250 lines
7.1 KiB
Go
250 lines
7.1 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package os provides a platform-independent interface to operating system
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// functionality. The design is Unix-like, although the error handling is
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// Go-like; failing calls return values of type error rather than error numbers.
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// Often, more information is available within the error. For example,
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// if a call that takes a file name fails, such as Open or Stat, the error
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// will include the failing file name when printed and will be of type
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// *PathError, which may be unpacked for more information.
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//
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// The os interface is intended to be uniform across all operating systems.
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// Features not generally available appear in the system-specific package syscall.
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//
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// Here is a simple example, opening a file and reading some of it.
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//
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// file, err := os.Open("file.go") // For read access.
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// if err != nil {
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// log.Fatal(err)
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// }
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//
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// If the open fails, the error string will be self-explanatory, like
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//
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// open file.go: no such file or directory
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//
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// The file's data can then be read into a slice of bytes. Read and
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// Write take their byte counts from the length of the argument slice.
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//
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// data := make([]byte, 100)
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// count, err := file.Read(data)
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// if err != nil {
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// log.Fatal(err)
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// }
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// fmt.Printf("read %d bytes: %q\n", count, data[:count])
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//
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package os
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import (
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"io"
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"syscall"
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)
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// Name returns the name of the file as presented to Open.
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func (f *File) Name() string { return f.name }
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// Stdin, Stdout, and Stderr are open Files pointing to the standard input,
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// standard output, and standard error file descriptors.
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var (
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Stdin = NewFile(uintptr(syscall.Stdin), "/dev/stdin")
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Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout")
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Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr")
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)
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// Flags to Open wrapping those of the underlying system. Not all flags
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// may be implemented on a given system.
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const (
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O_RDONLY int = syscall.O_RDONLY // open the file read-only.
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O_WRONLY int = syscall.O_WRONLY // open the file write-only.
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O_RDWR int = syscall.O_RDWR // open the file read-write.
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O_APPEND int = syscall.O_APPEND // append data to the file when writing.
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O_CREATE int = syscall.O_CREAT // create a new file if none exists.
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O_EXCL int = syscall.O_EXCL // used with O_CREATE, file must not exist
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O_SYNC int = syscall.O_SYNC // open for synchronous I/O.
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O_TRUNC int = syscall.O_TRUNC // if possible, truncate file when opened.
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)
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// Seek whence values.
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const (
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SEEK_SET int = 0 // seek relative to the origin of the file
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SEEK_CUR int = 1 // seek relative to the current offset
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SEEK_END int = 2 // seek relative to the end
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)
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// LinkError records an error during a link or symlink or rename
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// system call and the paths that caused it.
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type LinkError struct {
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Op string
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Old string
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New string
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Err error
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}
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func (e *LinkError) Error() string {
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return e.Op + " " + e.Old + " " + e.New + ": " + e.Err.Error()
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}
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// Read reads up to len(b) bytes from the File.
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// It returns the number of bytes read and an error, if any.
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// EOF is signaled by a zero count with err set to io.EOF.
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func (f *File) Read(b []byte) (n int, err error) {
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if f == nil {
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return 0, ErrInvalid
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}
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n, e := f.read(b)
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if n < 0 {
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n = 0
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}
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if n == 0 && len(b) > 0 && e == nil {
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return 0, io.EOF
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}
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if e != nil {
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err = &PathError{"read", f.name, e}
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}
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return n, err
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}
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// ReadAt reads len(b) bytes from the File starting at byte offset off.
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// It returns the number of bytes read and the error, if any.
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// ReadAt always returns a non-nil error when n < len(b).
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// At end of file, that error is io.EOF.
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func (f *File) ReadAt(b []byte, off int64) (n int, err error) {
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if f == nil {
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return 0, ErrInvalid
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}
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for len(b) > 0 {
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m, e := f.pread(b, off)
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if m == 0 && e == nil {
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return n, io.EOF
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}
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if e != nil {
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err = &PathError{"read", f.name, e}
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break
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}
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n += m
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b = b[m:]
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off += int64(m)
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}
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return
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}
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// Write writes len(b) bytes to the File.
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// It returns the number of bytes written and an error, if any.
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// Write returns a non-nil error when n != len(b).
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func (f *File) Write(b []byte) (n int, err error) {
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if f == nil {
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return 0, ErrInvalid
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}
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n, e := f.write(b)
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if n < 0 {
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n = 0
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}
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epipecheck(f, e)
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if e != nil {
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err = &PathError{"write", f.name, e}
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}
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return n, err
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}
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// WriteAt writes len(b) bytes to the File starting at byte offset off.
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// It returns the number of bytes written and an error, if any.
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// WriteAt returns a non-nil error when n != len(b).
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func (f *File) WriteAt(b []byte, off int64) (n int, err error) {
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if f == nil {
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return 0, ErrInvalid
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}
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for len(b) > 0 {
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m, e := f.pwrite(b, off)
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if e != nil {
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err = &PathError{"write", f.name, e}
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break
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}
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n += m
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b = b[m:]
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off += int64(m)
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}
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return
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}
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// Seek sets the offset for the next Read or Write on file to offset, interpreted
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// according to whence: 0 means relative to the origin of the file, 1 means
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// relative to the current offset, and 2 means relative to the end.
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// It returns the new offset and an error, if any.
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func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
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if f == nil {
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return 0, ErrInvalid
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}
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r, e := f.seek(offset, whence)
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if e == nil && f.dirinfo != nil && r != 0 {
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e = syscall.EISDIR
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}
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if e != nil {
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return 0, &PathError{"seek", f.name, e}
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}
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return r, nil
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}
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// WriteString is like Write, but writes the contents of string s rather than
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// a slice of bytes.
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func (f *File) WriteString(s string) (ret int, err error) {
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if f == nil {
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return 0, ErrInvalid
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}
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return f.Write([]byte(s))
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}
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// Mkdir creates a new directory with the specified name and permission bits.
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// If there is an error, it will be of type *PathError.
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func Mkdir(name string, perm FileMode) error {
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e := syscall.Mkdir(name, syscallMode(perm))
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if e != nil {
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return &PathError{"mkdir", name, e}
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}
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return nil
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}
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// Chdir changes the current working directory to the named directory.
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// If there is an error, it will be of type *PathError.
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func Chdir(dir string) error {
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if e := syscall.Chdir(dir); e != nil {
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return &PathError{"chdir", dir, e}
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}
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return nil
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}
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// Chdir changes the current working directory to the file,
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// which must be a directory.
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// If there is an error, it will be of type *PathError.
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func (f *File) Chdir() error {
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if f == nil {
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return ErrInvalid
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}
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if e := syscall.Fchdir(f.fd); e != nil {
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return &PathError{"chdir", f.name, e}
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}
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return nil
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}
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// Open opens the named file for reading. If successful, methods on
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// the returned file can be used for reading; the associated file
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// descriptor has mode O_RDONLY.
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// If there is an error, it will be of type *PathError.
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func Open(name string) (file *File, err error) {
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return OpenFile(name, O_RDONLY, 0)
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}
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// Create creates the named file mode 0666 (before umask), truncating
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// it if it already exists. If successful, methods on the returned
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// File can be used for I/O; the associated file descriptor has mode
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// O_RDWR.
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// If there is an error, it will be of type *PathError.
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func Create(name string) (file *File, err error) {
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return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
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}
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// lstat is overridden in tests.
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var lstat = Lstat
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