merge branch 'pr-1158'

Closes #1158
LGTMs: @hqhq @cyphar

Author: cyphar

checkpoint.go

@@ -34,6 +34,9 @@ checkpointed.`,
 		cli.StringSliceFlag{Name: "empty-ns", Usage: "create a namespace, but don't restore its properies"},
 	},
 	Action: func(context *cli.Context) error {
+		if err := checkArgs(context, 1, exactArgs); err != nil {
+			return err
+		}
 		container, err := getContainer(context)
 		if err != nil {
 			return err

create.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"fmt"
 	"os"
 
 	"github.com/urfave/cli"
@@ -49,10 +48,8 @@ command(s) that get executed on start, edit the args parameter of the spec. See
 		},
 	},
 	Action: func(context *cli.Context) error {
-		if context.NArg() != 1 {
-			fmt.Printf("Incorrect Usage.\n\n")
-			cli.ShowCommandHelp(context, "create")
-			return fmt.Errorf("runc: \"create\" requires exactly one argument")
+		if err := checkArgs(context, 1, exactArgs); err != nil {
+			return err
 		}
 		if err := revisePidFile(context); err != nil {
 			return err

delete.go

@@ -45,11 +45,11 @@ status of "ubuntu01" as "stopped" the following will delete resources held for
 		},
 	},
 	Action: func(context *cli.Context) error {
-		hasError := false
-		if !context.Args().Present() {
-			return fmt.Errorf("runc: \"delete\" requires a minimum of 1 argument")
+		if err := checkArgs(context, 1, minArgs); err != nil {
+			return err
 		}
 
+		hasError := false
 		factory, err := loadFactory(context)
 		if err != nil {
 			return err

events.go

@@ -108,6 +108,9 @@ information is displayed once every 5 seconds.`,
 		cli.BoolFlag{Name: "stats", Usage: "display the container's stats then exit"},
 	},
 	Action: func(context *cli.Context) error {
+		if err := checkArgs(context, 1, exactArgs); err != nil {
+			return err
+		}
 		container, err := getContainer(context)
 		if err != nil {
 			return err

exec.go

@@ -86,6 +86,9 @@ following will output a list of processes running in the container:
 		},
 	},
 	Action: func(context *cli.Context) error {
+		if err := checkArgs(context, 2, minArgs); err != nil {
+			return err
+		}
 		if os.Geteuid() != 0 {
 			return fmt.Errorf("runc should be run as root")
 		}

kill.go

@@ -69,6 +69,9 @@ signal to the init process of the "ubuntu01" container:
 		},
 	},
 	Action: func(context *cli.Context) error {
+		if err := checkArgs(context, 2, exactArgs); err != nil {
+			return err
+		}
 		container, err := getContainer(context)
 		if err != nil {
 			return err

list.go

@@ -67,6 +67,9 @@ To list containers created using a non-default value for "--root":
 		},
 	},
 	Action: func(context *cli.Context) error {
+		if err := checkArgs(context, 0, exactArgs); err != nil {
+			return err
+		}
 		s, err := getContainers(context)
 		if err != nil {
 			return err

pause.go

@@ -20,11 +20,10 @@ paused. `,
 
 Use runc list to identiy instances of containers and their current status.`,
 	Action: func(context *cli.Context) error {
-		hasError := false
-		if !context.Args().Present() {
-			return fmt.Errorf("runc: \"pause\" requires a minimum of 1 argument")
+		if err := checkArgs(context, 1, minArgs); err != nil {
+			return err
 		}
-
+		hasError := false
 		factory, err := loadFactory(context)
 		if err != nil {
 			return err
@@ -61,11 +60,10 @@ resumed.`,
 
 Use runc list to identiy instances of containers and their current status.`,
 	Action: func(context *cli.Context) error {
-		hasError := false
-		if !context.Args().Present() {
-			return fmt.Errorf("runc: \"resume\" requires a minimum of 1 argument")
+		if err := checkArgs(context, 1, minArgs); err != nil {
+			return err
 		}
-
+		hasError := false
 		factory, err := loadFactory(context)
 		if err != nil {
 			return err

ps.go

@@ -25,6 +25,9 @@ var psCommand = cli.Command{
 		},
 	},
 	Action: func(context *cli.Context) error {
+		if err := checkArgs(context, 1, minArgs); err != nil {
+			return err
+		}
 		container, err := getContainer(context)
 		if err != nil {
 			return err

restore.go

@@ -83,6 +83,9 @@ using the runc checkpoint command.`,
 		},
 	},
 	Action: func(context *cli.Context) error {
+		if err := checkArgs(context, 1, exactArgs); err != nil {
+			return err
+		}
 		imagePath := context.String("image-path")
 		id := context.Args().First()
 		if id == "" {