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ABOUT SPLATTING
Short description
Describes how to use splatting to pass parameters to commands in
PowerShell.
Long description
Splatting is a method of passing a collection of parameter values to a
command as a 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 reuse 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 so you don't pass 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
Using the ArgumentList parameter
Several cmdlets have an ARGUMENTLIST parameter that is used to pass
parameter values to a script block that is executed by the cmdlet. The
ARGUMENTLIST parameter takes an array of values that is passed to the
script block. PowerShell is effectively using array splatting to bind the
values to the parameters of the script block. When using ARGUMENTLIST, if
you need to pass an array as a single object bound to a single parameter,
you must wrap the array in an array subexpression.
The following example has a script block that takes a single parameter that
is an array of strings.
$array = 'Hello', 'World!'
Invoke-Command -ScriptBlock { param([string[]]$words) $words -join ' '} -ArgumentList $array
In this example, only the first item in $array is passed to the script
script block.
Hello
$array = 'Hello', 'World!'
Invoke-Command -ScriptBlock { param([string[]]$words) $words -join ' '} -ArgumentList (,$array)
In this example, $array is wrapped in an array subexpress so that the
entire array is passed to the script block as a single object.
Hello World!
Examples
This example shows how to reuse 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
If you make a function into an advanced function by using either the
CMDLETBINDING or PARAMETER attributes, the $args automatic variable is no
longer available in the function. Advanced functions require explicit
parameter definition.
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.
See also
about_Arrays
about_Automatic_Variables
about_Hash_Tables
about_Parameters