426 lines
12 KiB
Go
426 lines
12 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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// The os package provides a platform-independent interface to operating
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// system 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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"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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}
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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, name, nil, 0}
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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_CREAT int = syscall.O_CREAT // create a new file if none exists.
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O_EXCL int = syscall.O_EXCL // used with O_CREAT, 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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O_CREATE int = O_CREAT // create a new file if none exists.
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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 := syscall.Read(file.fd, 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 && e == 0 {
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return 0, EOF
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}
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if e != 0 {
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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 := syscall.Pread(file.fd, b, off)
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if m == 0 && e == 0 {
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return n, EOF
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}
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if e != 0 {
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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 := syscall.Write(file.fd, b)
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if n < 0 {
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n = 0
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}
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if e == syscall.EPIPE {
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file.nepipe++
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if file.nepipe >= 10 {
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Exit(syscall.EPIPE)
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}
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} else {
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file.nepipe = 0
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}
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if e != 0 {
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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 := syscall.Pwrite(file.fd, b, off)
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if e != 0 {
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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 := syscall.Seek(file.fd, offset, whence)
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if e == 0 && file.dirinfo != nil && r != 0 {
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e = syscall.EISDIR
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}
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if e != 0 {
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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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// Pipe returns a connected pair of Files; reads from r return bytes written to w.
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// It returns the files and an Error, if any.
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func Pipe() (r *File, w *File, err Error) {
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var p [2]int
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// See ../syscall/exec.go for description of lock.
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syscall.ForkLock.RLock()
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e := syscall.Pipe(p[0:])
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if e != 0 {
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syscall.ForkLock.RUnlock()
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return nil, nil, NewSyscallError("pipe", e)
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}
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syscall.CloseOnExec(p[0])
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syscall.CloseOnExec(p[1])
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syscall.ForkLock.RUnlock()
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return NewFile(p[0], "|0"), NewFile(p[1], "|1"), nil
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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 e != 0 {
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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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// Stat returns a FileInfo structure describing the named file and an error, if any.
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// If name names a valid symbolic link, the returned FileInfo describes
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// the file pointed at by the link and has fi.FollowedSymlink set to true.
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// If name names an invalid symbolic link, the returned FileInfo describes
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// the link itself and has fi.FollowedSymlink set to false.
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func Stat(name string) (fi *FileInfo, err Error) {
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var lstat, stat syscall.Stat_t
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e := syscall.Lstat(name, &lstat)
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if e != 0 {
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return nil, &PathError{"stat", name, Errno(e)}
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}
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statp := &lstat
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if lstat.Mode&syscall.S_IFMT == syscall.S_IFLNK {
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e := syscall.Stat(name, &stat)
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if e == 0 {
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statp = &stat
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}
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}
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return fileInfoFromStat(name, new(FileInfo), &lstat, statp), nil
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}
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// Lstat returns the FileInfo structure describing the named file and an
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// error, if any. If the file is a symbolic link, the returned FileInfo
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// describes the symbolic link. Lstat makes no attempt to follow the link.
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func Lstat(name string) (fi *FileInfo, err Error) {
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var stat syscall.Stat_t
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e := syscall.Lstat(name, &stat)
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if e != 0 {
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return nil, &PathError{"lstat", name, Errno(e)}
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}
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return fileInfoFromStat(name, new(FileInfo), &stat, &stat), 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); e != 0 {
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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); e != 0 {
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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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// Remove removes the named file or directory.
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func Remove(name string) Error {
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// System call interface forces us to know
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// whether name is a file or directory.
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// Try both: it is cheaper on average than
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// doing a Stat plus the right one.
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e := syscall.Unlink(name)
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if e == 0 {
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return nil
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}
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e1 := syscall.Rmdir(name)
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if e1 == 0 {
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return nil
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}
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// Both failed: figure out which error to return.
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// OS X and Linux differ on whether unlink(dir)
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// returns EISDIR, so can't use that. However,
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// both agree that rmdir(file) returns ENOTDIR,
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// so we can use that to decide which error is real.
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// Rmdir might also return ENOTDIR if given a bad
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// file path, like /etc/passwd/foo, but in that case,
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// both errors will be ENOTDIR, so it's okay to
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// use the error from unlink.
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// For windows syscall.ENOTDIR is set
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// to syscall.ERROR_DIRECTORY, hopefully it should
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// do the trick.
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if e1 != syscall.ENOTDIR {
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e = e1
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}
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return &PathError{"remove", name, Errno(e)}
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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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Error Error
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}
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func (e *LinkError) String() string {
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return e.Op + " " + e.Old + " " + e.New + ": " + e.Error.String()
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}
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// Link creates a hard link.
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func Link(oldname, newname string) Error {
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e := syscall.Link(oldname, newname)
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if e != 0 {
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return &LinkError{"link", oldname, newname, Errno(e)}
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}
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return nil
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}
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// Symlink creates a symbolic link.
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func Symlink(oldname, newname string) Error {
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e := syscall.Symlink(oldname, newname)
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if e != 0 {
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return &LinkError{"symlink", oldname, newname, Errno(e)}
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}
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return nil
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}
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// Readlink reads the contents of a symbolic link: the destination of
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// the link. It returns the contents and an Error, if any.
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func Readlink(name string) (string, Error) {
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for len := 128; ; len *= 2 {
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b := make([]byte, len)
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n, e := syscall.Readlink(name, b)
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if e != 0 {
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return "", &PathError{"readlink", name, Errno(e)}
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}
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if n < len {
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return string(b[0:n]), nil
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}
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}
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// Silence 6g.
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return "", nil
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}
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// Rename renames a file.
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func Rename(oldname, newname string) Error {
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e := syscall.Rename(oldname, newname)
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if e != 0 {
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return &LinkError{"rename", oldname, newname, Errno(e)}
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}
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return nil
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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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func Chmod(name string, mode uint32) Error {
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if e := syscall.Chmod(name, mode); e != 0 {
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return &PathError{"chmod", name, Errno(e)}
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}
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return nil
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}
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// Chmod changes the mode of the file to mode.
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func (f *File) Chmod(mode uint32) Error {
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if e := syscall.Fchmod(f.fd, mode); e != 0 {
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return &PathError{"chmod", f.name, Errno(e)}
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}
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return nil
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}
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// Chown changes the numeric uid and gid of the named file.
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// If the file is a symbolic link, it changes the uid and gid of the link's target.
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func Chown(name string, uid, gid int) Error {
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if e := syscall.Chown(name, uid, gid); e != 0 {
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return &PathError{"chown", name, Errno(e)}
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}
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return nil
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}
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// Lchown changes the numeric uid and gid of the named file.
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// If the file is a symbolic link, it changes the uid and gid of the link itself.
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func Lchown(name string, uid, gid int) Error {
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if e := syscall.Lchown(name, uid, gid); e != 0 {
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return &PathError{"lchown", name, Errno(e)}
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}
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return nil
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}
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// Chown changes the numeric uid and gid of the named file.
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func (f *File) Chown(uid, gid int) Error {
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if e := syscall.Fchown(f.fd, uid, gid); e != 0 {
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return &PathError{"chown", f.name, Errno(e)}
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}
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return nil
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}
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// Truncate changes the size of the file.
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// It does not change the I/O offset.
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func (f *File) Truncate(size int64) Error {
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if e := syscall.Ftruncate(f.fd, size); e != 0 {
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return &PathError{"truncate", f.name, Errno(e)}
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}
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return nil
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}
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// Chtimes changes the access and modification times of the named
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// file, similar to the Unix utime() or utimes() functions.
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//
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// The argument times are in nanoseconds, although the underlying
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// filesystem may truncate or round the values to a more
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// coarse time unit.
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func Chtimes(name string, atime_ns int64, mtime_ns int64) Error {
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var utimes [2]syscall.Timeval
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utimes[0] = syscall.NsecToTimeval(atime_ns)
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utimes[1] = syscall.NsecToTimeval(mtime_ns)
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if e := syscall.Utimes(name, utimes[0:]); e != 0 {
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return &PathError{"chtimes", name, Errno(e)}
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}
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return nil
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}
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