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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.
//go:build unix || (js && wasm) || wasip1
package os
import (
"internal/poll"
"internal/syscall/unix"
"io/fs"
"runtime"
"syscall"
_ "unsafe" // for go:linkname
)
const _UTIME_OMIT = unix.UTIME_OMIT
// fixLongPath is a noop on non-Windows platforms.
func fixLongPath(path string) string {
return path
}
func rename(oldname, newname string) error {
fi, err := Lstat(newname)
if err == nil && fi.IsDir() {
// There are two independent errors this function can return:
// one for a bad oldname, and one for a bad newname.
// At this point we've determined the newname is bad.
// But just in case oldname is also bad, prioritize returning
// the oldname error because that's what we did historically.
// However, if the old name and new name are not the same, yet
// they refer to the same file, it implies a case-only
// rename on a case-insensitive filesystem, which is ok.
if ofi, err := Lstat(oldname); err != nil {
if pe, ok := err.(*PathError); ok {
err = pe.Err
}
return &LinkError{"rename", oldname, newname, err}
} else if newname == oldname || !SameFile(fi, ofi) {
return &LinkError{"rename", oldname, newname, syscall.EEXIST}
}
}
err = ignoringEINTR(func() error {
return syscall.Rename(oldname, newname)
})
if err != nil {
return &LinkError{"rename", oldname, newname, err}
}
return nil
}
// file is the real representation of *File.
// The extra level of indirection ensures that no clients of os
// can overwrite this data, which could cause the finalizer
// to close the wrong file descriptor.
type file struct {
pfd poll.FD
name string
dirinfo *dirInfo // nil unless directory being read
nonblock bool // whether we set nonblocking mode
stdoutOrErr bool // whether this is stdout or stderr
appendMode bool // whether file is opened for appending
}
// Fd returns the integer Unix file descriptor referencing the open file.
// If f is closed, the file descriptor becomes invalid.
// If f is garbage collected, a finalizer may close the file descriptor,
// making it invalid; see [runtime.SetFinalizer] for more information on when
// a finalizer might be run. On Unix systems this will cause the [File.SetDeadline]
// methods to stop working.
// Because file descriptors can be reused, the returned file descriptor may
// only be closed through the [File.Close] method of f, or by its finalizer during
// garbage collection. Otherwise, during garbage collection the finalizer
// may close an unrelated file descriptor with the same (reused) number.
//
// As an alternative, see the f.SyscallConn method.
func (f *File) Fd() uintptr {
if f == nil {
return ^(uintptr(0))
}
// If we put the file descriptor into nonblocking mode,
// then set it to blocking mode before we return it,
// because historically we have always returned a descriptor
// opened in blocking mode. The File will continue to work,
// but any blocking operation will tie up a thread.
if f.nonblock {
f.pfd.SetBlocking()
}
return uintptr(f.pfd.Sysfd)
}
// NewFile returns a new File with the given file descriptor and
// name. The returned value will be nil if fd is not a valid file
// descriptor. On Unix systems, if the file descriptor is in
// non-blocking mode, NewFile will attempt to return a pollable File
// (one for which the SetDeadline methods work).
//
// After passing it to NewFile, fd may become invalid under the same
// conditions described in the comments of the Fd method, and the same
// constraints apply.
func NewFile(fd uintptr, name string) *File {
fdi := int(fd)
if fdi < 0 {
return nil
}
flags, err := unix.Fcntl(fdi, syscall.F_GETFL, 0)
if err != nil {
flags = 0
}
f := newFile(fdi, name, kindNewFile, unix.HasNonblockFlag(flags))
f.appendMode = flags&syscall.O_APPEND != 0
return f
}
// net_newUnixFile is a hidden entry point called by net.conn.File.
// This is used so that a nonblocking network connection will become
// blocking if code calls the Fd method. We don't want that for direct
// calls to NewFile: passing a nonblocking descriptor to NewFile should
// remain nonblocking if you get it back using Fd. But for net.conn.File
// the call to NewFile is hidden from the user. Historically in that case
// the Fd method has returned a blocking descriptor, and we want to
// retain that behavior because existing code expects it and depends on it.
//
//go:linkname net_newUnixFile net.newUnixFile
func net_newUnixFile(fd int, name string) *File {
if fd < 0 {
panic("invalid FD")
}
return newFile(fd, name, kindSock, true)
}
// newFileKind describes the kind of file to newFile.
type newFileKind int
const (
// kindNewFile means that the descriptor was passed to us via NewFile.
kindNewFile newFileKind = iota
// kindOpenFile means that the descriptor was opened using
// Open, Create, or OpenFile.
kindOpenFile
// kindPipe means that the descriptor was opened using Pipe.
kindPipe
// kindSock means that the descriptor is a network file descriptor
// that was created from net package and was opened using net_newUnixFile.
kindSock
// kindNoPoll means that we should not put the descriptor into
// non-blocking mode, because we know it is not a pipe or FIFO.
// Used by openFdAt and openDirNolog for directories.
kindNoPoll
)
// newFile is like NewFile, but if called from OpenFile or Pipe
// (as passed in the kind parameter) it tries to add the file to
// the runtime poller.
func newFile(fd int, name string, kind newFileKind, nonBlocking bool) *File {
f := &File{&file{
pfd: poll.FD{
Sysfd: fd,
IsStream: true,
ZeroReadIsEOF: true,
},
name: name,
stdoutOrErr: fd == 1 || fd == 2,
}}
pollable := kind == kindOpenFile || kind == kindPipe || kind == kindSock || nonBlocking
// Things like regular files and FIFOs in kqueue on *BSD/Darwin
// may not work properly (or accurately according to its manual).
// As a result, we should avoid adding those to the kqueue-based
// netpoller. Check out #19093, #24164, and #66239 for more contexts.
//
// If the fd was passed to us via any path other than OpenFile,
// we assume those callers know what they were doing, so we won't
// perform this check and allow it to be added to the kqueue.
if kind == kindOpenFile {
switch runtime.GOOS {
case "darwin", "ios", "dragonfly", "freebsd", "netbsd", "openbsd":
var st syscall.Stat_t
err := ignoringEINTR(func() error {
return syscall.Fstat(fd, &st)
})
typ := st.Mode & syscall.S_IFMT
// Don't try to use kqueue with regular files on *BSDs.
// On FreeBSD a regular file is always
// reported as ready for writing.
// On Dragonfly, NetBSD and OpenBSD the fd is signaled
// only once as ready (both read and write).
// Issue 19093.
// Also don't add directories to the netpoller.
if err == nil && (typ == syscall.S_IFREG || typ == syscall.S_IFDIR) {
pollable = false
}
// In addition to the behavior described above for regular files,
// on Darwin, kqueue does not work properly with fifos:
// closing the last writer does not cause a kqueue event
// for any readers. See issue #24164.
if (runtime.GOOS == "darwin" || runtime.GOOS == "ios") && typ == syscall.S_IFIFO {
pollable = false
}
}
}
clearNonBlock := false
if pollable {
// The descriptor is already in non-blocking mode.
// We only set f.nonblock if we put the file into
// non-blocking mode.
if nonBlocking {
// See the comments on net_newUnixFile.
if kind == kindSock {
f.nonblock = true // tell Fd to return blocking descriptor
}
} else if err := syscall.SetNonblock(fd, true); err == nil {
f.nonblock = true
clearNonBlock = true
} else {
pollable = false
}
}
// An error here indicates a failure to register
// with the netpoll system. That can happen for
// a file descriptor that is not supported by
// epoll/kqueue; for example, disk files on
// Linux systems. We assume that any real error
// will show up in later I/O.
// We do restore the blocking behavior if it was set by us.
if pollErr := f.pfd.Init("file", pollable); pollErr != nil && clearNonBlock {
if err := syscall.SetNonblock(fd, false); err == nil {
f.nonblock = false
}
}
runtime.SetFinalizer(f.file, (*file).close)
return f
}
func sigpipe() // implemented in package runtime
// epipecheck raises SIGPIPE if we get an EPIPE error on standard
// output or standard error. See the SIGPIPE docs in os/signal, and
// issue 11845.
func epipecheck(file *File, e error) {
if e == syscall.EPIPE && file.stdoutOrErr {
sigpipe()
}
}
// DevNull is the name of the operating system's “null device.”
// On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
const DevNull = "/dev/null"
// openFileNolog is the Unix implementation of OpenFile.
// Changes here should be reflected in openFdAt and openDirNolog, if relevant.
func openFileNolog(name string, flag int, perm FileMode) (*File, error) {
setSticky := false
if !supportsCreateWithStickyBit && flag&O_CREATE != 0 && perm&ModeSticky != 0 {
if _, err := Stat(name); IsNotExist(err) {
setSticky = true
}
}
var (
r int
s poll.SysFile
e error
)
// We have to check EINTR here, per issues 11180 and 39237.
ignoringEINTR(func() error {
r, s, e = open(name, flag|syscall.O_CLOEXEC, syscallMode(perm))
return e
})
if e != nil {
return nil, &PathError{Op: "open", Path: name, Err: e}
}
// open(2) itself won't handle the sticky bit on *BSD and Solaris
if setSticky {
setStickyBit(name)
}
// There's a race here with fork/exec, which we are
// content to live with. See ../syscall/exec_unix.go.
if !supportsCloseOnExec {
syscall.CloseOnExec(r)
}
f := newFile(r, name, kindOpenFile, unix.HasNonblockFlag(flag))
f.pfd.SysFile = s
return f, nil
}
func openDirNolog(name string) (*File, error) {
var (
r int
s poll.SysFile
e error
)
ignoringEINTR(func() error {
r, s, e = open(name, O_RDONLY|syscall.O_CLOEXEC, 0)
return e
})
if e != nil {
return nil, &PathError{Op: "open", Path: name, Err: e}
}
if !supportsCloseOnExec {
syscall.CloseOnExec(r)
}
f := newFile(r, name, kindNoPoll, false)
f.pfd.SysFile = s
return f, nil
}
func (file *file) close() error {
if file == nil {
return syscall.EINVAL
}
if file.dirinfo != nil {
file.dirinfo.close()
file.dirinfo = nil
}
var err error
if e := file.pfd.Close(); e != nil {
if e == poll.ErrFileClosing {
e = ErrClosed
}
err = &PathError{Op: "close", Path: file.name, Err: e}
}
// no need for a finalizer anymore
runtime.SetFinalizer(file, nil)
return err
}
// seek sets the offset for the next Read or Write on file to offset, interpreted
// according to whence: 0 means relative to the origin of the file, 1 means
// relative to the current offset, and 2 means relative to the end.
// It returns the new offset and an error, if any.
func (f *File) seek(offset int64, whence int) (ret int64, err error) {
if f.dirinfo != nil {
// Free cached dirinfo, so we allocate a new one if we
// access this file as a directory again. See #35767 and #37161.
f.dirinfo.close()
f.dirinfo = nil
}
ret, err = f.pfd.Seek(offset, whence)
runtime.KeepAlive(f)
return ret, err
}
// Truncate changes the size of the named file.
// If the file is a symbolic link, it changes the size of the link's target.
// If there is an error, it will be of type *PathError.
func Truncate(name string, size int64) error {
e := ignoringEINTR(func() error {
return syscall.Truncate(name, size)
})
if e != nil {
return &PathError{Op: "truncate", Path: name, Err: e}
}
return nil
}
// Remove removes the named file or (empty) directory.
// If there is an error, it will be of type *PathError.
func Remove(name string) error {
// System call interface forces us to know
// whether name is a file or directory.
// Try both: it is cheaper on average than
// doing a Stat plus the right one.
e := ignoringEINTR(func() error {
return syscall.Unlink(name)
})
if e == nil {
return nil
}
e1 := ignoringEINTR(func() error {
return syscall.Rmdir(name)
})
if e1 == nil {
return nil
}
// Both failed: figure out which error to return.
// OS X and Linux differ on whether unlink(dir)
// returns EISDIR, so can't use that. However,
// both agree that rmdir(file) returns ENOTDIR,
// so we can use that to decide which error is real.
// Rmdir might also return ENOTDIR if given a bad
// file path, like /etc/passwd/foo, but in that case,
// both errors will be ENOTDIR, so it's okay to
// use the error from unlink.
if e1 != syscall.ENOTDIR {
e = e1
}
return &PathError{Op: "remove", Path: name, Err: e}
}
func tempDir() string {
dir := Getenv("TMPDIR")
if dir == "" {
if runtime.GOOS == "android" {
dir = "/data/local/tmp"
} else {
dir = "/tmp"
}
}
return dir
}
// Link creates newname as a hard link to the oldname file.
// If there is an error, it will be of type *LinkError.
func Link(oldname, newname string) error {
e := ignoringEINTR(func() error {
return syscall.Link(oldname, newname)
})
if e != nil {
return &LinkError{"link", oldname, newname, e}
}
return nil
}
// Symlink creates newname as a symbolic link to oldname.
// On Windows, a symlink to a non-existent oldname creates a file symlink;
// if oldname is later created as a directory the symlink will not work.
// If there is an error, it will be of type *LinkError.
func Symlink(oldname, newname string) error {
e := ignoringEINTR(func() error {
return syscall.Symlink(oldname, newname)
})
if e != nil {
return &LinkError{"symlink", oldname, newname, e}
}
return nil
}
func readlink(name string) (string, error) {
for len := 128; ; len *= 2 {
b := make([]byte, len)
var (
n int
e error
)
for {
n, e = fixCount(syscall.Readlink(name, b))
if e != syscall.EINTR {
break
}
}
// buffer too small
if (runtime.GOOS == "aix" || runtime.GOOS == "wasip1") && e == syscall.ERANGE {
continue
}
if e != nil {
return "", &PathError{Op: "readlink", Path: name, Err: e}
}
if n < len {
return string(b[0:n]), nil
}
}
}
type unixDirent struct {
parent string
name string
typ FileMode
info FileInfo
}
func (d *unixDirent) Name() string { return d.name }
func (d *unixDirent) IsDir() bool { return d.typ.IsDir() }
func (d *unixDirent) Type() FileMode { return d.typ }
func (d *unixDirent) Info() (FileInfo, error) {
if d.info != nil {
return d.info, nil
}
return lstat(d.parent + "/" + d.name)
}
func (d *unixDirent) String() string {
return fs.FormatDirEntry(d)
}
func newUnixDirent(parent, name string, typ FileMode) (DirEntry, error) {
ude := &unixDirent{
parent: parent,
name: name,
typ: typ,
}
if typ != ^FileMode(0) && !testingForceReadDirLstat {
return ude, nil
}
info, err := lstat(parent + "/" + name)
if err != nil {
return nil, err
}
ude.typ = info.Mode().Type()
ude.info = info
return ude, nil
}