func (u *Updater) update() error {
path, err := osext.Executable()
if err != nil {
return err
}
old, err := os.Open(path)
if err != nil {
return err
}
defer old.Close()
err = u.fetchInfo()
if err != nil {
return err
}
if u.info.Version == Version {
return nil
}
bin, err := u.fetchAndVerifyPatch(old)
if err != nil {
switch err {
case ErrNoPatchAvailable:
log.Println("update: no patch available, falling back to full binary")
case ErrHashMismatch:
log.Println("update: hash mismatch from patched binary")
default:
log.Println("update: patching binary,", err)
}
bin, err = u.fetchAndVerifyFullBin()
if err != nil {
if err == ErrHashMismatch {
log.Println("update: hash mismatch from full binary")
} else {
log.Println("update: fetching full binary,", err)
}
return err
}
}
// close the old binary before installing because on windows
// it can't be renamed if a handle to the file is still open
old.Close()
err, errRecover := update.FromStream(bytes.NewBuffer(bin))
if errRecover != nil {
return fmt.Errorf("update and recovery errors: %q %q", err, errRecover)
}
if err != nil {
return err
}
log.Printf("Updated v%s -> v%s.", Version, u.info.Version)
return nil
}
// FromStream reads the contents of the supplied io.Reader newBinary
// and uses them to update the current program's executable file.
//
// FromStream performs the following actions to ensure a cross-platform safe
// update:
//
// - Creates a new file, /path/to/.program-name.new with mode 0755 and copies
// the contents of newBinary into the file
//
// - Renames the current program's executable file from /path/to/program-name
// to /path/to/.program-name.old
//
// - Renames /path/to/.program-name.new to /path/to/program-name
//
// - If the rename is successful, it erases /path/to/.program.old. If this operation
// fails, no error is reported.
//
// - If the rename is unsuccessful, it attempts to rename /path/to/.program-name.old
// back to /path/to/program-name. If this operation fails, the error is not reported
// in order to not mask the error that caused the rename recovery attempt.
func FromStream(newBinary io.Reader) (err error, errRecover error) {
// get the path to the executable
thisExecPath, err := osext.Executable()
if err != nil {
return
}
// get the directory the executable exists in
execDir := filepath.Dir(thisExecPath)
execName := filepath.Base(thisExecPath)
// Copy the contents of of newbinary to a the new executable file
newExecPath := filepath.Join(execDir, fmt.Sprintf(".%s.new", execName))
fp, err := os.OpenFile(newExecPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0755)
if err != nil {
return
}
defer fp.Close()
_, err = io.Copy(fp, newBinary)
// if we don't call fp.Close(), windows won't let us move the new executable
// because the file will still be "in use"
fp.Close()
// this is where we'll move the executable to so that we can swap in the updated replacement
oldExecPath := filepath.Join(execDir, fmt.Sprintf(".%s.old", execName))
// delete any existing old exec file - this is necessary on Windows for two reasons:
// 1. after a successful update, windows can't remove the .old file because the process is still running
// 2. windows rename operations fail if the destination file already exists
_ = os.Remove(oldExecPath)
// move the existing executable to a new file in the same directory
err = os.Rename(thisExecPath, oldExecPath)
if err != nil {
return
}
// move the new exectuable in to become the new program
err = os.Rename(newExecPath, thisExecPath)
if err != nil {
// copy unsuccessful
errRecover = os.Rename(oldExecPath, thisExecPath)
} else {
// copy successful, remove the old binary
_ = os.Remove(oldExecPath)
}
return
}
// SanityCheck() attempts to determine whether an in-place executable update could
// succeed by performing preliminary checks (to establish valid permissions, etc).
// This helps avoid downloading updates when we know the update can't be successfully
// applied later.
func SanityCheck() (err error) {
// get the path to the executable
thisExecPath, err := osext.Executable()
if err != nil {
return
}
// get the directory the executable exists in
execDir := filepath.Dir(thisExecPath)
execName := filepath.Base(thisExecPath)
// attempt to open a file in the executable's directory
newExecPath := filepath.Join(execDir, fmt.Sprintf(".%s.new", execName))
fp, err := os.OpenFile(newExecPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0755)
if err != nil {
return
}
fp.Close()
_ = os.Remove(newExecPath)
return
}
func (u *Updater) backgroundRun() {
os.MkdirAll(u.dir, 0777)
if u.wantUpdate() {
if err := update.SanityCheck(); err != nil {
// fail
return
}
self, err := osext.Executable()
if err != nil {
// fail update, couldn't figure out path to self
return
}
// TODO(bgentry): logger isn't on Windows. Replace w/ proper error reports.
l := exec.Command("logger", "-tflynn")
c := exec.Command(self, "update")
if w, err := l.StdinPipe(); err == nil && l.Start() == nil {
c.Stdout = w
c.Stderr = w
}
c.Start()
}
}