練習 - 使用說明

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找到所要使用的 Cmdlet 之後，即可針對該 Cmdlet 深入了解。 例如，您可以了解呼叫命令的不同方式、能夠使用的參數，以及範例使用案例。

使用 Get-help 探索命令

使用 Get-Help Cmdlet 來了解 Cmdlet。

  1. 執行 Get-Help 命令：

    Get-Help -Name Get-FileHash

    此命令會產生類似下列文字的輸出：

    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"

    由於此輸出難以閱讀，因此您決定使用另一個較不冗長的方法。 亦即，您要使用 help 別名。

  2. 輸入 help 命令：

    help Get-FileHash

    現在會顯示簡化的說明輸出版本。 此輸出看起來如同下列文字：

    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.

    您可使用方向鍵，以垂直方式逐列查看結果。 使用空格鍵即可逐頁查看結果。

  3. 執行 help Get-FileHash -Examples：

    help Get-FileHash -Examples

    輸出看起來會如同下列文字：

    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

    此輸出包含使用 Cmdlet 的範例清單。 找出回應中包含 Example 1 文字的部分。 這部分的文字說明您如何透過將 Get-FileHash 以管線傳送到 Format-List Cmdlet，來將前者與檔案路徑搭配使用。

    提示

    若要快速查看範例，請在搜尋說明時新增 -Examples 旗標。