Add latest to wait

It is desirable to have a --latest switch on the podman wait
command so we can wait on the latest container created to end.

Also, fixes a panic with latest where no containers are available.

Signed-off-by: baude <bbaude@redhat.com>

Closes: #201
Approved by: baude

cmd/podman/wait.go

@@ -14,11 +14,12 @@ var (
 
 	Block until one or more containers stop and then print their exit codes
 `
-
+	waitFlags   = []cli.Flag{LatestFlag}
 	waitCommand = cli.Command{
 		Name:        "wait",
 		Usage:       "Block on one or more containers",
 		Description: waitDescription,
+		Flags:       waitFlags,
 		Action:      waitCmd,
 		ArgsUsage:   "CONTAINER-NAME [CONTAINER-NAME ...]",
 	}
@@ -26,7 +27,7 @@ var (
 
 func waitCmd(c *cli.Context) error {
 	args := c.Args()
-	if len(args) < 1 {
+	if len(args) < 1 && !c.Bool("latest") {
 		return errors.Errorf("you must provide at least one container name or id")
 	}
 
@@ -41,7 +42,15 @@ func waitCmd(c *cli.Context) error {
 	}
 
 	var lastError error
-	for _, container := range c.Args() {
+	if c.Bool("latest") {
+		latestCtr, err := runtime.GetLatestContainer()
+		if err != nil {
+			return errors.Wrapf(err, "unable to wait on latest container")
+		}
+		args = append(args, latestCtr.ID())
+	}
+
+	for _, container := range args {
 		ctr, err := runtime.LookupContainer(container)
 		if err != nil {
 			return errors.Wrapf(err, "unable to find container %s", container)

completions/bash/podman

@@ -1469,7 +1469,11 @@ _podman_unpause() {
 
 _podman_wait() {
      local options_with_args=""
-     local boolean_options="--help -h"
+     local boolean_options="
+        --help
+        -h
+        -l
+        --latest"
      _complete_ "$options_with_args" "$boolean_options"
 }
 

docs/podman-wait.1.md

@@ -21,10 +21,16 @@ After the container stops, the container's return code is printed.
 **--help, -h**
   Print usage statement
 
+**--latest, -l**
+  Instead of providing the container name or ID, use the last created container. If you use methods other than Podman
+to run containers such as CRI-O, the last started container could be from either of those methods.
+
 ## EXAMPLES
 
   podman wait mywebserver
 
+  podman wait --latest
+
   podman wait 860a4b23
 
   podman wait mywebserver myftpserver

libpod/runtime_ctr.go

@@ -271,12 +271,15 @@ func (r *Runtime) GetContainersByList(containers []string) ([]*Container, error)
 
 // GetLatestContainer returns a container object of the latest created container.
 func (r *Runtime) GetLatestContainer() (*Container, error) {
-	var lastCreatedIndex int
+	lastCreatedIndex := -1
 	var lastCreatedTime time.Time
 	ctrs, err := r.GetAllContainers()
 	if err != nil {
 		return nil, errors.Wrapf(err, "unable to find latest container")
 	}
+	if len(ctrs) == 0 {
+		return nil, ErrNoSuchCtr
+	}
 	for containerIndex, ctr := range ctrs {
 		createdTime := ctr.config.CreatedTime
 		if createdTime.After(lastCreatedTime) {

test/podman_wait.bats

@@ -34,3 +34,10 @@ function teardown() {
     run bash -c ${PODMAN_BINARY} ${PODMAN_OPTIONS} wait $ctr_id
     [ "$status" -eq 0 ]
 }
+
+@test "wait on the latest container" {
+    ${PODMAN_BINARY} ${PODMAN_OPTIONS} run -d ${ALPINE} sleep 5
+    run bash -c ${PODMAN_BINARY} ${PODMAN_OPTIONS} wait -l
+    echo "$output"
+    [ "$status" -eq 0 ]
+}