@@ -2677,12 +2677,15 @@ func (cli *DockerCli) CmdExec(args ...string) error {

 		return err

 	}

-	var execResult engine.Env

-	if err := execResult.Decode(stream); err != nil {

+	var response types.ContainerExecCreateResponse

+	if err := json.NewDecoder(stream).Decode(&response); err != nil {

 		return err

 	}

+	for _, warning := range response.Warnings {

+		fmt.Fprintf(cli.err, "WARNING: %s\n", warning)

+	}

-	execID := execResult.Get("Id")

+	execID := response.ID

 	if execID == "" {

 		fmt.Fprintf(cli.out, "exec ID empty")

@@ -1155,10 +1155,11 @@ func postContainerExecCreate(eng *engine.Engine, version version.Version, w http

 		return nil

 	}

 	var (

-		out          engine.Env

 		name         = vars["name"]

 		job          = eng.Job("execCreate", name)

 		stdoutBuffer = bytes.NewBuffer(nil)

+		outWarnings  []string

+		warnings     = bytes.NewBuffer(nil)

 	)

 	if err := job.DecodeEnv(r.Body); err != nil {

@@ -1166,15 +1167,23 @@ func postContainerExecCreate(eng *engine.Engine, version version.Version, w http

 	}

 	job.Stdout.Add(stdoutBuffer)

+	// Read warnings from stderr

+	job.Stderr.Add(warnings)

 	// Register an instance of Exec in container.

 	if err := job.Run(); err != nil {

 		fmt.Fprintf(os.Stderr, "Error setting up exec command in container %s: %s\n", name, err)

 		return err

 	}

-	// Return the ID

-	out.Set("Id", engine.Tail(stdoutBuffer, 1))

+	// Parse warnings from stderr

+	scanner := bufio.NewScanner(warnings)

+	for scanner.Scan() {

+		outWarnings = append(outWarnings, scanner.Text())

+	}

-	return writeJSONEnv(w, http.StatusCreated, out)

+	return writeJSON(w, http.StatusCreated, &types.ContainerExecCreateResponse{

+		ID:       engine.Tail(stdoutBuffer, 1),

+		Warnings: outWarnings,

+	})

 }

 // TODO(vishh): Refactor the code to avoid having to specify stream config as part of both create and start.

@@ -9,3 +9,12 @@ type ContainerCreateResponse struct {

 	// Warnings are any warnings encountered during the creation of the container.

 	Warnings []string `json:"Warnings"`

 }

+

+// POST /containers/{name:.*}/exec

+type ContainerExecCreateResponse struct {

+	// ID is the exec ID.

+	ID string `json:"Id"`

+

+	// Warnings are any warnings encountered during the execution of the command.

+	Warnings []string `json:"Warnings"`

+}