Powershell script to display a hex dump of a file's contents.

Write-HexDump.ps1

function Write-HexDump {
    <#
    .SYNOPSIS
    Displays a hex dump of a file's contents.

    .PARAMETER FilePath
    Path to the file to display as a hex dump.

    .PARAMETER ByteCount
    Number of bytes to read and display. Default is 256.

    .PARAMETER StartOffset
    Position of the first byte to read from the file. Default is 0.

    .EXAMPLE
    Write-HexDump -FilePath '/data/file.bin' -ByteCount 128 -StartOffset 16

    .NOTES
    Original code dreated by Claude Sonnet 4
    #>
    param(
        [string]$FilePath,
        [int]$ByteCount = 256,
        [int]$StartOffset = 0
    )
    
    $offsetColor = 'Blue'
    $hexColor = 'Green'
    $asciiColor = 'Gray'

    $bytes = [byte[]]::new($ByteCount)
    $fileStream = [System.IO.File]::OpenRead($FilePath)
    try {
        $null = $fileStream.Seek($StartOffset, [System.IO.SeekOrigin]::Begin)
        $bytesRead = $fileStream.Read($bytes, 0, $ByteCount)
        
        # Print header
        Write-Host 'Offset   ' -NoNewline -ForegroundColor "Dark$offsetColor"
        Write-Host '00 01 02 03 04 05 06 07  08 09 0A 0B 0C 0D 0E 0F  ' -NoNewline -ForegroundColor "Dark$hexColor"
        Write-Host '           ASCII' -ForegroundColor "Dark$asciiColor"

        Write-Host '-------- ' -NoNewline -ForegroundColor "Dark$offsetColor"
        Write-Host '------------------------------------------------ ' -NoNewline -ForegroundColor "Dark$hexColor"
        Write-Host '-----------------' -ForegroundColor "Dark$asciiColor"
        
        $firstCol = $StartOffset % 16
        $totalRows = [Math]::Ceiling(($bytesRead + $firstCol) / 16)
        for ($row = 0; $row -lt $totalRows; $row++) {
            $rowOffset = $row * 16
            $hexBuilder = [System.Text.StringBuilder]::new()
            $asciiBuilder = [System.Text.StringBuilder]::new()

            for ($col = 0; $col -lt 16; $col++) {
                $byteIndex = $rowOffset + $col - $firstCol
                if (($row -eq 0) -and ($col -lt $firstCol)) {
                    $null = $hexBuilder.Append('   ')
                    $null = $asciiBuilder.Append(' ')
                } elseif ($byteIndex -ge 0 -and $byteIndex -lt $bytesRead) {
                    $b = $bytes[$byteIndex]
                    $null = $hexBuilder.AppendFormat('{0:X2} ', $b)
                    
                    $c = if ([System.Char]::IsControl($b)) { '.' } else { [char]$b }
                    $null = $asciiBuilder.Append($c)
                } else {
                    $null = $hexBuilder.Append('   ')
                    $null = $asciiBuilder.Append(' ')
                }

                # Add space after 8th byte for readability
                if ($col -eq 7) {
                    $null = $hexBuilder.Append(' ')
                    $null = $asciiBuilder.Append(' ')
                }
            }

            # Print row offset
            Write-Host ('{0:X8} ' -f $rowOffset) -NoNewline -ForegroundColor $offsetColor

            # Print hex representation
            Write-Host $hexBuilder.ToString() -NoNewline -ForegroundColor $hexColor

            # Print ASCII representation
            Write-Host $asciiBuilder.ToString() -ForegroundColor $asciiColor
        }
    } finally {
        $fileStream.Close()
    }
}