PowerShell comes with a built-in help system. Use help to read more about a command, what the command does, and how to call it. Also, if you inspect what a command returns, you can use that information to customize the output, determine what commands are logically grouped, and determine how to use the commands together.
When you finish this module, you'll be able to:
PowerShell comes preinstalled with numerous commands. To use PowerShell commands efficiently, you need to understand how they work. For example, you need to know what parameters the commands take and that there might be more than one way to call a command.
It's also helpful to know what a command returns, what type it returns, and the command's properties. By knowing these things, you can configure how help is shown. You also get a hint of how a specific command fits with another command if you combine them.
When you finish this module, you'll be able to:
To complete this module, you should:
By using the built-in help system in PowerShell, you can find out more about a specific command. You use the Get-Command cmdlet to locate a command that you need. After you've located the command, you might want to know more about what the command does and various ways to call it.
You can use the Get-Help core cmdlet to learn more about a command. Typically, you invoke Get-Help by specifying it by name and adding the -Name flag that contains the name of the cmdlet you want to learn about. Here's an example:
>Get-Help -Name Get-Help
New versions of PowerShell don't include the help system by default. The first time you run Get-Help, you're asked to install the help files. You can also run the Update-Help cmdlet to install the help files. Because a call to Update-Help downloads many help files, the command can fetch only once per day by default. You can override this fetching behavior by using the -Force flag.
You update the help files differently on Windows compared to Linux or macOS. The process differs because when you run the Update-Help cmdlet, help files are fetched over the internet by matching your computer's culture. On Windows, a culture is already installed, but it's missing on Linux and macOS. So you need to specify a culture when you update help files on Linux and macOS.
Here's an example command:
>Update-Help -UICulture en-US -Verbose
This command specifies the -UICulture flag. It gives it the value en-US, which fetches US English help files. To update your help files on macOS or Linux, use a culture that corresponds to your machine's culture.
When you invoke Get-Help on a cmdlet, a help page is returned. The page includes many sections. You'll likely see these common sections:
If you don't want to display the full help page, narrow the response by adding flags to your Get-Help command. Here are some flags you can use:
For example, you can use the following command to return only the Examples section of the help page.
>Get-Help Get-FileHash -Examples
Running Get-Help returns the entire help page. The page might not provide the best reading experience. You might have to scroll to find the section you want to read. A better approach is to use the help alias. The help alias pipes Get-Help into a function that ensures that your output is readable line by line. It also makes the response readable page by page, by paginating the output.
Use the Get-Help cmdlet to learn about cmdlets.
Run the command Get-Help:
Get-Help -Name Get-FileHash
This command produces an output similar to the following text:
NAME
Get-FileHash
SYNOPSIS
Computes the hash value for a file by using a specified hash algorithm.
SYNTAX
Get-FileHash [-InputStream] <System.IO.Stream> [[-Algorithm] {SHA1 | SHA256 | SHA384 | SHA512 | MD5}]
[<CommonParameters>]
Get-FileHash [-LiteralPath] <System.String[]> [[-Algorithm] {SHA1 | SHA256 | SHA384 | SHA512 | MD5}]
[<CommonParameters>]
Get-FileHash [-Path] <System.String[]> [[-Algorithm] {SHA1 | SHA256 | SHA384 | SHA512 | MD5}]
[<CommonParameters>]
DESCRIPTION
The `Get-FileHash` cmdlet computes the hash value for a file by using a specified hash algorithm. A hash value
is a unique value that corresponds to the content of the file. Rather than identifying the contents of a file
by its file name, extension, or other designation, a hash assigns a unique value to the contents of a file.
File names and extensions can be changed without altering the content of the file, and without changing the
hash value. Similarly, the file's content can be changed without changing the name or extension. However,
changing even a single character in the contents of a file changes the hash value of the file.
The purpose of hash values is to provide a cryptographically-secure way to verify that the contents of a file
have not been changed. While some hash algorithms, including MD5 and SHA1, are no longer considered secure
against attack, the goal of a secure hash algorithm is to render it impossible to change the contents of a file
-- either by accident, or by malicious or unauthorized attempt -- and maintain the same hash value. You can
also use hash values to determine if two different files have exactly the same content. If the hash values of
two files are identical, the contents of the files are also identical.
By default, the `Get-FileHash` cmdlet uses the SHA256 algorithm, although any hash algorithm that is supported
by the target operating system can be used.
RELATED LINKS
Online Version: https://learn.microsoft.com/powershell/module/microsoft.powershell.utility/get-filehash?view=powe
rshell-7.2&WT.mc_id=ps-gethelp
Format-List
REMARKS
To see the examples, type: "Get-Help Get-FileHash -Examples"
For more information, type: "Get-Help Get-FileHash -Detailed"
For technical information, type: "Get-Help Get-FileHash -Full"
For online help, type: "Get-Help Get-FileHash -Online"
Because this output is difficult to read, you decide to use an alternative that is less verbose. That is, you use the help alias.
Enter the help command:
help Get-FileHash
Now, a reduced version of the help output is shown. It looks like the following text:
NAME
Get-FileHash
SYNOPSIS
Computes the hash value for a file by using a specified hash algorithm.
SYNTAX
Get-FileHash [-InputStream] <System.IO.Stream> [[-Algorithm] {SHA1 | SHA256 | SHA384 | SHA512 | MD5}]
[<CommonParameters>]
Get-FileHash [-LiteralPath] <System.String[]> [[-Algorithm] {SHA1 | SHA256 | SHA384 | SHA512 | MD5}]
[<CommonParameters>]
Get-FileHash [-Path] <System.String[]> [[-Algorithm] {SHA1 | SHA256 | SHA384 | SHA512 | MD5}]
[<CommonParameters>]
DESCRIPTION
The `Get-FileHash` cmdlet computes the hash value for a file by using a specified hash algorithm. A hash value
is a unique value that corresponds to the content of the file. Rather than identifying the contents of a file
by its file name, extension, or other designation, a hash assigns a unique value to the contents of a file.
File names and extensions can be changed without altering the content of the file, and without changing the
hash value. Similarly, the file's content can be changed without changing the name or extension. However,
changing even a single character in the contents of a file changes the hash value of the file.
The purpose of hash values is to provide a cryptographically-secure way to verify that the contents of a file
have not been changed. While some hash algorithms, including MD5 and SHA1, are no longer considered secure
against attack, the goal of a secure hash algorithm is to render it impossible to change the contents of a file
-- either by accident, or by malicious or unauthorized attempt -- and maintain the same hash value. You can
also use hash values to determine if two different files have exactly the same content. If the hash values of
two files are identical, the contents of the files are also identical.
By default, the `Get-FileHash` cmdlet uses the SHA256 algorithm, although any hash algorithm that is supported
by the target operating system can be used.
You can move through the results vertically, row by row, by using the arrow keys. To view the results page by page, use the Spacebar.
Run help Get-FileHash -Examples:
help Get-FileHash -Examples
The output looks like the following text:
NAME
Get-FileHash
SYNOPSIS
Computes the hash value for a file by using a specified hash algorithm.
--------- Example 1: Compute the hash value for a file ---------
> Get-FileHash /etc/apt/sources.list | Format-List
Algorithm : SHA256
Hash : 3CBCFDDEC145E3382D592266BE193E5BE53443138EE6AB6CA09FF20DF609E268
Path : /etc/apt/sources.list
------ Example 2: Compute the hash value for an ISO file ------
>Get-FileHash C:\Users\user1\Downloads\Contoso8_1_ENT.iso -Algorithm SHA384 | Format-List
Algorithm : SHA384
Hash : 20AB1C2EE19FC96A7C66E33917D191A24E3CE9DAC99DB7C786ACCE31E559144FEAFC695C58E508E2EBBC9D3C96F21FA3
Path : C:\Users\user1\Downloads\Contoso8_1_ENT.iso
This output contains a list of examples that use the cmdlet. Locate the part of the response that contains the text Example 1. This portion of the text shows how you can use Get-FileHash with a file path by piping it to the cmdlet Format-List.
Tip
To quickly see an example, add the flag -Examples when you search for help.
When a cmdlet runs, it returns an object. When you invoke a cmdlet, the response you see has been formatted and might not necessarily represent all the available information for the response. To know more about what's being returned and how you can modify what is returned, you can use the command Get-Member.
The Get-Member cmdlet is meant to be piped on top of the command you run so that you can filter the output. A typical command-line invocation of Get-Member might look like the following example:
>Get-Process -Name 'name-of-process' | Get-Member
This command first produces an object result by calling Get-Process. That result is passed as an input to Get-Member by using the pipe (|). In return, you get a table result that includes the Name, MemberType, and Definition columns. You also get the type of the returned object.
Tip
To get a list of the processes running on your machine, run Get-Process.
The first line of the response, running the Get-Member command, is the type of the returned object. When you know the type, you can search for other cmdlets that operate on the same type. Explore these related commands to quickly build your knowledge in the domain you're working in.
Let's say you invoked the PowerShell command that lists all members for a specific process. The first few rows of the result look something like this output:
TypeName: System.Diagnostics.Process
Name MemberType Definition
---- ---------- ----------
Handles AliasProperty Handles = Handlecount
The first row indicates that the type is System.Diagnostics.Process. Use this type as a search argument to look for other cmdlets that use this type. Here's an example command:
>Get-Command -ParameterType Process
The result is a list of cmdlets that operate on this type. Little by little, you can learn more about PowerShell by using Get-Member and by learning to interpret its result.
Tip
PowerShell is meant to be learned a little at a time. A great way to discover related cmdlets is by using the returned type to search for cmdlets by type.
When you run Get-Member, the result is verbose. That is, many rows are returned. The object might have properties, like events and methods. To make the answer less verbose, you can filter on specific columns and also decide which columns to display. Keep in mind that the returned answer is already a subset of all the columns in the response.
Take a look at a Get-Member response that includes many columns. By introducing the Select-Object cmdlet, you can choose which columns appear in the response. The command expects either a comma-separated list of column names or a wildcard character, such as an asterisk (*), which indicates all columns.
When you use the Select-Object command in the context of Select-Object Name, MemberType, you specify only the columns you want. In this case, the columns are Name and MemberType. The command line would look like this:
Get-Process -Name 'name-of-process' | Get-Member | Select-Object Name, MemberType
This filtering pattern returns an output that includes fewer columns. Here's an example of the result:
Name MemberType
---- ----------
Handles AliasProperty
You also can filter the response by rows. For example, you can use the -MemberType Method flag to specify that you're interested in the rows in which the member type is a method. You might want to show only specific rows, for example, if you want to locate and run a specific method.
Tip
It's generally better to use dedicated cmdlets than to run methods on an object.
You know that the Get-Process cmdlet lists information about processes. Now, you want to find what other cmdlets work with processes and what a process consists of.
In this scenario, you'll use the Get-Member cmdlet.
Run Get-Process:
Get-Process
The table-like response consists of all processes that are running on your machine. The exact response depends on what is running on your machine. Choose a process name from the column on the right, and then use it as an argument for your next command.
Run Get-Process again. This time, use the process name and pipe Get-Member.
Get-Process -Name 'selected-process-name' | Get-Member
Tip
This command produces a long response that consists of all members, events, and methods. At this point, focus on the first line, which lists the following information:
TypeName: System.Diagnostics.Process
Now you know that the type is Process. You can learn more about what other cmdlets use this type. Next, use Get-Command and add the type as a parameter.
Run Get-Command:
Get-Command -ParameterType Process
This command produces a response that's similar to the following text:
CommandType Name Version Source
----------- ---- ------- ------
Cmdlet Debug-Process 7.0.0.0 Microsoft.PowerShell.Management
Cmdlet Enter-PSHostProcess 7.0.3.0 Microsoft.PowerShell.Core
Cmdlet Get-Process 7.0.0.0 Microsoft.PowerShell.Management
Cmdlet Get-PSHostProcessInfo 7.0.3.0 Microsoft.PowerShell.Core
Cmdlet Stop-Process 7.0.0.0 Microsoft.PowerShell.Management
Cmdlet Wait-Process 7.0.0.0 Microsoft.PowerShell.Management
Congratulations! By knowing the name of the Get-Process cmdlet, you've discovered related commands. You can continue to learn about these commands by using Get-Help.
Choose the best response for each question. Then, select Check your answers.
In this module, you learned how to inspect a command that you intend to use. Looking at a command before you use it helps you call the command correctly and learn the different ways you can call the command.
You also looked at inspecting what a command returns. PowerShell commands return objects. By calling Get-Member, you learn what type of object will be returned and the object's properties. With that information, you can look for related commands that operate on same object type.
You'll learn how to use object type information in later modules that look at pipelines and combining multiple commands in a single command.