Merge branch 'machine-readable'

This adds the -machine-readable flag to Packer which turns all output
into machine-readable format. This is documented within the website
source.

command/build/command_test.go

@@ -9,7 +9,7 @@ import (
 
 func testEnvironment() packer.Environment {
 	config := packer.DefaultEnvironmentConfig()
-	config.Ui = &packer.ReaderWriterUi{
+	config.Ui = &packer.BasicUi{
 		Reader: new(bytes.Buffer),
 		Writer: new(bytes.Buffer),
 	}

command/build/help.go

@@ -10,6 +10,7 @@ Options:
 
   -debug                     Debug mode enabled for builds
   -force                     Force a build to continue if artifacts exist, deletes existing artifacts
+  -machine-readable          Machine-readable output
   -except=foo,bar,baz        Build all builds other than these
   -only=foo,bar,baz          Only build the given builds by name
   -var 'key=value'           Variable for templates, can be used multiple times.

packer.go

@@ -76,8 +76,13 @@ func main() {
 	log.Printf("Setting cache directory: %s", cacheDir)
 	cache := &packer.FileCache{CacheDir: cacheDir}
 
+	// Determine if we're in machine-readable mode by mucking around with
+	// the arguments...
+	args, machineReadable := extractMachineReadable(os.Args[1:])
+
 	defer plugin.CleanupClients()
 
+	// Create the environment configuration
 	envConfig := packer.DefaultEnvironmentConfig()
 	envConfig.Cache = cache
 	envConfig.Commands = config.CommandNames()
@@ -86,6 +91,11 @@ func main() {
 	envConfig.Components.Hook = config.LoadHook
 	envConfig.Components.PostProcessor = config.LoadPostProcessor
 	envConfig.Components.Provisioner = config.LoadProvisioner
+	if machineReadable {
+		envConfig.Ui = &packer.MachineReadableUi{
+			Writer: os.Stdout,
+		}
+	}
 
 	env, err := packer.NewEnvironment(envConfig)
 	if err != nil {
@@ -96,7 +106,7 @@ func main() {
 
 	setupSignalHandlers(env)
 
-	exitCode, err := env.Cli(os.Args[1:])
+	exitCode, err := env.Cli(args)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Error executing CLI: %s\n", err.Error())
 		plugin.CleanupClients()
@@ -107,6 +117,23 @@ func main() {
 	os.Exit(exitCode)
 }
 
+// extractMachineReadable checks the args for the machine readable
+// flag and returns whether or not it is on. It modifies the args
+// to remove this flag.
+func extractMachineReadable(args []string) ([]string, bool) {
+	for i, arg := range args {
+		if arg == "-machine-readable" {
+			// We found it. Slice it out.
+			result := make([]string, len(args)-1)
+			copy(result, args[:i])
+			copy(result[i:], args[i+1:])
+			return result, true
+		}
+	}
+
+	return args, false
+}
+
 func loadConfig() (*config, error) {
 	var config config
 	if err := decodeConfig(bytes.NewBufferString(defaultConfig), &config); err != nil {

packer/build.go

@@ -213,11 +213,10 @@ func (b *coreBuild) Run(originalUi Ui, cache Cache) ([]Artifact, error) {
 	hook := &DispatchHook{hooks}
 	artifacts := make([]Artifact, 0, 1)
 
-	// The builder just has a normal Ui, but prefixed
-	builderUi := &PrefixedUi{
-		fmt.Sprintf("==> %s", b.Name()),
-		fmt.Sprintf("    %s", b.Name()),
-		originalUi,
+	// The builder just has a normal Ui, but targetted
+	builderUi := &TargettedUi{
+		Target: b.Name(),
+		Ui:     originalUi,
 	}
 
 	log.Printf("Running builder: %s", b.builderType)
@@ -240,10 +239,9 @@ PostProcessorRunSeqLoop:
 	for _, ppSeq := range b.postProcessors {
 		priorArtifact := builderArtifact
 		for i, corePP := range ppSeq {
-			ppUi := &PrefixedUi{
-				fmt.Sprintf("==> %s (%s)", b.Name(), corePP.processorType),
-				fmt.Sprintf("    %s (%s)", b.Name(), corePP.processorType),
-				originalUi,
+			ppUi := &TargettedUi{
+				Target: fmt.Sprintf("%s (%s)", b.Name(), corePP.processorType),
+				Ui:     originalUi,
 			}
 
 			builderUi.Say(fmt.Sprintf("Running post-processor: %s", corePP.processorType))

packer/communicator_test.go

@@ -47,7 +47,7 @@ func TestRemoteCmd_StartWithUi(t *testing.T) {
 		Stdout: rcOutput,
 	}
 
-	testUi := &ReaderWriterUi{
+	testUi := &BasicUi{
 		Reader: new(bytes.Buffer),
 		Writer: uiOutput,
 	}

packer/environment.go

@@ -73,7 +73,7 @@ type EnvironmentConfig struct {
 func DefaultEnvironmentConfig() *EnvironmentConfig {
 	config := &EnvironmentConfig{}
 	config.Commands = make([]string, 0)
-	config.Ui = &ReaderWriterUi{
+	config.Ui = &BasicUi{
 		Reader: os.Stdin,
 		Writer: os.Stdout,
 	}
@@ -299,6 +299,9 @@ func (e *coreEnvironment) printHelp() {
 		// Output the command and the synopsis
 		e.ui.Say(fmt.Sprintf("    %v     %v", key, synopsis))
 	}
+
+	e.ui.Say("\nGlobally recognized options:")
+	e.ui.Say("    -machine-readable    Machine-readable output format.")
 }
 
 // Returns the UI for the environment. The UI is the interface that should

packer/environment_test.go

@@ -19,7 +19,7 @@ func init() {
 
 func testEnvironment() Environment {
 	config := DefaultEnvironmentConfig()
-	config.Ui = &ReaderWriterUi{
+	config.Ui = &BasicUi{
 		Reader: new(bytes.Buffer),
 		Writer: new(bytes.Buffer),
 	}
@@ -45,8 +45,8 @@ func TestEnvironment_DefaultConfig_Ui(t *testing.T) {
 	config := DefaultEnvironmentConfig()
 	assert.NotNil(config.Ui, "default UI should not be nil")
 
-	rwUi, ok := config.Ui.(*ReaderWriterUi)
-	assert.True(ok, "default UI should be ReaderWriterUi")
+	rwUi, ok := config.Ui.(*BasicUi)
+	assert.True(ok, "default UI should be BasicUi")
 	assert.Equal(rwUi.Writer, os.Stdout, "default UI should go to stdout")
 	assert.Equal(rwUi.Reader, os.Stdin, "default UI should read from stdin")
 }
@@ -175,7 +175,7 @@ func TestEnvironment_DefaultCli_Help(t *testing.T) {
 
 	// A little lambda to help us test the output actually contains help
 	testOutput := func() {
-		buffer := defaultEnv.Ui().(*ReaderWriterUi).Writer.(*bytes.Buffer)
+		buffer := defaultEnv.Ui().(*BasicUi).Writer.(*bytes.Buffer)
 		output := buffer.String()
 		buffer.Reset()
 		assert.True(strings.Contains(output, "usage: packer"), "should print help")
@@ -341,7 +341,7 @@ func TestEnvironmentProvisioner_Error(t *testing.T) {
 func TestEnvironment_SettingUi(t *testing.T) {
 	assert := asserts.NewTestingAsserts(t, true)
 
-	ui := &ReaderWriterUi{
+	ui := &BasicUi{
 		Reader: new(bytes.Buffer),
 		Writer: new(bytes.Buffer),
 	}

packer/rpc/ui.go

@@ -17,6 +17,12 @@ type UiServer struct {
 	ui packer.Ui
 }
 
+// The arguments sent to Ui.Machine
+type UiMachineArgs struct {
+	category string
+	args     []string
+}
+
 func (u *Ui) Ask(query string) (result string, err error) {
 	err = u.client.Call("Ui.Ask", query, &result)
 	return
@@ -28,6 +34,17 @@ func (u *Ui) Error(message string) {
 	}
 }
 
+func (u *Ui) Machine(t string, args ...string) {
+	rpcArgs := &UiMachineArgs{
+		category: t,
+		args:     args,
+	}
+
+	if err := u.client.Call("Ui.Message", rpcArgs, new(interface{})); err != nil {
+		panic(err)
+	}
+}
+
 func (u *Ui) Message(message string) {
 	if err := u.client.Call("Ui.Message", message, new(interface{})); err != nil {
 		panic(err)
@@ -52,6 +69,13 @@ func (u *UiServer) Error(message *string, reply *interface{}) error {
 	return nil
 }
 
+func (u *UiServer) Machine(args *UiMachineArgs, reply *interface{}) error {
+	u.ui.Machine(args.category, args.args...)
+
+	*reply = nil
+	return nil
+}
+
 func (u *UiServer) Message(message *string, reply *interface{}) error {
 	u.ui.Message(*message)
 	*reply = nil

packer/rpc/ui_test.go

@@ -11,6 +11,9 @@ type testUi struct {
 	askQuery       string
 	errorCalled    bool
 	errorMessage   string
+	machineCalled  bool
+	machineType    string
+	machineArgs    []string
 	messageCalled  bool
 	messageMessage string
 	sayCalled      bool
@@ -28,6 +31,12 @@ func (u *testUi) Error(message string) {
 	u.errorMessage = message
 }
 
+func (u *testUi) Machine(t string, args ...string) {
+	u.machineCalled = true
+	u.machineType = t
+	u.machineArgs = args
+}
+
 func (u *testUi) Message(message string) {
 	u.messageCalled = true
 	u.messageMessage = message

packer/ui.go

@@ -11,6 +11,7 @@ import (
 	"runtime"
 	"strings"
 	"sync"
+	"time"
 	"unicode"
 )
 
@@ -33,6 +34,7 @@ type Ui interface {
 	Say(string)
 	Message(string)
 	Error(string)
+	Machine(string, ...string)
 }
 
 // ColoredUi is a UI that is colored using terminal colors.
@@ -42,23 +44,32 @@ type ColoredUi struct {
 	Ui         Ui
 }
 
-// PrefixedUi is a UI that wraps another UI implementation and adds a
-// prefix to all the messages going out.
-type PrefixedUi struct {
-	SayPrefix     string
-	MessagePrefix string
+// TargettedUi is a UI that wraps another UI implementation and modifies
+// the output to indicate a specific target. Specifically, all Say output
+// is prefixed with the target name. Message output is not prefixed but
+// is offset by the length of the target so that output is lined up properly
+// with Say output. Machine-readable output has the proper target set.
+type TargettedUi struct {
+	Target string
 	Ui     Ui
 }
 
-// The ReaderWriterUi is a UI that writes and reads from standard Go
-// io.Reader and io.Writer.
-type ReaderWriterUi struct {
+// The BasicUI is a UI that reads and writes from a standard Go reader
+// and writer. It is safe to be called from multiple goroutines. Machine
+// readable output is simply logged for this UI.
+type BasicUi struct {
 	Reader      io.Reader
 	Writer      io.Writer
 	l           sync.Mutex
 	interrupted bool
 }
 
+// MachineReadableUi is a UI that only outputs machine-readable output
+// to the given Writer.
+type MachineReadableUi struct {
+	Writer io.Writer
+}
+
 func (u *ColoredUi) Ask(query string) (string, error) {
 	return u.Ui.Ask(u.colorize(query, u.Color, true))
 }
@@ -80,6 +91,11 @@ func (u *ColoredUi) Error(message string) {
 	u.Ui.Error(u.colorize(message, color, true))
 }
 
+func (u *ColoredUi) Machine(t string, args ...string) {
+	// Don't colorize machine-readable output
+	u.Ui.Machine(t, args...)
+}
+
 func (u *ColoredUi) colorize(message string, color UiColor, bold bool) string {
 	if !u.supportsColors() {
 		return message
@@ -107,33 +123,43 @@ func (u *ColoredUi) supportsColors() bool {
 	return cygwin
 }
 
-func (u *PrefixedUi) Ask(query string) (string, error) {
-	return u.Ui.Ask(u.prefixLines(u.SayPrefix, query))
+func (u *TargettedUi) Ask(query string) (string, error) {
+	return u.Ui.Ask(u.prefixLines(true, query))
 }
 
-func (u *PrefixedUi) Say(message string) {
-	u.Ui.Say(u.prefixLines(u.SayPrefix, message))
+func (u *TargettedUi) Say(message string) {
+	u.Ui.Say(u.prefixLines(true, message))
 }
 
-func (u *PrefixedUi) Message(message string) {
-	u.Ui.Message(u.prefixLines(u.MessagePrefix, message))
+func (u *TargettedUi) Message(message string) {
+	u.Ui.Message(u.prefixLines(false, message))
 }
 
-func (u *PrefixedUi) Error(message string) {
-	u.Ui.Error(u.prefixLines(u.SayPrefix, message))
+func (u *TargettedUi) Error(message string) {
+	u.Ui.Error(u.prefixLines(true, message))
 }
 
-func (u *PrefixedUi) prefixLines(prefix, message string) string {
+func (u *TargettedUi) Machine(t string, args ...string) {
+	// Prefix in the target, then pass through
+	u.Ui.Machine(fmt.Sprintf("%s,%s", u.Target, t), args...)
+}
+
+func (u *TargettedUi) prefixLines(arrow bool, message string) string {
+	arrowText := "==>"
+	if !arrow {
+		arrowText = strings.Repeat(" ", len(arrowText))
+	}
+
 	var result bytes.Buffer
 
 	for _, line := range strings.Split(message, "\n") {
-		result.WriteString(fmt.Sprintf("%s: %s\n", prefix, line))
+		result.WriteString(fmt.Sprintf("%s %s: %s\n", arrowText, u.Target, line))
 	}
 
 	return strings.TrimRightFunc(result.String(), unicode.IsSpace)
 }
 
-func (rw *ReaderWriterUi) Ask(query string) (string, error) {
+func (rw *BasicUi) Ask(query string) (string, error) {
 	rw.l.Lock()
 	defer rw.l.Unlock()
 
@@ -177,7 +203,7 @@ func (rw *ReaderWriterUi) Ask(query string) (string, error) {
 	}
 }
 
-func (rw *ReaderWriterUi) Say(message string) {
+func (rw *BasicUi) Say(message string) {
 	rw.l.Lock()
 	defer rw.l.Unlock()
 
@@ -188,7 +214,7 @@ func (rw *ReaderWriterUi) Say(message string) {
 	}
 }
 
-func (rw *ReaderWriterUi) Message(message string) {
+func (rw *BasicUi) Message(message string) {
 	rw.l.Lock()
 	defer rw.l.Unlock()
 
@@ -199,7 +225,7 @@ func (rw *ReaderWriterUi) Message(message string) {
 	}
 }
 
-func (rw *ReaderWriterUi) Error(message string) {
+func (rw *BasicUi) Error(message string) {
 	rw.l.Lock()
 	defer rw.l.Unlock()
 
@@ -209,3 +235,48 @@ func (rw *ReaderWriterUi) Error(message string) {
 		panic(err)
 	}
 }
+
+func (rw *BasicUi) Machine(t string, args ...string) {
+	log.Printf("machine readable: %s %#v", t, args)
+}
+
+func (u *MachineReadableUi) Ask(query string) (string, error) {
+	return "", errors.New("machine-readable UI can't ask")
+}
+
+func (u *MachineReadableUi) Say(message string) {
+	u.Machine("ui", "say", message)
+}
+
+func (u *MachineReadableUi) Message(message string) {
+	u.Machine("ui", "message", message)
+}
+
+func (u *MachineReadableUi) Error(message string) {
+	u.Machine("ui", "error", message)
+}
+
+func (u *MachineReadableUi) Machine(category string, args ...string) {
+	now := time.Now().UTC()
+
+	// Determine if we have a target, and set it
+	target := ""
+	commaIdx := strings.Index(category, ",")
+	if commaIdx > -1 {
+		target = category[0:commaIdx]
+		category = category[commaIdx+1:]
+	}
+
+	// Prepare the args
+	for i, v := range args {
+		args[i] = strings.Replace(v, ",", "%!(PACKER_COMMA)", -1)
+		args[i] = strings.Replace(args[i], "\r", "\\r", -1)
+		args[i] = strings.Replace(args[i], "\n", "\\n", -1)
+	}
+	argsString := strings.Join(args, ",")
+
+	_, err := fmt.Fprintf(u.Writer, "%d,%s,%s,%s\n", now.Unix(), target, category, argsString)
+	if err != nil {
+		panic(err)
+	}
+}

packer/ui_test.go

@@ -3,11 +3,12 @@ package packer
 import (
 	"bytes"
 	"cgl.tideland.biz/asserts"
+	"strings"
 	"testing"
 )
 
-func testUi() *ReaderWriterUi {
-	return &ReaderWriterUi{
+func testUi() *BasicUi {
+	return &BasicUi{
 		Reader: new(bytes.Buffer),
 		Writer: new(bytes.Buffer),
 	}
@@ -36,23 +37,26 @@ func TestColoredUi(t *testing.T) {
 	}
 }
 
-func TestPrefixedUi(t *testing.T) {
+func TestTargettedUi(t *testing.T) {
 	assert := asserts.NewTestingAsserts(t, true)
 
 	bufferUi := testUi()
-	prefixUi := &PrefixedUi{"mitchell", "bar", bufferUi}
+	targettedUi := &TargettedUi{
+		Target: "foo",
+		Ui:     bufferUi,
+	}
 
-	prefixUi.Say("foo")
-	assert.Equal(readWriter(bufferUi), "mitchell: foo\n", "should have prefix")
+	targettedUi.Say("foo")
+	assert.Equal(readWriter(bufferUi), "==> foo: foo\n", "should have prefix")
 
-	prefixUi.Message("foo")
-	assert.Equal(readWriter(bufferUi), "bar: foo\n", "should have prefix")
+	targettedUi.Message("foo")
+	assert.Equal(readWriter(bufferUi), "    foo: foo\n", "should have prefix")
 
-	prefixUi.Error("bar")
-	assert.Equal(readWriter(bufferUi), "mitchell: bar\n", "should have prefix")
+	targettedUi.Error("bar")
+	assert.Equal(readWriter(bufferUi), "==> foo: bar\n", "should have prefix")
 
-	prefixUi.Say("foo\nbar")
-	assert.Equal(readWriter(bufferUi), "mitchell: foo\nmitchell: bar\n", "should multiline")
+	targettedUi.Say("foo\nbar")
+	assert.Equal(readWriter(bufferUi), "==> foo: foo\n==> foo: bar\n", "should multiline")
 }
 
 func TestColoredUi_ImplUi(t *testing.T) {
@@ -63,23 +67,23 @@ func TestColoredUi_ImplUi(t *testing.T) {
 	}
 }
 
-func TestPrefixedUi_ImplUi(t *testing.T) {
+func TestTargettedUi_ImplUi(t *testing.T) {
 	var raw interface{}
-	raw = &PrefixedUi{}
+	raw = &TargettedUi{}
 	if _, ok := raw.(Ui); !ok {
-		t.Fatalf("PrefixedUi must implement Ui")
+		t.Fatalf("TargettedUi must implement Ui")
 	}
 }
 
-func TestReaderWriterUi_ImplUi(t *testing.T) {
+func TestBasicUi_ImplUi(t *testing.T) {
 	var raw interface{}
-	raw = &ReaderWriterUi{}
+	raw = &BasicUi{}
 	if _, ok := raw.(Ui); !ok {
-		t.Fatalf("ReaderWriterUi must implement Ui")
+		t.Fatalf("BasicUi must implement Ui")
 	}
 }
 
-func TestReaderWriterUi_Error(t *testing.T) {
+func TestBasicUi_Error(t *testing.T) {
 	assert := asserts.NewTestingAsserts(t, true)
 
 	bufferUi := testUi()
@@ -91,7 +95,7 @@ func TestReaderWriterUi_Error(t *testing.T) {
 	assert.Equal(readWriter(bufferUi), "5\n", "formatting")
 }
 
-func TestReaderWriterUi_Say(t *testing.T) {
+func TestBasicUi_Say(t *testing.T) {
 	assert := asserts.NewTestingAsserts(t, true)
 
 	bufferUi := testUi()
@@ -103,9 +107,59 @@ func TestReaderWriterUi_Say(t *testing.T) {
 	assert.Equal(readWriter(bufferUi), "5\n", "formatting")
 }
 
+func TestMachineReadableUi_ImplUi(t *testing.T) {
+	var raw interface{}
+	raw = &MachineReadableUi{}
+	if _, ok := raw.(Ui); !ok {
+		t.Fatalf("MachineReadableUi must implement Ui")
+	}
+}
+
+func TestMachineReadableUi(t *testing.T) {
+	var data, expected string
+
+	buf := new(bytes.Buffer)
+	ui := &MachineReadableUi{Writer: buf}
+
+	// No target
+	ui.Machine("foo", "bar", "baz")
+	data = strings.SplitN(buf.String(), ",", 2)[1]
+	expected = ",foo,bar,baz\n"
+	if data != expected {
+		t.Fatalf("bad: %s", data)
+	}
+
+	// Target
+	buf.Reset()
+	ui.Machine("mitchellh,foo", "bar", "baz")
+	data = strings.SplitN(buf.String(), ",", 2)[1]
+	expected = "mitchellh,foo,bar,baz\n"
+	if data != expected {
+		t.Fatalf("bad: %s", data)
+	}
+
+	// Commas
+	buf.Reset()
+	ui.Machine("foo", "foo,bar")
+	data = strings.SplitN(buf.String(), ",", 2)[1]
+	expected = ",foo,foo%!(PACKER_COMMA)bar\n"
+	if data != expected {
+		t.Fatalf("bad: %s", data)
+	}
+
+	// New lines
+	buf.Reset()
+	ui.Machine("foo", "foo\n")
+	data = strings.SplitN(buf.String(), ",", 2)[1]
+	expected = ",foo,foo\\n\n"
+	if data != expected {
+		t.Fatalf("bad: %#v", data)
+	}
+}
+
 // This reads the output from the bytes.Buffer in our test object
 // and then resets the buffer.
-func readWriter(ui *ReaderWriterUi) (result string) {
+func readWriter(ui *BasicUi) (result string) {
 	buffer := ui.Writer.(*bytes.Buffer)
 	result = buffer.String()
 	buffer.Reset()

packer/version.go

@@ -27,6 +27,10 @@ command-line flags for this command.`
 }
 
 func (versionCommand) Run(env Environment, args []string) int {
+	env.Ui().Machine("version", Version)
+	env.Ui().Machine("version-prelease", VersionPrerelease)
+	env.Ui().Machine("version-commit", GitCommit)
+
 	var versionString bytes.Buffer
 	fmt.Fprintf(&versionString, "Packer v%s", Version)
 	if VersionPrerelease != "" {

packer_test.go

@@ -1 +1,35 @@
 package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestExtractMachineReadable(t *testing.T) {
+	var args, expected, result []string
+	var mr bool
+
+	// Not
+	args = []string{"foo", "bar", "baz"}
+	result, mr = extractMachineReadable(args)
+	expected = []string{"foo", "bar", "baz"}
+	if !reflect.DeepEqual(result, expected) {
+		t.Fatalf("bad: %#v", result)
+	}
+
+	if mr {
+		t.Fatal("should not be mr")
+	}
+
+	// Yes
+	args = []string{"foo", "--machine-readable", "baz"}
+	result, mr = extractMachineReadable(args)
+	expected = []string{"foo", "baz"}
+	if !reflect.DeepEqual(result, expected) {
+		t.Fatalf("bad: %#v", result)
+	}
+
+	if !mr {
+		t.Fatal("should be mr")
+	}
+}

provisioner/file/provisioner_test.go

@@ -106,6 +106,9 @@ func (su *stubUi) Ask(string) (string, error) {
 func (su *stubUi) Error(string) {
 }
 
+func (su *stubUi) Machine(string, ...string) {
+}
+
 func (su *stubUi) Message(string) {
 }
 

website/source/docs/command-line/build.html.markdown

@@ -1,5 +1,6 @@
 ---
 layout: "docs"
+page_title: "Build - Command-Line"
 ---
 
 # Command-Line: Build

website/source/docs/command-line/fix.html.markdown

@@ -1,6 +1,6 @@
 ---
 layout: "docs"
-page_title: "Command-line: Fix"
+page_title: "Fix - Command-Line"
 ---
 
 # Command-Line: Fix

website/source/docs/command-line/machine-readable.html.markdown

@@ -0,0 +1,83 @@
+---
+layout: "docs"
+page_title: "Machine-Readable Output - Command-Line"
+---
+
+# Machine-Readable Output
+
+By default, the output of Packer is very human-readable. It uses nice
+formatting, spacing, and colors in order to make Packer a pleasure to use.
+However, Packer was built with automation in mind. To that end, Packer
+supports a fully machine-readable output setting, allowing you to use
+Packer in automated environments.
+
+The machine-readable output format is easy to use and read and was made
+with Unix tools in mind, so it is awk/sed/grep/etc. friendly.
+
+## Enabling
+
+The machine-readable output format can be enabled by passing the
+`-machine-readable` flag to any Packer command. This immediately enables
+all output to become machine-readable on stdout. Logging, if enabled,
+continues to appear on stderr. An example of the output is shown
+below:
+
+```
+$ packer -machine-readable version
+1376289459,,version,0.2.4
+1376289459,,version-prerelease,
+1376289459,,version-commit,eed6ece
+1376289459,,ui,say,Packer v0.2.4.dev (eed6ece+CHANGES)
+```
+
+The format will be covered in more detail later. But as you can see,
+the output immediately becomes machine-friendly. Try some other commands
+with the `-machine-readable` flag to see!
+
+## Format
+
+The machine readable format is a line-oriented, comma-delimeted text
+format. This makes it extremely to parse using standard Unix tools such
+as awk or grep in addition to full programming languages like Ruby or
+Python.
+
+The format is:
+
+```
+timestamp,target,type,data...
+```
+
+Each component is explained below:
+
+* **timestamp** is a Unix timestamp in UTC of when the message was
+  printed.
+
+* **target** is the target of the following output. This is empty if
+  the message is related to Packer globally. Otherwise, this is generally
+  a build name so you can relate output to a specific build while parallel
+  builds are running.
+
+* **type** is the type of machine-readable message being outputted. There
+  are a set of standard types which are covered later, but each component
+  of Packer (builders, provisioners, etc.) may output their own custom types
+  as well, allowing the machine-readable output to be infinitely flexible.
+
+* **data** is zero or more comma-seperated values associated with the prior
+  type. The exact amount and meaning of this data is type-dependent, so you
+  must read the documentation associated with the type to understand fully.
+
+Within the format, if data contains a comma, it is replaced with
+`%!(PACKER_COMMA)`. This was preferred over an escape character such as
+`\'` because it is more friendly to tools like awk.
+
+Newlines within the format are replaced with their respective standard
+escape sequence. Newlines become a literal `\n` within the output. Carriage
+returns become a literal `\r`.
+
+## Message Types
+
+The set of machine-readable message types can be found in the
+[machine-readable format](#)
+complete documentation section. This section contains documentation
+on all the message types exposed by Packer core as well as all the
+components that ship with Packer by default.

website/source/docs/command-line/validate.html.markdown

@@ -1,5 +1,6 @@
 ---
 layout: "docs"
+page_title: "Validate - Command-Line"
 ---
 
 # Command-Line: Validate

website/source/layouts/docs.erb

@@ -13,6 +13,7 @@
 			<li><a href="/docs/command-line/build.html">Build</a></li>
 			<li><a href="/docs/command-line/fix.html">Fix</a></li>
 			<li><a href="/docs/command-line/validate.html">Validate</a></li>
+			<li><a href="/docs/command-line/machine-readable.html">Machine-Readable Output</a></li>
 		</ul>
 
 		<ul>