About Operators
Short description
Describes the operators that are supported by PowerShell.
Long description
An operator is a language element that you can use in a command or expression. PowerShell supports several types of operators to help you manipulate values.
Arithmetic Operators
Use arithmetic operators (+
, -
, *
, /
, %
) to calculate values in a
command or expression. With these operators, you can add, subtract, multiply,
or divide values, and calculate the remainder (modulus) of a division
operation.
The addition operator concatenates elements. The multiplication operator
returns the specified number of copies of each element. You can use arithmetic
operators on any .NET type that implements them, such as: Int
, String
,
DateTime
, Hashtable
, and Arrays.
Bitwise operators (-band
, -bor
, -bxor
, -bnot
, -shl
, -shr
)
manipulate the bit patterns in values.
For more information, see about_Arithmetic_Operators.
Assignment Operators
Use assignment operators (=
, +=
, -=
, *=
, /=
, %=
) to assign, change,
or append values to variables. You can combine arithmetic operators with
assignment to assign the result of the arithmetic operation to a variable.
For more information, see about_Assignment_Operators.
Comparison Operators
Use comparison operators (-eq
, -ne
, -gt
, -lt
, -le
, -ge
) to compare
values and test conditions. For example, you can compare two string values to
determine whether they are equal.
The comparison operators also include operators that find or replace patterns
in text. The (-match
, -notmatch
, -replace
) operators use regular
expressions, and (-like
, -notlike
) use wildcards *
.
Containment comparison operators determine whether a test value appears in a
reference set (-in
, -notin
, -contains
, -notcontains
).
Type comparison operators (-is
, -isnot
) determine whether an object is of a
given type.
For more information, see about_Comparison_Operators.
Logical Operators
Use logical operators (-and
, -or
, -xor
, -not
, !
) to connect
conditional statements into a single complex conditional. For example, you can
use a logical -and
operator to create an object filter with two different
conditions.
For more information, see about_Logical_Operators.
Redirection Operators
Use redirection operators (>
, >>
, 2>
, 2>>
, and 2>&1
) to send the
output of a command or expression to a text file. The redirection operators
work like the Out-File
cmdlet (without parameters) but they also let you
redirect error output to specified files. You can also use the Tee-Object
cmdlet to redirect output.
For more information, see about_Redirection
Split and Join Operators
The -split
and -join
operators divide and combine substrings. The -split
operator splits a string into substrings. The -join
operator concatenates
multiple strings into a single string.
For more information, see about_Split and about_Join.
Type Operators
Use the type operators (-is
, -isnot
, -as
) to find or change the .NET
Framework type of an object.
For more information, see about_Type_Operators.
Unary Operators
Use unary operators to increment or decrement variables or object properties
and to set integers to positive or negative numbers. For example, to increment
the variable $a
from 9
to 10
, you type $a++
.
Special Operators
Special operators have specific use-cases that do not fit into any other operator group. For example, special operators allow you to run commands, change a value's data type, or retrieve elements from an array.
Grouping operator ( )
As in other languages, (...)
serves to override operator precedence in
expressions. For example: (1 + 2) / 3
However, in PowerShell, there are additional behaviors.
(...)
allows you to let output from a command participate in an expression. For example:PS> (Get-Item *.txt).Count -gt 10 True
When used as the first segment of a pipeline, wrapping a command or expression in parentheses invariably causes enumeration of the expression result. If the parentheses wrap a command, it is run to completion with all output collected in memory before the results are sent through the pipeline.
Note
Wrapping a command in parentheses causes the automatic variable $?
to be
set to $true
, even when the enclosed command itself set $?
to $false
.
For example, (Get-Item /Nosuch); $?
unexpectedly yields True. For
more information about $?
, see
about_Automatic_Variables.
Subexpression operator $( )
Returns the result of one or more statements. For a single result, returns a scalar. For multiple results, returns an array. Use this when you want to use an expression within another expression. For example, to embed the results of command in a string expression.
PS> "Today is $(Get-Date)"
Today is 12/02/2019 13:15:20
PS> "Folder list: $((dir c:\ -dir).Name -join ', ')"
Folder list: Program Files, Program Files (x86), Users, Windows
Array subexpression operator @( )
Returns the result of one or more statements as an array. If there is only one item, the array has only one member.
@(Get-CimInstance win32_logicalDisk)
Hash table literal syntax @{}
Similar to the array subexpression, this syntax is used to declare a hash table. For more information, see about_Hash_Tables.
Call operator &
Runs a command, script, or script block. The call operator, also known as the "invocation operator", lets you run commands that are stored in variables and represented by strings or script blocks. The call operator executes in a child scope. For more about scopes, see about_Scopes.
This example stores a command in a string and executes it using the call operator.
PS> $c = "get-executionpolicy"
PS> $c
get-executionpolicy
PS> & $c
AllSigned
The call operator does not parse strings. This means that you cannot use command parameters within a string when you use the call operator.
PS> $c = "Get-Service -Name Spooler"
PS> $c
Get-Service -Name Spooler
PS> & $c
& : The term 'Get-Service -Name Spooler' is not recognized as the name of a
cmdlet, function, script file, or operable program. Check the spelling of
the name, or if a path was included, verify that the path is correct and
try again.
At line:1 char:2
+ & $c
+ ~~
+ CategoryInfo : ObjectNotFound: (Get-Service -Name Spooler:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException
The Invoke-Expression cmdlet can execute code that causes parsing errors when using the call operator.
PS> & "1+1"
& : The term '1+1' is not recognized as the name of a cmdlet, function, script
file, or operable program. Check the spelling of the name, or if a path was
included, verify that the path is correct and try again.
At line:1 char:2
+ & "1+1"
+ ~~~~~
+ CategoryInfo : ObjectNotFound: (1+1:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException
PS> Invoke-Expression "1+1"
2
You can use the call operator to execute scripts using their filenames. The example below shows a script filename that contains spaces. When you try to execute the script, PowerShell instead displays the contents of the quoted string containing the filename. The call operator allows you to execute the contents of the string containing the filename.
PS C:\Scripts> Get-ChildItem
Directory: C:\Scripts
Mode LastWriteTime Length Name
---- ------------- ------ ----
-a---- 8/28/2018 1:36 PM 58 script name with spaces.ps1
PS C:\Scripts> ".\script name with spaces.ps1"
.\script name with spaces.ps1
PS C:\Scripts> & ".\script name with spaces.ps1"
Hello World!
For more about script blocks, see about_Script_Blocks.
Background operator &
Runs the pipeline before it in the background, in a PowerShell job. This
operator acts similarly to the UNIX control operator ampersand (&
), which
runs the command before it asynchronously in subshell as a job.
This operator is functionally equivalent to Start-Job
. The following example
demonstrates basic usage of the background job operator.
Get-Process -Name pwsh &
That command is functionally equivalent to the following usage of Start-Job
:
Start-Job -ScriptBlock {Get-Process -Name pwsh}
Just like Start-Job
, the &
background operator returns a Job
object. This
object can be used with Receive-Job
and Remove-Job
, just as if you had used
Start-Job
to start the job.
$job = Get-Process -Name pwsh &
Receive-Job $job -Wait
NPM(K) PM(M) WS(M) CPU(s) Id SI ProcessName
------ ----- ----- ------ -- -- -----------
0 0.00 221.16 25.90 6988 988 pwsh
0 0.00 140.12 29.87 14845 845 pwsh
0 0.00 85.51 0.91 19639 988 pwsh
Remove-Job $job
The &
background operator is also a statement terminator, just like the UNIX
control operator ampersand (&
). This allows you to invoke additional commands
after the &
background operator. The following example demonstrates the
invocation of additional commands after the &
background operator.
$job = Get-Process -Name pwsh & Receive-Job $job -Wait
NPM(K) PM(M) WS(M) CPU(s) Id SI ProcessName
------ ----- ----- ------ -- -- -----------
0 0.00 221.16 25.90 6988 988 pwsh
0 0.00 140.12 29.87 14845 845 pwsh
0 0.00 85.51 0.91 19639 988 pwsh
This is equivalent to the following script:
$job = Start-Job -ScriptBlock {Get-Process -Name pwsh}
Receive-Job $job -Wait
If you want to run multiple commands, each in their own background process but
all on one line, simply place &
between and after each of the commands.
Get-Process -Name pwsh & Get-Service -Name BITS & Get-CimInstance -ClassName Win32_ComputerSystem &
For more information on PowerShell jobs, see about_Jobs.
Cast operator [ ]
Converts or limits objects to the specified type. If the objects cannot be converted, PowerShell generates an error.
[DateTime]"2/20/88" - [DateTime]"1/20/88"
[Int] (7/2)
[String] 1 + 0
[Int] '1' + 0
A cast can also be performed when a variable is assigned to using cast notation.
Comma operator ,
As a binary operator, the comma creates an array or appends to the array being created. In expression mode, as a unary operator, the comma creates an array with just one member. Place the comma before the member.
$myArray = 1,2,3
$SingleArray = ,1
Write-Output (,1)
Since Write-Object
expects an argument, you must put the expression in
parentheses.
Dot sourcing operator .
Runs a script in the current scope so that any functions, aliases, and
variables that the script creates are added to the current scope, overriding
existing ones. Parameters declared by the script become variables. Parameters
for which no value has been given become variables with no value. However, the
automatic variable $args
is preserved.
. c:\scripts\sample.ps1 1 2 -Also:3
Note
The dot sourcing operator is followed by a space. Use the space to
distinguish the dot from the dot (.
) symbol that represents the current
directory.
In the following example, the Sample.ps1 script in the current directory is run in the current scope.
. .\sample.ps1
Format operator -f
Formats strings by using the format method of string objects. Enter the format string on the left side of the operator and the objects to be formatted on the right side of the operator.
"{0} {1,-10} {2:N}" -f 1,"hello",[math]::pi
1 hello 3.14
If you need to keep the curly braces ({}
) in the formatted string, you can
escape them by doubling the curly braces.
"{0} vs. {{0}}" -f 'foo'
foo vs. {0}
For more information, see the String.Format method and Composite Formatting.
Index operator [ ]
Selects objects from indexed collections, such as arrays and hash tables. Array
indexes are zero-based, so the first object is indexed as [0]
. For arrays
(only), you can also use negative indexes to get the last values. Hash tables
are indexed by key value.
PS> $a = 1, 2, 3
PS> $a[0]
1
PS> $a[-1]
3
(Get-HotFix | Sort-Object installedOn)[-1]
$h = @{key="value"; name="PowerShell"; version="2.0"}
$h["name"]
PowerShell
$x = [xml]"<doc><intro>Once upon a time...</intro></doc>"
$x["doc"]
intro
-----
Once upon a time...
Pipeline operator |
Sends ("pipes") the output of the command that precedes it to the command that follows it. When the output includes more than one object (a "collection"), the pipeline operator sends the objects one at a time.
Get-Process | Get-Member
Get-Service | Where-Object {$_.StartType -eq 'Automatic'}
Range operator ..
Represents the sequential integers in an integer array, given an upper, and lower boundary.
1..10
foreach ($a in 1..$max) {Write-Host $a}
You can also create ranges in reverse order.
10..1
5..-5 | ForEach-Object {Write-Output $_}
Beginning in PowerShell 6, the range operator works with Characters as well as Integers.
To create a range of characters, enclose the boundary characters in quotes.
PS> 'a'..'f'
a
b
c
d
e
f
PS> 'F'..'A'
F
E
D
C
B
A
Member access operator .
Accesses the properties and methods of an object. The member name may be an expression.
$myProcess.peakWorkingSet
(Get-Process PowerShell).kill()
'OS', 'Platform' | Foreach-Object { $PSVersionTable. $_ }
Static member operator ::
Calls the static properties and methods of a .NET Framework class. To
find the static properties and methods of an object, use the Static parameter
of the Get-Member
cmdlet. The member name may be an expression.
[datetime]::Now
'MinValue', 'MaxValue' | Foreach-Object { [int]:: $_ }