TOPIC
about_Scripts
SHORT DESCRIPTION
Describes how to write and run 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.
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 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.
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.
To run a script, type the full name and the full path to the script file.
For example, to run the ServicesLog script in the C:\Scripts directory, type:
c:\scripts\ServicesLog.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:
.\ServicesLog.ps1
As a security feature, Windows PowerShell does not run scripts when you
double-click the script icon in Windows 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.
RUNNING SCRIPTS REMOTELY
To run a script on a remote computer, 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 ServicesLog.ps1 script on the Server01 remote
computer.
invoke-command -computername Server01 -filepath C:\scripts\servicesLog.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.
HELP FOR SCRIPTS
The Get-Help cmdlet gets Help for scripts as well as for cmdlets,
providers, and functions. To get Help for a script, type Get-Help and 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
You can write Help 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
https://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.
$MyInvocation
The $MyInvocation automatic variable contains information about the
current command, including the current script. 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.
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_Scopes
about_Script_Blocks
about_Signing
Invoke-Command