236 lines
6.9 KiB
Go
236 lines
6.9 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.
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package os
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import (
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"runtime"
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"sync"
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"syscall"
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)
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// File represents an open file descriptor.
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type File struct {
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fd int
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name string
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dirinfo *dirInfo // nil unless directory being read
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nepipe int // number of consecutive EPIPE in Write
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l sync.Mutex // used to implement windows pread/pwrite
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}
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// Fd returns the integer Unix file descriptor referencing the open file.
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func (file *File) Fd() int { return file.fd }
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// Name returns the name of the file as presented to Open.
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func (file *File) Name() string { return file.name }
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// NewFile returns a new File with the given file descriptor and name.
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func NewFile(fd int, name string) *File {
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if fd < 0 {
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return nil
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}
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f := &File{fd: fd, name: name}
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runtime.SetFinalizer(f, (*File).Close)
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return f
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}
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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(syscall.Stdin, "/dev/stdin")
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Stdout = NewFile(syscall.Stdout, "/dev/stdout")
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Stderr = NewFile(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_ASYNC int = syscall.O_ASYNC // generate a signal when I/O is available.
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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_NOCTTY int = syscall.O_NOCTTY // do not make file the controlling tty.
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O_NONBLOCK int = syscall.O_NONBLOCK // open in non-blocking mode.
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O_NDELAY int = O_NONBLOCK // synonym for O_NONBLOCK
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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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type eofError int
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func (eofError) String() string { return "EOF" }
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// EOF is the Error returned by Read when no more input is available.
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// Functions should return EOF only to signal a graceful end of input.
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// If the EOF occurs unexpectedly in a structured data stream,
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// the appropriate error is either io.ErrUnexpectedEOF or some other error
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// giving more detail.
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var EOF Error = eofError(0)
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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 EOF.
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func (file *File) Read(b []byte) (n int, err Error) {
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if file == nil {
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return 0, EINVAL
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}
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n, e := file.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 && !iserror(e) {
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return 0, EOF
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}
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if iserror(e) {
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err = &PathError{"read", file.name, Errno(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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// EOF is signaled by a zero count with err set to EOF.
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// ReadAt always returns a non-nil Error when n != len(b).
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func (file *File) ReadAt(b []byte, off int64) (n int, err Error) {
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if file == nil {
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return 0, EINVAL
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}
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for len(b) > 0 {
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m, e := file.pread(b, off)
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if m == 0 && !iserror(e) {
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return n, EOF
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}
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if iserror(e) {
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err = &PathError{"read", file.name, Errno(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 (file *File) Write(b []byte) (n int, err Error) {
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if file == nil {
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return 0, EINVAL
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}
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n, e := file.write(b)
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if n < 0 {
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n = 0
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}
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epipecheck(file, e)
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if iserror(e) {
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err = &PathError{"write", file.name, Errno(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 (file *File) WriteAt(b []byte, off int64) (n int, err Error) {
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if file == nil {
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return 0, EINVAL
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}
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for len(b) > 0 {
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m, e := file.pwrite(b, off)
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if iserror(e) {
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err = &PathError{"write", file.name, Errno(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 (file *File) Seek(offset int64, whence int) (ret int64, err Error) {
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r, e := file.seek(offset, whence)
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if !iserror(e) && file.dirinfo != nil && r != 0 {
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e = syscall.EISDIR
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}
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if iserror(e) {
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return 0, &PathError{"seek", file.name, Errno(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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// an array of bytes.
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func (file *File) WriteString(s string) (ret int, err Error) {
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if file == nil {
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return 0, EINVAL
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}
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b := syscall.StringByteSlice(s)
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b = b[0 : len(b)-1]
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return file.Write(b)
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}
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// Mkdir creates a new directory with the specified name and permission bits.
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// It returns an error, if any.
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func Mkdir(name string, perm uint32) Error {
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e := syscall.Mkdir(name, perm)
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if iserror(e) {
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return &PathError{"mkdir", name, Errno(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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func Chdir(dir string) Error {
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if e := syscall.Chdir(dir); iserror(e) {
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return &PathError{"chdir", dir, Errno(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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func (f *File) Chdir() Error {
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if e := syscall.Fchdir(f.fd); iserror(e) {
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return &PathError{"chdir", f.name, Errno(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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// It returns the File and an Error, if any.
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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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// It returns the File and an Error, if any.
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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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