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about_Comment_Based_Help

Updated: May 8, 2014

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

TOPIC
    about_Comment_Based_Help

SHORT DESCRIPTION
    Describes how to write comment-based help topics for functions and scripts.

LONG DESCRIPTION
    You can write comment-based help topics for functions and scripts by using
    special help comment keywords.  

    The Get-Help cmdlet displays comment-based help in the same format in which
    it displays the cmdlet help topics that are generated from XML files. Users
    can use all of the parameters of Get-Help, such as Detailed, Full, Example,
    and Online, to display the contents of comment-based help.

    You can also write XML-based help files for functions and scripts. To 
    enable the Get-Help cmdlet to find the XML-based help file for a function
    or script, use the ExternalHelp keyword. Without this keyword, Get-Help 
    cannot find XML-based help topics for functions or scripts. 

    This topic explains how to write help topics for functions and scripts. For 
    information about how to display help topics for functions and scripts, see
    Get-Help.

NOTE: 
    The Update-Help and Save-Help cmdlets work only on XML files. Updatable Help
    does not support comment-based help topics.
 
TROUBLESHOOTING NOTE: 
    Default values and a value for "Accept Wildcard characters" do not appear in
    the parameter attribute table even when they are defined in the function or
    script. To help users, provide this information in the parameter description.


 SYNTAX FOR COMMENT-BASED HELP
    The syntax for comment-based help is as follows:

        # .< help keyword>
        # <help content>
 
    -or -

        <#
            .< help keyword>
            < help content>
        #>


    Comment-based help is written as a series of comments. You can type a
    comment symbol (#) before each line of comments, or you can use the "<#" and "#>"
    symbols to create a comment block. All the lines within the comment block are
    interpreted as comments.

    All of the lines in a comment-based help topic must be contiguous. If a
    comment-based help topic follows a comment that is not part of the help
    topic, there must be at least one blank line between the last non-help 
    comment line and the beginning of the comment-based help.

    Keywords define each section of comment-based help. Each comment-based help
    keyword is preceded by a dot (.). The keywords can appear in any order. The
    keyword names are not case-sensitive.

    For example, the Description keyword precedes a description of a function or
    script.

        <#
    .Description
            Get-Function displays the name and syntax of all functions in the session.
        #>

    The comment block must contain at least one keyword. Some of the keywords,
    such as EXAMPLE, can appear many times in the same comment block. The help
    content for each keyword begins on the line after the keyword and can span
    multiple lines. 



 SYNTAX FOR COMMENT-BASED HELP IN FUNCTIONS

    Comment-based help for a function can appear in one of three locations:

        -- At the beginning of the function body.

        -- At the end of the function body.

        -- Before the Function keyword. There cannot be more than one blank
           line between the last line of the function help and the Function
           keyword. 

 

    For example:

        function Get-Function 
        {
            <#
            .< help keyword>
            < help content>
            #>

            <function commands>
        }


    -or -

        function Get-Function 
        {
            <function commands>

            <#
            .< help keyword>
            < help content>
            #>
        }

    -or -

        <#
        .< help keyword>
        < help content>
        #>
        function Get-Function { }



 SYNTAX FOR COMMENT-BASED HELP IN SCRIPTS

    Comment-based help for a script can appear in one of the following two
    locations in the script.

    -- At the beginning of the script file. Script help can be preceded in the
       script only by comments and blank lines. 

    -- If the first item in the script body (after the help) is a function
       declaration, there must be at least two blank lines between the end of the
       script help and the function declaration. Otherwise, the help is
       interpreted as being help for the function, not help for the script.

    -- At the end of the script file. However, if the script is signed, place
       Comment-based help at the beginning of the script file. The end of the 
       script is occupied by the signature block.

    For example:

        <#
        .< help keyword>
        < help content>
        #>


        function Get-Function { }

    -or-


        function Get-Function { }

        <#
        .< help keyword>
        < help content>
        #>


 SYNTAX FOR COMMENT-BASED HELP IN SCRIPT MODULES
    In a script module (.psm1), comment-based help uses the syntax 
    for functions, not the syntax for scripts. You cannot use the
    script syntax to provide help for all functions defined in a 
    script module. 

    For example, if you are using the ExternalHelp keyword to 
    identify the XML-based help files for the functions in a script
    module, you must add an ExternalHelp comment to each function.

    # .ExternalHelp <XML-file-name>
    function <function-name>
    {
        ...
    }


 COMMENT-BASED HELP KEYWORDS
    The following are valid comment-based help keywords. They are listed in the order in
    which they typically appear in a help topic along with their intended use.
    These keywords can appear in any order in the comment-based help, and they
    are not case-sensitive.


    .SYNOPSIS
        A brief description of the function or script. This keyword can be used
        only once in each topic.

    .DESCRIPTION
        A detailed description of the function or script. This keyword can be
        used only once in each topic.

    .PARAMETER  <Parameter-Name>
        The description of a parameter. Add a .PARAMETER keyword for
        each parameter in the function or script syntax.

        Type the parameter name on the same line as the .PARAMETER keyword. 
        Type the parameter description on the lines following the .PARAMETER
        keyword. Windows PowerShell interprets all text between the .PARAMETER
        line and the next keyword or the end of the comment block as part of
        the parameter description. The description can include paragraph breaks.

        The Parameter keywords can appear in any order in the comment block, but
        the function or script syntax determines the order in which the parameters
        (and their descriptions) appear in help topic. To change the order,
        change the syntax.
 
        You can also specify a parameter description by placing a comment in the
        function or script syntax immediately before the parameter variable name.
        If you use both a syntax comment and a Parameter keyword, the description
        associated with the Parameter keyword is used, and the syntax comment is
        ignored.


    .EXAMPLE
        A sample command that uses the function or script, optionally followed
        by sample output and a description. Repeat this keyword for each example.

    .INPUTS
        The Microsoft .NET Framework types of objects that can be piped to the
        function or script. You can also include a description of the input 
        objects.

    .OUTPUTS
        The .NET Framework type of the objects that the cmdlet returns. You can
        also include a description of the returned objects.

    .NOTES
        Additional information about the function or script.

    .LINK
        The name of a related topic. The value appears on the line below
        the .LINE keyword and must be preceded by a comment symbol (#) or
        included in the comment block. 

        Repeat the .LINK keyword for each related topic.

        This content appears in the Related Links section of the help topic.

        The Link keyword content can also include a Uniform Resource Identifier
        (URI) to an online version of the same help topic. The online version 
        opens when you use the Online parameter of Get-Help. The URI must begin
        with "http" or "https".

    .COMPONENT
        The technology or feature that the function or script uses, or to which
        it is related. This content appears when the Get-Help command includes
        the Component parameter of Get-Help.

    .ROLE
        The user role for the help topic. This content appears when the Get-Help
        command includes the Role parameter of Get-Help.

    .FUNCTIONALITY
        The intended use of the function. This content appears when the Get-Help
        command includes the Functionality parameter of Get-Help.

    .FORWARDHELPTARGETNAME <Command-Name>
        Redirects to the help topic for the specified command. You can redirect
        users to any help topic, including help topics for a function, script,
        cmdlet, or provider. 

    .FORWARDHELPCATEGORY  <Category>
        Specifies the help category of the item in ForwardHelpTargetName.
        Valid values are Alias, Cmdlet, HelpFile, Function, Provider, General,
        FAQ, Glossary, ScriptCommand, ExternalScript, Filter, or All. Use this
        keyword to avoid conflicts when there are commands with the same name.

    .REMOTEHELPRUNSPACE <PSSession-variable>
        Specifies a session that contains the help topic. Enter a variable that
        contains a PSSession. This keyword is used by the Export-PSSession
        cmdlet to find the help topics for the exported commands.

    .EXTERNALHELP  <XML Help File>
        Specifies an XML-based help file for the script or function.  

        The ExternalHelp keyword is required when a function or script
        is documented in XML files. Without this keyword, Get-Help cannot
        find the XML-based help file for the function or script.

        The ExternalHelp keyword takes precedence over other comment-based 
        help keywords. If ExternalHelp is present, Get-Help does not display
        comment-based help, even if it cannot find a help topic that matches 
        the value of the ExternalHelp keyword.

        If the function is exported by a module, set the value of the 
        ExternalHelp keyword to a file name without a path. Get-Help looks for 
        the specified file name in a language-specific subdirectory of the module 
        directory. There are no requirements for the name of the XML-based help 
        file for a function, but a best practice is to use the following format:
        <ScriptModule.psm1>-help.xml

        If the function is not included in a module, include a path to the 
        XML-based help file. If the value includes a path and the path contains 
        UI-culture-specific subdirectories, Get-Help searches the subdirectories 
        recursively for an XML file with the name of the script or function in 
        accordance with the language fallback standards established for Windows, 
        just as it does in a module directory.

        For more information about the cmdlet help XML-based help file format,
        see "How to Create Cmdlet Help" in the MSDN (Microsoft Developer Network) 
        library at http://go.microsoft.com/fwlink/?LinkID=123415.


 AUTOGENERATED CONTENT
    The name, syntax, parameter list, parameter attribute table, common
    parameters, and remarks are automatically generated by the Get-Help cmdlet.

        Name: 
            The Name section of a function help topic is taken from the function
            name in the function syntax. The Name of a script help topic is
            taken from the script file name. To change the name or its 
            capitalization, change the function syntax or the script file name.
 
        Syntax: 
            The Syntax section of the help topic is generated from the function
            or script syntax. To add detail to the help topic syntax, such as
            the .NET Framework type of a parameter, add the detail to the syntax.
            If you do not specify a parameter type, the "Object" type is 
            inserted as the default value.

        Parameter List: 
            The Parameter list in the help topic is generated from the function
            or script syntax and from the descriptions that you add by using the
            Parameters keyword. The function parameters appear in the "Parameters"
            section of the help topic in the same order that they appear in
            the function or script syntax. The spelling and capitalization of
            parameter names is also taken from the syntax; it is not affected
            by the parameter name specified by the Parameter keyword. 

        Common Parameters: 
            The common parameters are added to the syntax and parameter list
            of the help topic, even if they have no effect. For more information
            about the common parameters, see about_CommonParameters.

        Parameter Attribute Table: 
            Get-Help generates the table of parameter attributes that appears
            when you use the Full or Parameter parameter of Get-help. The value
            of the Required, Position, and Default value attributes is taken
            from the function or script syntax.

            TROUBLESHOOTING NOTE: 
                Default values do not appear in the parameter attribute table, even
                when they are defined in the function or script. To help users, list
                the default value in the parameter description.

        Remarks: 
            The Remarks section of the help topic is automatically generated
            from the function or script name. You cannot change or affect its
            content.


 DISABLING COMMENT-BASED HELP
    [This technique was suggested by Rich Prescott, a Windows engineer 
     from New York, NY.]

    You can disable comment-based help. This makes the comment-based
    help ineffective without deleting it.

    To disable comment-based help, enclose the comments in a here-string. To
    hide the here-string, assign it to a variable or pipe it to the Out-Null
    cmdlet.

    While it is disabled, the comment-based help has no effect.

    For example, the following function has comment-based help.

            <#
            .SYNOPSIS 
            Adds a file name extension to a supplied name.
            #>            
            function Add-Extension 
            {
                param ([string]$Name,[string]$Extension = "txt")
                ...
            } 

    To disable the comment-based help, enclose it in a here-string,
    as shown in the following example.

            @"  
            <#
            .SYNOPSIS 
            Adds a file name extension to a supplied name.
            #>
            "@            
            function Add-Extension 
            {
                param ([string]$Name,[string]$Extension = "txt")
                ...
            }

    To hide the disabled comment-based help, assign the here-string to 
    a local variable that is not otherwise used in the function, as 
    shown in the following example. You can also pipe it to the Out-Null 
    cmdlet.

            $x = @"  
            <#
            .SYNOPSIS 
            Adds a file name extension to a supplied name.
            #>
            "@            
            function Add-Extension 
            {
                param ([string]$Name,[string]$Extension = "txt")
                ...
            }

    For more information about here-strings, see about_Quoting_Rules
    (http://go.microsoft.com/fwlink/?LinkID=113253).


EXAMPLES

    Example 1: Comment-based Help for a Function

        The following sample function includes comment-based help:

            function Add-Extension 
            {
                param ([string]$Name,[string]$Extension = "txt")
                $name = $name + "." + $extension
                $name

            <#
            .SYNOPSIS 
            Adds a file name extension to a supplied name.

            .DESCRIPTION
            Adds a file name extension to a supplied name. 
            Takes any strings for the file name or extension.

            .PARAMETER Name
            Specifies the file name.

            .PARAMETER Extension
            Specifies the extension. "Txt" is the default.

            .INPUTS
            None. You cannot pipe objects to Add-Extension.

            .OUTPUTS
            System.String. Add-Extension returns a string with the extension or file name.

            .EXAMPLE
            C:\PS> extension -name "File"
            File.txt

            .EXAMPLE
            C:\PS> extension -name "File" -extension "doc"
            File.doc

            .EXAMPLE
            C:\PS> extension "File" "doc"
            File.doc

            .LINK
            http://www.fabrikam.com/extension.html

            .LINK
            Set-Item
            #>
            }



        The results are as follows:

        C:\PS> get-help add-extension -full

        NAME
            Add-Extension
    
        SYNOPSIS
            Adds a file name extension to a supplied name.
    
        SYNTAX
            Add-Extension [[-Name] <String>] [[-Extension] <String>] [<CommonParameters>]
    
        DESCRIPTION
            Adds a file name extension to a supplied name. Takes any strings for the file name or extension.
    
        PARAMETERS
           -Name
               Specifies the file name.
        
               Required?                    false
               Position?                    0
               Default value                
               Accept pipeline input?       false
               Accept wildcard characters?  
        
           -Extension
               Specifies the extension. "Txt" is the default.
        
               Required?                    false
               Position?                    1
               Default value                
               Accept pipeline input?       false
               Accept wildcard characters?  
        
            <CommonParameters>
               This cmdlet supports the common parameters: -Verbose, -Debug,
               -ErrorAction, -ErrorVariable, -WarningAction, -WarningVariable,
               -OutBuffer and -OutVariable. For more information, type
               "get-help about_commonparameters".
    

        INPUTs
            None. You cannot pipe objects to Add-Extension.
    
        OUTPUTS
            System.String. Add-Extension returns a string with the extension or file name.
        
            -------------------------- EXAMPLE 1 --------------------------
    
            C:\PS> extension -name "File"
            File.txt
    
            -------------------------- EXAMPLE 2 --------------------------
    
            C:\PS> extension -name "File" -extension "doc"
            File.doc
    
            -------------------------- EXAMPLE 3 --------------------------
    
            C:\PS> extension "File" "doc"
            File.doc
    
        RELATED LINKS
            http://www.fabrikam.com/extension.html
            Set-Item



    Example 2: Parameter Descriptions in Function Syntax

        This example is the same as the previous one, except that the parameter
        descriptions are inserted in the function syntax. This format is most
        useful when the descriptions are brief. 


        function Add-Extension 
        {
            param 
            (
                [string]
                # Specifies the file name.
                $name,

                [string]
                # Specifies the file name extension. "Txt" is the default.
                $extension = "txt"
            )
            $name = $name + "." + $extension
            $name
      
            <#
            .SYNOPSIS 
            Adds a file name extension to a supplied name.

            .DESCRIPTION
            Adds a file name extension to a supplied name. Takes any strings for the file name or extension.

            .INPUTS
            None. You cannot pipe objects to Add-Extension.

            .OUTPUTS
            System.String. Add-Extension returns a string with the extension or file name.

            .EXAMPLE
            C:\PS> extension -name "File"
            File.txt

            .EXAMPLE
            C:\PS> extension -name "File" -extension "doc"
            File.doc

            .EXAMPLE
            C:\PS> extension "File" "doc"
            File.doc
 
            .LINK
            http://www.fabrikam.com/extension.html

            .LINK
            Set-Item
            #>
        }




    Example 3: Comment-based Help for a Script

        The following sample script includes comment-based help. 

        Notice the blank lines between the closing "#>" and the Param statement. 
        In a script that does not have a Param statement, there must be at least
        two blank lines between the final comment in the help topic and the first
        function declaration. Without these blank lines, Get-Help associates the
        help topic with the function, not the script.

           <#
           .SYNOPSIS 
           Performs monthly data updates.

           .DESCRIPTION
           The Update-Month.ps1 script updates the registry with new data generated
           during the past month and generates a report.
    
           .PARAMETER InputPath
           Specifies the path to the CSV-based input file.

           .PARAMETER OutputPath
           Specifies the name and path for the CSV-based output file. By default, 
           MonthlyUpdates.ps1 generates a name from the date and time it runs, and
           saves the output in the local directory.

           .INPUTS
           None. You cannot pipe objects to Update-Month.ps1.

           .OUTPUTS
           None. Update-Month.ps1 does not generate any output.

           .EXAMPLE
           C:\PS> .\Update-Month.ps1

           .EXAMPLE
           C:\PS> .\Update-Month.ps1 -inputpath C:\Data\January.csv

           .EXAMPLE
           C:\PS> .\Update-Month.ps1 -inputpath C:\Data\January.csv -outputPath C:\Reports\2009\January.csv
           #>

           param ([string]$InputPath, [string]$OutPutPath)

           function Get-Data { }
           ...


        The following command gets the script help. Because the script is not
        in a directory that is listed in the Path environment variable, the
        Get-Help command that gets the script help must specify the script path.


            PS C:\ps-test> get-help .\update-month.ps1 -full

            NAME
                C:\ps-test\Update-Month.ps1
    
            SYNOPSIS
                Performs monthly data updates.
    
            SYNTAX
                C:\ps-test\Update-Month.ps1 [-InputPath] <String> [[-OutputPath]
                <String>] [<CommonParameters>]
    
            DESCRIPTION
                The Update-Month.ps1 script updates the registry with new data
                generated during the past month and generates a report.
    
            PARAMETERS
               -InputPath
                   Specifies the path to the CSV-based input file.
        
                   Required?                    true
                   Position?                    0
                   Default value                
                   Accept pipeline input?       false
                   Accept wildcard characters?  
        
               -OutputPath
                   Specifies the name and path for the CSV-based output file. By
                   default, MonthlyUpdates.ps1 generates a name from the date
                   and time it runs, and saves the output in the local directory.
        
                   Required?                    false
                   Position?                    1
                   Default value                
                   Accept pipeline input?       false
                   Accept wildcard characters?  
        
               <CommonParameters>
                   This cmdlet supports the common parameters: -Verbose, -Debug,
                   -ErrorAction, -ErrorVariable, -WarningAction, -WarningVariable,
                   -OutBuffer and -OutVariable. For more information, type,
                   "get-help about_commonparameters".
    
            INPUTS
                   None. You cannot pipe objects to Update-Month.ps1.
    
            OUTPUTS
                   None. Update-Month.ps1 does not generate any output.
    
    
            -------------------------- EXAMPLE 1 --------------------------
        
            C:\PS> .\Update-Month.ps1
    
            -------------------------- EXAMPLE 2 --------------------------
       
            C:\PS> .\Update-Month.ps1 -inputpath C:\Data\January.csv
    
            -------------------------- EXAMPLE 3 --------------------------
    
            C:\PS> .\Update-Month.ps1 -inputpath C:\Data\January.csv -outputPath 
            C:\Reports\2009\January.csv
        
            RELATED LINKS



    Example 4:  Redirecting to an XML File

        You can write XML-based help topics for functions and scripts. Although
        comment-based help is easier to implement, XML-based help is required
        for Updatable Help and to provide help topics in multiple languages.  

        The following example shows the first few lines of the Update-Month.ps1
        script. The script uses the ExternalHelp keyword to specify the path to
        an XML-based help topic for the script.

        Note that the value of the ExternalHelp keyword appears on the same
        line as the keyword. Any other placement is ineffective.


            #  .ExternalHelp C:\MyScripts\Update-Month-Help.xml

            param ([string]$InputPath, [string]$OutPutPath)
            function Get-Data { }
            ...


       The following example shows three valid placements of the ExternalHelp keyword
       in a function.


            function Add-Extension 
            {
                # .ExternalHelp C:\ps-test\Add-Extension.xml

                param ([string] $name, [string]$extension = "txt")
                $name = $name + "." + $extension
                $name
            }
            
            function Add-Extension 
            {
                param ([string] $name, [string]$extension = "txt")
                $name = $name + "." + $extension
                $name
      
                # .ExternalHelp C:\ps-test\Add-Extension.xml
            }

           # .ExternalHelp C:\ps-test\Add-Extension.xml
           function Add-Extension 
            {
                param ([string] $name, [string]$extension = "txt")
                $name = $name + "." + $extension
                $name
            }



    Example 5:  Redirecting to a Different Help Topic

        The following code is an excerpt from the beginning of the built-in
        help function in Windows PowerShell, which displays one screen of help
        text at a time. Because the help topic for the Get-Help cmdlet describes
        the help function, the help function uses the ForwardHelpTargetName and
        ForwardHelpCategory keywords to redirect the user to the Get-Help cmdlet
        help topic.

            function help 
            {

            <#
            .FORWARDHELPTARGETNAME Get-Help
            .FORWARDHELPCATEGORY Cmdlet
            #>
            [CmdletBinding(DefaultParameterSetName='AllUsersView')]
            param(
                [Parameter(Position=0, ValueFromPipelineByPropertyName=$true)]
                [System.String]
                ${Name},
                   ...


        The following command uses this feature:

            C:\PS> get-help help

            NAME
                Get-Help

            SYNOPSIS
                Displays information about Windows PowerShell cmdlets and concepts.
            ...

KEYWORDS
    about_Comment-Based_Help

SEE ALSO
    about_Functions
    about_Functions_Advanced_Parameters
    about_Scripts
    "How to Write Cmdlet Help" (http://go.microsoft.com/fwlink/?LinkID=123415)



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