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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"
- "internal/unsafeheader"
- "io"
- "io/fs"
- "runtime"
- "syscall"
- "time"
- "unsafe"
- )
- // 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 and stores them in b.
- // 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 from b 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) {
- var b []byte
- hdr := (*unsafeheader.Slice)(unsafe.Pointer(&b))
- hdr.Data = (*unsafeheader.String)(unsafe.Pointer(&s)).Data
- hdr.Cap = len(s)
- hdr.Len = len(s)
- return f.Write(b)
- }
- // 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
- }
- func (dir dirFS) Stat(name string) (fs.FileInfo, error) {
- if !fs.ValidPath(name) || runtime.GOOS == "windows" && containsAny(name, `\:`) {
- return nil, &PathError{Op: "stat", Path: name, Err: ErrInvalid}
- }
- f, err := Stat(string(dir) + "/" + name)
- if err != nil {
- return nil, err
- }
- 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
- }
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