PowerShell: Create a GZip (*.gz)

PowerShell natively does not contain a CmdLet for creating a GZip file. There are third-party modules/CmdLets that create GZip. It is a straightforward process to access the CLI using PowerShell to create a GZip.

In support of creating a Gzip the following PowerShell functions were implemented:

• New-GZipArchive: function that creates the actual GZip file
• Close-Stream: helper function that handles closing/disposing the streams used.

The code is as follows:

function Close-Stream {

    param

    (

        [Parameter(Mandatory=$false)]        

        [System.IO.Stream] $stream

    )

    if ($null -ne $stream) {

        $stream.Close()

        $stream.Dispose()

    }

}

function New-GZipArchive {

    param

    (

        [Parameter(Mandatory=$true)]        

        [string] $sourceFilePath,

        [Parameter(Mandatory=$true)]

        [string] $destinationFilePath,

        [switch] $overwrite

    )

    [System.IO.FileStream] $sourceFileStream = $null

    [System.IO.FileStream] $destinationFileStream = $null

    [System.IO.Compression.GZipStream] $gzipStream

    try {

        if ($overwrite)

        {

            if (Test-Path `

                    -Path $destinationFilePath `

                    -PathType Leaf `

                    -ErrorAction:Stop) {

                Remove-Item `

                    -Path $destinationFilePath`

                    -ErrorAction:Stop

            }

        }

        [byte[]] $buffer = [System.Byte[]]::new([Math]::Pow(2, 20))

        $sourceFileStream = [System.IO.FileStream]::new(

                                $sourceFilePath,

                                [System.IO.FileMode]::Open,

                                [System.IO.FileAccess]::Read,

                                [System.IO.FileShare]::Read)

        $destinationFileStream = [System.IO.FileStream]::new(

                                    $destinationFilePath,

                                    [System.IO.FileMode]::CreateNew,

                                    [System.IO.FileAccess]::Write,

                                    [System.IO.FileShare]::None)

        $gzipStream = [System.IO.Compression.GZipStream]::new(

                $destinationFileStream,

                [System.IO.Compression.CompressionMode]::Compress)

        do {

            [int] $bytesRead = $sourceFileStream.Read(

                                     $buffer,

                                     0,

                                     $buffer.Length)

            $gzipStream.Write($buffer, 0, $bytesRead)

        } while($bytesRead -ne 0)

    }

    

    finally {

        Close-Stream $sourceFileStream

        Close-Stream $gzipStream

        Close-Stream $destinationFileStream

    }

}