Source file src/os/file_posix.go

Documentation: os

  // 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.
  
  // +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
  
  package os
  
  import (
  	"syscall"
  	"time"
  )
  
  func sigpipe() // implemented in package runtime
  
  // Readlink returns the destination of the named symbolic link.
  // If there is an error, it will be of type *PathError.
  func Readlink(name string) (string, error) {
  	for len := 128; ; len *= 2 {
  		b := make([]byte, len)
  		n, e := fixCount(syscall.Readlink(fixLongPath(name), b))
  		if e != nil {
  			return "", &PathError{"readlink", name, e}
  		}
  		if n < len {
  			return string(b[0:n]), nil
  		}
  	}
  }
  
  // syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
  func syscallMode(i FileMode) (o uint32) {
  	o |= uint32(i.Perm())
  	if i&ModeSetuid != 0 {
  		o |= syscall.S_ISUID
  	}
  	if i&ModeSetgid != 0 {
  		o |= syscall.S_ISGID
  	}
  	if i&ModeSticky != 0 {
  		o |= syscall.S_ISVTX
  	}
  	// No mapping for Go's ModeTemporary (plan9 only).
  	return
  }
  
  // See docs in file.go:Chmod.
  func chmod(name string, mode FileMode) error {
  	if e := syscall.Chmod(fixLongPath(name), syscallMode(mode)); e != nil {
  		return &PathError{"chmod", name, e}
  	}
  	return nil
  }
  
  // See docs in file.go:(*File).Chmod.
  func (f *File) chmod(mode FileMode) error {
  	if err := f.checkValid("chmod"); err != nil {
  		return err
  	}
  	if e := f.pfd.Fchmod(syscallMode(mode)); e != nil {
  		return f.wrapErr("chmod", e)
  	}
  	return nil
  }
  
  // Chown changes the numeric uid and gid of the named file.
  // If the file is a symbolic link, it changes the uid and gid of the link's target.
  // If there is an error, it will be of type *PathError.
  //
  // On Windows, it always returns the syscall.EWINDOWS error, wrapped
  // in *PathError.
  func Chown(name string, uid, gid int) error {
  	if e := syscall.Chown(name, uid, gid); e != nil {
  		return &PathError{"chown", name, e}
  	}
  	return nil
  }
  
  // Lchown changes the numeric uid and gid of the named file.
  // If the file is a symbolic link, it changes the uid and gid of the link itself.
  // If there is an error, it will be of type *PathError.
  //
  // On Windows, it always returns the syscall.EWINDOWS error, wrapped
  // in *PathError.
  func Lchown(name string, uid, gid int) error {
  	if e := syscall.Lchown(name, uid, gid); e != nil {
  		return &PathError{"lchown", name, e}
  	}
  	return nil
  }
  
  // Chown changes the numeric uid and gid of the named file.
  // If there is an error, it will be of type *PathError.
  //
  // On Windows, it always returns the syscall.EWINDOWS error, wrapped
  // in *PathError.
  func (f *File) Chown(uid, gid int) error {
  	if err := f.checkValid("chown"); err != nil {
  		return err
  	}
  	if e := f.pfd.Fchown(uid, gid); e != nil {
  		return f.wrapErr("chown", e)
  	}
  	return nil
  }
  
  // Truncate changes the size of the file.
  // It does not change the I/O offset.
  // If there is an error, it will be of type *PathError.
  func (f *File) Truncate(size int64) error {
  	if err := f.checkValid("truncate"); err != nil {
  		return err
  	}
  	if e := f.pfd.Ftruncate(size); e != nil {
  		return f.wrapErr("truncate", e)
  	}
  	return nil
  }
  
  // Sync commits the current contents of the file to stable storage.
  // Typically, this means flushing the file system's in-memory copy
  // of recently written data to disk.
  func (f *File) Sync() error {
  	if err := f.checkValid("sync"); err != nil {
  		return err
  	}
  	if e := f.pfd.Fsync(); e != nil {
  		return f.wrapErr("sync", e)
  	}
  	return nil
  }
  
  // Chtimes changes the access and modification times of the named
  // file, similar to the Unix utime() or utimes() functions.
  //
  // The underlying filesystem may truncate or round the values to a
  // less precise time unit.
  // If there is an error, it will be of type *PathError.
  func Chtimes(name string, atime time.Time, mtime time.Time) error {
  	var utimes [2]syscall.Timespec
  	utimes[0] = syscall.NsecToTimespec(atime.UnixNano())
  	utimes[1] = syscall.NsecToTimespec(mtime.UnixNano())
  	if e := syscall.UtimesNano(fixLongPath(name), utimes[0:]); e != nil {
  		return &PathError{"chtimes", name, e}
  	}
  	return nil
  }
  
  // Chdir changes the current working directory to the file,
  // which must be a directory.
  // If there is an error, it will be of type *PathError.
  func (f *File) Chdir() error {
  	if err := f.checkValid("chdir"); err != nil {
  		return err
  	}
  	if e := f.pfd.Fchdir(); e != nil {
  		return f.wrapErr("chdir", e)
  	}
  	return nil
  }
  
  // checkValid checks whether f is valid for use.
  // If not, it returns an appropriate error, perhaps incorporating the operation name op.
  func (f *File) checkValid(op string) error {
  	if f == nil {
  		return ErrInvalid
  	}
  	return nil
  }
  

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