Add check-subnet-mask.ps1

Scripts/check-subnet-mask.ps1

@@ -0,0 +1,39 @@
+<#
+.SYNOPSIS
+	check-subnet-mask.ps1 [<address>]
+.DESCRIPTION
+	Checks the given subnet mask for validity
+.EXAMPLE
+	PS> .\check-subnet-mask.ps1 255.255.255.0
+.LINK
+	https://github.com/fleschutz/PowerShell
+.NOTES
+	Author:  Markus Fleschutz
+	License: CC0
+#>
+
+param([string]$address = "")
+
+function IsSubNetMaskValid { param([string]$IP)
+	$RegEx = "^(254|252|248|240|224|192|128).0.0.0$|^255.(254|252|248|240|224|192|128|0).0.0$|^255.255.(254|252|248|240|224|192|128|0).0$|^255.255.255.(255|254|252|248|240|224|192|128|0)$"
+	if ($IP -match $RegEx) {
+		return $true
+	} else {
+		return $false
+	}
+}
+
+try {
+	if ($address -eq "" ) { $address = read-host "Enter subnet mask to validate" }
+
+	if (IsSubNetMaskValid $address) {
+		"✔️ subnet mask $Address is valid"
+		exit 0
+	} else {
+		write-warning "Invalid subnet mask: $address"
+		exit 1
+	}
+} catch {
+	write-error "⚠️ Error in line $($_.InvocationInfo.ScriptLineNumber): $($Error[0])"
+	exit 1
+}