Add exec and terminal support

Signed-off-by: Kenfe-Mickael Laventure <mickael.laventure@gmail.com>

cmd/ctr/exec.go

@@ -0,0 +1,87 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+
+	gocontext "context"
+
+	"github.com/docker/containerd/api/execution"
+	"github.com/urfave/cli"
+)
+
+var execCommand = cli.Command{
+	Name:  "exec",
+	Usage: "exec a new process in a running container",
+	Flags: []cli.Flag{
+		cli.StringFlag{
+			Name:  "id, i",
+			Usage: "target container id",
+		},
+		cli.StringFlag{
+			Name:  "cwd, c",
+			Usage: "current working directory for the process",
+		},
+		cli.BoolFlag{
+			Name:  "tty, t",
+			Usage: "create a terminal for the process",
+		},
+		cli.StringSliceFlag{
+			Name:  "env, e",
+			Value: &cli.StringSlice{},
+			Usage: "environment variables for the process",
+		},
+	},
+	Action: func(context *cli.Context) error {
+		executionService, err := getExecutionService(context)
+		if err != nil {
+			return err
+		}
+
+		id := context.String("id")
+		tmpDir, err := getTempDir(id)
+		if err != nil {
+			return err
+		}
+		defer os.RemoveAll(tmpDir)
+
+		sOpts := &execution.StartProcessRequest{
+			ContainerId: id,
+			Process: &execution.Process{
+				Cwd:      context.String("cwd"),
+				Terminal: context.Bool("tty"),
+				Args:     context.Args(),
+				Env:      context.StringSlice("env"),
+			},
+			Stdin:   filepath.Join(tmpDir, "stdin"),
+			Stdout:  filepath.Join(tmpDir, "stdout"),
+			Stderr:  filepath.Join(tmpDir, "stderr"),
+			Console: context.Bool("tty"),
+		}
+
+		fwg, err := prepareStdio(sOpts.Stdin, sOpts.Stdout, sOpts.Stderr)
+		if err != nil {
+			return err
+		}
+
+		sr, err := executionService.StartProcess(gocontext.Background(), sOpts)
+		if err != nil {
+			return err
+		}
+
+		_, err = executionService.DeleteProcess(gocontext.Background(), &execution.DeleteProcessRequest{
+			Container: &execution.Container{
+				ID: id,
+			},
+			Process: sr.Process,
+		})
+		if err != nil {
+			return err
+		}
+
+		// Ensure we read all io
+		fwg.Wait()
+
+		return nil
+	},
+}