add support to kill container process by pid

This adds support for signalling a container process by pid.

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

make Ps more extensible

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

ps: windows support

Signed-off-by: Evan Hazlett <ejhazlett@gmail.com>

cmd/ctr/ps.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	gocontext "context"
+	"fmt"
+	"os"
+	"text/tabwriter"
+
+	"github.com/containerd/containerd/api/services/execution"
+	"github.com/pkg/errors"
+	"github.com/urfave/cli"
+)
+
+var psCommand = cli.Command{
+	Name:  "ps",
+	Usage: "list processes for container",
+	Flags: []cli.Flag{
+		cli.StringFlag{
+			Name:  "id",
+			Usage: "id of the container",
+		},
+	},
+	Action: func(context *cli.Context) error {
+		id := context.String("id")
+		if id == "" {
+			return errors.New("container id must be provided")
+		}
+
+		psRequest := &execution.PsRequest{
+			ID: id,
+		}
+
+		containers, err := getExecutionService(context)
+		if err != nil {
+			return err
+		}
+
+		resp, err := containers.Ps(gocontext.Background(), psRequest)
+		if err != nil {
+			return err
+		}
+
+		w := tabwriter.NewWriter(os.Stdout, 10, 1, 3, ' ', 0)
+		fmt.Fprintln(w, "PID")
+		for _, ps := range resp.Ps {
+			if _, err := fmt.Fprintf(w, "%d\n",
+				ps.Pid,
+			); err != nil {
+				return err
+			}
+			if err := w.Flush(); err != nil {
+				return err
+			}
+		}
+
+		return nil
+	},
+}