 1, 2, 3
$Path = "C:\Windows\System32" |
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To display the value of a variable, type the variable name, preceded by a dollar sign ($).
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$MyVariable
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1
2 3 |
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To change the value of a variable, assign a new value to the variable.
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$MyVariable = "The green cat."
$MyVariable |
The green cat.
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To delete the value of a variable, use the Clear-Variable cmdlet or change the value to $null.
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Clear-Variable -Name MyVariable
$MyVariable = $null |
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To delete the variable, use Remove-Variable or Remove-Item.
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Remove-Variable -Name MyVariable
Remove-Item -Path Variable:\MyVariable |
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To get a list of all the variables in your PowerShell session, type Get-Variable.
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Variables are useful for storing the results of commands.
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$Processes = Get-Process
$Today = (Get-Date).DateTime |
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It is also possible to assign values to multiple variables with one statement.
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$a = $b = $c = 0
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The next example assigns multiple values to multiple variables.
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$i,$j,$k = 10, "red", $true
$i,$j = 10, "red", $true |
# $i is 10, $j is "red", $k is True
# $i is 10, $j is [object[]], Length 2 |
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$a = 12
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System.Int32
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$a = "Word"
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System.String
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$a = 12, "Word"
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array of System.Int32, System.String
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$a = Get-ChildItem C:\Windows
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FileInfo and DirectoryInfo types
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To use cast notation, enter a type name, enclosed in brackets, before the variable name (on the left side of the assignment statement).
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[int]$number = 8
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Concatenation
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$name = 'Kevin Marquette'
$message = 'Hello, ' + $name |
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Variable substitution
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$first = 'Kevin'
$last = 'Marquette' $message = "Hello, $first $last." |
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To create and initialize an array, assign multiple values to a variable.
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$A = 22,5,10,8,12,9,80
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The array sub-expression operator creates an array from the statements inside it.
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@( ... )
$a = @("Hello World") $p = @(Get-Process Notepad) |
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Where-Object filtering
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$data | Where-Object {$_.FirstName -eq 'Kevin'}
$data | Where FirstName -eq Kevin |
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Where()
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$data.Where({$_.FirstName -eq 'Kevin'})
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Selects objects or object properties.
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Get-Process | Select-Object -Property ProcessName, Id, WS
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To create an empty hashtable in the value of $hash, type:
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$hash = @{}
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You can also add keys and values to a hashtable when you create it.
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$hash = @{ Number = 1; Shape = "Square"; Color = "Blue"}
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To display a hashtable that's saved in a variable, type the variable name.
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$hash
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hashtables have Keys and Values properties.
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$hash.keys
$hash.values |
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You can iterate over the keys in a hashtable to process the values in several ways.
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foreach ($Key in $hash.Keys) {
"The value of '$Key' is: $($hash[$Key])" } |
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To add keys and values to a hashtable, use the following command format.
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$hash["<key>"] = "<value>"
$hash["Time"] = "Now" |
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You can also add keys and values to a hashtable using the Add method of the System.Collections.Hashtable object.
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Add(Key, Value)
$hash.Add("Time", "Now") |
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Creating a PSCustomObject
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$myObject = [PSCustomObject]@{
Name = 'Kevin' Language = 'PowerShell' State = 'Texas' } |
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Converting a hashtable
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$myHashtable = @{
Name = 'Kevin' Language = 'PowerShell' State = 'Texas' } $myObject = [pscustomobject]$myHashtable |
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Saving to a file
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$myObject | ConvertTo-Json -depth 1 | Set-Content -Path $Path
$myObject = Get-Content -Path $Path | ConvertFrom-Json |
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Adding properties
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$myObject | Add-Member -MemberType NoteProperty -Name 'ID' -Value 'KevinMarquette'
$myObject.ID |
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Remove properties
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$myObject.psobject.properties.remove('ID')
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Enumerating property names
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$myObject | Get-Member -MemberType NoteProperty | Select -ExpandProperty Name
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Dynamically accessing properties
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$myObject.'Name'
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Convert PSCustomObject into a hashtable
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$hashtable = @{}
foreach( $property in $myobject.psobject.properties.name ) { $hashtable[$property] = $myObject.$property } |
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Testing for properties
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if( $null -ne $myObject.ID )
if( $myobject.psobject.properties.match('ID').Count ) |
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A simple function
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function Get-Version {
$PSVersionTable.PSVersion } |
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Parameters
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function Test-MrParameter {
param ( $ComputerName ) Write-Output $ComputerName } |
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