docker cp: report both content size and transferred size

Report the actual file/content size in the success message, with the
transferred (tar stream) size shown in parentheses when it differs from
the content size. For copyToContainer, use localContentSize() which
performs fast stat-only metadata lookups on local files. For
copyFromContainer, use the PathStat.Size from the container API response
for regular files, falling back to the tar stream size for directories.

When content size equals transferred size (e.g. directory downloads or
stdin input where content size is unknown), only the single size is
shown to avoid redundant output.

Example output:
  Successfully copied 0B (transferred 1.54kB) to my-container:/empty
  Successfully copied 5B (transferred 2.05kB) to my-container:/file
  Successfully copied 10.5kB to /local/dir

Fixes #5777

Signed-off-by: 4RH1T3CT0R7 <iprintercanon@gmail.com>

Author: 4RH1T3CT0R7

cli/command/container/client_test.go

@@ -36,6 +36,7 @@ type fakeClient struct {
 	infoFunc                func() (client.SystemInfoResult, error)
 	containerStatPathFunc   func(containerID, path string) (client.ContainerStatPathResult, error)
 	containerCopyFromFunc   func(containerID, srcPath string) (client.CopyFromContainerResult, error)
+	containerCopyToFunc     func(containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error)
 	logFunc                 func(string, client.ContainerLogsOptions) (client.ContainerLogsResult, error)
 	waitFunc                func(string) client.ContainerWaitResult
 	containerListFunc       func(client.ContainerListOptions) (client.ContainerListResult, error)
@@ -128,6 +129,13 @@ func (f *fakeClient) CopyFromContainer(_ context.Context, containerID string, op
 	return client.CopyFromContainerResult{}, nil
 }
 
+func (f *fakeClient) CopyToContainer(_ context.Context, containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error) {
+	if f.containerCopyToFunc != nil {
+		return f.containerCopyToFunc(containerID, options)
+	}
+	return client.CopyToContainerResult{}, nil
+}
+
 func (f *fakeClient) ContainerLogs(_ context.Context, containerID string, options client.ContainerLogsOptions) (client.ContainerLogsResult, error) {
 	if f.logFunc != nil {
 		return f.logFunc(containerID, options)

cli/command/container/cp.go

@@ -168,6 +168,37 @@ func progressHumanSize(n int64) string {
 	return units.HumanSizeWithPrecision(float64(n), 3)
 }
 
+// localContentSize returns the total size of regular file content at path.
+// For a regular file it returns the file size. For a directory it walks
+// the tree and sums sizes of all regular files.
+func localContentSize(path string) (int64, error) {
+	fi, err := os.Lstat(path)
+	if err != nil {
+		return -1, err
+	}
+	if !fi.IsDir() {
+		if fi.Mode().IsRegular() {
+			return fi.Size(), nil
+		}
+		return 0, nil
+	}
+	var total int64
+	err = filepath.WalkDir(path, func(_ string, d os.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.Type().IsRegular() {
+			info, err := d.Info()
+			if err != nil {
+				return err
+			}
+			total += info.Size()
+		}
+		return nil
+	})
+	return total, err
+}
+
 func runCopy(ctx context.Context, dockerCli command.Cli, opts copyOptions) error {
 	srcContainer, srcPath := splitCpArg(opts.source)
 	destContainer, destPath := splitCpArg(opts.destination)
@@ -295,7 +326,19 @@ func copyFromContainer(ctx context.Context, dockerCLI command.Cli, copyConfig cp
 	cancel()
 	<-done
 	restore()
-	_, _ = fmt.Fprintln(dockerCLI.Err(), "Successfully copied", progressHumanSize(copiedSize), "to", dstPath)
+	reportedSize := copiedSize
+	if !cpRes.Stat.Mode.IsDir() {
+		reportedSize = cpRes.Stat.Size
+	}
+	if reportedSize != copiedSize {
+		_, _ = fmt.Fprintf(dockerCLI.Err(), "Successfully copied %s (transferred %s) to %s\n",
+			progressHumanSize(reportedSize), progressHumanSize(copiedSize), dstPath,
+		)
+	} else {
+		_, _ = fmt.Fprintf(dockerCLI.Err(), "Successfully copied %s to %s\n",
+			progressHumanSize(reportedSize), dstPath,
+		)
+	}
 
 	return res
 }
@@ -354,11 +397,14 @@ func copyToContainer(ctx context.Context, dockerCLI command.Cli, copyConfig cpCo
 		content         io.ReadCloser
 		resolvedDstPath string
 		copiedSize      int64
+		contentSize     int64
+		sizeErr         error
 	)
 
 	if srcPath == "-" {
 		content = os.Stdin
 		resolvedDstPath = dstInfo.Path
+		sizeErr = errors.New("content size not available for stdin")
 		if !dstInfo.IsDir {
 			return fmt.Errorf(`destination "%s:%s" must be a directory`, copyConfig.container, dstPath)
 		}
@@ -369,6 +415,8 @@ func copyToContainer(ctx context.Context, dockerCLI command.Cli, copyConfig cpCo
 			return err
 		}
 
+		contentSize, sizeErr = localContentSize(srcInfo.Path)
+
 		srcArchive, err := archive.TarResource(srcInfo)
 		if err != nil {
 			return err
@@ -421,7 +469,19 @@ func copyToContainer(ctx context.Context, dockerCLI command.Cli, copyConfig cpCo
 	cancel()
 	<-done
 	restore()
-	_, _ = fmt.Fprintln(dockerCLI.Err(), "Successfully copied", progressHumanSize(copiedSize), "to", copyConfig.container+":"+dstInfo.Path)
+	reportedSize := copiedSize
+	if sizeErr == nil {
+		reportedSize = contentSize
+	}
+	if reportedSize != copiedSize {
+		_, _ = fmt.Fprintf(dockerCLI.Err(), "Successfully copied %s (transferred %s) to %s:%s\n",
+			progressHumanSize(reportedSize), progressHumanSize(copiedSize), copyConfig.container, dstInfo.Path,
+		)
+	} else {
+		_, _ = fmt.Fprintf(dockerCLI.Err(), "Successfully copied %s to %s:%s\n",
+			progressHumanSize(reportedSize), copyConfig.container, dstInfo.Path,
+		)
+	}
 
 	return err
 }

cli/command/container/cp_test.go

@@ -11,6 +11,7 @@ import (
 	"github.com/docker/cli/internal/test"
 	"github.com/moby/go-archive"
 	"github.com/moby/go-archive/compression"
+	"github.com/moby/moby/api/types/container"
 	"github.com/moby/moby/client"
 	"gotest.tools/v3/assert"
 	is "gotest.tools/v3/assert/cmp"
@@ -211,3 +212,156 @@ func TestRunCopyFromContainerToFilesystemIrregularDestination(t *testing.T) {
 	expected := `"/dev/random" must be a directory or a regular file`
 	assert.ErrorContains(t, err, expected)
 }
+
+func TestCopyFromContainerReportsFileSize(t *testing.T) {
+	// The file content is "hello" (5 bytes), but the TAR archive wrapping
+	// it is much larger due to headers and padding. The success message
+	// should report the actual file size (5B), not the TAR stream size.
+	srcDir := fs.NewDir(t, "cp-test-from",
+		fs.WithFile("file1", "hello"))
+
+	destDir := fs.NewDir(t, "cp-test-from-dest")
+
+	const fileSize int64 = 5
+	fakeCli := test.NewFakeCli(&fakeClient{
+		containerCopyFromFunc: func(ctr, srcPath string) (client.CopyFromContainerResult, error) {
+			readCloser, err := archive.Tar(srcDir.Path(), compression.None)
+			return client.CopyFromContainerResult{
+				Content: readCloser,
+				Stat: container.PathStat{
+					Name: "file1",
+					Size: fileSize,
+				},
+			}, err
+		},
+	})
+	err := runCopy(context.TODO(), fakeCli, copyOptions{
+		source:      "container:/file1",
+		destination: destDir.Path(),
+	})
+	assert.NilError(t, err)
+	errOut := fakeCli.ErrBuffer().String()
+	assert.Check(t, is.Contains(errOut, "Successfully copied 5B"))
+	assert.Check(t, is.Contains(errOut, "(transferred"))
+}
+
+func TestCopyToContainerReportsFileSize(t *testing.T) {
+	// Create a temp file with known content ("hello" = 5 bytes).
+	// The TAR archive sent to the container is larger, but the success
+	// message should report the actual content size.
+	srcFile := fs.NewFile(t, "cp-test-to", fs.WithContent("hello"))
+
+	fakeCli := test.NewFakeCli(&fakeClient{
+		containerStatPathFunc: func(containerID, path string) (client.ContainerStatPathResult, error) {
+			return client.ContainerStatPathResult{
+				Stat: container.PathStat{
+					Name: "tmp",
+					Mode: os.ModeDir | 0o755,
+				},
+			}, nil
+		},
+		containerCopyToFunc: func(containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error) {
+			_, _ = io.Copy(io.Discard, options.Content)
+			return client.CopyToContainerResult{}, nil
+		},
+	})
+	err := runCopy(context.TODO(), fakeCli, copyOptions{
+		source:      srcFile.Path(),
+		destination: "container:/tmp",
+	})
+	assert.NilError(t, err)
+	errOut := fakeCli.ErrBuffer().String()
+	assert.Check(t, is.Contains(errOut, "Successfully copied 5B"))
+	assert.Check(t, is.Contains(errOut, "(transferred"))
+}
+
+func TestCopyToContainerReportsEmptyFileSize(t *testing.T) {
+	srcFile := fs.NewFile(t, "cp-test-empty", fs.WithContent(""))
+
+	fakeCli := test.NewFakeCli(&fakeClient{
+		containerStatPathFunc: func(containerID, path string) (client.ContainerStatPathResult, error) {
+			return client.ContainerStatPathResult{
+				Stat: container.PathStat{
+					Name: "tmp",
+					Mode: os.ModeDir | 0o755,
+				},
+			}, nil
+		},
+		containerCopyToFunc: func(containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error) {
+			_, _ = io.Copy(io.Discard, options.Content)
+			return client.CopyToContainerResult{}, nil
+		},
+	})
+	err := runCopy(context.TODO(), fakeCli, copyOptions{
+		source:      srcFile.Path(),
+		destination: "container:/tmp",
+	})
+	assert.NilError(t, err)
+	errOut := fakeCli.ErrBuffer().String()
+	assert.Check(t, is.Contains(errOut, "Successfully copied 0B"))
+	assert.Check(t, is.Contains(errOut, "(transferred"))
+}
+
+func TestCopyToContainerReportsDirectorySize(t *testing.T) {
+	// Create a temp directory with files "aaa" (3 bytes) + "bbb" (3 bytes) = 6 bytes.
+	// The TAR archive is much larger, but the success message should report 6B.
+	srcDir := fs.NewDir(t, "cp-test-dir",
+		fs.WithFile("aaa", "aaa"),
+		fs.WithFile("bbb", "bbb"),
+	)
+
+	fakeCli := test.NewFakeCli(&fakeClient{
+		containerStatPathFunc: func(containerID, path string) (client.ContainerStatPathResult, error) {
+			return client.ContainerStatPathResult{
+				Stat: container.PathStat{
+					Name: "tmp",
+					Mode: os.ModeDir | 0o755,
+				},
+			}, nil
+		},
+		containerCopyToFunc: func(containerID string, options client.CopyToContainerOptions) (client.CopyToContainerResult, error) {
+			_, _ = io.Copy(io.Discard, options.Content)
+			return client.CopyToContainerResult{}, nil
+		},
+	})
+	err := runCopy(context.TODO(), fakeCli, copyOptions{
+		source:      srcDir.Path() + string(os.PathSeparator),
+		destination: "container:/tmp",
+	})
+	assert.NilError(t, err)
+	errOut := fakeCli.ErrBuffer().String()
+	assert.Check(t, is.Contains(errOut, "Successfully copied 6B"))
+	assert.Check(t, is.Contains(errOut, "(transferred"))
+}
+
+func TestCopyFromContainerReportsDirectorySize(t *testing.T) {
+	// When copying a directory from a container, cpRes.Stat.Mode.IsDir() is true,
+	// so reportedSize falls back to copiedSize (the tar stream bytes).
+	srcDir := fs.NewDir(t, "cp-test-fromdir",
+		fs.WithFile("file1", "hello"))
+
+	destDir := fs.NewDir(t, "cp-test-fromdir-dest")
+
+	fakeCli := test.NewFakeCli(&fakeClient{
+		containerCopyFromFunc: func(ctr, srcPath string) (client.CopyFromContainerResult, error) {
+			readCloser, err := archive.Tar(srcDir.Path(), compression.None)
+			return client.CopyFromContainerResult{
+				Content: readCloser,
+				Stat: container.PathStat{
+					Name: "mydir",
+					Mode: os.ModeDir | 0o755,
+				},
+			}, err
+		},
+	})
+	err := runCopy(context.TODO(), fakeCli, copyOptions{
+		source:      "container:/mydir",
+		destination: destDir.Path(),
+	})
+	assert.NilError(t, err)
+	errOut := fakeCli.ErrBuffer().String()
+	assert.Check(t, is.Contains(errOut, "Successfully copied"))
+	// For directories from container, content size is unknown so
+	// reportedSize == copiedSize and "(transferred ...)" is omitted.
+	assert.Check(t, !strings.Contains(errOut, "(transferred"))
+}