os: some examples use functions obviated by errors.Is #77643
Description
In the os package, there are two examples that use functions "not recommended" anymore.
The new recommendations were added in Commit: b641f0d in response to issue #41122
The fix is already indicated in each function, so the actual update should be pretty straightforward.
Functions that indicate new usage.
func IsExist(err error) bool
// IsExist returns a boolean indicating whether its argument is known to report
// that a file or directory already exists. It is satisfied by [ErrExist] as
// well as some syscall errors.
//
// This function predates [errors.Is]. It only supports errors returned by
// the os package. New code should use errors.Is(err, fs.ErrExist).
func ExampleMkdir() {
err := os.Mkdir("testdir", 0750)
if err != nil && !os.IsExist(err) {
log.Fatal(err)
}
err = os.WriteFile("testdir/testfile.txt", []byte("Hello, Gophers!"), 0660)
if err != nil {
log.Fatal(err)
}
}func IsNotExist(err error) bool
// IsNotExist returns a boolean indicating whether its argument is known to
// report that a file or directory does not exist. It is satisfied by
// [ErrNotExist] as well as some syscall errors.
//
// This function predates [errors.Is]. It only supports errors returned by
// the os package. New code should use errors.Is(err, fs.ErrNotExist).
func ExampleUserConfigDir() {
dir, dirErr := os.UserConfigDir()
var (
configPath string
origConfig []byte
)
if dirErr == nil {
configPath = filepath.Join(dir, "ExampleUserConfigDir", "example.conf")
var err error
origConfig, err = os.ReadFile(configPath)
if err != nil && !os.IsNotExist(err) {
// The user has a config file but we couldn't read it.
// Report the error instead of ignoring their configuration.
log.Fatal(err)
}
}
// Use and perhaps make changes to the config.
config := bytes.Clone(origConfig)
// …
// Save changes.
if !bytes.Equal(config, origConfig) {
if configPath == "" {
log.Printf("not saving config changes: %v", dirErr)
} else {
err := os.MkdirAll(filepath.Dir(configPath), 0700)
if err == nil {
err = os.WriteFile(configPath, config, 0600)
}
if err != nil {
log.Printf("error saving config changes: %v", err)
}
}
}
// Output:
}No other examples were found using the functions in the os package or any other in the standard library.
I am up to making a PR for this if there is consensus that it should be updated.