Use hex byte in PowerShell?

Question

This simple PowerShell script "fills in" the bad sectors of a USB flash drive. But I need to fill the drive with files containing 0x00 (all bits zero) and 0x255 (all bits 1). How can I use hex in PowerShell?

function filler {
    Param( [byte]$hex )

    $filearray = @()
    $count = 1
    $freespace = Get-PSDrive H
    $maxfiles = [int]($freespace.Free / 1048576)

    do {
        $randomnum = Get-Random -Minimum 100000000 -Maximum 999999999

        "$hex" * 1048576 | Out-File $randomnum

        $filecontent = Get-Content $randomnum -Raw

        if ($filecontent -notcontains ('$hex')) {
            # do nothing because the content is incorrect
        } else {
            $filearray += $randomnum
        }

        $count++
    } while ($count -le $maxfiles)

    foreach ($filename in $filearray) {
        Remove-Item $filename
    }
}

filler -hex 0x00
filler -hex 0xFF

[byte]$hex = 0xff; "$hex" * 5 doesn't do what you seem to expect. It creates the string "255255255255255" (repeat the string representation of the integer value 0xFF 5 times). — Ansgar Wiechers
– Ansgar Wiechers, Commented Mar 15, 2018 at 13:06

Mathias R. Jessen · Accepted Answer · 2018-03-15 13:34:27Z

1

The string "0x00" is different from the numeric value represented by 0x00.

Make sure you specify -Encoding Byte when trying to read and write raw data to/from files:

,$hex * 1048576 | Set-Content $randomnum -Encoding Byte

And, similarly when reading from files:

$filecontent = Get-Content $randomnum -Encoding Byte
if($filecontent |Where-Object {$_ -notin @(0x00,0xFF)}){
    # do nothing
}

edited Mar 15, 2018 at 13:34

answered Mar 15, 2018 at 12:20

Mathias R. Jessen

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2 Comments

Bill Paxtonn Over a year ago

Out-File: -Encoding Byte not exist. Used others but fills file more than 1MB. Get-Content: Should be -Encoding Byte.

Mathias R. Jessen Over a year ago

@BillPaxtonn That's what I get for trying to write answers on my phone :-P Updated the answer

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