HostNameUtils

1.2.0

Get-Hostnames.ps1

function Get-Hostnames {
    <#
    .SYNOPSIS
    Gets the hostnames (and corresponding IP addresses) specified in the hosts file.
 
    .DESCRIPTION
    The hosts file is used to map hostnames to IP addresses.
 
    .EXAMPLE
    Get-TecBoxHostNames
 
    Hostname IpAddress
    -------- ---------
    localhost 127.0.0.1
    fabrikam-local 127.0.0.1
    www-local.fabrikam.com 127.0.0.1
    #>
    [CmdletBinding()]
    param()
    begin
    {
        Set-StrictMode -Version Latest
        $ErrorActionPreference = "Stop"

        function CreateHostsEntryObject(
            [string] $ipAddress,
            [string[]] $hostnames,
            <# [string] #> $comment) #HACK: never $null if type is specified
        {
            $hostsEntry = New-Object PSObject
            $hostsEntry | Add-Member NoteProperty -Name "IpAddress" `
                -Value $ipAddress

            [System.Collections.ArrayList] $hostnamesList =
                New-Object System.Collections.ArrayList

            $hostsEntry | Add-Member NoteProperty -Name "Hostnames" `
                -Value $hostnamesList

            If ($hostnames -ne $null)
            {
                $hostnames | foreach {
                    $hostsEntry.Hostnames.Add($_) | Out-Null
                }
            }

            $hostsEntry | Add-Member NoteProperty -Name "Comment" -Value $comment

            return $hostsEntry
        }

        function ParseHostsEntry(
            [string] $line)
        {
            $hostsEntry = CreateHostsEntryObject

            Write-Debug "Parsing hosts entry: $line"

            If ($line.Contains("#") -eq $true)
            {
                If ($line -eq "#")
                {
                    $hostsEntry.Comment = [string]::Empty
                }
                Else
                {
                    $hostsEntry.Comment = $line.Substring($line.IndexOf("#") + 1)
                }

                $line = $line.Substring(0, $line.IndexOf("#"))
            }

            $line = $line.Trim()

            If ($line.Length -gt 0)
            {
                $hostsEntry.IpAddress = ($line -Split "\s+")[0]

                Write-Debug "Parsed address: $($hostsEntry.IpAddress)"

                [string[]] $parsedHostnames = $line.Substring(
                    $hostsEntry.IpAddress.Length + 1).Trim() -Split "\s+"

                Write-Debug ("Parsed hostnames ($($parsedHostnames.Length)):" `
                    + " $parsedHostnames")

                $parsedHostnames | foreach {
                    $hostsEntry.Hostnames.Add($_) | Out-Null
                }
            }

            return $hostsEntry
        }

        function ParseHostsFile
        {
            $hostsEntries = New-Object System.Collections.ArrayList

            [string] $hostsFile = $env:WINDIR + "\System32\drivers\etc\hosts"

            If ((Test-Path $hostsFile) -eq $false)
            {
                Write-Verbose "Hosts file does not exist."
            }
            Else
            {
                [string[]] $hostsContent = Get-Content $hostsFile

                $hostsContent | foreach {
                    $hostsEntry = ParseHostsEntry $_

                    $hostsEntries.Add($hostsEntry) | Out-Null
                }
            }

            # HACK: Return an array (containing the ArrayList) to avoid issue with
            # PowerShell returning $null (when hosts file does not exist)
            return ,$hostsEntries
        }

        [Collections.ArrayList] $hostsEntries = ParseHostsFile
    }

    process
    {
        $hostsEntries | foreach {
            $hostsEntry = $_

            $hostsEntry.Hostnames | foreach {
                $properties = @{
                    Hostname = $_
                    IpAddress = $hostsEntry.IpAddress
                }

                New-Object PSObject -Property $properties
            }
        }
    }
}