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about_Scripts

Updated: May 8, 2014

Applies To: Windows PowerShell 2.0, Windows PowerShell 3.0, Windows PowerShell 4.0

TOPIC
    about_Scripts

SHORT DESCRIPTION
    Describes how to run and write scripts in Windows PowerShell.

LONG DESCRIPTION
    A script is a plain text file that contains one or more Windows PowerShell
    commands. Windows PowerShell scripts have a .ps1 file name extension. 

    Running a script is a lot like running cmdlet. You type the path and file 
    name of the script and use parameters to submit data and set options. You
    can run scripts on your computer or in a remote session on a different
    computer.

    Writing a script saves a command for later use and makes it easy to share
    with others. Most importantly, it lets you run the commands simply by typing
    the script path and the file name. Scripts can be as simple as a single 
    command in a file or as extensive as a complex program.

    Scripts have additional features, such as the #Requires special comment,
    the use of parameters, support for data sections, and digital signing for
    security. You can also write Help topics for scripts and for any functions
    in the script. 

  HOW TO RUN A SCRIPT

    Before you can run a script, you need to change the default Windows
    PowerShell execution policy. The default execution policy, "Restricted",
    prevents all scripts from running, including scripts that you write on the
    local computer. For more information, see about_Execution_Policies.

    The execution policy is saved in the registry, so you need to change it
    only once on each computer.

    To change the execution policy, use the following procedure.

        1.  Start Windows PowerShell with the "Run  as administrator" 
            option.

        2.  At the command prompt, type:

            Set-ExecutionPolicy AllSigned
        -or-
            Set-ExecutionPolicy RemoteSigned

     The change is effective immediately


    To run a script, type the full name and the full path to the script
    file. 

    For example, to run the Get-ServiceLog.ps1 script in the C:\Scripts 
    directory, type:

        C:\Scripts\Get-ServiceLog.ps1

    To run a script in the current directory, type the path to the
    current directory, or use a dot to represent the current directory,
    followed by a path backslash (.\).

    For example, to run the ServicesLog.ps1 script in the local
    directory, type:

        .\Get-ServiceLog.ps1

    If the script has parameters, type the parameters and parameter
    values after the script file name.

    For example, the following command uses the ServiceName parameter of
    the Get-ServiceLog script to request a log of WinRM service activity.

        .\Get-ServiceLog.ps1 -ServiceName WinRM

    As a security feature, Windows PowerShell does not run scripts when you
    double-click the script icon in File Explorer or when you type the 
    script name without a full path, even when the script is in the current 
    directory. For more information about running commands and scripts in
    Windows PowerShell, see about_Command_Precedence.

  RUN WITH POWERSHELL
    Beginning in Windows PowerShell 3.0, you can run scripts from File
    Explorer (or Windows Explorer, in earlier versions of Windows). 

    To use the "Run with PowerShell" feature:

        In File Explorer (or Windows Explorer), right-click the 
        script file name and then select "Run with PowerShell".

    The "Run with PowerShell" feature is designed to run scripts 
    that do not have required parameters and do not return output 
    to the command prompt. 

    For more information, see about_Run_With_PowerShell


  RUNNING SCRIPTS ON OTHER COMPUTERS

    To run a script on one or more remote computers, use the FilePath
    parameter of the Invoke-Command cmdlet.

    Enter the path and file name of the script as the value of the FilePath 
    parameter. The script must reside on the local computer or in a directory
    that the local computer can access. 

    The following command runs the Get-ServiceLog.ps1 script on the Server01
    and Server02 remote computers.

        Invoke-Command -ComputerName Server01, Server02 -FilePath C:\Scripts\Get-ServiceLog.ps1 


  GET HELP FOR SCRIPTS

    The Get-Help cmdlet gets the help topics for scripts as well as for 
    cmdlets and other types of commands. To get the help topic for a script, 
    type "Get-Help" followed by the path and file name of the script. If the
    script path is in your Path environment variable, you can omit the path.

    For example, to get help for the ServicesLog.ps1 script, type:

        get-help C:\admin\scripts\ServicesLog.ps1




  HOW TO WRITE A SCRIPT

    A script can contain any valid Windows PowerShell commands, including single
    commands, commands that use the pipeline, functions, and control structures
    such as If statements and For loops.

    To write a script, start a text editor (such as Notepad) or a script editor
    (such as the Windows PowerShell Integrated Scripting Environment [ISE]). Type 
    the commands and save them in a file with a valid file name and the .ps1 file
    name extension. 

    The following example is a simple script that gets the services that are
    running on the current system and saves them to a log file. The log file name
    is created from the current date.

        $date = (get-date).dayofyear
        get-service | out-file "$date.log"

    To create this script, open a text editor or a script editor, type these
    commands, and then save them in a file named ServiceLog.ps1. 




  PARAMETERS IN SCRIPTS

    To define parameters in a script, use a Param statement. The Param statement
    must be the first statement in a script, except for comments and any 
    #Requires statements.

    Script parameters work like function parameters. The parameter values are
    available to all of the commands in the script. All of the features of
    function parameters, including the Parameter attribute and its named
    arguments, are also valid in scripts.

    When running the script, script users type the parameters after the script
    name. 

    The following example shows a Test-Remote.ps1 script that has a ComputerName
    parameter. Both of the script functions can access the ComputerName
    parameter value.

        param ($ComputerName = $(throw "ComputerName parameter is required."))

        function CanPing {
           $error.clear()
           $tmp = test-connection $computername -erroraction SilentlyContinue

           if (!$?) 
               {write-host "Ping failed: $ComputerName."; return $false}
           else
               {write-host "Ping succeeded: $ComputerName"; return $true}
        }

        function CanRemote {
            $s = new-pssession $computername -erroraction SilentlyContinue

            if ($s -is [System.Management.Automation.Runspaces.PSSession])
                {write-host "Remote test succeeded: $ComputerName."}
            else
                {write-host "Remote test failed: $ComputerName."}
        }

        if (CanPing $computername) {CanRemote $computername}


    To run this script, type the parameter name after the script name.  
    For example:

C:\PS> .\test-remote.ps1 -computername Server01

Ping succeeded: Server01
Remote test failed: Server01


    For more information about the Param statement and the function parameters,
    see about_Functions and about_Functions_Advanced_Parameters.



 WRITING HELP FOR SCRIPTS

    You can write a help topic for a script by using either of the two following methods:

    --  Comment-Based Help for Scripts

        Create a Help topic by using special keywords in the comments. To create
        comment-based Help for a script, the comments must be placed at the
        beginning or end of the script file. For more information about
        comment-based Help, see about_Comment_Based_Help.

    --  XML-Based Help  for Scripts

        Create an XML-based Help topic, such as the type that is typically
        created for cmdlets. XML-based Help is required if you are translating
        Help topics into multiple languages.  

        To associate the script with the XML-based Help topic, use the
        .ExternalHelp Help comment keyword. For more information about the
        ExternalHelp keyword, see about_Comment_Based_Help. For more information
        about XML-based help, see "How to Write Cmdlet Help" in the MSDN
        (Microsoft Developer Network) library at 
        http://go.microsoft.com/fwlink/?LinkID=123415.


  SCRIPT SCOPE AND DOT SOURCING

    Each script runs in its own scope. The functions, variables, aliases, and
    drives that are created in the script exist only in the script scope. You
    cannot access these items or their values in the scope in which the
    script runs.

    To run a script in a different scope, you can specify a scope, such as
    Global or Local, or you can dot source the script.

    The dot sourcing feature lets you run a script in the current scope instead
    of in the script scope. When you run a script that is dot sourced, the 
    commands in the script run as though you had typed them at the command 
    prompt. The functions, variables, aliases, and drives that the script 
    creates are created in the scope in which you are working. After the script
    runs, you can use the created items and access their values in your session.

    To dot source a script, type a dot (.) and a space before the script path.

    For example:

        . C:\scripts\UtilityFunctions.ps1

    -or-

        . .\UtilityFunctions.ps1


    After the UtilityFunctions script runs, the functions and variables that the
    script creates are added to the current scope. 
  
    For example, the UtilityFunctions.ps1 script creates the New-Profile
    function and the $ProfileName variable.

        #In UtilityFunctions.ps1

        function New-Profile
        {
            Write-Host "Running New-Profile function"
            $profileName = split-path $profile -leaf

            if (test-path $profile)
               {write-error "There is already a $profileName profile on this computer."}
            else
       {new-item -type file -path $profile -force }
        }


    If you run the UtilityFunctions.ps1 script in its own script scope, the
    New-Profile function and the $ProfileName variable exist only while the
    script is running. When the script exits, the function and variable are
    removed, as shown in the following example.

        C:\PS> .\UtilityFunctions.ps1

        C:\PS> New-Profile
        The term 'new-profile' is not recognized as a cmdlet, function, operable
        program, or script file. Verify the term and try again.
        At line:1 char:12
        + new-profile <<<< 
           + CategoryInfo          : ObjectNotFound: (new-profile:String) [], 
           + FullyQualifiedErrorId : CommandNotFoundException

        C:\PS> $profileName
        C:\PS>


    When you dot source the script and run it, the script creates the
    New-Profile function and the $ProfileName variable in your session in your
    scope. After the script runs, you can use the New-Profile function in your
    session, as shown in the following example.

        C:\PS> . .\UtilityFunctions.ps1

        C:\PS> New-Profile


            Directory: C:\Users\juneb\Documents\WindowsPowerShell


            Mode    LastWriteTime     Length Name                                                                   
            ----    -------------     ------ ----                                                                   
            -a---   1/14/2009 3:08 PM      0 Microsoft.PowerShellISE_profile.ps1                                    


        C:\PS> $profileName
        Microsoft.PowerShellISE_profile.ps1


    For more information about scope, see about_Scopes.


  SCRIPTS IN MODULES

    A module is a set of related Windows PowerShell resources that can be
    distributed as a unit. You can use modules to organize your scripts,
    functions, and other resources. You can also use modules to distribute your
    code to others, and to get code from trusted sources.

    You can include scripts in your modules, or you can create a script module,
    which is a module that consists entirely or primarily of a script and 
    supporting resources. A script module is just a script with a .psm1 file
    name extension.

    For more information about modules, see about_Modules.


  OTHER SCRIPT FEATURES 

    Windows PowerShell has many useful features that you can use in scripts.

    #Requires 
        You can use a #Requires statement to prevent a script from running
        without specified modules or snap-ins and a specified version of
        Windows PowerShell. For more information, see about_Requires.

    $PSCommandPath
       Contains the full path and name of the script that is being run.
       This parameter is valid in all scripts. This automatic variable is
       introduced in Windows PowerShell 3.0.


    $PSScriptRoot
       Contains the directory from which a script is being run. In
       Windows PowerShell 2.0, this variable is valid only in script modules
       (.psm1). Beginning in Windows PowerShell 3.0, it is valid in all scripts.


    $MyInvocation
        The $MyInvocation automatic variable contains information about the
        current script, including information about how it was started or 
        "invoked." You can use this variable and its properties to get
        information about the script while it is  running. For example, the
        $MyInvocation.MyCommand.Path variable contains the path and file name
        of the script. $MyInvocation.Line contains the command that started
        the script, including all parameters and values.        

        Beginning in Windows PowerShell 3.0, $MyInvocation has two new properties
        that provide information about the script that called or invoked the
        current script. The values of these properties are populated only when
        the invoker or caller is a script.

        -- PSCommandPath contains the full path and name of the script that called
           or invoked the current script. 
        -- PSScriptRoot contains the directory of the script that called or invoked
           the current script. 

        Unlike the $PSCommandPath and $PSScriptRoot automatic variables, which
        contain information about the current script, the PSCommandPath and
        PSScriptRoot properties of the $MyInvocation variable contain information
        about the script that called or invoke the current script.


    Data sections
        You can use the Data keyword to separate data from logic in scripts.
        Data sections can also make localization easier. For more information,
        see about_Data_Sections and about_Script_Localization.

    Script Signing
        You can add a digital signature to a script. Depending on the execution
        policy, you can use digital signatures to restrict the running of scripts
        that could include unsafe commands. For more information, see
        about_Execution_Policies and about_Signing.



SEE ALSO
    about_Command_Precedence
    about_Comment_Based_Help
    about_Execution_Policies
    about_Functions
    about_Modules
    about_Profiles
    about_Requires
    about_Run_With_PowerShell
    about_Scopes
    about_Script_Blocks
    about_Signing
    Invoke-Command



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