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+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package os provides a platform-independent interface to operating system
+// functionality. The design is Unix-like, although the error handling is
+// Go-like; failing calls return values of type error rather than error numbers.
+// Often, more information is available within the error. For example,
+// if a call that takes a file name fails, such as Open or Stat, the error
+// will include the failing file name when printed and will be of type
+// *PathError, which may be unpacked for more information.
+//
+// The os interface is intended to be uniform across all operating systems.
+// Features not generally available appear in the system-specific package syscall.
+//
+// Here is a simple example, opening a file and reading some of it.
+//
+// file, err := os.Open("file.go") // For read access.
+// if err != nil {
+// log.Fatal(err)
+// }
+//
+// If the open fails, the error string will be self-explanatory, like
+//
+// open file.go: no such file or directory
+//
+// The file's data can then be read into a slice of bytes. Read and
+// Write take their byte counts from the length of the argument slice.
+//
+// data := make([]byte, 100)
+// count, err := file.Read(data)
+// if err != nil {
+// log.Fatal(err)
+// }
+// fmt.Printf("read %d bytes: %q\n", count, data[:count])
+//
+// Note: The maximum number of concurrent operations on a File may be limited by
+// the OS or the system. The number should be high, but exceeding it may degrade
+// performance or cause other issues.
+//
+package os
+
+import (
+ "errors"
+ "internal/poll"
+ "internal/testlog"
+ "io"
+ "io/fs"
+ "runtime"
+ "syscall"
+ "time"
+)
+
+// Name returns the name of the file as presented to Open.
+func (f *File) Name() string { return f.name }
+
+// Stdin, Stdout, and Stderr are open Files pointing to the standard input,
+// standard output, and standard error file descriptors.
+//
+// Note that the Go runtime writes to standard error for panics and crashes;
+// closing Stderr may cause those messages to go elsewhere, perhaps
+// to a file opened later.
+var (
+ Stdin = NewFile(uintptr(syscall.Stdin), "/dev/stdin")
+ Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")
+ Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr")
+)
+
+// Flags to OpenFile wrapping those of the underlying system. Not all
+// flags may be implemented on a given system.
+const (
+ // Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified.
+ O_RDONLY int = syscall.O_RDONLY // open the file read-only.
+ O_WRONLY int = syscall.O_WRONLY // open the file write-only.
+ O_RDWR int = syscall.O_RDWR // open the file read-write.
+ // The remaining values may be or'ed in to control behavior.
+ O_APPEND int = syscall.O_APPEND // append data to the file when writing.
+ O_CREATE int = syscall.O_CREAT // create a new file if none exists.
+ O_EXCL int = syscall.O_EXCL // used with O_CREATE, file must not exist.
+ O_SYNC int = syscall.O_SYNC // open for synchronous I/O.
+ O_TRUNC int = syscall.O_TRUNC // truncate regular writable file when opened.
+)
+
+// Seek whence values.
+//
+// Deprecated: Use io.SeekStart, io.SeekCurrent, and io.SeekEnd.
+const (
+ SEEK_SET int = 0 // seek relative to the origin of the file
+ SEEK_CUR int = 1 // seek relative to the current offset
+ SEEK_END int = 2 // seek relative to the end
+)
+
+// LinkError records an error during a link or symlink or rename
+// system call and the paths that caused it.
+type LinkError struct {
+ Op string
+ Old string
+ New string
+ Err error
+}
+
+func (e *LinkError) Error() string {
+ return e.Op + " " + e.Old + " " + e.New + ": " + e.Err.Error()
+}
+
+func (e *LinkError) Unwrap() error {
+ return e.Err
+}
+
+// Read reads up to len(b) bytes from the File.
+// It returns the number of bytes read and any error encountered.
+// At end of file, Read returns 0, io.EOF.
+func (f *File) Read(b []byte) (n int, err error) {
+ if err := f.checkValid("read"); err != nil {
+ return 0, err
+ }
+ n, e := f.read(b)
+ return n, f.wrapErr("read", e)
+}
+
+// ReadAt reads len(b) bytes from the File starting at byte offset off.
+// It returns the number of bytes read and the error, if any.
+// ReadAt always returns a non-nil error when n < len(b).
+// At end of file, that error is io.EOF.
+func (f *File) ReadAt(b []byte, off int64) (n int, err error) {
+ if err := f.checkValid("read"); err != nil {
+ return 0, err
+ }
+
+ if off < 0 {
+ return 0, &PathError{Op: "readat", Path: f.name, Err: errors.New("negative offset")}
+ }
+
+ for len(b) > 0 {
+ m, e := f.pread(b, off)
+ if e != nil {
+ err = f.wrapErr("read", e)
+ break
+ }
+ n += m
+ b = b[m:]
+ off += int64(m)
+ }
+ return
+}
+
+// ReadFrom implements io.ReaderFrom.
+func (f *File) ReadFrom(r io.Reader) (n int64, err error) {
+ if err := f.checkValid("write"); err != nil {
+ return 0, err
+ }
+ n, handled, e := f.readFrom(r)
+ if !handled {
+ return genericReadFrom(f, r) // without wrapping
+ }
+ return n, f.wrapErr("write", e)
+}
+
+func genericReadFrom(f *File, r io.Reader) (int64, error) {
+ return io.Copy(onlyWriter{f}, r)
+}
+
+type onlyWriter struct {
+ io.Writer
+}
+
+// Write writes len(b) bytes to the File.
+// It returns the number of bytes written and an error, if any.
+// Write returns a non-nil error when n != len(b).
+func (f *File) Write(b []byte) (n int, err error) {
+ if err := f.checkValid("write"); err != nil {
+ return 0, err
+ }
+ n, e := f.write(b)
+ if n < 0 {
+ n = 0
+ }
+ if n != len(b) {
+ err = io.ErrShortWrite
+ }
+
+ epipecheck(f, e)
+
+ if e != nil {
+ err = f.wrapErr("write", e)
+ }
+
+ return n, err
+}
+
+var errWriteAtInAppendMode = errors.New("os: invalid use of WriteAt on file opened with O_APPEND")
+
+// WriteAt writes len(b) bytes to the File starting at byte offset off.
+// It returns the number of bytes written and an error, if any.
+// WriteAt returns a non-nil error when n != len(b).
+//
+// If file was opened with the O_APPEND flag, WriteAt returns an error.
+func (f *File) WriteAt(b []byte, off int64) (n int, err error) {
+ if err := f.checkValid("write"); err != nil {
+ return 0, err
+ }
+ if f.appendMode {
+ return 0, errWriteAtInAppendMode
+ }
+
+ if off < 0 {
+ return 0, &PathError{Op: "writeat", Path: f.name, Err: errors.New("negative offset")}
+ }
+
+ for len(b) > 0 {
+ m, e := f.pwrite(b, off)
+ if e != nil {
+ err = f.wrapErr("write", e)
+ break
+ }
+ n += m
+ b = b[m:]
+ off += int64(m)
+ }
+ return
+}
+
+// Seek sets the offset for the next Read or Write on file to offset, interpreted
+// according to whence: 0 means relative to the origin of the file, 1 means
+// relative to the current offset, and 2 means relative to the end.
+// It returns the new offset and an error, if any.
+// The behavior of Seek on a file opened with O_APPEND is not specified.
+//
+// If f is a directory, the behavior of Seek varies by operating
+// system; you can seek to the beginning of the directory on Unix-like
+// operating systems, but not on Windows.
+func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
+ if err := f.checkValid("seek"); err != nil {
+ return 0, err
+ }
+ r, e := f.seek(offset, whence)
+ if e == nil && f.dirinfo != nil && r != 0 {
+ e = syscall.EISDIR
+ }
+ if e != nil {
+ return 0, f.wrapErr("seek", e)
+ }
+ return r, nil
+}
+
+// WriteString is like Write, but writes the contents of string s rather than
+// a slice of bytes.
+func (f *File) WriteString(s string) (n int, err error) {
+ return f.Write([]byte(s))
+}
+
+// Mkdir creates a new directory with the specified name and permission
+// bits (before umask).
+// If there is an error, it will be of type *PathError.
+func Mkdir(name string, perm FileMode) error {
+ if runtime.GOOS == "windows" && isWindowsNulName(name) {
+ return &PathError{Op: "mkdir", Path: name, Err: syscall.ENOTDIR}
+ }
+ longName := fixLongPath(name)
+ e := ignoringEINTR(func() error {
+ return syscall.Mkdir(longName, syscallMode(perm))
+ })
+
+ if e != nil {
+ return &PathError{Op: "mkdir", Path: name, Err: e}
+ }
+
+ // mkdir(2) itself won't handle the sticky bit on *BSD and Solaris
+ if !supportsCreateWithStickyBit && perm&ModeSticky != 0 {
+ e = setStickyBit(name)
+
+ if e != nil {
+ Remove(name)
+ return e
+ }
+ }
+
+ return nil
+}
+
+// setStickyBit adds ModeSticky to the permission bits of path, non atomic.
+func setStickyBit(name string) error {
+ fi, err := Stat(name)
+ if err != nil {
+ return err
+ }
+ return Chmod(name, fi.Mode()|ModeSticky)
+}
+
+// Chdir changes the current working directory to the named directory.
+// If there is an error, it will be of type *PathError.
+func Chdir(dir string) error {
+ if e := syscall.Chdir(dir); e != nil {
+ testlog.Open(dir) // observe likely non-existent directory
+ return &PathError{Op: "chdir", Path: dir, Err: e}
+ }
+ if log := testlog.Logger(); log != nil {
+ wd, err := Getwd()
+ if err == nil {
+ log.Chdir(wd)
+ }
+ }
+ return nil
+}
+
+// Open opens the named file for reading. If successful, methods on
+// the returned file can be used for reading; the associated file
+// descriptor has mode O_RDONLY.
+// If there is an error, it will be of type *PathError.
+func Open(name string) (*File, error) {
+ return OpenFile(name, O_RDONLY, 0)
+}
+
+// Create creates or truncates the named file. If the file already exists,
+// it is truncated. If the file does not exist, it is created with mode 0666
+// (before umask). If successful, methods on the returned File can
+// be used for I/O; the associated file descriptor has mode O_RDWR.
+// If there is an error, it will be of type *PathError.
+func Create(name string) (*File, error) {
+ return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
+}
+
+// OpenFile is the generalized open call; most users will use Open
+// or Create instead. It opens the named file with specified flag
+// (O_RDONLY etc.). If the file does not exist, and the O_CREATE flag
+// is passed, it is created with mode perm (before umask). If successful,
+// methods on the returned File can be used for I/O.
+// If there is an error, it will be of type *PathError.
+func OpenFile(name string, flag int, perm FileMode) (*File, error) {
+ testlog.Open(name)
+ f, err := openFileNolog(name, flag, perm)
+ if err != nil {
+ return nil, err
+ }
+ f.appendMode = flag&O_APPEND != 0
+
+ return f, nil
+}
+
+// lstat is overridden in tests.
+var lstat = Lstat
+
+// Rename renames (moves) oldpath to newpath.
+// If newpath already exists and is not a directory, Rename replaces it.
+// OS-specific restrictions may apply when oldpath and newpath are in different directories.
+// If there is an error, it will be of type *LinkError.
+func Rename(oldpath, newpath string) error {
+ return rename(oldpath, newpath)
+}
+
+// Many functions in package syscall return a count of -1 instead of 0.
+// Using fixCount(call()) instead of call() corrects the count.
+func fixCount(n int, err error) (int, error) {
+ if n < 0 {
+ n = 0
+ }
+ return n, err
+}
+
+// wrapErr wraps an error that occurred during an operation on an open file.
+// It passes io.EOF through unchanged, otherwise converts
+// poll.ErrFileClosing to ErrClosed and wraps the error in a PathError.
+func (f *File) wrapErr(op string, err error) error {
+ if err == nil || err == io.EOF {
+ return err
+ }
+ if err == poll.ErrFileClosing {
+ err = ErrClosed
+ }
+ return &PathError{Op: op, Path: f.name, Err: err}
+}
+
+// TempDir returns the default directory to use for temporary files.
+//
+// On Unix systems, it returns $TMPDIR if non-empty, else /tmp.
+// On Windows, it uses GetTempPath, returning the first non-empty
+// value from %TMP%, %TEMP%, %USERPROFILE%, or the Windows directory.
+// On Plan 9, it returns /tmp.
+//
+// The directory is neither guaranteed to exist nor have accessible
+// permissions.
+func TempDir() string {
+ return tempDir()
+}
+
+// UserCacheDir returns the default root directory to use for user-specific
+// cached data. Users should create their own application-specific subdirectory
+// within this one and use that.
+//
+// On Unix systems, it returns $XDG_CACHE_HOME as specified by
+// https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if
+// non-empty, else $HOME/.cache.
+// On Darwin, it returns $HOME/Library/Caches.
+// On Windows, it returns %LocalAppData%.
+// On Plan 9, it returns $home/lib/cache.
+//
+// If the location cannot be determined (for example, $HOME is not defined),
+// then it will return an error.
+func UserCacheDir() (string, error) {
+ var dir string
+
+ switch runtime.GOOS {
+ case "windows":
+ dir = Getenv("LocalAppData")
+ if dir == "" {
+ return "", errors.New("%LocalAppData% is not defined")
+ }
+
+ case "darwin", "ios":
+ dir = Getenv("HOME")
+ if dir == "" {
+ return "", errors.New("$HOME is not defined")
+ }
+ dir += "/Library/Caches"
+
+ case "plan9":
+ dir = Getenv("home")
+ if dir == "" {
+ return "", errors.New("$home is not defined")
+ }
+ dir += "/lib/cache"
+
+ default: // Unix
+ dir = Getenv("XDG_CACHE_HOME")
+ if dir == "" {
+ dir = Getenv("HOME")
+ if dir == "" {
+ return "", errors.New("neither $XDG_CACHE_HOME nor $HOME are defined")
+ }
+ dir += "/.cache"
+ }
+ }
+
+ return dir, nil
+}
+
+// UserConfigDir returns the default root directory to use for user-specific
+// configuration data. Users should create their own application-specific
+// subdirectory within this one and use that.
+//
+// On Unix systems, it returns $XDG_CONFIG_HOME as specified by
+// https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if
+// non-empty, else $HOME/.config.
+// On Darwin, it returns $HOME/Library/Application Support.
+// On Windows, it returns %AppData%.
+// On Plan 9, it returns $home/lib.
+//
+// If the location cannot be determined (for example, $HOME is not defined),
+// then it will return an error.
+func UserConfigDir() (string, error) {
+ var dir string
+
+ switch runtime.GOOS {
+ case "windows":
+ dir = Getenv("AppData")
+ if dir == "" {
+ return "", errors.New("%AppData% is not defined")
+ }
+
+ case "darwin", "ios":
+ dir = Getenv("HOME")
+ if dir == "" {
+ return "", errors.New("$HOME is not defined")
+ }
+ dir += "/Library/Application Support"
+
+ case "plan9":
+ dir = Getenv("home")
+ if dir == "" {
+ return "", errors.New("$home is not defined")
+ }
+ dir += "/lib"
+
+ default: // Unix
+ dir = Getenv("XDG_CONFIG_HOME")
+ if dir == "" {
+ dir = Getenv("HOME")
+ if dir == "" {
+ return "", errors.New("neither $XDG_CONFIG_HOME nor $HOME are defined")
+ }
+ dir += "/.config"
+ }
+ }
+
+ return dir, nil
+}
+
+// UserHomeDir returns the current user's home directory.
+//
+// On Unix, including macOS, it returns the $HOME environment variable.
+// On Windows, it returns %USERPROFILE%.
+// On Plan 9, it returns the $home environment variable.
+func UserHomeDir() (string, error) {
+ env, enverr := "HOME", "$HOME"
+ switch runtime.GOOS {
+ case "windows":
+ env, enverr = "USERPROFILE", "%userprofile%"
+ case "plan9":
+ env, enverr = "home", "$home"
+ }
+ if v := Getenv(env); v != "" {
+ return v, nil
+ }
+ // On some geese the home directory is not always defined.
+ switch runtime.GOOS {
+ case "android":
+ return "/sdcard", nil
+ case "ios":
+ return "/", nil
+ }
+ return "", errors.New(enverr + " is not defined")
+}
+
+// Chmod changes the mode of the named file to mode.
+// If the file is a symbolic link, it changes the mode of the link's target.
+// If there is an error, it will be of type *PathError.
+//
+// A different subset of the mode bits are used, depending on the
+// operating system.
+//
+// On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and
+// ModeSticky are used.
+//
+// On Windows, only the 0200 bit (owner writable) of mode is used; it
+// controls whether the file's read-only attribute is set or cleared.
+// The other bits are currently unused. For compatibility with Go 1.12
+// and earlier, use a non-zero mode. Use mode 0400 for a read-only
+// file and 0600 for a readable+writable file.
+//
+// On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive,
+// and ModeTemporary are used.
+func Chmod(name string, mode FileMode) error { return chmod(name, mode) }
+
+// Chmod changes the mode of the file to mode.
+// If there is an error, it will be of type *PathError.
+func (f *File) Chmod(mode FileMode) error { return f.chmod(mode) }
+
+// SetDeadline sets the read and write deadlines for a File.
+// It is equivalent to calling both SetReadDeadline and SetWriteDeadline.
+//
+// Only some kinds of files support setting a deadline. Calls to SetDeadline
+// for files that do not support deadlines will return ErrNoDeadline.
+// On most systems ordinary files do not support deadlines, but pipes do.
+//
+// A deadline is an absolute time after which I/O operations fail with an
+// error instead of blocking. The deadline applies to all future and pending
+// I/O, not just the immediately following call to Read or Write.
+// After a deadline has been exceeded, the connection can be refreshed
+// by setting a deadline in the future.
+//
+// If the deadline is exceeded a call to Read or Write or to other I/O
+// methods will return an error that wraps ErrDeadlineExceeded.
+// This can be tested using errors.Is(err, os.ErrDeadlineExceeded).
+// That error implements the Timeout method, and calling the Timeout
+// method will return true, but there are other possible errors for which
+// the Timeout will return true even if the deadline has not been exceeded.
+//
+// An idle timeout can be implemented by repeatedly extending
+// the deadline after successful Read or Write calls.
+//
+// A zero value for t means I/O operations will not time out.
+func (f *File) SetDeadline(t time.Time) error {
+ return f.setDeadline(t)
+}
+
+// SetReadDeadline sets the deadline for future Read calls and any
+// currently-blocked Read call.
+// A zero value for t means Read will not time out.
+// Not all files support setting deadlines; see SetDeadline.
+func (f *File) SetReadDeadline(t time.Time) error {
+ return f.setReadDeadline(t)
+}
+
+// SetWriteDeadline sets the deadline for any future Write calls and any
+// currently-blocked Write call.
+// Even if Write times out, it may return n > 0, indicating that
+// some of the data was successfully written.
+// A zero value for t means Write will not time out.
+// Not all files support setting deadlines; see SetDeadline.
+func (f *File) SetWriteDeadline(t time.Time) error {
+ return f.setWriteDeadline(t)
+}
+
+// SyscallConn returns a raw file.
+// This implements the syscall.Conn interface.
+func (f *File) SyscallConn() (syscall.RawConn, error) {
+ if err := f.checkValid("SyscallConn"); err != nil {
+ return nil, err
+ }
+ return newRawConn(f)
+}
+
+// isWindowsNulName reports whether name is os.DevNull ('NUL') on Windows.
+// True is returned if name is 'NUL' whatever the case.
+func isWindowsNulName(name string) bool {
+ if len(name) != 3 {
+ return false
+ }
+ if name[0] != 'n' && name[0] != 'N' {
+ return false
+ }
+ if name[1] != 'u' && name[1] != 'U' {
+ return false
+ }
+ if name[2] != 'l' && name[2] != 'L' {
+ return false
+ }
+ return true
+}
+
+// DirFS returns a file system (an fs.FS) for the tree of files rooted at the directory dir.
+//
+// Note that DirFS("/prefix") only guarantees that the Open calls it makes to the
+// operating system will begin with "/prefix": DirFS("/prefix").Open("file") is the
+// same as os.Open("/prefix/file"). So if /prefix/file is a symbolic link pointing outside
+// the /prefix tree, then using DirFS does not stop the access any more than using
+// os.Open does. DirFS is therefore not a general substitute for a chroot-style security
+// mechanism when the directory tree contains arbitrary content.
+func DirFS(dir string) fs.FS {
+ return dirFS(dir)
+}
+
+func containsAny(s, chars string) bool {
+ for i := 0; i < len(s); i++ {
+ for j := 0; j < len(chars); j++ {
+ if s[i] == chars[j] {
+ return true
+ }
+ }
+ }
+ return false
+}
+
+type dirFS string
+
+func (dir dirFS) Open(name string) (fs.File, error) {
+ if !fs.ValidPath(name) || runtime.GOOS == "windows" && containsAny(name, `\:`) {
+ return nil, &PathError{Op: "open", Path: name, Err: ErrInvalid}
+ }
+ f, err := Open(string(dir) + "/" + name)
+ if err != nil {
+ return nil, err // nil fs.File
+ }
+ return f, nil
+}
+
+// ReadFile reads the named file and returns the contents.
+// A successful call returns err == nil, not err == EOF.
+// Because ReadFile reads the whole file, it does not treat an EOF from Read
+// as an error to be reported.
+func ReadFile(name string) ([]byte, error) {
+ f, err := Open(name)
+ if err != nil {
+ return nil, err
+ }
+ defer f.Close()
+
+ var size int
+ if info, err := f.Stat(); err == nil {
+ size64 := info.Size()
+ if int64(int(size64)) == size64 {
+ size = int(size64)
+ }
+ }
+ size++ // one byte for final read at EOF
+
+ // If a file claims a small size, read at least 512 bytes.
+ // In particular, files in Linux's /proc claim size 0 but
+ // then do not work right if read in small pieces,
+ // so an initial read of 1 byte would not work correctly.
+ if size < 512 {
+ size = 512
+ }
+
+ data := make([]byte, 0, size)
+ for {
+ if len(data) >= cap(data) {
+ d := append(data[:cap(data)], 0)
+ data = d[:len(data)]
+ }
+ n, err := f.Read(data[len(data):cap(data)])
+ data = data[:len(data)+n]
+ if err != nil {
+ if err == io.EOF {
+ err = nil
+ }
+ return data, err
+ }
+ }
+}
+
+// WriteFile writes data to the named file, creating it if necessary.
+// If the file does not exist, WriteFile creates it with permissions perm (before umask);
+// otherwise WriteFile truncates it before writing, without changing permissions.
+func WriteFile(name string, data []byte, perm FileMode) error {
+ f, err := OpenFile(name, O_WRONLY|O_CREATE|O_TRUNC, perm)
+ if err != nil {
+ return err
+ }
+ _, err = f.Write(data)
+ if err1 := f.Close(); err1 != nil && err == nil {
+ err = err1
+ }
+ return err
+}