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Powershell script for adding/removing/viewing entries to the hosts file.
#
# Powershell script for adding/removing 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'."
}
} catch {
Write-Host $error[0]
Write-Host "`nUsage: hosts add <ip> <hostname>`n hosts remove <hostname>`n hosts show"
}

for removing a host, if you simply append a `n at the end of each line, then just write out the newLines as a text, it saves exponential work compared to simply writing over the files n times (# of lines)! I only noticed it got really slow since my host file has many, many lines from spybot entries, but though it'd speed it up for some other people too :)

very useful thanks. Using it to auto create IIS sites, app pools, dirs and host files

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