mirror of
https://github.com/restic/restic.git
synced 2024-08-21 20:03:23 +02:00
498 lines
11 KiB
Go
498 lines
11 KiB
Go
package sftp
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import (
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"bufio"
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"context"
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"fmt"
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"io"
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"os"
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"os/exec"
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"path"
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"strings"
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"time"
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"github.com/restic/restic/internal/errors"
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"github.com/restic/restic/internal/restic"
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"github.com/restic/restic/internal/backend"
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"github.com/restic/restic/internal/debug"
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"github.com/pkg/sftp"
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)
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// SFTP is a backend in a directory accessed via SFTP.
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type SFTP struct {
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c *sftp.Client
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p string
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cmd *exec.Cmd
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result <-chan error
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backend.Layout
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Config
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}
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var _ restic.Backend = &SFTP{}
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const defaultLayout = "default"
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func startClient(program string, args ...string) (*SFTP, error) {
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debug.Log("start client %v %v", program, args)
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// Connect to a remote host and request the sftp subsystem via the 'ssh'
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// command. This assumes that passwordless login is correctly configured.
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cmd := exec.Command(program, args...)
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// prefix the errors with the program name
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stderr, err := cmd.StderrPipe()
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if err != nil {
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return nil, errors.Wrap(err, "cmd.StderrPipe")
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}
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go func() {
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sc := bufio.NewScanner(stderr)
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for sc.Scan() {
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fmt.Fprintf(os.Stderr, "subprocess %v: %v\n", program, sc.Text())
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}
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}()
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// ignore signals sent to the parent (e.g. SIGINT)
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cmd.SysProcAttr = ignoreSigIntProcAttr()
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// get stdin and stdout
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wr, err := cmd.StdinPipe()
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if err != nil {
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return nil, errors.Wrap(err, "cmd.StdinPipe")
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}
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rd, err := cmd.StdoutPipe()
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if err != nil {
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return nil, errors.Wrap(err, "cmd.StdoutPipe")
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}
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// start the process
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if err := cmd.Start(); err != nil {
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return nil, errors.Wrap(err, "cmd.Start")
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}
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// wait in a different goroutine
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ch := make(chan error, 1)
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go func() {
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err := cmd.Wait()
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debug.Log("ssh command exited, err %v", err)
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ch <- errors.Wrap(err, "cmd.Wait")
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}()
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// open the SFTP session
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client, err := sftp.NewClientPipe(rd, wr)
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if err != nil {
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return nil, errors.Errorf("unable to start the sftp session, error: %v", err)
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}
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return &SFTP{c: client, cmd: cmd, result: ch}, nil
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}
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// clientError returns an error if the client has exited. Otherwise, nil is
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// returned immediately.
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func (r *SFTP) clientError() error {
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select {
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case err := <-r.result:
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debug.Log("client has exited with err %v", err)
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return err
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default:
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}
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return nil
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}
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// Open opens an sftp backend as described by the config by running
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// "ssh" with the appropriate arguments (or cfg.Command, if set).
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func Open(cfg Config) (*SFTP, error) {
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debug.Log("open backend with config %#v", cfg)
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cmd, args, err := buildSSHCommand(cfg)
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if err != nil {
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return nil, err
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}
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sftp, err := startClient(cmd, args...)
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if err != nil {
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debug.Log("unable to start program: %v", err)
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return nil, err
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}
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sftp.Layout, err = backend.ParseLayout(sftp, cfg.Layout, defaultLayout, cfg.Path)
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if err != nil {
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return nil, err
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}
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debug.Log("layout: %v\n", sftp.Layout)
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if err := sftp.checkDataSubdirs(); err != nil {
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debug.Log("checkDataSubdirs returned %v", err)
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return nil, err
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}
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sftp.Config = cfg
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sftp.p = cfg.Path
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return sftp, nil
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}
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func (r *SFTP) checkDataSubdirs() error {
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datadir := r.Dirname(restic.Handle{Type: restic.DataFile})
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// check if all paths for data/ exist
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entries, err := r.c.ReadDir(datadir)
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if err != nil {
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return err
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}
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subdirs := make(map[string]struct{}, len(entries))
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for _, entry := range entries {
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subdirs[entry.Name()] = struct{}{}
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}
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for i := 0; i < 256; i++ {
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subdir := fmt.Sprintf("%02x", i)
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if _, ok := subdirs[subdir]; !ok {
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debug.Log("subdir %v is missing, creating", subdir)
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err := r.mkdirAll(path.Join(datadir, subdir), backend.Modes.Dir)
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if err != nil {
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return err
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}
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}
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}
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return nil
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}
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func (r *SFTP) mkdirAllDataSubdirs() error {
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for _, d := range r.Paths() {
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err := r.mkdirAll(d, backend.Modes.Dir)
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debug.Log("mkdirAll %v -> %v", d, err)
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if err != nil {
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return err
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}
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}
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return nil
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}
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// Join combines path components with slashes (according to the sftp spec).
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func (r *SFTP) Join(p ...string) string {
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return path.Join(p...)
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}
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// ReadDir returns the entries for a directory.
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func (r *SFTP) ReadDir(dir string) ([]os.FileInfo, error) {
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return r.c.ReadDir(dir)
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}
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// IsNotExist returns true if the error is caused by a not existing file.
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func (r *SFTP) IsNotExist(err error) bool {
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if os.IsNotExist(err) {
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return true
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}
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statusError, ok := err.(*sftp.StatusError)
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if !ok {
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return false
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}
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return statusError.Error() == `sftp: "No such file" (SSH_FX_NO_SUCH_FILE)`
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}
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func buildSSHCommand(cfg Config) (cmd string, args []string, err error) {
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if cfg.Command != "" {
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return SplitShellArgs(cfg.Command)
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}
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cmd = "ssh"
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hostport := strings.Split(cfg.Host, ":")
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args = []string{hostport[0]}
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if len(hostport) > 1 {
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args = append(args, "-p", hostport[1])
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}
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if cfg.User != "" {
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args = append(args, "-l")
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args = append(args, cfg.User)
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}
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args = append(args, "-s")
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args = append(args, "sftp")
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return cmd, args, nil
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}
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// Create creates an sftp backend as described by the config by running
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// "ssh" with the appropriate arguments (or cfg.Command, if set).
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func Create(cfg Config) (*SFTP, error) {
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cmd, args, err := buildSSHCommand(cfg)
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if err != nil {
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return nil, err
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}
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sftp, err := startClient(cmd, args...)
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if err != nil {
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debug.Log("unable to start program: %v", err)
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return nil, err
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}
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sftp.Layout, err = backend.ParseLayout(sftp, cfg.Layout, defaultLayout, cfg.Path)
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if err != nil {
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return nil, err
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}
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// test if config file already exists
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_, err = sftp.c.Lstat(Join(cfg.Path, backend.Paths.Config))
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if err == nil {
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return nil, errors.New("config file already exists")
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}
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// create paths for data and refs
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if err = sftp.mkdirAllDataSubdirs(); err != nil {
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return nil, err
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}
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err = sftp.Close()
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if err != nil {
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return nil, errors.Wrap(err, "Close")
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}
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// open backend
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return Open(cfg)
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}
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// Location returns this backend's location (the directory name).
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func (r *SFTP) Location() string {
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return r.p
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}
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func (r *SFTP) mkdirAll(dir string, mode os.FileMode) error {
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// check if directory already exists
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fi, err := r.c.Lstat(dir)
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if err == nil {
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if fi.IsDir() {
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return nil
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}
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return errors.Errorf("mkdirAll(%s): entry exists but is not a directory", dir)
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}
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// create parent directories
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errMkdirAll := r.mkdirAll(path.Dir(dir), backend.Modes.Dir)
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// create directory
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errMkdir := r.c.Mkdir(dir)
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// test if directory was created successfully
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fi, err = r.c.Lstat(dir)
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if err != nil {
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// return previous errors
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return errors.Errorf("mkdirAll(%s): unable to create directories: %v, %v", dir, errMkdirAll, errMkdir)
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}
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if !fi.IsDir() {
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return errors.Errorf("mkdirAll(%s): entry exists but is not a directory", dir)
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}
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// set mode
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return r.c.Chmod(dir, mode)
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}
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// Join joins the given paths and cleans them afterwards. This always uses
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// forward slashes, which is required by sftp.
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func Join(parts ...string) string {
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return path.Clean(path.Join(parts...))
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}
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// Save stores data in the backend at the handle.
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func (r *SFTP) Save(ctx context.Context, h restic.Handle, rd io.Reader) (err error) {
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debug.Log("Save %v", h)
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if err := r.clientError(); err != nil {
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return err
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}
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if err := h.Valid(); err != nil {
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return err
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}
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filename := r.Filename(h)
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// create new file
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f, err := r.c.OpenFile(filename, os.O_CREATE|os.O_EXCL|os.O_WRONLY)
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if r.IsNotExist(errors.Cause(err)) {
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// create the locks dir, then try again
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err = r.mkdirAll(r.Dirname(h), backend.Modes.Dir)
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if err != nil {
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return errors.Wrap(err, "MkdirAll")
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}
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return r.Save(ctx, h, rd)
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}
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if err != nil {
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return errors.Wrap(err, "OpenFile")
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}
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// save data
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_, err = io.Copy(f, rd)
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if err != nil {
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_ = f.Close()
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return errors.Wrap(err, "Write")
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}
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err = f.Close()
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if err != nil {
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return errors.Wrap(err, "Close")
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}
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// set mode to read-only
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fi, err := r.c.Lstat(filename)
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if err != nil {
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return errors.Wrap(err, "Lstat")
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}
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err = r.c.Chmod(filename, fi.Mode()&os.FileMode(^uint32(0222)))
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return errors.Wrap(err, "Chmod")
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}
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// Load returns a reader that yields the contents of the file at h at the
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// given offset. If length is nonzero, only a portion of the file is
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// returned. rd must be closed after use.
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func (r *SFTP) Load(ctx context.Context, h restic.Handle, length int, offset int64) (io.ReadCloser, error) {
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debug.Log("Load %v, length %v, offset %v", h, length, offset)
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if err := h.Valid(); err != nil {
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return nil, err
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}
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if offset < 0 {
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return nil, errors.New("offset is negative")
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}
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f, err := r.c.Open(r.Filename(h))
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if err != nil {
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return nil, err
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}
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if offset > 0 {
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_, err = f.Seek(offset, 0)
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if err != nil {
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_ = f.Close()
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return nil, err
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}
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}
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if length > 0 {
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return backend.LimitReadCloser(f, int64(length)), nil
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}
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return f, nil
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}
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// Stat returns information about a blob.
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func (r *SFTP) Stat(ctx context.Context, h restic.Handle) (restic.FileInfo, error) {
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debug.Log("Stat(%v)", h)
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if err := r.clientError(); err != nil {
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return restic.FileInfo{}, err
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}
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if err := h.Valid(); err != nil {
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return restic.FileInfo{}, err
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}
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fi, err := r.c.Lstat(r.Filename(h))
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if err != nil {
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return restic.FileInfo{}, errors.Wrap(err, "Lstat")
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}
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return restic.FileInfo{Size: fi.Size()}, nil
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}
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// Test returns true if a blob of the given type and name exists in the backend.
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func (r *SFTP) Test(ctx context.Context, h restic.Handle) (bool, error) {
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debug.Log("Test(%v)", h)
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if err := r.clientError(); err != nil {
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return false, err
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}
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_, err := r.c.Lstat(r.Filename(h))
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if os.IsNotExist(errors.Cause(err)) {
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return false, nil
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}
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if err != nil {
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return false, errors.Wrap(err, "Lstat")
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}
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return true, nil
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}
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// Remove removes the content stored at name.
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func (r *SFTP) Remove(ctx context.Context, h restic.Handle) error {
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debug.Log("Remove(%v)", h)
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if err := r.clientError(); err != nil {
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return err
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}
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return r.c.Remove(r.Filename(h))
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}
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// List returns a channel that yields all names of blobs of type t. A
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// goroutine is started for this. If the channel done is closed, sending
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// stops.
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func (r *SFTP) List(ctx context.Context, t restic.FileType) <-chan string {
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debug.Log("List %v", t)
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ch := make(chan string)
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go func() {
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defer close(ch)
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walker := r.c.Walk(r.Basedir(t))
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for walker.Step() {
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if walker.Err() != nil {
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continue
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}
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if !walker.Stat().Mode().IsRegular() {
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continue
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}
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select {
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case ch <- path.Base(walker.Path()):
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case <-ctx.Done():
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return
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}
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}
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}()
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return ch
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}
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var closeTimeout = 2 * time.Second
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// Close closes the sftp connection and terminates the underlying command.
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func (r *SFTP) Close() error {
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debug.Log("")
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if r == nil {
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return nil
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}
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err := r.c.Close()
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debug.Log("Close returned error %v", err)
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// wait for closeTimeout before killing the process
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select {
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case err := <-r.result:
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return err
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case <-time.After(closeTimeout):
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}
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if err := r.cmd.Process.Kill(); err != nil {
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return err
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}
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// get the error, but ignore it
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<-r.result
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return nil
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}
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