Windows PowerShell command on Get-command Invoke-Expression

NAME
    Invoke-Expression
    
SYNOPSIS
    Runs commands or expressions on the local computer.
    
    
SYNTAX
    Invoke-Expression [-Command]  []
    
    
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 
        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?                    0
        Default value                None
        Accept pipeline input?       True (ByValue)
        Accept wildcard characters?  false
        
    
        This cmdlet supports the common parameters: Verbose, Debug,
        ErrorAction, ErrorVariable, WarningAction, WarningVariable,
        OutBuffer, PipelineVariable, and OutVariable. For more information, see 
        about_CommonParameters (https:/go.microsoft.com/fwlink/?LinkID=113216). 
    
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: Evaluate an expression
    
    PS C:\>$Command = "Get-Process"
    PS C:\>$Command
    Get-Process PS C:\>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
    ...
    
    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: Run a script on the local computer
    
    PS C:\>Invoke-Expression -Command "C:\ps-test\testscript.ps1"
    PS C:\>"C:\ps-test\testscript.ps1" | Invoke-Expression
    
    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: Run a command in a variable
    
    PS C:\>$Command = 'Get-Process | where {$_.cpu -gt 1000}'
    PS C:\>Invoke-Expression $Command
    
    This example runs a command string that is saved in the $Command 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 variable.
    Example 4: Get and run a cmdlet Help example
    
    PS C:\>$Cmdlet_name = "Get-EventLog"
    PS C:\>$Example_number = 1
    PS C:\>$Example_code = (Get-Help $Cmdlet_name).examples.example[($Example_number-1)].code
    PS C:\>Invoke-Expression $Example_code
    
    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.
    
RELATED LINKS
    Online Version: http://go.microsoft.com/fwlink/?LinkId=821823