package etchosts import ( "bytes" "fmt" "io" "io/ioutil" "regexp" ) // Record Structure for a single host record type Record struct { Hosts string IP string } // WriteTo writes record to file and returns bytes written or error func (r Record) WriteTo(w io.Writer) (int64, error) { n, err := fmt.Fprintf(w, "%s\t%s\n", r.IP, r.Hosts) return int64(n), err } // Default hosts config records slice var defaultContent = []Record{ {Hosts: "localhost", IP: "127.0.0.1"}, {Hosts: "localhost ip6-localhost ip6-loopback", IP: "::1"}, {Hosts: "ip6-localnet", IP: "fe00::0"}, {Hosts: "ip6-mcastprefix", IP: "ff00::0"}, {Hosts: "ip6-allnodes", IP: "ff02::1"}, {Hosts: "ip6-allrouters", IP: "ff02::2"}, } // Build function // path is path to host file string required // IP, hostname, and domainname set main record leave empty for no master record // extraContent is an array of extra host records. func Build(path, IP, hostname, domainname string, extraContent []Record) error { content := bytes.NewBuffer(nil) if IP != "" { //set main record var mainRec Record mainRec.IP = IP if domainname != "" { mainRec.Hosts = fmt.Sprintf("%s.%s %s", hostname, domainname, hostname) } else { mainRec.Hosts = hostname } if _, err := mainRec.WriteTo(content); err != nil { return err } } // Write defaultContent slice to buffer for _, r := range defaultContent { if _, err := r.WriteTo(content); err != nil { return err } } // Write extra content from function arguments for _, r := range extraContent { if _, err := r.WriteTo(content); err != nil { return err } } return ioutil.WriteFile(path, content.Bytes(), 0644) } // Update all IP addresses where hostname matches. // path is path to host file // IP is new IP address // hostname is hostname to search for to replace IP func Update(path, IP, hostname string) error { old, err := ioutil.ReadFile(path) if err != nil { return err } var re = regexp.MustCompile(fmt.Sprintf("(\\S*)(\\t%s)", regexp.QuoteMeta(hostname))) return ioutil.WriteFile(path, re.ReplaceAll(old, []byte(IP+"$2")), 0644) }