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Get-FileHash

Windows PowerShell 4.0

Updated: May 8, 2014

Applies To: Windows PowerShell 4.0

Get-FileHash

Computes the hash value for a file by using a specified hash algorithm.

Syntax

Parameter Set: Path
Get-FileHash [-Path] <String[]> [-Algorithm <String> ] [ <CommonParameters>]

Parameter Set: LiteralPath
Get-FileHash -LiteralPath <String[]> [-Algorithm <String> ] [ <CommonParameters>]




Detailed Description

Get-FileHash 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.

Parameters

-Algorithm<String>

Specifies the cryptographic hash function to use for computing the hash value of the contents of the specified file. A cryptographic hash function includes the property that it is not possible to find two distinct inputs that generate the same hash values. Hash functions are commonly used with digital signatures and for data integrity. Valid values for this parameter are SHA1, SHA256, SHA384, SHA512, MACTripleDES, MD5, and RIPEMD160. If no value is specified, or if the parameter is omitted, the default value is SHA256.

For security reasons, MD5 and SHA1, which are no longer considered secure, should only be used for simple change validation, and should not be used to generate hash values for files that require protection from attack or tampering.


Aliases

none

Required?

false

Position?

named

Default Value

none

Accept Pipeline Input?

false

Accept Wildcard Characters?

false

-LiteralPath<String[]>

Specifies the path to a file. Unlike the Path parameter, the value of the LiteralPath parameter is used exactly as it is typed. No characters are interpreted as wildcard characters. If the path includes escape characters, enclose the path in single quotation marks. Single quotation marks instruct Windows PowerShell not to interpret characters as escape sequences.


Aliases

PSPath

Required?

true

Position?

named

Default Value

none

Accept Pipeline Input?

True (ByPropertyName)

Accept Wildcard Characters?

false

-Path<String[]>

Specifies the path to one or more files. Wildcard characters are permitted.


Aliases

none

Required?

true

Position?

1

Default Value

none

Accept Pipeline Input?

false

Accept Wildcard Characters?

false

<CommonParameters>

This cmdlet supports the common parameters: -Verbose, -Debug, -ErrorAction, -ErrorVariable, -OutBuffer, and -OutVariable. For more information, see  about_CommonParameters (http://go.microsoft.com/fwlink/p/?LinkID=113216).

Inputs

The input type is the type of the objects that you can pipe to the cmdlet.

  • System.String

    You can pipe a string to the Get-FileHash cmdlet that contains a path to one or more files.


Outputs

The output type is the type of the objects that the cmdlet emits.

  • Microsoft.Powershell.Utility.FileHash

    Get-FileHash returns an object that represents the path to the specified file, the value of the computed hash, and the algorithm used to compute the hash.


Examples

Example 1

This example uses the Get-FileHash cmdlet to compute the hash value for the Powershell.exe file. The hash algorithm used is the default, SHA256. The output is piped to the Format-List cmdlet to format the output as a list.


PS C:\>  Get-FileHash $pshome\powershell.exe | Format-List

Algorithm : SHA256
Hash : 6A785ADC0263238DAB3EB37F4C185C8FBA7FEB5D425D034CA9864F1BE1C1B473
Path : C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe

Example 2

This command uses the Get-FileHash cmdlet and the SHA384 algorithm to compute the hash value for an ISO file that an administrator has downloaded from the Internet. The output is piped to the Format-List cmdlet to format the output as a list.


PS C:\>  Get-FileHash C:\Users\Andris\Downloads\Contoso8_1_ENT.iso -Algorithm SHA384 | Format-List

Algorithm : SHA384
Hash : 20AB1C2EE19FC96A7C66E33917D191A24E3CE9DAC99DB7C786ACCE31E559144FEAFC695C58E508E2EBBC9D3C96F21FA3
Path : C:\Users\Andris\Downloads\Contoso8_1_ENT.iso



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