练习 - 使用帮助

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找到要使用的 cmdlet 后，可以了解有关该 cmdlet 的详细信息。 例如，可了解不同的调用方法、可使用的参数和示例用例。

使用 Get-Help 来发现命令

使用 Get-Help cmdlet 了解 cmdlet。

  1. 运行命令 Get-Help：

    Get-Help -Name Get-FileHash

    此命令生成的输出类似于以下文本：

    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"

    由于此输出难以阅读，因此你决定使用一种详细程度略低的替代方法。 也就是说，使用 help 别名。

  2. 输入 help 命令：

    help Get-FileHash

    现在将显示更精简的帮助输出版本。 此输出类似于以下文本：

    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.

    可使用箭头键，按行垂直移动结果。 若要逐页查看结果，请使用空格键。

  3. 运行 help Get-FileHash -Examples：

    help Get-FileHash -Examples

    输出类似于以下文本：

    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

    此输出包含使用 cmdlet 的示例列表。 查找包含 Example 1 文本的响应部分。 此部分文本显示了如何将 Get-FileHash 传递到 cmdlet Format-List，以便与文件路径一起使用。

    提示

    若要快速查看示例，请在搜索帮助时添加标志 -Examples。