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Set permission on atomic file write

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Perform chmod before rename with the atomic file writer.
Ensure writeErr is set on short write and file is removed on write error.

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)
This commit is contained in:
Derek McGowan 2016-06-29 13:09:13 -07:00
parent 754ae20ec5
commit 003449018b
2 changed files with 19 additions and 4 deletions
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13
ioutils/fswriters.go
View file

@ -15,13 +15,15 @@ func NewAtomicFileWriter(filename string, perm os.FileMode) (io.WriteCloser, err
if err != nil {
return nil, err
}
abspath, err := filepath.Abs(filename)
if err != nil {
return nil, err
}
return &atomicFileWriter{
f: f,
fn: abspath,
f: f,
fn: abspath,
perm: perm,
}, nil
}
@ -34,6 +36,7 @@ func AtomicWriteFile(filename string, data []byte, perm os.FileMode) error {
n, err := f.Write(data)
if err == nil && n < len(data) {
err = io.ErrShortWrite
f.(*atomicFileWriter).writeErr = err
}
if err1 := f.Close(); err == nil {
err = err1
@ -45,6 +48,7 @@ type atomicFileWriter struct {
f *os.File
fn string
writeErr error
perm os.FileMode
}
func (w *atomicFileWriter) Write(dt []byte) (int, error) {
@ -57,7 +61,7 @@ func (w *atomicFileWriter) Write(dt []byte) (int, error) {
func (w *atomicFileWriter) Close() (retErr error) {
defer func() {
if retErr != nil {
if retErr != nil || w.writeErr != nil {
os.Remove(w.f.Name())
}
}()
@ -68,6 +72,9 @@ func (w *atomicFileWriter) Close() (retErr error) {
if err := w.f.Close(); err != nil {
return err
}
if err := os.Chmod(w.f.Name(), w.perm); err != nil {
return err
}
if w.writeErr == nil {
return os.Rename(w.f.Name(), w.fn)
}

10
ioutils/fswriters_test.go
View file

@ -16,7 +16,7 @@ func TestAtomicWriteToFile(t *testing.T) {
defer os.RemoveAll(tmpDir)
expected := []byte("barbaz")
if err := AtomicWriteFile(filepath.Join(tmpDir, "foo"), expected, 0600); err != nil {
if err := AtomicWriteFile(filepath.Join(tmpDir, "foo"), expected, 0666); err != nil {
t.Fatalf("Error writing to file: %v", err)
}
@ -28,4 +28,12 @@ func TestAtomicWriteToFile(t *testing.T) {
if bytes.Compare(actual, expected) != 0 {
t.Fatalf("Data mismatch, expected %q, got %q", expected, actual)
}
st, err := os.Stat(filepath.Join(tmpDir, "foo"))
if err != nil {
t.Fatalf("Error statting file: %v", err)
}
if expected := os.FileMode(0666); st.Mode() != expected {
t.Fatalf("Mode mismatched, expected %o, got %o", expected, st.Mode())
}
}