Export (0) Print
Expand All

Invoke-Expression

Updated: April 21, 2010

Applies To: Windows PowerShell 2.0

Runs commands or expressions on the local computer.

Syntax

Invoke-Expression [-Command] <string> [<CommonParameters>]

Description

The Invoke-Expression cmdlet evaluates or runs a specified string as a command and returns the results of the expression or command. Without Invoke-Expression, a string submitted at the command line would be returned (echoed) unchanged.

Parameters

-Command <string>

Specifies the command or expression to run. Type the command or expression or enter a variable that contains the command or expression. The Command parameter is required.

 

Required?

true

Position?

1

Default Value

none

Accept Pipeline Input?

true (ByValue)

Accept Wildcard Characters?

false

<CommonParameters>

This command supports the common parameters: Verbose, Debug, ErrorAction, ErrorVariable, OutBuffer, OutVariable, WarningAction, and WarningVariable. For more information, see about_CommonParameters.

Inputs and Outputs

The input type is the type of the objects that you can pipe to the cmdlet. The return type is the type of the objects that the cmdlet returns.

 

Inputs

System.String or PSObject

You can pipe an object that represents the command to Invoke-Expression. Use the $input automatic variable to represent the input objects in the command.

Outputs

PSObject

Returns the output that is generated by the invoked command (the value of the Command parameter).

Notes

-- An expression is a statement that can be evaluated and produces a result, such as a Windows PowerShell command.

-- Take reasonable precautions when using the Invoke-Expression cmdlet in scripts. When using Invoke-Expression to run a command that the user enters, verify that the command is safe to run before running it. In general, it is best to design your script with predefined input options, rather than allowing freeform input.

Example 1

C:\PS>$command = "Get-Process"

C:\PS> $command
Get-Process


C:\PS> invoke-expression $command

Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)     Id ProcessName
-------  ------    -----      ----- -----   ------     -- -----------
    296       4     1572       1956    20     0.53   1348 AdtAgent
    270       6     1328        800    34     0.06   2396 alg
     67       2      620        484    20     0.22    716 ati2evxx
   1060      15    12904      11840    74    11.48    892 CcmExec
   1400      33    25280      37544   223    38.44   2564 communicator
...

Description

-----------

This example demonstrates the use of Invoke-Expression to evaluate an expression. Without Invoke-Expression, the expression is printed, but not evaluated.

The first command assigns a value of "Get-Process" (a string) to the $command variable.

The second command shows the effect of typing the variable name at the command line. Windows PowerShell echoes the string.

The third command uses Invoke-Expression to evaluate the string.

Example 2

C:\PS>invoke-expression -command "C:\ps-test\testscript.ps1"

C:\PS> "C:\ps-test\testscript.ps1" | invoke-expression

Description

-----------

These commands use Invoke-Expression to run a script, TestScript.ps1, on the local computer. The two commands are equivalent. The first uses the Command parameter to specify the command to run. The second uses a pipeline operator (|) to send the command string to Invoke-Expression.

Example 3

C:\PS>$cmd = 'get-process | where {$_.cpu -gt 1000}'

C:\PS> iex $command

Description

-----------

This example runs a command string that is saved in the $cmd variable.

The command string is enclosed in single quotation marks because it includes a variable, $_, which represents the current object. If it were enclosed in double quotation marks, the $_ variable would be replaced by its value before it was saved in the $command string.

Example 4

C:\PS>$cmdlet_name = "get-eventlog"

C:\PS> $example_number = 1

C:\PS> $example_code = (get-help $cmdlet_name).examples.example[($example_number-1)].code

C:\PS> invoke-expression $example_code

Description

-----------

This command retrieves and runs the first example in the Get-EventLog cmdlet help topic.

To run an example of a different cmdlet, change the value of the $cmdlet_name variable to the name of the cmdlet. And, change the $example_number variable to the example number you want to run. The command will fail if the example number is not valid.

See Also

Concepts

Invoke-Command

Was this page helpful?
(1500 characters remaining)
Thank you for your feedback

Community Additions

Show:
© 2014 Microsoft