PowerShell function for updating hosts file on Windows.

UpdateHosts.ps1

<#
    Check using a regex pattern whether or not the domain is considered valid.
#>
function Test-WebsiteDomainValid
{
    Param([Parameter(Mandatory=$True,HelpMessage="Determine if the domain name for the website is considered valid.")][string]$WebsiteDomainName)
    return [Text.Regex]::IsMatch($WebsiteDomainName,"[^a-zA-Z0-9\-]+")
}
<# 
    Update the hosts file on the system so that it specifies our new website domain name.

    This function might fail if this script is not running as admin.
#>
function Update-SystemHostsFile()
{
    Param(
        [Parameter(HelpMessage="The domain name for the website to update the hosts file with.",Mandatory=$True)][string]$WebsiteDomainName,
        [Parameter(HelpMessage="The target to update the hosts file with.",Mandatory=$True)][string]$Target
    )
    $HostsFilePath="C:\Windows\System32\drivers\etc\hosts"
    $HostsFileContents=Get-Item -Path $HostsFilePath -Force

    if ((Test-WebsiteDomainValid -WebsiteDomainName $WebsiteDomainName) -ne $True)
    {
        Write-Error "Failed: the website domain name ""${WebsiteDomainName}"" is invalid." -ErrorAction Stop
        return $False
    }

    if ([string]::IsNullOrEmpty($HostsFileContents))
    {
        Write-Error "Failed: the hosts file is empty or null. Check the path ""${HostsFilePath}""" -ErrorAction Stop
        return $False
    }
    
    Write-Host "Updating: system hosts file ""${WebsiteDomainName}"" -> ""${Target}"""
    if ($HostsFileContents.Contains($WebsiteDomainName) -eq $False)
    {
        $SiteAppend="${WebsiteDomainName}  ${Target}"
        $SiteAppend | Out-File -FilePath $HostsFilePath -Force -Append
    }
}

Update-SystemHostsFile -WebsiteDomainName "arcanedreams.local" "127.0.0.1"