dns.cgi: Move grab_address_from_file function to general-functions.pl

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>

config/cfgroot/general-functions.pl

@@ -1177,4 +1177,35 @@ sub number_cpu_cores() {
 	return $cores;
 }
 
+# Tiny function to grab a single IP-address from a given file.
+sub grab_address_from_file($) {
+	my ($file) = @_;
+
+	my $address;
+
+	# Check if the given file exists.
+	if(-f $file) {
+		# Open the file for reading.
+		open(FILE, $file) or die "Could not read from $file. $!\n";
+
+		# Read the address from the file.
+		$address = <FILE>;
+
+		# Close filehandle.
+		close(FILE);
+
+		# Remove newlines.
+		chomp($address);
+
+		# Check if the obtained address is valid.
+		if (&validip($address)) {
+			# Return the address.
+			return $address;
+		}
+	}
+
+	# Return nothing.
+	return;
+}
+
 1;