diff --git a/.gitignore b/.gitignore
index daf913b..55e3c34 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,3 +22,6 @@ _testmain.go
 *.exe
 *.test
 *.prof
+*.zip
+slack-dum*
+slackdum*
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..b20c21f
--- /dev/null
+++ b/main.go
@@ -0,0 +1,328 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/jhoonb/archivex"
+	"github.com/nlopes/slack"
+)
+
+func check(e error) {
+	if e != nil {
+		panic(e)
+	}
+}
+
+var token string
+
+func main() {
+	flag.StringVar(&token, "token", "", "a Slack API token: (see: https://api.slack.com/web)")
+	flag.Parse()
+
+	rooms := flag.Args()
+	api := slack.New(token)
+
+	// Create working directory
+	dir, err := ioutil.TempDir("", "slack-dump")
+	check(err)
+
+	// Dump Users
+	dumpUsers(api, dir)
+
+	// Dump Channels and Groups
+	dumpRooms(api, dir, rooms)
+
+	archive(dir)
+}
+
+func archive(dir string) {
+	zip := new(archivex.ZipFile)
+	pwd, err := os.Getwd()
+	check(err)
+	zip.Create(path.Join(pwd, "slackdump.zip"))
+	zip.AddAll(dir, true)
+	zip.Close()
+}
+
+// MarshalIndent is like json.MarshalIndent but applies Slack's weird JSON
+// escaping rules to the output.
+func MarshalIndent(v interface{}, prefix string, indent string) ([]byte, error) {
+	b, err := json.MarshalIndent(v, "", "    ")
+	if err != nil {
+		return nil, err
+	}
+
+	b = bytes.Replace(b, []byte("\\u003c"), []byte("<"), -1)
+	b = bytes.Replace(b, []byte("\\u003e"), []byte(">"), -1)
+	b = bytes.Replace(b, []byte("\\u0026"), []byte("&"), -1)
+	b = bytes.Replace(b, []byte("/"), []byte("\\/"), -1)
+
+	return b, nil
+}
+
+func dumpUsers(api *slack.Slack, dir string) {
+	users, err := api.GetUsers()
+	check(err)
+
+	data, err := MarshalIndent(users, "", "    ")
+	check(err)
+	err = ioutil.WriteFile(path.Join(dir, "users.json"), data, 0644)
+	check(err)
+}
+
+func dumpRooms(api *slack.Slack, dir string, rooms []string) {
+	// Dump Channels
+	channels := dumpChannels(api, dir, rooms)
+
+	// Dump Private Groups
+	groups := dumpGroups(api, dir, rooms)
+
+	if len(groups) > 0 {
+		for _, group := range groups {
+			channel := slack.Channel{}
+			channel.Id = group.Id
+			channel.Name = group.Name
+			channel.Created = group.Created
+			channel.Creator = group.Creator
+			channel.IsArchived = group.IsArchived
+			channel.IsChannel = true
+			channel.IsGeneral = false
+			channel.IsMember = true
+			channel.LastRead = group.LastRead
+			channel.Latest = group.Latest
+			channel.Members = group.Members
+			channel.NumMembers = group.NumMembers
+			channel.Purpose = group.Purpose
+			channel.Topic = group.Topic
+			channel.UnreadCount = group.UnreadCount
+			channel.UnreadCountDisplay = group.UnreadCountDisplay
+			channels = append(channels, channel)
+		}
+	}
+
+	data, err := MarshalIndent(channels, "", "    ")
+	check(err)
+	err = ioutil.WriteFile(path.Join(dir, "channels.json"), data, 0644)
+	check(err)
+}
+
+func dumpChannels(api *slack.Slack, dir string, rooms []string) []slack.Channel {
+	channels, err := api.GetChannels(false)
+	check(err)
+
+	if len(rooms) > 0 {
+		channels = FilterChannels(channels, func(channel slack.Channel) bool {
+			for _, room := range rooms {
+				if room == channel.Name {
+					return true
+				}
+			}
+			return false
+		})
+	}
+
+	if len(channels) == 0 {
+		var channels []slack.Channel
+		return channels
+	}
+
+	for _, channel := range channels {
+		dumpChannel(api, dir, channel.Id, channel.Name, "channel")
+	}
+
+	return channels
+}
+
+func dumpGroups(api *slack.Slack, dir string, rooms []string) []slack.Group {
+	groups, err := api.GetGroups(false)
+	check(err)
+	if len(rooms) > 0 {
+		groups = FilterGroups(groups, func(group slack.Group) bool {
+			for _, room := range rooms {
+				if room == group.Name {
+					return true
+				}
+			}
+			return false
+		})
+	}
+
+	if len(groups) == 0 {
+		var groups []slack.Group
+		return groups
+	}
+
+	for _, group := range groups {
+		dumpChannel(api, dir, group.Id, group.Name, "group")
+	}
+
+	return groups
+}
+
+func dumpChannel(api *slack.Slack, dir, id, name, channelType string) {
+	var messages []slack.Message
+	if channelType == "group" {
+		messages = fetchGroupHistory(api, id)
+	} else {
+		messages = fetchChannelHistory(api, id)
+	}
+
+	if len(messages) == 0 {
+		return
+	}
+
+	sort.Sort(byTimestamp(messages))
+
+	currentFilename := ""
+	var currentMessages []slack.Message
+	for _, message := range messages {
+		ts := parseTimestamp(message.Timestamp)
+		filename := fmt.Sprintf("%d-%02d-%02d.json", ts.Year(), ts.Month(), ts.Day())
+		if currentFilename != filename {
+			writeMessagesFile(currentMessages, dir, name, currentFilename)
+			currentMessages = make([]slack.Message, 0, 5)
+			currentFilename = filename
+		}
+
+		currentMessages = append(currentMessages, message)
+	}
+	writeMessagesFile(currentMessages, dir, name, currentFilename)
+}
+
+func writeMessagesFile(messages []slack.Message, dir string, name string, filename string) {
+	if len(messages) == 0 || dir == "" || name == "" || filename == "" {
+		return
+	}
+	channelDir := path.Join(dir, name)
+	err := os.MkdirAll(channelDir, 0755)
+	check(err)
+
+	data, err := MarshalIndent(messages, "", "    ")
+	check(err)
+	err = ioutil.WriteFile(path.Join(channelDir, filename), data, 0644)
+	check(err)
+}
+
+func fetchGroupHistory(api *slack.Slack, ID string) []slack.Message {
+	historyParams := slack.NewHistoryParameters()
+	historyParams.Count = 1000
+
+	// Fetch History
+	history, err := api.GetGroupHistory(ID, historyParams)
+	check(err)
+	messages := history.Messages
+	latest := messages[len(messages)-1].Timestamp
+	for {
+		if history.HasMore != true {
+			break
+		}
+
+		historyParams.Latest = latest
+		history, err = api.GetGroupHistory(ID, historyParams)
+		check(err)
+		length := len(history.Messages)
+		if length > 0 {
+			latest = history.Messages[length-1].Timestamp
+			messages = append(messages, history.Messages...)
+		}
+
+	}
+
+	return messages
+}
+
+func fetchChannelHistory(api *slack.Slack, ID string) []slack.Message {
+	historyParams := slack.NewHistoryParameters()
+	historyParams.Count = 1000
+
+	// Fetch History
+	history, err := api.GetChannelHistory(ID, historyParams)
+	check(err)
+	messages := history.Messages
+	latest := messages[len(messages)-1].Timestamp
+	for {
+		if history.HasMore != true {
+			break
+		}
+
+		historyParams.Latest = latest
+		history, err = api.GetChannelHistory(ID, historyParams)
+		check(err)
+		length := len(history.Messages)
+		if length > 0 {
+			latest = history.Messages[length-1].Timestamp
+			messages = append(messages, history.Messages...)
+		}
+
+	}
+
+	return messages
+}
+
+func parseTimestamp(timestamp string) *time.Time {
+	if utf8.RuneCountInString(timestamp) <= 0 {
+		return nil
+	}
+
+	ts := timestamp
+
+	if strings.Contains(timestamp, ".") {
+		e := strings.Split(timestamp, ".")
+		if len(e) != 2 {
+			return nil
+		}
+		ts = e[0]
+	}
+
+	i, err := strconv.ParseInt(ts, 10, 64)
+	check(err)
+	tm := time.Unix(i, 0).Local()
+	return &tm
+}
+
+// FilterGroups returns a new slice holding only
+// the elements of s that satisfy f()
+func FilterGroups(s []slack.Group, fn func(slack.Group) bool) []slack.Group {
+	var p []slack.Group // == nil
+	for _, v := range s {
+		if fn(v) {
+			p = append(p, v)
+		}
+	}
+	return p
+}
+
+// FilterChannels returns a new slice holding only
+// the elements of s that satisfy f()
+func FilterChannels(s []slack.Channel, fn func(slack.Channel) bool) []slack.Channel {
+	var p []slack.Channel // == nil
+	for _, v := range s {
+		if fn(v) {
+			p = append(p, v)
+		}
+	}
+	return p
+}
+
+// FilterUsers returns a new slice holding only
+// the elements of s that satisfy f()
+func FilterUsers(s []slack.User, fn func(slack.User) bool) []slack.User {
+	var p []slack.User // == nil
+	for _, v := range s {
+		if fn(v) {
+			p = append(p, v)
+		}
+	}
+	return p
+}
diff --git a/sort.go b/sort.go
new file mode 100644
index 0000000..7d63bf2
--- /dev/null
+++ b/sort.go
@@ -0,0 +1,9 @@
+package main
+
+import "github.com/nlopes/slack"
+
+type byTimestamp []slack.Message
+
+func (m byTimestamp) Len() int           { return len(m) }
+func (m byTimestamp) Swap(i, j int)      { m[i], m[j] = m[j], m[i] }
+func (m byTimestamp) Less(i, j int) bool { return m[i].Timestamp < m[j].Timestamp }