update exec to pass args and --tty on run

Signed-off-by: Jessica Frazelle <acidburn@docker.com>

exec.go

@@ -3,13 +3,14 @@
 package main
 
 import (
-	"encoding/json"
 	"fmt"
 	"os"
+	"path"
+	"strconv"
+	"strings"
 
 	"github.com/Sirupsen/logrus"
 	"github.com/codegangsta/cli"
-	"github.com/opencontainers/specs"
 )
 
 var execCommand = cli.Command{
@@ -18,22 +19,33 @@ var execCommand = cli.Command{
 	Flags: []cli.Flag{
 		cli.StringFlag{
 			Name:  "console",
-			Value: "",
 			Usage: "specify the pty slave path for use with the container",
 		},
+		cli.StringFlag{
+			Name:  "cwd",
+			Usage: "current working directory in the container",
+		},
+		cli.StringSliceFlag{
+			Name:  "env, e",
+			Usage: "set environment variables",
+		},
+		cli.BoolFlag{
+			Name:  "tty, t",
+			Usage: "allocate a pseudo-TTY",
+		},
+		cli.StringFlag{
+			Name:  "user, u",
+			Usage: "UID (format: <uid>[:<gid>])",
+		},
 	},
 	Action: func(context *cli.Context) {
-		config, err := loadProcessConfig(context.Args().First())
-		if err != nil {
-			fatal(err)
+		if len(context.Args()) == 0 {
+			logrus.Fatal("pass the command")
 		}
 		if os.Geteuid() != 0 {
 			logrus.Fatal("runc should be run as root")
 		}
-		if config.Args == nil {
-			logrus.Fatal("args missing in process configuration")
-		}
-		status, err := execProcess(context, config)
+		status, err := execProcess(context, context.Args())
 		if err != nil {
 			logrus.Fatalf("exec failed: %v", err)
 		}
@@ -41,42 +53,72 @@ var execCommand = cli.Command{
 	},
 }
 
-func execProcess(context *cli.Context, config *specs.Process) (int, error) {
+func execProcess(context *cli.Context, args []string) (int, error) {
 	container, err := getContainer(context)
 	if err != nil {
 		return -1, err
 	}
-	process := newProcess(*config)
 
+	bundle := container.Config().Rootfs
+	if err := os.Chdir(path.Dir(bundle)); err != nil {
+		return -1, err
+	}
+	spec, _, err := loadSpec(specConfig, runtimeConfig)
+	if err != nil {
+		return -1, err
+	}
+
+	p := spec.Process
+
+	// override the cwd, if passed
+	if context.String("cwd") != "" {
+		p.Cwd = context.String("cwd")
+	}
+
+	// append the passed env variables
+	for _, e := range context.StringSlice("env") {
+		p.Env = append(p.Env, e)
+	}
+
+	// set the tty
+	if context.IsSet("tty") {
+		p.Terminal = context.Bool("tty")
+	}
+
+	// override the user, if passed
+	if context.String("user") != "" {
+		u := strings.SplitN(context.String("user"), ":", 2)
+		if len(u) > 1 {
+			gid, err := strconv.Atoi(u[1])
+			if err != nil {
+				return -1, fmt.Errorf("parsing %s as int for gid failed: %v", u[1], err)
+			}
+			p.User.GID = uint32(gid)
+		}
+		uid, err := strconv.Atoi(u[0])
+		if err != nil {
+			return -1, fmt.Errorf("parsing %s as int for uid failed: %v", u[0], err)
+		}
+		p.User.UID = uint32(uid)
+	}
+
+	process := newProcess(p)
+	process.Args = args
 	rootuid, err := container.Config().HostUID()
 	if err != nil {
 		return -1, err
 	}
-	tty, err := newTty(config.Terminal, process, rootuid, context.String("console"))
+
+	tty, err := newTty(p.Terminal, process, rootuid, context.String("console"))
 	if err != nil {
 		return -1, err
 	}
+
 	handler := newSignalHandler(tty)
 	defer handler.Close()
 	if err := container.Start(process); err != nil {
 		return -1, err
 	}
+
 	return handler.forward(process)
 }
-
-// loadProcessConfig loads the process configuration from the provided path.
-func loadProcessConfig(path string) (*specs.Process, error) {
-	f, err := os.Open(path)
-	if err != nil {
-		if os.IsNotExist(err) {
-			return nil, fmt.Errorf("JSON configuration file for %s not found", path)
-		}
-		return nil, err
-	}
-	defer f.Close()
-	var s *specs.Process
-	if err := json.NewDecoder(f).Decode(&s); err != nil {
-		return nil, err
-	}
-	return s, nil
-}