Initial commit

main.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+var fileName = filepath.Base(os.Args[0])
+
+func init() {
+	fmt.Println("DNSHelper v1.0")
+	fmt.Println("Copyright (c) 2024 Emberkom LLC")
+	fmt.Println("")
+	if len(os.Args) < 2 {
+		printUsage()
+		defer os.Exit(1)
+	}
+}
+
+func printUsage() {
+	fmt.Println("This utility will update the local hosts file with DNS entries obtained by the specified DNS server.")
+	fmt.Println("Usage: " + fileName + " [add|delete] -host hostname [-server dns.example.com]")
+	fmt.Println("Example:")
+	fmt.Println("       " + fileName + " add -host xyz.acme.com -server dns.example.com")
+	fmt.Println("         This will use dns.example.com to find and add all IP addresses for xyz.acme.com to the local hosts file.")
+	fmt.Println("       " + fileName + " delete -host hostname.example.com")
+	fmt.Println("         This will delete all entries for hostname.example.com from the local hosts file.")
+	fmt.Println("       " + fileName + " delete all")
+	fmt.Println("         This will delete all entries from the local hosts file that were added by this utility.")
+	fmt.Println("Note: Adding a hostname will first remove all entries in the hosts file that match the same hostname.")
+	fmt.Println("      This utility will only remove entries from the hosts file that it added.")
+}
+
+func term(err error) {
+	fmt.Println("Error: " + err.Error())
+	defer os.Exit(1)
+}
+
+func main() {
+	modePing := flag.NewFlagSet("ping", flag.ExitOnError)
+	modeAdd := flag.NewFlagSet("add", flag.ExitOnError)
+	hostToAdd := modeAdd.String("host", "", "Comma separated list of hostnames to add")
+	dnsResolver := modeAdd.String("server", "", "DNS resolver to use")
+	modeDelete := flag.NewFlagSet("delete", flag.ExitOnError)
+	hostToDelete := modeDelete.String("host", "", "Comma separated list of hostnames to delete")
+
+	data := new(workingData)
+
+	var err error
+	data.HostsFileLocation, err = getHostsFileLocation()
+	if err != nil {
+		term(err)
+	}
+
+	data.DefaultContent, err = getFileContentLines(data.HostsFileLocation)
+	if err != nil {
+		term(err)
+	}
+
+	if err = extractLinesToEdit(data); err != nil {
+		term(err)
+	}
+
+	switch strings.ToLower(os.Args[1]) {
+	case "a", "add":
+		err = modeAdd.Parse(os.Args[2:])
+		if err != nil {
+			term(err)
+		}
+		addHostsToWorkingData(data, hostToAdd)
+		addResolversToWorkingData(data, dnsResolver)
+		removeHostsFromExistingContent(data)
+		addNameToIPMappingsToNewContent(data)
+	case "d", "del", "delete":
+		err = modeDelete.Parse(os.Args[2:])
+		if err != nil {
+			term(err)
+		}
+		if strings.ToLower(*hostToDelete) != "all" && strings.ToLower(*hostToDelete) != "a" {
+			addHostsToWorkingData(data, hostToDelete)
+			removeHostsFromExistingContent(data)
+		}
+	default:
+		printUsage()
+	}
+
+	err = writeHostsFile(data)
+	if err != nil {
+		term(err)
+	}
+}