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, Examples, 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.

The Update-Help and Save-Help cmdlets work only on XML files. Updatable Help does not support comment-based help topics.

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 logic
}

or

function Get-Function
{
   # function logic

<#
.<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

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.

.PARAMETER  <Parameter-Name>

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. For this to work, you must also have a comment block with at least one keyword.

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.

<#
.SYNOPSIS
    Short description here
#>
function Verb-Noun {
    [CmdletBinding()]
    param (
        # This is the same as .Parameter
        [string]$Computername
    )
    # Verb the Noun on the computer
}

.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 .NET 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 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 ".LINK" 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 name of the technology or feature that the function or script uses, or to which it is related. The Component parameter of Get-Help uses this value to filter the search results returned by Get-Help.

.ROLE

The name of the user role for the help topic. The Role parameter of Get-Help uses this value to filter the search results returned by Get-Help.

.FUNCTIONALITY

The keywords that describe the intended use of the function. The Functionality parameter of Get-Help uses this value to filter the search results returned by Get-Help.

.FORWARDHELPTARGETNAME

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.

# .FORWARDHELPTARGETNAME <Command-Name>

.FORWARDHELPCATEGORY

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.

# .FORWARDHELPCATEGORY <Category>

.REMOTEHELPRUNSPACE

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

# .REMOTEHELPRUNSPACE <PSSession-variable>

.EXTERNALHELP

Specifies an XML-based help file for the script or function.

# .EXTERNALHELP <XML Help File>

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 filename 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 Write Cmdlet Help.

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 filename. To change the name or its capitalization, change the function syntax or the script filename.

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 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 .Parameter 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.

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.

Remarks

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

Examples

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

PS> extension -name "File"
File.txt

.EXAMPLE

PS> extension -name "File" -extension "doc"
File.doc

.EXAMPLE

PS> extension "File" "doc"
File.doc

.LINK

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

.LINK

Set-Item
#>
}

The results are as follows:

Get-Help -Name "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

PS> extension -name "File"
File.txt

Example 2

PS> extension -name "File" -extension "doc"
File.doc

Example 3

PS> extension "File" "doc"
File.doc

RELATED LINKS

http://www.fabrikam.com/extension.html
Set-Item

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

PS> extension -name "File"
File.txt

.EXAMPLE

PS> extension -name "File" -extension "doc"
File.doc

.EXAMPLE

PS> extension "File" "doc"
File.doc

.LINK

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

.LINK

Set-Item
#>
}

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

PS> .\Update-Month.ps1

.EXAMPLE

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

.EXAMPLE

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 $env:Path environment variable, the Get-Help command that gets the script help must specify the script path.

Get-Help -Name .\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

PS> .\Update-Month.ps1

Example 2

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

Example 3

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

# RELATED LINKS

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 examples show 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
}

Redirecting to a Different Help Topic

The following code is an excerpt from the beginning of the built-in help function in 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:

Get-Help -Name help

NAME

Get-Help

SYNOPSIS

Displays information about PowerShell cmdlets and concepts.
...

See also

• about_Functions
• about_Functions_Advanced_Parameters
• about_Scripts
• Writing Comment-Based Help Topics