build: support --quiet

Signed-off-by: Akihiro Suda <[email protected]>

cmd/nerdctl/build.go

@@ -84,6 +84,11 @@ var buildCommand = &cli.Command{
 			Name:  "ssh",
 			Usage: "SSH agent socket or keys to expose to the build (format: default|<id>[=<socket>|<key>[,<key>]])",
 		},
+		&cli.BoolFlag{
+			Name:    "quiet",
+			Aliases: []string{"q"},
+			Usage:   "Suppress the build output and print image ID on success",
+		},
 	},
 }
 
@@ -98,6 +103,8 @@ func buildAction(clicontext *cli.Context) error {
 		return err
 	}
 
+	quiet := clicontext.Bool("quiet")
+
 	logrus.Debugf("running %s %v", buildctlBinary, buildctlArgs)
 	buildctlCmd := exec.Command(buildctlBinary, buildctlArgs...)
 	buildctlCmd.Env = os.Environ()
@@ -111,14 +118,17 @@ func buildAction(clicontext *cli.Context) error {
 	} else {
 		buildctlCmd.Stdout = clicontext.App.Writer
 	}
-	buildctlCmd.Stderr = clicontext.App.ErrWriter
+
+	if !quiet {
+		buildctlCmd.Stderr = clicontext.App.ErrWriter
+	}
 
 	if err := buildctlCmd.Start(); err != nil {
 		return err
 	}
 
 	if needsLoading {
-		if err = loadImage(buildctlStdout, clicontext); err != nil {
+		if err = loadImage(buildctlStdout, clicontext, quiet); err != nil {
 			return err
 		}
 	}

cmd/nerdctl/load.go

@@ -55,10 +55,10 @@ func loadAction(clicontext *cli.Context) error {
 		defer f.Close()
 		in = f
 	}
-	return loadImage(in, clicontext)
+	return loadImage(in, clicontext, false)
 }
 
-func loadImage(in io.Reader, clicontext *cli.Context) error {
+func loadImage(in io.Reader, clicontext *cli.Context, quiet bool) error {
 	client, ctx, cancel, err := newClient(clicontext, containerd.WithDefaultPlatform(platforms.DefaultStrict()))
 	if err != nil {
 		return err
@@ -74,12 +74,18 @@ func loadImage(in io.Reader, clicontext *cli.Context) error {
 		image := containerd.NewImage(client, img)
 
 		// TODO: Show unpack status
-		fmt.Fprintf(clicontext.App.Writer, "unpacking %s (%s)...", img.Name, img.Target.Digest)
+		if !quiet {
+			fmt.Fprintf(clicontext.App.Writer, "unpacking %s (%s)...", img.Name, img.Target.Digest)
+		}
 		err = image.Unpack(ctx, sn)
 		if err != nil {
 			return err
 		}
-		fmt.Fprintf(clicontext.App.Writer, "done\n")
+		if quiet {
+			fmt.Fprintln(clicontext.App.Writer, img.Target.Digest)
+		} else {
+			fmt.Fprintf(clicontext.App.Writer, "done\n")
+		}
 	}
 
 	return nil