About Splatting
SHORT DESCRIPTION
Describes how to use splatting to pass parameters to commands in PowerShell.
LONG DESCRIPTION
[This topic was contributed by Rohn Edwards of Gulfport, Mississippi, a system administrator and the winner of the Advanced Division of the 2012 Scripting Games. Revised for Windows PowerShell 3.0.]
Splatting is a method of passing a collection of parameter values to a command
as unit. PowerShell associates each value in the collection with a command
parameter. Splatted parameter values are stored in named splatting variables,
which look like standard variables, but begin with an At symbol (@) instead
of a dollar sign ($). The At symbol tells PowerShell that you are passing a
collection of values, instead of a single value.
Splatting makes your commands shorter and easier to read. You can re-use the
splatting values in different command calls and use splatting to pass parameter
values from the $PSBoundParameters automatic variable to other scripts and
functions.
Beginning in Windows PowerShell 3.0, you can also use splatting to represent all parameters of a command.
SYNTAX
<CommandName> <optional parameters> @<HashTable> <optional parameters>
<CommandName> <optional parameters> @<Array> <optional parameters>
To provide parameter values for positional parameters, in which parameter names are not required, use the array syntax. To provide parameter name and value pairs, use the hash table syntax. The splatted value can appear anywhere in the parameter list.
When splatting, you do not need to use a hash table or an array to pass all parameters. You may pass some parameters by using splatting and pass others by position or by parameter name. Also, you can splat multiple objects in a single command just so you pass no more than one value for each parameter.
SPLATTING WITH HASH TABLES
Use a hash table to splat parameter name and value pairs. You can use this format for all parameter types, including positional and switch parameters. Positional parameters must be assigned by name.
The following examples compare two Copy-Item commands that copy the Test.txt
file to the Test2.txt file in the same directory.
The first example uses the traditional format in which parameter names are included.
Copy-Item -Path "test.txt" -Destination "test2.txt" -WhatIf
The second example uses hash table splatting. The first command creates a hash
table of parameter-name and parameter-value pairs and stores it in the
$HashArguments variable. The second command uses the $HashArguments
variable in a command with splatting. The At symbol (@HashArguments) replaces
the dollar sign ($HashArguments) in the command.
To provide a value for the WhatIf switch parameter, use $True or $False.
$HashArguments = @{
Path = "test.txt"
Destination = "test2.txt"
WhatIf = $true
}
Copy-Item @HashArguments
Note: In the first command, the At symbol (@) indicates a hash table, not a
splatted value. The syntax for hash tables in PowerShell is:
@{\<name\>=\<value\>; \<name\>=\<value\>; ...}*
SPLATTING WITH ARRAYS
Use an array to splat values for positional parameters, which do not require parameter names. The values must be in position-number order in the array.
The following examples compare two Copy-Item commands that copy the Test.txt
file to the Test2.txt file in the same directory.
The first example uses the traditional format in which parameter names are omitted. The parameter values appear in position order in the command.
Copy-Item "test.txt" "test2.txt" -WhatIf
The second example uses array splatting. The first command creates an array of
the parameter values and stores it in the $ArrayArguments variable. The
values are in position order in the array. The second command uses the
$ArrayArguments variable in a command in splatting. The At symbol
(@ArrayArguments) replaces the dollar sign ($ArrayArguments) in the
command.
$ArrayArguments = "test.txt", "test2.txt"
Copy-Item @ArrayArguments -WhatIf
EXAMPLES
This example shows how to re-use splatted values in different commands. The
commands in this example use the Write-Host cmdlet to write messages to the
host program console. It uses splatting to specify the foreground and
background colors.
To change the colors of all commands, just change the value of the $Colors
variable.
The first command creates a hash table of parameter names and values and stores
the hash table in the $Colors variable.
$Colors = @{ForegroundColor = "black"; BackgroundColor = "white"}
The second and third commands use the $Colors variable for splatting in a
Write-Host command. To use the $Colors variable, replace the dollar sign
($Colors) with an At symbol (@Colors).
#Write a message with the colors in $Colors
Write-Host "This is a test." @Colors
#Write second message with same colors. The position of splatted
#hash table does not matter.
Write-Host @Colors "This is another test."
This example shows how to forward their parameters to other commands by using
splatting and the $PSBoundParameters automatic variable.
The $PSBoundParameters automatic variable is a dictionary object
(System.Collections.Generic.Dictionary) that contains all the parameter names
and values that are used when a script or function is run.
In the following example, we use the $PSBoundParameters variable to forward
the parameters values passed to a script or function from Test2 function to
the Test1 function. Both calls to the Test1 function from Test2 use
splatting.
function Test1
{
param($a, $b, $c)
$a
$b
$c
}
function Test2
{
param($a, $b, $c)
#Call the Test1 function with $a, $b, and $c.
Test1 @PsBoundParameters
#Call the Test1 function with $b and $c, but not with $a
$LimitedParameters = $PSBoundParameters
$LimitedParameters.Remove("a") | Out-Null
Test1 @LimitedParameters
}
Test2 -a 1 -b 2 -c 3
1
2
3
2
3
SPLATTING COMMAND PARAMETERS
You can use splatting to represent the parameters of a command. This technique is useful when you are creating a proxy function, that is, a function that calls another command. This feature is introduced in Windows PowerShell 3.0.
To splat the parameters of a command, use @Args to represent the command
parameters. This technique is easier than enumerating command parameters and
it works without revision even if the parameters of the called command change.
The feature uses the $Args automatic variable, which contains all unassigned
parameter values.
For example, the following function calls the Get-Process cmdlet. In this
function, @Args represents all the parameters of the Get-Process cmdlet.
function Get-MyProcess { Get-Process @Args }
When you use the Get-MyProcess function, all unassigned parameters and
parameter values are passed to @Args, as shown in the following commands.
Get-MyProcess -Name PowerShell
Handles NPM(K) PM(K) WS(K) VM(M) CPU(s) Id ProcessName
------- ------ ----- ----- ----- ------ -- -----------
463 46 225484 237196 719 15.86 3228 powershell
Get-MyProcess -Name PowerShell_Ise -FileVersionInfo
ProductVersion FileVersion FileName
-------------- ----------- --------
6.2.9200.16384 6.2.9200.1638... C:\Windows\system32\WindowsPowerShell\...
You can use @Args in a function that has explicitly declared parameters. You
can use it more than once in a function, but all parameters that you enter are
passed to all instances of @Args, as shown in the following example.
function Get-MyCommand
{
Param ([switch]$P, [switch]$C)
if ($P) { Get-Process @Args }
if ($C) { Get-Command @Args }
}
Get-MyCommand -P -C -Name PowerShell
Handles NPM(K) PM(K) WS(K) VM(M) CPU(s) Id ProcessName
------- ------ ----- ----- ----- ------ -- -----------
408 28 75568 83176 620 1.33 1692 powershell
Path : C:\Windows\System32\WindowsPowerShell\v1.0\powershell.e
Extension : .exe
Definition : C:\Windows\System32\WindowsPowerShell\v1.0\powershell.e
Visibility : Public
OutputType : {System.String}
Name : powershell.exe
CommandType : Application
ModuleName :
Module :
RemotingCapability : PowerShell
Parameters :
ParameterSets :
HelpUri :
FileVersionInfo : File: C:\Windows\System32\WindowsPowerShell
\v1.0\powershell.exe
InternalName: POWERSHELL
OriginalFilename: PowerShell.EXE.MUI
FileVersion: 10.0.14393.0 (rs1_release.160715-1616
FileDescription: Windows PowerShell
Product: Microsoft Windows Operating System
ProductVersion: 10.0.14393.0
Debug: False
Patched: False
PreRelease: False
PrivateBuild: False
SpecialBuild: False
Language: English (United States)
NOTES
PowerShell Desired State Configuration (DSC) was not designed to use splatting. You cannot use splatting to pass values into a DSC resource. For more information, see Gael Colas' article Pseudo-Splatting DSC Resources.