Get-FileHash (Microsoft.PowerShell.Utility) - PowerShell (2024)

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

Syntax

Get-FileHash [-Path] <String[]> [[-Algorithm] <String>] [<CommonParameters>]

Get-FileHash [-LiteralPath] <String[]> [[-Algorithm] <String>] [<CommonParameters>]

Get-FileHash [-InputStream] <Stream> [[-Algorithm] <String>] [<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 identifyingthe contents of a file by its file name, extension, or other designation, a hash assigns a uniquevalue to the contents of a file. File names and extensions can be changed without altering thecontent of the file, and without changing the hash value. Similarly, the file's content can bechanged without changing the name or extension. However, changing even a single character in thecontents 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 contentsof a file have not been changed. While some hash algorithms, including MD5 and SHA1, are no longerconsidered secure against attack, the goal of a secure hash algorithm is to render it impossible tochange the contents of a file -- either by accident, or by malicious or unauthorized attempt -- andmaintain the same hash value. You can also use hash values to determine if two different files haveexactly the same content. If the hash values of two files are identical, the contents of the filesare also identical.

By default, the Get-FileHash cmdlet uses the SHA256 algorithm, although any hash algorithm thatis supported by the target operating system can be used.

Examples

Example 1: Compute the hash value for a file

This example uses the Get-FileHash cmdlet to compute the hash value for the/etc/apt/sources.list file. The hash algorithm used is the default, SHA256. The output ispiped to the Format-List cmdlet to format the output as a list.

Get-FileHash /etc/apt/sources.list | Format-ListAlgorithm : SHA256Hash : 3CBCFDDEC145E3382D592266BE193E5BE53443138EE6AB6CA09FF20DF609E268Path : /etc/apt/sources.list

Example 2: Compute the hash value for an ISO file

This example uses the Get-FileHash cmdlet and the SHA384 algorithm to compute the hash valuefor an ISO file that an administrator has downloaded from the internet. The output is piped to theFormat-List cmdlet to format the output as a list.

Get-FileHash C:\Users\user1\Downloads\Contoso8_1_ENT.iso -Algorithm SHA384 | Format-ListAlgorithm : SHA384Hash : 20AB1C2EE19FC96A7C66E33917D191A24E3CE9DAC99DB7C786ACCE31E559144FEAFC695C58E508E2EBBC9D3C96F21FA3Path : C:\Users\user1\Downloads\Contoso8_1_ENT.iso

Example 3: Compute the hash value of a stream

For this example, we get are using System.Net.WebClient to download a package from thePowershell release page. The releasepage also documents the SHA256 hash of each package file. We can compare the published hash valuewith the one we calculate with Get-FileHash.

$wc = [System.Net.WebClient]::new()$pkgurl = 'https://github.com/PowerShell/PowerShell/releases/download/v6.2.4/powershell_6.2.4-1.debian.9_amd64.deb'$publishedHash = '8E28E54D601F0751922DE24632C1E716B4684876255CF82304A9B19E89A9CCAC'$FileHash = Get-FileHash -InputStream ($wc.OpenRead($pkgurl))$FileHash.Hash -eq $publishedHashTrue

Example 4: Compute the hash of a string

PowerShell does not provide a cmdlet to compute the hash of a string. However, you can write astring to a stream and use the InputStream parameter of Get-FileHash to get the hash value.

$stringAsStream = [System.IO.MemoryStream]::new()$writer = [System.IO.StreamWriter]::new($stringAsStream)$writer.write("Hello world")$writer.Flush()$stringAsStream.Position = 0Get-FileHash -InputStream $stringAsStream | Select-Object HashHash----64EC88CA00B268E5BA1A35678A1B5316D212F4F366B2477232534A8AECA37F3C

Parameters

-Algorithm

-InputStream

-LiteralPath

-Path

Inputs

String

You can pipe a string containing a path to a file to this cmdlet.

Outputs

Microsoft.PowerShell.Utility.FileHash

This cmdlet returns an object representing the path to the specified file, the value of thecomputed hash, and the algorithm used to compute the hash.

• Format-List