Powershell to manipulate host file - powershell

Question

I am looking at to see if I can create powershell script to update the contents in the host file.
Anybody know if there are any examples that manipulate the host file using powershell or any other scripting lanaguages?
Thanks.

Answer 1

All of these answers are pretty elaborate. This is all you need to add a hosts file entry:
Add-Content -Path $env:windir\System32\drivers\etc\hosts -Value "`n127.0.0.1`tlocalhost" -Force
IP address and hostname are separated by `t which is the PowerShell notation for a tab character.
`n is the PowerShell notation for a newline.

Answer 2

First up, if you're on Vista or Windows 7 make sure you run these commands from an elevated prompt:
# Uncomment lines with localhost on them:
$hostsPath = "$env:windir\System32\drivers\etc\hosts"
$hosts = get-content $hostsPath
$hosts = $hosts | Foreach {if ($_ -match '^\s*#\s*(.*?\d{1,3}.*?localhost.*)')
{$matches[1]} else {$_}}
$hosts | Out-File $hostsPath -enc ascii
# Comment lines with localhost on them:
$hosts = get-content $hostsPath
$hosts | Foreach {if ($_ -match '^\s*([^#].*?\d{1,3}.*?localhost.*)')
{"# " + $matches[1]} else {$_}} |
Out-File $hostsPath -enc ascii
Given this I think you can see how to use a regex to manipulate entries as necessary.

Answer 3

The Carbon module has a Set-HostsEntry function for setting a hosts entry:
Set-HostsEntry -IPAddress 10.2.3.4 -HostName 'myserver' -Description "myserver's IP address"

Answer 4

If anyone is looking for a more advanced example, I've always been particularly fond of this gist: https://gist.github.com/markembling/173887
#
# Powershell script for adding/removing/showing entries to the hosts file.
#
# Known limitations:
# - does not handle entries with comments afterwards ("<ip> <host> # comment")
#
$file = "C:\Windows\System32\drivers\etc\hosts"
function add-host([string]$filename, [string]$ip, [string]$hostname) {
remove-host $filename $hostname
$ip + "`t`t" + $hostname | Out-File -encoding ASCII -append $filename
}
function remove-host([string]$filename, [string]$hostname) {
$c = Get-Content $filename
$newLines = #()
foreach ($line in $c) {
$bits = [regex]::Split($line, "\t+")
if ($bits.count -eq 2) {
if ($bits[1] -ne $hostname) {
$newLines += $line
}
} else {
$newLines += $line
}
}
# Write file
Clear-Content $filename
foreach ($line in $newLines) {
$line | Out-File -encoding ASCII -append $filename
}
}
function print-hosts([string]$filename) {
$c = Get-Content $filename
foreach ($line in $c) {
$bits = [regex]::Split($line, "\t+")
if ($bits.count -eq 2) {
Write-Host $bits[0] `t`t $bits[1]
}
}
}
try {
if ($args[0] -eq "add") {
if ($args.count -lt 3) {
throw "Not enough arguments for add."
} else {
add-host $file $args[1] $args[2]
}
} elseif ($args[0] -eq "remove") {
if ($args.count -lt 2) {
throw "Not enough arguments for remove."
} else {
remove-host $file $args[1]
}
} elseif ($args[0] -eq "show") {
print-hosts $file
} else {
throw "Invalid operation '" + $args[0] + "' - must be one of 'add', 'remove', 'show'."
}
} catch {
Write-Host $error[0]
Write-Host "`nUsage: hosts add <ip> <hostname>`n hosts remove <hostname>`n hosts show"
}

Answer 5

Starting with Kevin Remisoski's excellent answer above, I came up with this which lets me add/update multiple entries at once. I also changed the regex in the split to look for any white space, not just tab.
function setHostEntries([hashtable] $entries) {
$hostsFile = "$env:windir\System32\drivers\etc\hosts"
$newLines = #()
$c = Get-Content -Path $hostsFile
foreach ($line in $c) {
$bits = [regex]::Split($line, "\s+")
if ($bits.count -eq 2) {
$match = $NULL
ForEach($entry in $entries.GetEnumerator()) {
if($bits[1] -eq $entry.Key) {
$newLines += ($entry.Value + ' ' + $entry.Key)
Write-Host Replacing HOSTS entry for $entry.Key
$match = $entry.Key
break
}
}
if($match -eq $NULL) {
$newLines += $line
} else {
$entries.Remove($match)
}
} else {
$newLines += $line
}
}
foreach($entry in $entries.GetEnumerator()) {
Write-Host Adding HOSTS entry for $entry.Key
$newLines += $entry.Value + ' ' + $entry.Key
}
Write-Host Saving $hostsFile
Clear-Content $hostsFile
foreach ($line in $newLines) {
$line | Out-File -encoding ASCII -append $hostsFile
}
}
$entries = #{
'aaa.foo.local' = "127.0.0.1"
'bbb.foo.local' = "127.0.0.1"
'ccc.foo.local' = "127.0.0.1"
};
setHostEntries($entries)

Answer 6

I have written a code to delete entries from host. You can easily change the code to add entries to it from the code.
$domainName = "www.abc.com"
$rplaceStr = ""
$rHost = "C:\Windows\System32\drivers\etc\hosts"
$items = Get-Content $rHost | Select-String $domainName
Write-host $items
foreach( $item in $items)
{
(Get-Content $rHost) -replace $item, $rplaceStr| Set-Content $rHost
}
For more information see
http://nisanthkv.blog.com/2012/06/13/remove-host-entries-using-powershell/

Answer 7

99% of the time admin rights are needed to modify a host record. Try adding this code at the top of your Powershell script.
If (-NOT ([Security.Principal.WindowsPrincipal][Security.Principal.WindowsIdentity]::GetCurrent()).IsInRole([Security.Principal.WindowsBuiltInRole] "Administrator"))
{
$arguments = "& '" + $myinvocation.mycommand.definition + "'"
Start-Process powershell -Verb runAs -ArgumentList $arguments
Break
}

Answer 8

For me the biggest pain in dealing with the hosts file is remembering where it is. I set a variable that points to my hosts file in my PowerShell profile, which makes it easy to edit in a text editor.
In PowerShell, type the following to open your profile:
C:\> Notepad $profile
Add this:
$hosts = "$env:windir\System32\drivers\etc\hosts"
Save the file, then close and re-open PowerShell, running as administrator. You can't edit the hosts file without elevated permissions.
Now you can edit your hosts file the same way you'd edit your profile:
C:\> Notepad $hosts

Answer 9

I wrote a quick script that creates a simple GUI for adding new records to the HOSTS file. It will open a window, ask for hostname and IP, then append your input to the HOSTS file.
I'm sure it could be simplified and look cleaner... but works fine for my use case.
Enjoy!
Add-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing
$hostsfilelocation = "$env:windir\System32\drivers\etc\hosts"
$readhostsfile = Get-Content $hostsfilelocation
$form = New-Object System.Windows.Forms.Form
$form.Text = 'Update HOSTS File'
$form.Size = New-Object System.Drawing.Size(300,200)
$form.StartPosition = 'CenterScreen'
$AddHosts = New-Object System.Windows.Forms.Button
$AddHosts.Location = New-Object System.Drawing.Point(55,120)
$AddHosts.Size = New-Object System.Drawing.Size(90,25)
$AddHosts.Text = 'Add Record'
$AddHosts.DialogResult = [System.Windows.Forms.DialogResult]::OK
$form.AcceptButton = $AddHosts
$form.Controls.Add($AddHosts)
$CancelButton = New-Object System.Windows.Forms.Button
$CancelButton.Location = New-Object System.Drawing.Point(170,120)
$CancelButton.Size = New-Object System.Drawing.Size(75,25)
$CancelButton.Text = 'Cancel'
$CancelButton.DialogResult = [System.Windows.Forms.DialogResult]::Cancel
$form.CancelButton = $CancelButton
$form.Controls.Add($CancelButton)
$Hostslabel = New-Object System.Windows.Forms.Label
$Hostslabel.Location = New-Object System.Drawing.Point(10,20)
$Hostslabel.Size = New-Object System.Drawing.Size(280,20)
$Hostslabel.Text = 'Enter New HOSTNAME/FQDN:'
$form.Controls.Add($Hostslabel)
$HoststextBox = New-Object System.Windows.Forms.TextBox
$HoststextBox.Location = New-Object System.Drawing.Point(10,40)
$HoststextBox.Size = New-Object System.Drawing.Size(260,20)
$form.Controls.Add($HoststextBox)
$IPlabel = New-Object System.Windows.Forms.Label
$IPlabel.Location = New-Object System.Drawing.Point(10,60)
$IPlabel.Size = New-Object System.Drawing.Size(280,20)
$IPlabel.Text = 'Enter IP:'
$form.Controls.Add($IPlabel)
$IPtextBox = New-Object System.Windows.Forms.TextBox
$IPtextBox.Location = New-Object System.Drawing.Point(10,80)
$IPtextBox.Size = New-Object System.Drawing.Size(260,20)
$form.Controls.Add($IPtextBox)
$form.Topmost = $true
$form.Add_Shown({($HoststextBox,$IPtextbox).Select()})
$result = $form.ShowDialog()
if ($result -eq [System.Windows.Forms.DialogResult]::OK)
{
$inputhosts = $HoststextBox.Text
$inputip = $IPtextBox.Text
$newrecord = "$inputip $inputhosts"
Add-Content -Path $hostsfilelocation -Value $newrecord
}

Answer 10

This is the one I ended up using. I made an Active Directory group policy to run on every update, so if one of the entries is missing it is added, if it already exists you don't get a double entry:
function Test-FileLock {
param (
[parameter(Mandatory=$true)][string]$Path
)
$oFile = New-Object System.IO.FileInfo $Path
if ((Test-Path -Path $Path) -eq $false) {
return $false
}
try {
$oStream = $oFile.Open([System.IO.FileMode]::Open, [System.IO.FileAccess]::ReadWrite, [System.IO.FileShare]::None)
if ($oStream) {
$oStream.Close()
}
return $false
} catch {
# file is locked by a process.
return $true
}
}
$hostsFile = "$($env:windir)\system32\Drivers\etc\hosts"
$hostsEntry = #('192.168.223.223 w2012', '192.168.223.224 w2019', '192.168.223.5 tbstorage', '192.168.223.7 tgcstorage','192.168.223.202 paneladmin.local.com')
foreach ($HostFileEntry in $hostsEntry)
{
While(Test-FileLock($hostsFile)) {
Write-Host "File locked! waiting 1 seconds."
Start-Sleep -s 1
}
# split the entry into separate variables
$ipAddress, $hostName = $HostFileEntry -split '\s+',2
# prepare the regex
$re = '(?m)^{0}[ ]+{1}' -f [Regex]::Escape($ipAddress), [Regex]::Escape($hostName)
# Write-Host $re
If ((Get-Content $hostsFile -Raw) -notmatch $re) {
Add-Content -Path $hostsFile -Value $HostFileEntry
Write-Host "Writing $HostFileEntry"
}
}

Answer 11

I have checked the entry if exists or not before write-in the host file.
$domainCheck = "installer.example.com"
$rHost = "C:\Windows\System32\drivers\etc\hosts"
$domainName = "`n8.8.8.8`tinstaller.example.com"
if((Get-Content $rHost | Select-String $domainCheck ).length -eq 0){
Add-Content -Path $rHost -Value $domainName -Force
}

Answer 12

#Kevin Remisoski's answer was nice but I wanted to be able to Add, Remove and Find (so I could determine if the host was in the set before trying to remove or add)
Simplified hosts.ps1:
# Original file - https://gist.github.com/markembling/173887
$DefaultHostsFilePath = "C:\Windows\System32\drivers\etc\hosts"
Function Add-Host([string]$Ip, [string]$HostName, [string]$HostsFilePath = $DefaultHostsFilePath) {
Remove-Host $HostsFilePath $HostsFilePath
$Ip + "`t`t" + $HostName | Out-File -Encoding ASCII -Append $HostsFilePath
}
Function Remove-Host([string]$HostName, [string]$HostsFilePath = $DefaultHostsFilePath) {
$Content = Get-Content $HostsFilePath
$NewLines = #()
foreach ($Line in $Content) {
$Bits = [regex]::Split($Line, "\t+")
if ($Bits.Count -eq 2) {
if ($Bits[1] -ne $HostName) {
$NewLines += $Line
}
} else {
$NewLines += $Line
}
}
# Write file
Clear-Content $HostsFilePath
foreach ($Line in $NewLines) {
$Line | Out-File -Encoding ASCII -Append $HostsFilePath
}
}
Function Get-Hosts([string]$HostsFilePath = $DefaultHostsFilePath) {
$Content = Get-Content $HostsFilePath
$Result = #()
foreach ($Line in $Content) {
$Bits = [regex]::Split($Line, "\t+")
if ($Bits.Count -eq 2) {
$Result += "$Bits[0] `t`t $Bits[1]"
}
}
return $Result;
}
Function Find-Host([string]$Pattern, [string]$HostsFilePath = $DefaultHostsFilePath) {
$Hosts = Get-Hosts $HostsFilePath;
$Filtered = ($Hosts | Select-String $Pattern)
return $Filtered
}
Example usage script:
. ".\hosts.ps1"
if ((Find-Host "MyNewEntry").Count -eq 0)
{
Add-Host "127.0.0.1:5000" "MyNewEntry"
Write-Host "Added Entry"
}
else
{
Remove-Host "MyNewEntry"
Write-Host "Removed Entry"
}
Write-Host "-- Begin Printing Hosts --"
Get-Hosts | Write-Host
Write-Host "-- End Printing Hosts --"

Answer 13

Best Solution!
if(!((Select-String -Path $env:windir\System32\drivers\etc\hosts -Pattern "localhost") -ne $null)){
Add-Content -Path $env:windir\System32\drivers\etc\hosts -Value "`n127.0.0.1`tlocalhost" -Force
}