adds list command, and a timestamp in the container state

Signed-off-by: Mike Brown <brownwm@us.ibm.com>

list.go

@@ -0,0 +1,83 @@
+// +build linux
+
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"text/tabwriter"
+	"time"
+
+	"github.com/Sirupsen/logrus"
+	"github.com/codegangsta/cli"
+)
+
+var listCommand = cli.Command{
+	Name:  "list",
+	Usage: "lists containers started by runc with the given root",
+	Action: func(context *cli.Context) {
+
+		// preload the container factory
+		if factory == nil {
+			err := factoryPreload(context)
+			if err != nil {
+				logrus.Fatal(err)
+				return
+			}
+		}
+
+		// get the list of containers
+		root := context.GlobalString("root")
+		absRoot, err := filepath.Abs(root)
+		if err != nil {
+			logrus.Fatal(err)
+			return
+		}
+		list, err := ioutil.ReadDir(absRoot)
+
+		w := tabwriter.NewWriter(os.Stdout, 12, 1, 3, ' ', 0)
+		fmt.Fprint(w, "ID\tPID\tSTATUS\tCREATED\n")
+
+		// output containers
+		for _, item := range list {
+			switch {
+			case !item.IsDir():
+				// do nothing with misc files in the containers directory
+			case item.IsDir():
+				outputListInfo(item.Name(), w)
+			}
+		}
+
+		if err := w.Flush(); err != nil {
+			logrus.Fatal(err)
+		}
+	},
+}
+
+func outputListInfo(id string, w *tabwriter.Writer) {
+	container, err := factory.Load(id)
+	if err != nil {
+		logrus.Fatal(err)
+		return
+	}
+
+	containerStatus, err := container.Status()
+	if err != nil {
+		logrus.Fatal(err)
+		return
+	}
+
+	state, err := container.State()
+	if err != nil {
+		logrus.Fatal(err)
+		return
+	}
+
+	fmt.Fprintf(w, "%s\t%d\t%s\t%s\n", container.ID(),
+		state.BaseState.InitProcessPid,
+		containerStatus.String(),
+		state.BaseState.CreatedTime.Format(time.RFC3339Nano))
+
+}