319 lines
9.8 KiB
Go
319 lines
9.8 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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"errors"
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"internal/poll"
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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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//
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// Note that the Go runtime writes to standard error for panics and crashes;
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// closing Stderr may cause those messages to go elsewhere, perhaps
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// to a file opened later.
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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 OpenFile wrapping those of the underlying system. Not all
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// flags 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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//
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// Deprecated: Use io.SeekStart, io.SeekCurrent, and io.SeekEnd.
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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 any error encountered.
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// At end of file, Read returns 0, io.EOF.
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func (f *File) Read(b []byte) (n int, err error) {
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if err := f.checkValid("read"); err != nil {
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return 0, err
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}
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n, e := f.read(b)
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return n, f.wrapErr("read", e)
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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 err := f.checkValid("read"); err != nil {
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return 0, err
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}
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if off < 0 {
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return 0, &PathError{"readat", f.name, errors.New("negative offset")}
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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 e != nil {
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err = f.wrapErr("read", 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 err := f.checkValid("write"); err != nil {
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return 0, err
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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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if n != len(b) {
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err = io.ErrShortWrite
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}
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epipecheck(f, e)
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if e != nil {
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err = f.wrapErr("write", 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 err := f.checkValid("write"); err != nil {
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return 0, err
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}
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if off < 0 {
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return 0, &PathError{"writeat", f.name, errors.New("negative offset")}
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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 = f.wrapErr("write", 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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// The behavior of Seek on a file opened with O_APPEND is not specified.
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func (f *File) Seek(offset int64, whence int) (ret int64, err error) {
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if err := f.checkValid("seek"); err != nil {
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return 0, err
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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, f.wrapErr("seek", 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) (n int, err error) {
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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(fixLongPath(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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// mkdir(2) itself won't handle the sticky bit on *BSD and Solaris
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if !supportsCreateWithStickyBit && perm&ModeSticky != 0 {
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Chmod(name, perm)
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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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// 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, error) {
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return OpenFile(name, O_RDONLY, 0)
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}
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// Create creates the named file with 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, 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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// Rename renames (moves) oldpath to newpath.
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// If newpath already exists and is not a directory, Rename replaces it.
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// OS-specific restrictions may apply when oldpath and newpath are in different directories.
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// If there is an error, it will be of type *LinkError.
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func Rename(oldpath, newpath string) error {
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return rename(oldpath, newpath)
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}
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// Many functions in package syscall return a count of -1 instead of 0.
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// Using fixCount(call()) instead of call() corrects the count.
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func fixCount(n int, err error) (int, error) {
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if n < 0 {
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n = 0
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}
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return n, err
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}
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// wrapErr wraps an error that occurred during an operation on an open file.
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// It passes io.EOF through unchanged, otherwise converts
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// poll.ErrFileClosing to ErrClosed and wraps the error in a PathError.
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func (f *File) wrapErr(op string, err error) error {
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if err == nil || err == io.EOF {
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return err
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}
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if err == poll.ErrFileClosing {
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err = ErrClosed
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}
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return &PathError{op, f.name, err}
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}
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// TempDir returns the default directory to use for temporary files.
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//
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// On Unix systems, it returns $TMPDIR if non-empty, else /tmp.
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// On Windows, it uses GetTempPath, returning the first non-empty
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// value from %TMP%, %TEMP%, %USERPROFILE%, or the Windows directory.
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// On Plan 9, it returns /tmp.
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//
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// The directory is neither guaranteed to exist nor have accessible
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// permissions.
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func TempDir() string {
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return tempDir()
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}
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// Chmod changes the mode of the named file to mode.
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// If the file is a symbolic link, it changes the mode of the link's target.
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// If there is an error, it will be of type *PathError.
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//
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// A different subset of the mode bits are used, depending on the
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// operating system.
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//
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// On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and
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// ModeSticky are used.
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//
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// On Windows, the mode must be non-zero but otherwise only the 0200
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// bit (owner writable) of mode is used; it controls whether the
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// file's read-only attribute is set or cleared. attribute. The other
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// bits are currently unused. Use mode 0400 for a read-only file and
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// 0600 for a readable+writable file.
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//
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// On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive,
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// and ModeTemporary are used.
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func Chmod(name string, mode FileMode) error { return chmod(name, mode) }
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// Chmod changes the mode of the file to mode.
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// If there is an error, it will be of type *PathError.
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func (f *File) Chmod(mode FileMode) error { return f.chmod(mode) }
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