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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
import (
// Getpagesize returns the underlying system's memory page size.
func Getpagesize() int { return syscall.Getpagesize() }
// A FileInfo describes a file and is returned by Stat and Lstat.
type FileInfo interface {
Name() string // base name of the file
Size() int64 // length in bytes for regular files; system-dependent for others
Mode() FileMode // file mode bits
ModTime() time.Time // modification time
IsDir() bool // abbreviation for Mode().IsDir()
Sys() interface{} // underlying data source (can return nil)
// A FileMode represents a file's mode and permission bits.
// The bits have the same definition on all systems, so that
// information about files can be moved from one system
// to another portably. Not all bits apply to all systems.
// The only required bit is ModeDir for directories.
type FileMode uint32
// The defined file mode bits are the most significant bits of the FileMode.
// The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
// The values of these bits should be considered part of the public API and
// may be used in wire protocols or disk representations: they must not be
// changed, although new bits might be added.
const (
// The single letters are the abbreviations
// used by the String method's formatting.
ModeDir FileMode = 1 << (32 - 1 - iota) // d: is a directory
ModeAppend // a: append-only
ModeExclusive // l: exclusive use
ModeTemporary // T: temporary file (not backed up)
ModeSymlink // L: symbolic link
ModeDevice // D: device file
ModeNamedPipe // p: named pipe (FIFO)
ModeSocket // S: Unix domain socket
ModeSetuid // u: setuid
ModeSetgid // g: setgid
ModeCharDevice // c: Unix character device, when ModeDevice is set
ModeSticky // t: sticky
// Mask for the type bits. For regular files, none will be set.
ModeType = ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice
ModePerm FileMode = 0777 // permission bits
func (m FileMode) String() string {
const str = "dalTLDpSugct"
var buf [32]byte // Mode is uint32.
w := 0
for i, c := range str {
if m&(1<<uint(32-1-i)) != 0 {
buf[w] = byte(c)
if w == 0 {
buf[w] = '-'
const rwx = "rwxrwxrwx"
for i, c := range rwx {
if m&(1<<uint(9-1-i)) != 0 {
buf[w] = byte(c)
} else {
buf[w] = '-'
return string(buf[:w])
// IsDir reports whether m describes a directory.
// That is, it tests for the ModeDir bit being set in m.
func (m FileMode) IsDir() bool {
return m&ModeDir != 0
// IsRegular reports whether m describes a regular file.
// That is, it tests that no mode type bits are set.
func (m FileMode) IsRegular() bool {
return m&ModeType == 0
// Perm returns the Unix permission bits in m.
func (m FileMode) Perm() FileMode {
return m & ModePerm
func (fs *fileStat) Name() string { return }
func (fs *fileStat) IsDir() bool { return fs.Mode().IsDir() }
// SameFile reports whether fi1 and fi2 describe the same file.
// For example, on Unix this means that the device and inode fields
// of the two underlying structures are identical; on other systems
// the decision may be based on the path names.
// SameFile only applies to results returned by this package's Stat.
// It returns false in other cases.
func SameFile(fi1, fi2 FileInfo) bool {
fs1, ok1 := fi1.(*fileStat)
fs2, ok2 := fi2.(*fileStat)
if !ok1 || !ok2 {
return false
return sameFile(fs1, fs2)