github.com/guilhermebr/docker@v1.4.2-0.20150428121140-67da055cebca/pkg/etchosts/etchosts.go (about)

     1  package etchosts
     2  
     3  import (
     4  	"bytes"
     5  	"fmt"
     6  	"io"
     7  	"io/ioutil"
     8  	"regexp"
     9  )
    10  
    11  // Structure for a single host record
    12  type Record struct {
    13  	Hosts string
    14  	IP    string
    15  }
    16  
    17  // Writes record to file and returns bytes written or error
    18  func (r Record) WriteTo(w io.Writer) (int64, error) {
    19  	n, err := fmt.Fprintf(w, "%s\t%s\n", r.IP, r.Hosts)
    20  	return int64(n), err
    21  }
    22  
    23  // Default hosts config records slice
    24  var defaultContent = []Record{
    25  	{Hosts: "localhost", IP: "127.0.0.1"},
    26  	{Hosts: "localhost ip6-localhost ip6-loopback", IP: "::1"},
    27  	{Hosts: "ip6-localnet", IP: "fe00::0"},
    28  	{Hosts: "ip6-mcastprefix", IP: "ff00::0"},
    29  	{Hosts: "ip6-allnodes", IP: "ff02::1"},
    30  	{Hosts: "ip6-allrouters", IP: "ff02::2"},
    31  }
    32  
    33  // Build function
    34  // path is path to host file string required
    35  // IP, hostname, and domainname set main record leave empty for no master record
    36  // extraContent is an array of extra host records.
    37  func Build(path, IP, hostname, domainname string, extraContent []Record) error {
    38  	content := bytes.NewBuffer(nil)
    39  	if IP != "" {
    40  		//set main record
    41  		var mainRec Record
    42  		mainRec.IP = IP
    43  		if domainname != "" {
    44  			mainRec.Hosts = fmt.Sprintf("%s.%s %s", hostname, domainname, hostname)
    45  		} else {
    46  			mainRec.Hosts = hostname
    47  		}
    48  		if _, err := mainRec.WriteTo(content); err != nil {
    49  			return err
    50  		}
    51  	}
    52  	// Write defaultContent slice to buffer
    53  	for _, r := range defaultContent {
    54  		if _, err := r.WriteTo(content); err != nil {
    55  			return err
    56  		}
    57  	}
    58  	// Write extra content from function arguments
    59  	for _, r := range extraContent {
    60  		if _, err := r.WriteTo(content); err != nil {
    61  			return err
    62  		}
    63  	}
    64  
    65  	return ioutil.WriteFile(path, content.Bytes(), 0644)
    66  }
    67  
    68  // Update all IP addresses where hostname matches.
    69  // path is path to host file
    70  // IP is new IP address
    71  // hostname is hostname to search for to replace IP
    72  func Update(path, IP, hostname string) error {
    73  	old, err := ioutil.ReadFile(path)
    74  	if err != nil {
    75  		return err
    76  	}
    77  	var re = regexp.MustCompile(fmt.Sprintf("(\\S*)(\\t%s)", regexp.QuoteMeta(hostname)))
    78  	return ioutil.WriteFile(path, re.ReplaceAll(old, []byte(IP+"$2")), 0644)
    79  }