restic/cmd/restic/cmd_dump.go

package main

import (
	"context"
	"fmt"
	"os"
	"path"
	"path/filepath"

	"github.com/restic/restic/internal/debug"
	"github.com/restic/restic/internal/dump"
	"github.com/restic/restic/internal/errors"
	"github.com/restic/restic/internal/restic"

	"github.com/spf13/cobra"
)

var cmdDump = &cobra.Command{
	Use:   "dump [flags] snapshotID file",
	Short: "Print a backed-up file to stdout",
	Long: `
The "dump" command extracts files from a snapshot from the repository. If a
single file is selected, it prints its contents to stdout. Folders are output
as a tar (default) or zip file containing the contents of the specified folder.
Pass "/" as file name to dump the whole snapshot as an archive file.

The special snapshotID "latest" can be used to use the latest snapshot in the
repository.

To include the folder content at the root of the archive, you can use the
"<snapshotID>:<subfolder>" syntax, where "subfolder" is a path within the
snapshot.

EXIT STATUS
===========

Exit status is 0 if the command was successful, and non-zero if there was any error.
`,
	DisableAutoGenTag: true,
	RunE: func(cmd *cobra.Command, args []string) error {
		return runDump(cmd.Context(), dumpOptions, globalOptions, args)
	},
}

// DumpOptions collects all options for the dump command.
type DumpOptions struct {
	restic.SnapshotFilter
	Archive string
	Target  string
}

var dumpOptions DumpOptions

func init() {
	cmdRoot.AddCommand(cmdDump)

	flags := cmdDump.Flags()
	initSingleSnapshotFilter(flags, &dumpOptions.SnapshotFilter)
	flags.StringVarP(&dumpOptions.Archive, "archive", "a", "tar", "set archive `format` as \"tar\" or \"zip\"")
	flags.StringVarP(&dumpOptions.Target, "target", "t", "", "write the output to target `path`")
}

func splitPath(p string) []string {
	d, f := path.Split(p)
	if d == "" || d == "/" {
		return []string{f}
	}
	s := splitPath(path.Join("/", d))
	return append(s, f)
}

func printFromTree(ctx context.Context, tree *restic.Tree, repo restic.BlobLoader, prefix string, pathComponents []string, d *dump.Dumper, canWriteArchiveFunc func() error) error {
	// If we print / we need to assume that there are multiple nodes at that
	// level in the tree.
	if pathComponents[0] == "" {
		if err := canWriteArchiveFunc(); err != nil {
			return err
		}
		return d.DumpTree(ctx, tree, "/")
	}

	item := filepath.Join(prefix, pathComponents[0])
	l := len(pathComponents)
	for _, node := range tree.Nodes {
		// If dumping something in the highest level it will just take the
		// first item it finds and dump that according to the switch case below.
		if node.Name == pathComponents[0] {
			switch {
			case l == 1 && dump.IsFile(node):
				return d.WriteNode(ctx, node)
			case l > 1 && dump.IsDir(node):
				subtree, err := restic.LoadTree(ctx, repo, *node.Subtree)
				if err != nil {
					return errors.Wrapf(err, "cannot load subtree for %q", item)
				}
				return printFromTree(ctx, subtree, repo, item, pathComponents[1:], d, canWriteArchiveFunc)
			case dump.IsDir(node):
				if err := canWriteArchiveFunc(); err != nil {
					return err
				}
				subtree, err := restic.LoadTree(ctx, repo, *node.Subtree)
				if err != nil {
					return err
				}
				return d.DumpTree(ctx, subtree, item)
			case l > 1:
				return fmt.Errorf("%q should be a dir, but is a %q", item, node.Type)
			case !dump.IsFile(node):
				return fmt.Errorf("%q should be a file, but is a %q", item, node.Type)
			}
		}
	}
	return fmt.Errorf("path %q not found in snapshot", item)
}

func runDump(ctx context.Context, opts DumpOptions, gopts GlobalOptions, args []string) error {
	if len(args) != 2 {
		return errors.Fatal("no file and no snapshot ID specified")
	}

	switch opts.Archive {
	case "tar", "zip":
	default:
		return fmt.Errorf("unknown archive format %q", opts.Archive)
	}

	snapshotIDString := args[0]
	pathToPrint := args[1]

	debug.Log("dump file %q from %q", pathToPrint, snapshotIDString)

	splittedPath := splitPath(path.Clean(pathToPrint))

	ctx, repo, unlock, err := openWithReadLock(ctx, gopts, gopts.NoLock)
	if err != nil {
		return err
	}
	defer unlock()

	sn, subfolder, err := (&restic.SnapshotFilter{
		Hosts: opts.Hosts,
		Paths: opts.Paths,
		Tags:  opts.Tags,
	}).FindLatest(ctx, repo, repo, snapshotIDString)
	if err != nil {
		return errors.Fatalf("failed to find snapshot: %v", err)
	}

	bar := newIndexProgress(gopts.Quiet, gopts.JSON)
	err = repo.LoadIndex(ctx, bar)
	if err != nil {
		return err
	}

	sn.Tree, err = restic.FindTreeDirectory(ctx, repo, sn.Tree, subfolder)
	if err != nil {
		return err
	}

	tree, err := restic.LoadTree(ctx, repo, *sn.Tree)
	if err != nil {
		return errors.Fatalf("loading tree for snapshot %q failed: %v", snapshotIDString, err)
	}

	outputFileWriter := os.Stdout
	canWriteArchiveFunc := checkStdoutArchive

	if opts.Target != "" {
		file, err := os.Create(opts.Target)
		if err != nil {
			return fmt.Errorf("cannot dump to file: %w", err)
		}
		defer func() {
			_ = file.Close()
		}()

		outputFileWriter = file
		canWriteArchiveFunc = func() error { return nil }
	}

	d := dump.New(opts.Archive, repo, outputFileWriter)
	err = printFromTree(ctx, tree, repo, "/", splittedPath, d, canWriteArchiveFunc)
	if err != nil {
		return errors.Fatalf("cannot dump file: %v", err)
	}

	return nil
}

func checkStdoutArchive() error {
	if stdoutIsTerminal() {
		return fmt.Errorf("stdout is the terminal, please redirect output")
	}
	return nil
}