Variables and Types
Variables
Basic
Variables are defined by prefixing them with $.
In PowerShell, it is not case sensitive.
PS> $a = 1
PS> $a
1
PS> $A
1
You can save the results of commandlets, methods, etc. as objects.
PS> $date = Get-Date
PS> $date.Year
2018
When including special characters
To include special characters (-, (, ), . , :etc.), use ${}.
PS> ${test-test} = "test"
Items in the PSDrive can be treated as variables.
# Example: Targeting an item (script.ps1) in the FileSystem provider
PS C:\Users\user\Desktop> ${C:\Users\user\Desktop\script.ps1}
Write-Host "Hello!"
PS C:\Users\user\Desktop> .\script.ps1
Hello!
Types
About types
Both fully qualified names and aliases can be used.
PS> [System.Int32]$a = 1 # Fully qualified name
PS> [int]$a = 1 # Aliase
How to check the type
- Use Get-Member
- Use the GetType method
PS> $a = 1
PS> $a | Get-Member
TypeName: System.Int32
～Abbreviation～
PS> $a.GetType().FullName
System.Int32
Type Checking
PS> $a -is [int]
True
PS> $a -isnot [int]
False
Type Conversion
Explicit type conversion ( cast )
There are multiple methods.
- $variable = [type] cast-target
For impossible cast: Error. - $variable = cast-target -as [type]
For impossible cast: Does not result in an error, returns Null
If you want to cast a variable, you need to know that $variable = [type] cast-target.
It will give you an error.
# $variable = [type] cast-target
PS> $date = [datetime]"2018/05/16"
PS> $date.Date
2018年5月16日 0:00:00
PS> $date.Day
16
# $variable = cast-target -as [type]
PS> $date = "2018/05/16" -as [datetime]
PS> $date.DayOfWeek
Wednesday
PS> $date = "a" -as [datetime] # impossible cast
PS> $date
PS>
Implicit Type Conversion
The type of the right side is converted to match the type of the left side.
PS> $a = 1
PS> $b = "1"
PS> $a + $b # $b is converted to [int].
2
PS> $b + $a # $a is converted to [string].
11
YouTube
Click here for a video explanation.