Imported Upstream version 60upstream/60

55 files changed, 5662 insertions, 0 deletions

diff --git a/src/pkg/os/Makefile b/src/pkg/os/Makefile
new file mode 100644
index 000000000..8923a8b48
--- /dev/null
+++ b/src/pkg/os/Makefile
@@ -0,0 +1,100 @@
+# 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.
+
+include ../../Make.inc
+
+TARG=os
+GOFILES=\
+	error.go\
+	env.go\
+	exec.go\
+	file.go\
+	getwd.go\
+	path.go\
+	proc.go\
+	stat_$(GOOS).go\
+	time.go\
+	types.go\
+
+GOFILES_freebsd=\
+	dir_unix.go\
+	error_posix.go\
+	env_unix.go\
+	file_posix.go\
+	file_unix.go\
+	path_unix.go\
+	sys_bsd.go\
+	exec_posix.go\
+	exec_unix.go\
+	signal_unix.go\
+
+GOFILES_darwin=\
+	dir_unix.go\
+	error_posix.go\
+	env_unix.go\
+	file_posix.go\
+	file_unix.go\
+	path_unix.go\
+	sys_bsd.go\
+	exec_posix.go\
+	exec_unix.go\
+	signal_unix.go\
+
+GOFILES_linux=\
+	dir_unix.go\
+	error_posix.go\
+	env_unix.go\
+	file_posix.go\
+	file_unix.go\
+	path_unix.go\
+	sys_linux.go\
+	exec_posix.go\
+	exec_unix.go\
+	signal_unix.go\
+
+GOFILES_openbsd=\
+	dir_unix.go\
+	error_posix.go\
+	env_unix.go\
+	file_posix.go\
+	file_unix.go\
+	path_unix.go\
+	sys_bsd.go\
+	exec_posix.go\
+	exec_unix.go\
+	signal_unix.go\
+
+GOFILES_windows=\
+	dir_windows.go\
+	error_posix.go\
+	env_windows.go\
+	file_posix.go\
+	file_windows.go\
+	path_windows.go\
+	sys_windows.go\
+	exec_posix.go\
+	exec_windows.go\
+	signal_windows.go\
+
+GOFILES_plan9=\
+	dir_plan9.go\
+	error_plan9.go\
+	env_plan9.go\
+	file_plan9.go\
+	path_plan9.go\
+	sys_plan9.go\
+	exec_plan9.go\
+	str.go\
+
+GOFILES+=$(GOFILES_$(GOOS))
+
+CLEANFILES+=signal_unix.go signal_windows.go
+
+include ../../Make.pkg
+
+signal_unix.go: ../syscall/zerrors_$(GOOS)_$(GOARCH).go
+	./mkunixsignals.sh $< > $@ || rm -f $@
+
+signal_windows.go: ../syscall/ztypes_$(GOOS).go
+	./mkunixsignals.sh $< > $@ || rm -f $@
diff --git a/src/pkg/os/dir_plan9.go b/src/pkg/os/dir_plan9.go
new file mode 100644
index 000000000..bbc2cb647
--- /dev/null
+++ b/src/pkg/os/dir_plan9.go
@@ -0,0 +1,300 @@
+// 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 (
+	"syscall"
+)
+
+// Readdir reads the contents of the directory associated with file and
+// returns an array of up to n FileInfo structures, as would be returned
+// by Lstat, in directory order. Subsequent calls on the same file will yield
+// further FileInfos.
+//
+// If n > 0, Readdir returns at most n FileInfo structures. In this case, if
+// Readdirnames returns an empty slice, it will return a non-nil error
+// explaining why. At the end of a directory, the error is os.EOF.
+//
+// If n <= 0, Readdir returns all the FileInfo from the directory in
+// a single slice. In this case, if Readdir succeeds (reads all
+// the way to the end of the directory), it returns the slice and a
+// nil os.Error. If it encounters an error before the end of the
+// directory, Readdir returns the FileInfo read until that point
+// and a non-nil error.
+func (file *File) Readdir(n int) (fi []FileInfo, err Error) {
+	// If this file has no dirinfo, create one.
+	if file.dirinfo == nil {
+		file.dirinfo = new(dirInfo)
+	}
+	d := file.dirinfo
+	size := n
+	if size <= 0 {
+		size = 100
+		n = -1
+	}
+	result := make([]FileInfo, 0, size) // Empty with room to grow.
+	for n != 0 {
+		// Refill the buffer if necessary
+		if d.bufp >= d.nbuf {
+			d.bufp = 0
+			var e Error
+			d.nbuf, e = file.Read(d.buf[:])
+			if e != nil && e != EOF {
+				return result, &PathError{"readdir", file.name, e}
+			}
+			if e == EOF {
+				break
+			}
+			if d.nbuf < syscall.STATFIXLEN {
+				return result, &PathError{"readdir", file.name, Eshortstat}
+			}
+		}
+
+		// Get a record from buffer
+		m, _ := gbit16(d.buf[d.bufp:])
+		m += 2
+		if m < syscall.STATFIXLEN {
+			return result, &PathError{"readdir", file.name, Eshortstat}
+		}
+		dir, e := UnmarshalDir(d.buf[d.bufp : d.bufp+int(m)])
+		if e != nil {
+			return result, &PathError{"readdir", file.name, e}
+		}
+		var f FileInfo
+		fileInfoFromStat(&f, dir)
+		result = append(result, f)
+
+		d.bufp += int(m)
+		n--
+	}
+
+	if n >= 0 && len(result) == 0 {
+		return result, EOF
+	}
+	return result, nil
+}
+
+// Readdirnames reads and returns a slice of names from the directory f.
+//
+// If n > 0, Readdirnames returns at most n names. In this case, if
+// Readdirnames returns an empty slice, it will return a non-nil error
+// explaining why. At the end of a directory, the error is os.EOF.
+//
+// If n <= 0, Readdirnames returns all the names from the directory in
+// a single slice. In this case, if Readdirnames succeeds (reads all
+// the way to the end of the directory), it returns the slice and a
+// nil os.Error. If it encounters an error before the end of the
+// directory, Readdirnames returns the names read until that point and
+// a non-nil error.
+func (file *File) Readdirnames(n int) (names []string, err Error) {
+	fi, err := file.Readdir(n)
+	names = make([]string, len(fi))
+	for i := range fi {
+		names[i] = fi[i].Name
+	}
+	return
+}
+
+type Dir struct {
+	// system-modified data
+	Type uint16 // server type
+	Dev  uint32 // server subtype
+	// file data
+	Qid    Qid    // unique id from server
+	Mode   uint32 // permissions
+	Atime  uint32 // last read time
+	Mtime  uint32 // last write time
+	Length uint64 // file length
+	Name   string // last element of path
+	Uid    string // owner name
+	Gid    string // group name
+	Muid   string // last modifier name
+}
+
+type Qid struct {
+	Path uint64 // the file server's unique identification for the file
+	Vers uint32 // version number for given Path
+	Type uint8  // the type of the file (syscall.QTDIR for example)
+}
+
+var nullDir = Dir{
+	^uint16(0),
+	^uint32(0),
+	Qid{^uint64(0), ^uint32(0), ^uint8(0)},
+	^uint32(0),
+	^uint32(0),
+	^uint32(0),
+	^uint64(0),
+	"",
+	"",
+	"",
+	"",
+}
+
+// Null assigns members of d with special "don't care" values indicating
+// they should not be written by syscall.Wstat. 
+func (d *Dir) Null() {
+	*d = nullDir
+}
+
+// pdir appends a 9P Stat message based on the contents of Dir d to a byte slice b.
+func pdir(b []byte, d *Dir) []byte {
+	n := len(b)
+	b = pbit16(b, 0) // length, filled in later	
+	b = pbit16(b, d.Type)
+	b = pbit32(b, d.Dev)
+	b = pqid(b, d.Qid)
+	b = pbit32(b, d.Mode)
+	b = pbit32(b, d.Atime)
+	b = pbit32(b, d.Mtime)
+	b = pbit64(b, d.Length)
+	b = pstring(b, d.Name)
+	b = pstring(b, d.Uid)
+	b = pstring(b, d.Gid)
+	b = pstring(b, d.Muid)
+	pbit16(b[0:n], uint16(len(b)-(n+2)))
+	return b
+}
+
+// UnmarshalDir reads a 9P Stat message from a 9P protocol message stored in b,
+// returning the corresponding Dir struct.
+func UnmarshalDir(b []byte) (d *Dir, err Error) {
+	n := uint16(0)
+	n, b = gbit16(b)
+
+	if int(n) != len(b) {
+		return nil, Ebadstat
+	}
+
+	d = new(Dir)
+	d.Type, b = gbit16(b)
+	d.Dev, b = gbit32(b)
+	d.Qid, b = gqid(b)
+	d.Mode, b = gbit32(b)
+	d.Atime, b = gbit32(b)
+	d.Mtime, b = gbit32(b)
+	d.Length, b = gbit64(b)
+	d.Name, b = gstring(b)
+	d.Uid, b = gstring(b)
+	d.Gid, b = gstring(b)
+	d.Muid, b = gstring(b)
+
+	if len(b) != 0 {
+		return nil, Ebadstat
+	}
+
+	return d, nil
+}
+
+// gqid reads the qid part of a 9P Stat message from a 9P protocol message stored in b,
+// returning the corresponding Qid struct and the remaining slice of b.
+func gqid(b []byte) (Qid, []byte) {
+	var q Qid
+	q.Path, b = gbit64(b)
+	q.Vers, b = gbit32(b)
+	q.Type, b = gbit8(b)
+	return q, b
+}
+
+// pqid appends a Qid struct q to a 9P message b.
+func pqid(b []byte, q Qid) []byte {
+	b = pbit64(b, q.Path)
+	b = pbit32(b, q.Vers)
+	b = pbit8(b, q.Type)
+	return b
+}
+
+// gbit8 reads a byte-sized numeric value from a 9P protocol message stored in b,
+// returning the value and the remaining slice of b.
+func gbit8(b []byte) (uint8, []byte) {
+	return uint8(b[0]), b[1:]
+}
+
+// gbit16 reads a 16-bit numeric value from a 9P protocol message stored in b,
+// returning the value and the remaining slice of b.
+func gbit16(b []byte) (uint16, []byte) {
+	return uint16(b[0]) | uint16(b[1])<<8, b[2:]
+}
+
+// gbit32 reads a 32-bit numeric value from a 9P protocol message stored in b,
+// returning the value and the remaining slice of b.
+func gbit32(b []byte) (uint32, []byte) {
+	return uint32(b[0]) | uint32(b[1])<<8 | uint32(b[2])<<16 | uint32(b[3])<<24, b[4:]
+}
+
+// gbit64 reads a 64-bit numeric value from a 9P protocol message stored in b,
+// returning the value and the remaining slice of b.
+func gbit64(b []byte) (uint64, []byte) {
+	lo, b := gbit32(b)
+	hi, b := gbit32(b)
+	return uint64(hi)<<32 | uint64(lo), b
+}
+
+// gstring reads a string from a 9P protocol message stored in b,
+// returning the value as a Go string and the remaining slice of b.
+func gstring(b []byte) (string, []byte) {
+	n, b := gbit16(b)
+	return string(b[0:n]), b[n:]
+}
+
+// pbit8 appends a byte-sized numeric value x to a 9P message b.
+func pbit8(b []byte, x uint8) []byte {
+	n := len(b)
+	if n+1 > cap(b) {
+		nb := make([]byte, n, 100+2*cap(b))
+		copy(nb, b)
+		b = nb
+	}
+	b = b[0 : n+1]
+	b[n] = x
+	return b
+}
+
+// pbit16 appends a 16-bit numeric value x to a 9P message b.
+func pbit16(b []byte, x uint16) []byte {
+	n := len(b)
+	if n+2 > cap(b) {
+		nb := make([]byte, n, 100+2*cap(b))
+		copy(nb, b)
+		b = nb
+	}
+	b = b[0 : n+2]
+	b[n] = byte(x)
+	b[n+1] = byte(x >> 8)
+	return b
+}
+
+// pbit32 appends a 32-bit numeric value x to a 9P message b.
+func pbit32(b []byte, x uint32) []byte {
+	n := len(b)
+	if n+4 > cap(b) {
+		nb := make([]byte, n, 100+2*cap(b))
+		copy(nb, b)
+		b = nb
+	}
+	b = b[0 : n+4]
+	b[n] = byte(x)
+	b[n+1] = byte(x >> 8)
+	b[n+2] = byte(x >> 16)
+	b[n+3] = byte(x >> 24)
+	return b
+}
+
+// pbit64 appends a 64-bit numeric value x to a 9P message b.
+func pbit64(b []byte, x uint64) []byte {
+	b = pbit32(b, uint32(x))
+	b = pbit32(b, uint32(x>>32))
+	return b
+}
+
+// pstring appends a Go string s to a 9P message b.
+func pstring(b []byte, s string) []byte {
+	if len(s) >= 1<<16 {
+		panic(NewError("string too long"))
+	}
+	b = pbit16(b, uint16(len(s)))
+	b = append(b, []byte(s)...)
+	return b
+}
diff --git a/src/pkg/os/dir_unix.go b/src/pkg/os/dir_unix.go
new file mode 100644
index 000000000..7835ed52b
--- /dev/null
+++ b/src/pkg/os/dir_unix.go
@@ -0,0 +1,67 @@
+// 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 (
+	"syscall"
+)
+
+const (
+	blockSize = 4096
+)
+
+// Readdirnames reads and returns a slice of names from the directory f.
+//
+// If n > 0, Readdirnames returns at most n names. In this case, if
+// Readdirnames returns an empty slice, it will return a non-nil error
+// explaining why. At the end of a directory, the error is os.EOF.
+//
+// If n <= 0, Readdirnames returns all the names from the directory in
+// a single slice. In this case, if Readdirnames succeeds (reads all
+// the way to the end of the directory), it returns the slice and a
+// nil os.Error. If it encounters an error before the end of the
+// directory, Readdirnames returns the names read until that point and
+// a non-nil error.
+func (f *File) Readdirnames(n int) (names []string, err Error) {
+	// If this file has no dirinfo, create one.
+	if f.dirinfo == nil {
+		f.dirinfo = new(dirInfo)
+		// The buffer must be at least a block long.
+		f.dirinfo.buf = make([]byte, blockSize)
+	}
+	d := f.dirinfo
+
+	size := n
+	if size <= 0 {
+		size = 100
+		n = -1
+	}
+
+	names = make([]string, 0, size) // Empty with room to grow.
+	for n != 0 {
+		// Refill the buffer if necessary
+		if d.bufp >= d.nbuf {
+			d.bufp = 0
+			var errno int
+			d.nbuf, errno = syscall.ReadDirent(f.fd, d.buf)
+			if errno != 0 {
+				return names, NewSyscallError("readdirent", errno)
+			}
+			if d.nbuf <= 0 {
+				break // EOF
+			}
+		}
+
+		// Drain the buffer
+		var nb, nc int
+		nb, nc, names = syscall.ParseDirent(d.buf[d.bufp:d.nbuf], n, names)
+		d.bufp += nb
+		n -= nc
+	}
+	if n >= 0 && len(names) == 0 {
+		return names, EOF
+	}
+	return names, nil
+}
diff --git a/src/pkg/os/dir_windows.go b/src/pkg/os/dir_windows.go
new file mode 100644
index 000000000..d76e88fdb
--- /dev/null
+++ b/src/pkg/os/dir_windows.go
@@ -0,0 +1,14 @@
+// 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
+
+func (file *File) Readdirnames(n int) (names []string, err Error) {
+	fis, err := file.Readdir(n)
+	names = make([]string, len(fis))
+	for i, fi := range fis {
+		names[i] = fi.Name
+	}
+	return names, err
+}
diff --git a/src/pkg/os/env.go b/src/pkg/os/env.go
new file mode 100644
index 000000000..3772c090b
--- /dev/null
+++ b/src/pkg/os/env.go
@@ -0,0 +1,75 @@
+// Copyright 2010 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.
+
+// General environment variables.
+
+package os
+
+func setenv_c(k, v string)
+
+// Expand replaces ${var} or $var in the string based on the mapping function.
+// Invocations of undefined variables are replaced with the empty string.
+func Expand(s string, mapping func(string) string) string {
+	buf := make([]byte, 0, 2*len(s))
+	// ${} is all ASCII, so bytes are fine for this operation.
+	i := 0
+	for j := 0; j < len(s); j++ {
+		if s[j] == '$' && j+1 < len(s) {
+			buf = append(buf, []byte(s[i:j])...)
+			name, w := getShellName(s[j+1:])
+			buf = append(buf, []byte(mapping(name))...)
+			j += w
+			i = j + 1
+		}
+	}
+	return string(buf) + s[i:]
+}
+
+// ShellExpand replaces ${var} or $var in the string according to the values
+// of the operating system's environment variables.  References to undefined
+// variables are replaced by the empty string.
+func ShellExpand(s string) string {
+	return Expand(s, Getenv)
+}
+
+// isSpellSpecialVar reports whether the character identifies a special
+// shell variable such as $*.
+func isShellSpecialVar(c uint8) bool {
+	switch c {
+	case '*', '#', '$', '@', '!', '?', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
+		return true
+	}
+	return false
+}
+
+// isAlphaNum reports whether the byte is an ASCII letter, number, or underscore
+func isAlphaNum(c uint8) bool {
+	return c == '_' || '0' <= c && c <= '9' || 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z'
+}
+
+// getName returns the name that begins the string and the number of bytes
+// consumed to extract it.  If the name is enclosed in {}, it's part of a ${}
+// expansion and two more bytes are needed than the length of the name.
+func getShellName(s string) (string, int) {
+	switch {
+	case s[0] == '{':
+		if len(s) > 2 && isShellSpecialVar(s[1]) && s[2] == '}' {
+			return s[1:2], 3
+		}
+		// Scan to closing brace
+		for i := 1; i < len(s); i++ {
+			if s[i] == '}' {
+				return s[1:i], i + 1
+			}
+		}
+		return "", 1 // Bad syntax; just eat the brace.
+	case isShellSpecialVar(s[0]):
+		return s[0:1], 1
+	}
+	// Scan alphanumerics.
+	var i int
+	for i = 0; i < len(s) && isAlphaNum(s[i]); i++ {
+	}
+	return s[:i], i
+}
diff --git a/src/pkg/os/env_plan9.go b/src/pkg/os/env_plan9.go
new file mode 100644
index 000000000..1fed89f92
--- /dev/null
+++ b/src/pkg/os/env_plan9.go
@@ -0,0 +1,96 @@
+// Copyright 2011 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.
+
+// Plan 9 environment variables.
+
+package os
+
+import "syscall"
+
+// ENOENV is the Error indicating that an environment variable does not exist.
+var ENOENV = NewError("no such environment variable")
+
+// Getenverror retrieves the value of the environment variable named by the key.
+// It returns the value and an error, if any.
+func Getenverror(key string) (value string, err Error) {
+	if len(key) == 0 {
+		return "", EINVAL
+	}
+	f, e := Open("/env/" + key)
+	if iserror(e) {
+		return "", ENOENV
+	}
+	defer f.Close()
+
+	l, _ := f.Seek(0, 2)
+	f.Seek(0, 0)
+	buf := make([]byte, l)
+	n, e := f.Read(buf)
+	if iserror(e) {
+		return "", ENOENV
+	}
+
+	if n > 0 && buf[n-1] == 0 {
+		buf = buf[:n-1]
+	}
+	return string(buf), nil
+}
+
+// Getenv retrieves the value of the environment variable named by the key.
+// It returns the value, which will be empty if the variable is not present.
+func Getenv(key string) string {
+	v, _ := Getenverror(key)
+	return v
+}
+
+// Setenv sets the value of the environment variable named by the key.
+// It returns an Error, if any.
+func Setenv(key, value string) Error {
+	if len(key) == 0 {
+		return EINVAL
+	}
+
+	f, e := Create("/env/" + key)
+	if iserror(e) {
+		return e
+	}
+	defer f.Close()
+
+	_, e = f.Write([]byte(value))
+	return nil
+}
+
+// Clearenv deletes all environment variables.
+func Clearenv() {
+	syscall.RawSyscall(syscall.SYS_RFORK, syscall.RFCENVG, 0, 0)
+}
+
+// Environ returns an array of strings representing the environment,
+// in the form "key=value".
+func Environ() []string {
+	env := make([]string, 0, 100)
+
+	f, e := Open("/env")
+	if iserror(e) {
+		panic(e)
+	}
+	defer f.Close()
+
+	names, e := f.Readdirnames(-1)
+	if iserror(e) {
+		panic(e)
+	}
+
+	for _, k := range names {
+		if v, e := Getenverror(k); !iserror(e) {
+			env = append(env, k+"="+v)
+		}
+	}
+	return env[0:len(env)]
+}
+
+// TempDir returns the default directory to use for temporary files.
+func TempDir() string {
+	return "/tmp"
+}
diff --git a/src/pkg/os/env_test.go b/src/pkg/os/env_test.go
new file mode 100644
index 000000000..04ff39072
--- /dev/null
+++ b/src/pkg/os/env_test.go
@@ -0,0 +1,59 @@
+// Copyright 2010 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_test
+
+import (
+	. "os"
+	"testing"
+)
+
+// testGetenv gives us a controlled set of variables for testing Expand.
+func testGetenv(s string) string {
+	switch s {
+	case "*":
+		return "all the args"
+	case "#":
+		return "NARGS"
+	case "$":
+		return "PID"
+	case "1":
+		return "ARGUMENT1"
+	case "HOME":
+		return "/usr/gopher"
+	case "H":
+		return "(Value of H)"
+	case "home_1":
+		return "/usr/foo"
+	case "_":
+		return "underscore"
+	}
+	return ""
+}
+
+var expandTests = []struct {
+	in, out string
+}{
+	{"", ""},
+	{"$*", "all the args"},
+	{"$$", "PID"},
+	{"${*}", "all the args"},
+	{"$1", "ARGUMENT1"},
+	{"${1}", "ARGUMENT1"},
+	{"now is the time", "now is the time"},
+	{"$HOME", "/usr/gopher"},
+	{"$home_1", "/usr/foo"},
+	{"${HOME}", "/usr/gopher"},
+	{"${H}OME", "(Value of H)OME"},
+	{"A$$$#$1$H$home_1*B", "APIDNARGSARGUMENT1(Value of H)/usr/foo*B"},
+}
+
+func TestExpand(t *testing.T) {
+	for _, test := range expandTests {
+		result := Expand(test.in, testGetenv)
+		if result != test.out {
+			t.Errorf("Expand(%q)=%q; expected %q", test.in, result, test.out)
+		}
+	}
+}
diff --git a/src/pkg/os/env_unix.go b/src/pkg/os/env_unix.go
new file mode 100644
index 000000000..9cc0b03d8
--- /dev/null
+++ b/src/pkg/os/env_unix.go
@@ -0,0 +1,109 @@
+// Copyright 2010 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.
+
+// Unix environment variables.
+
+package os
+
+import (
+	"sync"
+)
+
+// ENOENV is the Error indicating that an environment variable does not exist.
+var ENOENV = NewError("no such environment variable")
+
+var env map[string]string
+var once sync.Once
+
+func copyenv() {
+	env = make(map[string]string)
+	for _, s := range Envs {
+		for j := 0; j < len(s); j++ {
+			if s[j] == '=' {
+				env[s[0:j]] = s[j+1:]
+				break
+			}
+		}
+	}
+}
+
+var envLock sync.RWMutex
+
+// Getenverror retrieves the value of the environment variable named by the key.
+// It returns the value and an error, if any.
+func Getenverror(key string) (value string, err Error) {
+	once.Do(copyenv)
+
+	if len(key) == 0 {
+		return "", EINVAL
+	}
+
+	envLock.RLock()
+	defer envLock.RUnlock()
+
+	v, ok := env[key]
+	if !ok {
+		return "", ENOENV
+	}
+	return v, nil
+}
+
+// Getenv retrieves the value of the environment variable named by the key.
+// It returns the value, which will be empty if the variable is not present.
+func Getenv(key string) string {
+	v, _ := Getenverror(key)
+	return v
+}
+
+// Setenv sets the value of the environment variable named by the key.
+// It returns an Error, if any.
+func Setenv(key, value string) Error {
+	once.Do(copyenv)
+	if len(key) == 0 {
+		return EINVAL
+	}
+
+	envLock.Lock()
+	defer envLock.Unlock()
+
+	env[key] = value
+	setenv_c(key, value) // is a no-op if cgo isn't loaded
+	return nil
+}
+
+// Clearenv deletes all environment variables.
+func Clearenv() {
+	once.Do(copyenv) // prevent copyenv in Getenv/Setenv
+
+	envLock.Lock()
+	defer envLock.Unlock()
+
+	env = make(map[string]string)
+
+	// TODO(bradfitz): pass through to C
+}
+
+// Environ returns an array of strings representing the environment,
+// in the form "key=value".
+func Environ() []string {
+	once.Do(copyenv)
+	envLock.RLock()
+	defer envLock.RUnlock()
+	a := make([]string, len(env))
+	i := 0
+	for k, v := range env {
+		a[i] = k + "=" + v
+		i++
+	}
+	return a
+}
+
+// TempDir returns the default directory to use for temporary files.
+func TempDir() string {
+	dir := Getenv("TMPDIR")
+	if dir == "" {
+		dir = "/tmp"
+	}
+	return dir
+}
diff --git a/src/pkg/os/env_windows.go b/src/pkg/os/env_windows.go
new file mode 100644
index 000000000..e6ddc4065
--- /dev/null
+++ b/src/pkg/os/env_windows.go
@@ -0,0 +1,127 @@
+// Copyright 2010 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.
+
+// Windows environment variables.
+
+package os
+
+import (
+	"syscall"
+	"utf16"
+	"unsafe"
+)
+
+// ENOENV is the Error indicating that an environment variable does not exist.
+var ENOENV = NewError("no such environment variable")
+
+// Getenverror retrieves the value of the environment variable named by the key.
+// It returns the value and an error, if any.
+func Getenverror(key string) (value string, err Error) {
+	b := make([]uint16, 100)
+	n, e := syscall.GetEnvironmentVariable(syscall.StringToUTF16Ptr(key), &b[0], uint32(len(b)))
+	if n == 0 && e == syscall.ERROR_ENVVAR_NOT_FOUND {
+		return "", ENOENV
+	}
+	if n > uint32(len(b)) {
+		b = make([]uint16, n)
+		n, e = syscall.GetEnvironmentVariable(syscall.StringToUTF16Ptr(key), &b[0], uint32(len(b)))
+		if n > uint32(len(b)) {
+			n = 0
+		}
+	}
+	if n == 0 {
+		return "", NewSyscallError("GetEnvironmentVariable", e)
+	}
+	return string(utf16.Decode(b[0:n])), nil
+}
+
+// Getenv retrieves the value of the environment variable named by the key.
+// It returns the value, which will be empty if the variable is not present.
+func Getenv(key string) string {
+	v, _ := Getenverror(key)
+	return v
+}
+
+// Setenv sets the value of the environment variable named by the key.
+// It returns an Error, if any.
+func Setenv(key, value string) Error {
+	var v *uint16
+	if len(value) > 0 {
+		v = syscall.StringToUTF16Ptr(value)
+	}
+	e := syscall.SetEnvironmentVariable(syscall.StringToUTF16Ptr(key), v)
+	if e != 0 {
+		return NewSyscallError("SetEnvironmentVariable", e)
+	}
+	return nil
+}
+
+// Clearenv deletes all environment variables.
+func Clearenv() {
+	for _, s := range Environ() {
+		// Environment variables can begin with =
+		// so start looking for the separator = at j=1.
+		// http://blogs.msdn.com/b/oldnewthing/archive/2010/05/06/10008132.aspx
+		for j := 1; j < len(s); j++ {
+			if s[j] == '=' {
+				Setenv(s[0:j], "")
+				break
+			}
+		}
+	}
+}
+
+// Environ returns an array of strings representing the environment,
+// in the form "key=value".
+func Environ() []string {
+	s, e := syscall.GetEnvironmentStrings()
+	if e != 0 {
+		return nil
+	}
+	defer syscall.FreeEnvironmentStrings(s)
+	r := make([]string, 0, 50) // Empty with room to grow.
+	for from, i, p := 0, 0, (*[1 << 24]uint16)(unsafe.Pointer(s)); true; i++ {
+		if p[i] == 0 {
+			// empty string marks the end
+			if i <= from {
+				break
+			}
+			r = append(r, string(utf16.Decode(p[from:i])))
+			from = i + 1
+		}
+	}
+	return r
+}
+
+// TempDir returns the default directory to use for temporary files.
+func TempDir() string {
+	const pathSep = '\\'
+	dirw := make([]uint16, syscall.MAX_PATH)
+	n, _ := syscall.GetTempPath(uint32(len(dirw)), &dirw[0])
+	if n > uint32(len(dirw)) {
+		dirw = make([]uint16, n)
+		n, _ = syscall.GetTempPath(uint32(len(dirw)), &dirw[0])
+		if n > uint32(len(dirw)) {
+			n = 0
+		}
+	}
+	if n > 0 && dirw[n-1] == pathSep {
+		n--
+	}
+	return string(utf16.Decode(dirw[0:n]))
+}
+
+func init() {
+	var argc int32
+	cmd := syscall.GetCommandLine()
+	argv, e := syscall.CommandLineToArgv(cmd, &argc)
+	if e != 0 {
+		return
+	}
+	defer syscall.LocalFree(syscall.Handle(uintptr(unsafe.Pointer(argv))))
+	Args = make([]string, argc)
+	for i, v := range (*argv)[:argc] {
+		Args[i] = string(syscall.UTF16ToString((*v)[:]))
+	}
+}
diff --git a/src/pkg/os/error.go b/src/pkg/os/error.go
new file mode 100644
index 000000000..b4511dd2f
--- /dev/null
+++ b/src/pkg/os/error.go
@@ -0,0 +1,31 @@
+// 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
+
+// An Error can represent any printable error condition.
+type Error interface {
+	String() string
+}
+
+// // errorString is a helper type used by NewError.
+type errorString string
+
+func (e errorString) String() string { return string(e) }
+
+// Note: If the name of the function NewError changes,
+// pkg/go/doc/doc.go should be adjusted since it hardwires
+// this name in a heuristic.
+
+// // NewError returns a new error with error.String() == s.
+func NewError(s string) Error { return errorString(s) }
+
+// PathError records an error and the operation and file path that caused it.
+type PathError struct {
+	Op    string
+	Path  string
+	Error Error
+}
+
+func (e *PathError) String() string { return e.Op + " " + e.Path + ": " + e.Error.String() }
diff --git a/src/pkg/os/error_plan9.go b/src/pkg/os/error_plan9.go
new file mode 100644
index 000000000..cacfc150c
--- /dev/null
+++ b/src/pkg/os/error_plan9.go
@@ -0,0 +1,61 @@
+// Copyright 2011 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 syscall "syscall"
+
+// SyscallError records an error from a specific system call.
+type SyscallError struct {
+	Syscall string
+	Err     string
+}
+
+func (e *SyscallError) String() string { return e.Syscall + ": " + e.Err }
+
+// Note: If the name of the function NewSyscallError changes,
+// pkg/go/doc/doc.go should be adjusted since it hardwires
+// this name in a heuristic.
+
+// NewSyscallError returns, as an Error, a new SyscallError
+// with the given system call name and error details.
+// As a convenience, if err is nil, NewSyscallError returns nil.
+func NewSyscallError(syscall string, err syscall.Error) Error {
+	if err == nil {
+		return nil
+	}
+	return &SyscallError{syscall, err.String()}
+}
+
+var (
+	Eshortstat = NewError("stat buffer too small")
+	Ebadstat   = NewError("malformed stat buffer")
+	Ebadfd     = NewError("fd out of range or not open")
+	Ebadarg    = NewError("bad arg in system call")
+	Enotdir    = NewError("not a directory")
+	Enonexist  = NewError("file does not exist")
+	Eexist     = NewError("file already exists")
+	Eio        = NewError("i/o error")
+	Eperm      = NewError("permission denied")
+
+	EINVAL  = Ebadarg
+	ENOTDIR = Enotdir
+	ENOENT  = Enonexist
+	EEXIST  = Eexist
+	EIO     = Eio
+	EACCES  = Eperm
+	EPERM   = Eperm
+	EISDIR  = syscall.EISDIR
+
+	ENAMETOOLONG = NewError("file name too long")
+	ERANGE       = NewError("math result not representable")
+	EPIPE        = NewError("Broken Pipe")
+	EPLAN9       = NewError("not supported by plan 9")
+)
+
+func iserror(err syscall.Error) bool {
+	return err != nil
+}
+
+func Errno(e syscall.Error) syscall.Error { return e }
diff --git a/src/pkg/os/error_posix.go b/src/pkg/os/error_posix.go
new file mode 100644
index 000000000..d43f1786d
--- /dev/null
+++ b/src/pkg/os/error_posix.go
@@ -0,0 +1,90 @@
+// 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 syscall "syscall"
+
+// Errno is the Unix error number.  Names such as EINVAL are simple
+// wrappers to convert the error number into an Error.
+type Errno int64
+
+func (e Errno) String() string { return syscall.Errstr(int(e)) }
+
+func (e Errno) Temporary() bool {
+	return e == Errno(syscall.EINTR) || e == Errno(syscall.EMFILE) || e.Timeout()
+}
+
+func (e Errno) Timeout() bool {
+	return e == Errno(syscall.EAGAIN) || e == Errno(syscall.EWOULDBLOCK) || e == Errno(syscall.ETIMEDOUT)
+}
+
+// Commonly known Unix errors.
+var (
+	EPERM        Error = Errno(syscall.EPERM)
+	ENOENT       Error = Errno(syscall.ENOENT)
+	ESRCH        Error = Errno(syscall.ESRCH)
+	EINTR        Error = Errno(syscall.EINTR)
+	EIO          Error = Errno(syscall.EIO)
+	ENXIO        Error = Errno(syscall.ENXIO)
+	E2BIG        Error = Errno(syscall.E2BIG)
+	ENOEXEC      Error = Errno(syscall.ENOEXEC)
+	EBADF        Error = Errno(syscall.EBADF)
+	ECHILD       Error = Errno(syscall.ECHILD)
+	EDEADLK      Error = Errno(syscall.EDEADLK)
+	ENOMEM       Error = Errno(syscall.ENOMEM)
+	EACCES       Error = Errno(syscall.EACCES)
+	EFAULT       Error = Errno(syscall.EFAULT)
+	EBUSY        Error = Errno(syscall.EBUSY)
+	EEXIST       Error = Errno(syscall.EEXIST)
+	EXDEV        Error = Errno(syscall.EXDEV)
+	ENODEV       Error = Errno(syscall.ENODEV)
+	ENOTDIR      Error = Errno(syscall.ENOTDIR)
+	EISDIR       Error = Errno(syscall.EISDIR)
+	EINVAL       Error = Errno(syscall.EINVAL)
+	ENFILE       Error = Errno(syscall.ENFILE)
+	EMFILE       Error = Errno(syscall.EMFILE)
+	ENOTTY       Error = Errno(syscall.ENOTTY)
+	EFBIG        Error = Errno(syscall.EFBIG)
+	ENOSPC       Error = Errno(syscall.ENOSPC)
+	ESPIPE       Error = Errno(syscall.ESPIPE)
+	EROFS        Error = Errno(syscall.EROFS)
+	EMLINK       Error = Errno(syscall.EMLINK)
+	EPIPE        Error = Errno(syscall.EPIPE)
+	EAGAIN       Error = Errno(syscall.EAGAIN)
+	EDOM         Error = Errno(syscall.EDOM)
+	ERANGE       Error = Errno(syscall.ERANGE)
+	EADDRINUSE   Error = Errno(syscall.EADDRINUSE)
+	ECONNREFUSED Error = Errno(syscall.ECONNREFUSED)
+	ENAMETOOLONG Error = Errno(syscall.ENAMETOOLONG)
+	EAFNOSUPPORT Error = Errno(syscall.EAFNOSUPPORT)
+	ETIMEDOUT    Error = Errno(syscall.ETIMEDOUT)
+	ENOTCONN     Error = Errno(syscall.ENOTCONN)
+)
+
+// SyscallError records an error from a specific system call.
+type SyscallError struct {
+	Syscall string
+	Errno   Errno
+}
+
+func (e *SyscallError) String() string { return e.Syscall + ": " + e.Errno.String() }
+
+// Note: If the name of the function NewSyscallError changes,
+// pkg/go/doc/doc.go should be adjusted since it hardwires
+// this name in a heuristic.
+
+// NewSyscallError returns, as an Error, a new SyscallError
+// with the given system call name and error details.
+// As a convenience, if errno is 0, NewSyscallError returns nil.
+func NewSyscallError(syscall string, errno int) Error {
+	if errno == 0 {
+		return nil
+	}
+	return &SyscallError{syscall, Errno(errno)}
+}
+
+func iserror(errno int) bool {
+	return errno != 0
+}
diff --git a/src/pkg/os/exec.go b/src/pkg/os/exec.go
new file mode 100644
index 000000000..33e223fd2
--- /dev/null
+++ b/src/pkg/os/exec.go
@@ -0,0 +1,58 @@
+// 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 (
+	"runtime"
+	"syscall"
+)
+
+// Process stores the information about a process created by StartProcess.
+type Process struct {
+	Pid    int
+	handle int
+	done   bool // process has been successfuly waited on
+}
+
+func newProcess(pid, handle int) *Process {
+	p := &Process{Pid: pid, handle: handle}
+	runtime.SetFinalizer(p, (*Process).Release)
+	return p
+}
+
+// ProcAttr holds the attributes that will be applied to a new process
+// started by StartProcess.
+type ProcAttr struct {
+	// If Dir is non-empty, the child changes into the directory before
+	// creating the process.
+	Dir string
+	// If Env is non-nil, it gives the environment variables for the
+	// new process in the form returned by Environ.
+	// If it is nil, the result of Environ will be used.
+	Env []string
+	// Files specifies the open files inherited by the new process.  The
+	// first three entries correspond to standard input, standard output, and
+	// standard error.  An implementation may support additional entries,
+	// depending on the underlying operating system.  A nil entry corresponds
+	// to that file being closed when the process starts.
+	Files []*File
+
+	// Operating system-specific process creation attributes.
+	// Note that setting this field means that your program
+	// may not execute properly or even compile on some
+	// operating systems.
+	Sys *syscall.SysProcAttr
+}
+
+// A Signal can represent any operating system signal.
+type Signal interface {
+	String() string
+}
+
+// Getpid returns the process id of the caller.
+func Getpid() int { return syscall.Getpid() }
+
+// Getppid returns the process id of the caller's parent.
+func Getppid() int { return syscall.Getppid() }
diff --git a/src/pkg/os/exec_plan9.go b/src/pkg/os/exec_plan9.go
new file mode 100644
index 000000000..6f0722a22
--- /dev/null
+++ b/src/pkg/os/exec_plan9.go
@@ -0,0 +1,153 @@
+// 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 (
+	"runtime"
+	"syscall"
+)
+
+// StartProcess starts a new process with the program, arguments and attributes
+// specified by name, argv and attr.
+func StartProcess(name string, argv []string, attr *ProcAttr) (p *Process, err Error) {
+	sysattr := &syscall.ProcAttr{
+		Dir: attr.Dir,
+		Env: attr.Env,
+		Sys: attr.Sys,
+	}
+
+	// Create array of integer (system) fds.
+	intfd := make([]int, len(attr.Files))
+	for i, f := range attr.Files {
+		if f == nil {
+			intfd[i] = -1
+		} else {
+			intfd[i] = f.Fd()
+		}
+	}
+
+	sysattr.Files = intfd
+
+	pid, h, e := syscall.StartProcess(name, argv, sysattr)
+	if iserror(e) {
+		return nil, &PathError{"fork/exec", name, e}
+	}
+
+	return newProcess(pid, h), nil
+}
+
+// Plan9Note implements the Signal interface on Plan 9.
+type Plan9Note string
+
+func (note Plan9Note) String() string {
+	return string(note)
+}
+
+func (p *Process) Signal(sig Signal) Error {
+	if p.done {
+		return NewError("os: process already finished")
+	}
+
+	f, e := OpenFile("/proc/"+itoa(p.Pid)+"/note", O_WRONLY, 0)
+	if iserror(e) {
+		return NewSyscallError("signal", e)
+	}
+	defer f.Close()
+	_, e = f.Write([]byte(sig.String()))
+	return e
+}
+
+// Kill causes the Process to exit immediately.
+func (p *Process) Kill() Error {
+	f, e := OpenFile("/proc/"+itoa(p.Pid)+"/ctl", O_WRONLY, 0)
+	if iserror(e) {
+		return NewSyscallError("kill", e)
+	}
+	defer f.Close()
+	_, e = f.Write([]byte("kill"))
+	return e
+}
+
+// Exec replaces the current process with an execution of the
+// named binary, with arguments argv and environment envv.
+// If successful, Exec never returns.  If it fails, it returns an Error.
+// ForkExec is almost always a better way to execute a program.
+func Exec(name string, argv []string, envv []string) Error {
+	e := syscall.Exec(name, argv, envv)
+	if iserror(e) {
+		return &PathError{"exec", name, e}
+	}
+
+	return nil
+}
+
+// Waitmsg stores the information about an exited process as reported by Wait.
+type Waitmsg struct {
+	syscall.Waitmsg
+}
+
+// Wait waits for the Process to exit or stop, and then returns a
+// Waitmsg describing its status and an Error, if any. The options
+// (WNOHANG etc.) affect the behavior of the Wait call.
+func (p *Process) Wait(options int) (w *Waitmsg, err Error) {
+	var waitmsg syscall.Waitmsg
+
+	if p.Pid == -1 {
+		return nil, EINVAL
+	}
+
+	for true {
+		err = syscall.Await(&waitmsg)
+
+		if iserror(err) {
+			return nil, NewSyscallError("wait", err)
+		}
+
+		if waitmsg.Pid == p.Pid {
+			p.done = true
+			break
+		}
+	}
+
+	return &Waitmsg{waitmsg}, nil
+}
+
+// Wait waits for process pid to exit or stop, and then returns a
+// Waitmsg describing its status and an Error, if any. The options
+// (WNOHANG etc.) affect the behavior of the Wait call.
+// Wait is equivalent to calling FindProcess and then Wait
+// and Release on the result.
+func Wait(pid int, options int) (w *Waitmsg, err Error) {
+	p, e := FindProcess(pid)
+	if e != nil {
+		return nil, e
+	}
+	defer p.Release()
+	return p.Wait(options)
+}
+
+// Release releases any resources associated with the Process.
+func (p *Process) Release() Error {
+	// NOOP for Plan 9.
+	p.Pid = -1
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(p, nil)
+	return nil
+}
+
+// FindProcess looks for a running process by its pid.
+// The Process it returns can be used to obtain information
+// about the underlying operating system process.
+func FindProcess(pid int) (p *Process, err Error) {
+	// NOOP for Plan 9.
+	return newProcess(pid, 0), nil
+}
+
+func (w *Waitmsg) String() string {
+	if w == nil {
+		return "<nil>"
+	}
+	return "exit status: " + w.Msg
+}
diff --git a/src/pkg/os/exec_posix.go b/src/pkg/os/exec_posix.go
new file mode 100644
index 000000000..f37bfab58
--- /dev/null
+++ b/src/pkg/os/exec_posix.go
@@ -0,0 +1,147 @@
+// 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 (
+	"runtime"
+	"syscall"
+)
+
+type UnixSignal int32
+
+func (sig UnixSignal) String() string {
+	s := runtime.Signame(int32(sig))
+	if len(s) > 0 {
+		return s
+	}
+	return "UnixSignal"
+}
+
+// StartProcess starts a new process with the program, arguments and attributes
+// specified by name, argv and attr.
+//
+// StartProcess is a low-level interface. The exec package provides
+// higher-level interfaces.
+func StartProcess(name string, argv []string, attr *ProcAttr) (p *Process, err Error) {
+	sysattr := &syscall.ProcAttr{
+		Dir: attr.Dir,
+		Env: attr.Env,
+		Sys: attr.Sys,
+	}
+	if sysattr.Env == nil {
+		sysattr.Env = Environ()
+	}
+	for _, f := range attr.Files {
+		sysattr.Files = append(sysattr.Files, f.Fd())
+	}
+
+	pid, h, e := syscall.StartProcess(name, argv, sysattr)
+	if iserror(e) {
+		return nil, &PathError{"fork/exec", name, Errno(e)}
+	}
+	return newProcess(pid, h), nil
+}
+
+// Kill causes the Process to exit immediately.
+func (p *Process) Kill() Error {
+	return p.Signal(SIGKILL)
+}
+
+// Exec replaces the current process with an execution of the
+// named binary, with arguments argv and environment envv.
+// If successful, Exec never returns.  If it fails, it returns an Error.
+//
+// To run a child process, see StartProcess (for a low-level interface)
+// or the exec package (for higher-level interfaces).
+func Exec(name string, argv []string, envv []string) Error {
+	if envv == nil {
+		envv = Environ()
+	}
+	e := syscall.Exec(name, argv, envv)
+	if iserror(e) {
+		return &PathError{"exec", name, Errno(e)}
+	}
+	return nil
+}
+
+// TODO(rsc): Should os implement its own syscall.WaitStatus
+// wrapper with the methods, or is exposing the underlying one enough?
+//
+// TODO(rsc): Certainly need to have Rusage struct,
+// since syscall one might have different field types across
+// different OS.
+
+// Waitmsg stores the information about an exited process as reported by Wait.
+type Waitmsg struct {
+	Pid                int             // The process's id.
+	syscall.WaitStatus                 // System-dependent status info.
+	Rusage             *syscall.Rusage // System-dependent resource usage info.
+}
+
+// Wait waits for process pid to exit or stop, and then returns a
+// Waitmsg describing its status and an Error, if any. The options
+// (WNOHANG etc.) affect the behavior of the Wait call.
+// Wait is equivalent to calling FindProcess and then Wait
+// and Release on the result.
+func Wait(pid int, options int) (w *Waitmsg, err Error) {
+	p, e := FindProcess(pid)
+	if e != nil {
+		return nil, e
+	}
+	defer p.Release()
+	return p.Wait(options)
+}
+
+// Convert i to decimal string.
+func itod(i int) string {
+	if i == 0 {
+		return "0"
+	}
+
+	u := uint64(i)
+	if i < 0 {
+		u = -u
+	}
+
+	// Assemble decimal in reverse order.
+	var b [32]byte
+	bp := len(b)
+	for ; u > 0; u /= 10 {
+		bp--
+		b[bp] = byte(u%10) + '0'
+	}
+
+	if i < 0 {
+		bp--
+		b[bp] = '-'
+	}
+
+	return string(b[bp:])
+}
+
+func (w *Waitmsg) String() string {
+	if w == nil {
+		return "<nil>"
+	}
+	// TODO(austin) Use signal names when possible?
+	res := ""
+	switch {
+	case w.Exited():
+		res = "exit status " + itod(w.ExitStatus())
+	case w.Signaled():
+		res = "signal " + itod(w.Signal())
+	case w.Stopped():
+		res = "stop signal " + itod(w.StopSignal())
+		if w.StopSignal() == syscall.SIGTRAP && w.TrapCause() != 0 {
+			res += " (trap " + itod(w.TrapCause()) + ")"
+		}
+	case w.Continued():
+		res = "continued"
+	}
+	if w.CoreDump() {
+		res += " (core dumped)"
+	}
+	return res
+}
diff --git a/src/pkg/os/exec_unix.go b/src/pkg/os/exec_unix.go
new file mode 100644
index 000000000..8a4b2e1b8
--- /dev/null
+++ b/src/pkg/os/exec_unix.go
@@ -0,0 +1,77 @@
+// 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 (
+	"runtime"
+	"syscall"
+)
+
+// Options for Wait.
+const (
+	WNOHANG   = syscall.WNOHANG   // Don't wait if no process has exited.
+	WSTOPPED  = syscall.WSTOPPED  // If set, status of stopped subprocesses is also reported.
+	WUNTRACED = syscall.WUNTRACED // Usually an alias for WSTOPPED.
+	WRUSAGE   = 1 << 20           // Record resource usage.
+)
+
+// WRUSAGE must not be too high a bit, to avoid clashing with Linux's
+// WCLONE, WALL, and WNOTHREAD flags, which sit in the top few bits of
+// the options
+
+// Wait waits for the Process to exit or stop, and then returns a
+// Waitmsg describing its status and an Error, if any. The options
+// (WNOHANG etc.) affect the behavior of the Wait call.
+func (p *Process) Wait(options int) (w *Waitmsg, err Error) {
+	if p.Pid == -1 {
+		return nil, EINVAL
+	}
+	var status syscall.WaitStatus
+	var rusage *syscall.Rusage
+	if options&WRUSAGE != 0 {
+		rusage = new(syscall.Rusage)
+		options ^= WRUSAGE
+	}
+	pid1, e := syscall.Wait4(p.Pid, &status, options, rusage)
+	if e != 0 {
+		return nil, NewSyscallError("wait", e)
+	}
+	if options&WSTOPPED == 0 {
+		p.done = true
+	}
+	w = new(Waitmsg)
+	w.Pid = pid1
+	w.WaitStatus = status
+	w.Rusage = rusage
+	return w, nil
+}
+
+// Signal sends a signal to the Process.
+func (p *Process) Signal(sig Signal) Error {
+	if p.done {
+		return NewError("os: process already finished")
+	}
+	if e := syscall.Kill(p.Pid, int(sig.(UnixSignal))); e != 0 {
+		return Errno(e)
+	}
+	return nil
+}
+
+// Release releases any resources associated with the Process.
+func (p *Process) Release() Error {
+	// NOOP for unix.
+	p.Pid = -1
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(p, nil)
+	return nil
+}
+
+// FindProcess looks for a running process by its pid.
+// The Process it returns can be used to obtain information
+// about the underlying operating system process.
+func FindProcess(pid int) (p *Process, err Error) {
+	// NOOP for unix.
+	return newProcess(pid, 0), nil
+}
diff --git a/src/pkg/os/exec_windows.go b/src/pkg/os/exec_windows.go
new file mode 100644
index 000000000..65e94ac4a
--- /dev/null
+++ b/src/pkg/os/exec_windows.go
@@ -0,0 +1,66 @@
+// 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 (
+	"runtime"
+	"syscall"
+)
+
+func (p *Process) Wait(options int) (w *Waitmsg, err Error) {
+	s, e := syscall.WaitForSingleObject(syscall.Handle(p.handle), syscall.INFINITE)
+	switch s {
+	case syscall.WAIT_OBJECT_0:
+		break
+	case syscall.WAIT_FAILED:
+		return nil, NewSyscallError("WaitForSingleObject", e)
+	default:
+		return nil, NewError("os: unexpected result from WaitForSingleObject")
+	}
+	var ec uint32
+	e = syscall.GetExitCodeProcess(syscall.Handle(p.handle), &ec)
+	if e != 0 {
+		return nil, NewSyscallError("GetExitCodeProcess", e)
+	}
+	p.done = true
+	return &Waitmsg{p.Pid, syscall.WaitStatus{s, ec}, new(syscall.Rusage)}, nil
+}
+
+// Signal sends a signal to the Process.
+func (p *Process) Signal(sig Signal) Error {
+	if p.done {
+		return NewError("os: process already finished")
+	}
+	switch sig.(UnixSignal) {
+	case SIGKILL:
+		e := syscall.TerminateProcess(syscall.Handle(p.handle), 1)
+		return NewSyscallError("TerminateProcess", e)
+	}
+	return Errno(syscall.EWINDOWS)
+}
+
+func (p *Process) Release() Error {
+	if p.handle == -1 {
+		return EINVAL
+	}
+	e := syscall.CloseHandle(syscall.Handle(p.handle))
+	if e != 0 {
+		return NewSyscallError("CloseHandle", e)
+	}
+	p.handle = -1
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(p, nil)
+	return nil
+}
+
+func FindProcess(pid int) (p *Process, err Error) {
+	const da = syscall.STANDARD_RIGHTS_READ |
+		syscall.PROCESS_QUERY_INFORMATION | syscall.SYNCHRONIZE
+	h, e := syscall.OpenProcess(da, false, uint32(pid))
+	if e != 0 {
+		return nil, NewSyscallError("OpenProcess", e)
+	}
+	return newProcess(pid, int(h)), nil
+}
diff --git a/src/pkg/os/file.go b/src/pkg/os/file.go
new file mode 100644
index 000000000..4335d45e5
--- /dev/null
+++ b/src/pkg/os/file.go
@@ -0,0 +1,211 @@
+// 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 provides a platform-independent interface to operating system
+// functionality.  The design is Unix-like.
+// The os interface is intended to be uniform across all operating systems.
+// Features not generally available appear in the system-specific package syscall.
+package os
+
+import (
+	"syscall"
+)
+
+// Name returns the name of the file as presented to Open.
+func (file *File) Name() string { return file.name }
+
+// Stdin, Stdout, and Stderr are open Files pointing to the standard input,
+// standard output, and standard error file descriptors.
+var (
+	Stdin  = NewFile(syscall.Stdin, "/dev/stdin")
+	Stdout = NewFile(syscall.Stdout, "/dev/stdout")
+	Stderr = NewFile(syscall.Stderr, "/dev/stderr")
+)
+
+// Flags to Open wrapping those of the underlying system. Not all flags
+// may be implemented on a given system.
+const (
+	O_RDONLY   int = syscall.O_RDONLY   // open the file read-only.
+	O_WRONLY   int = syscall.O_WRONLY   // open the file write-only.
+	O_RDWR     int = syscall.O_RDWR     // open the file read-write.
+	O_APPEND   int = syscall.O_APPEND   // append data to the file when writing.
+	O_ASYNC    int = syscall.O_ASYNC    // generate a signal when I/O is available.
+	O_CREATE   int = syscall.O_CREAT    // create a new file if none exists.
+	O_EXCL     int = syscall.O_EXCL     // used with O_CREATE, file must not exist
+	O_NOCTTY   int = syscall.O_NOCTTY   // do not make file the controlling tty.
+	O_NONBLOCK int = syscall.O_NONBLOCK // open in non-blocking mode.
+	O_NDELAY   int = O_NONBLOCK         // synonym for O_NONBLOCK
+	O_SYNC     int = syscall.O_SYNC     // open for synchronous I/O.
+	O_TRUNC    int = syscall.O_TRUNC    // if possible, truncate file when opened.
+)
+
+// Seek whence values.
+const (
+	SEEK_SET int = 0 // seek relative to the origin of the file
+	SEEK_CUR int = 1 // seek relative to the current offset
+	SEEK_END int = 2 // seek relative to the end
+)
+
+type eofError int
+
+func (eofError) String() string { return "EOF" }
+
+// EOF is the Error returned by Read when no more input is available.
+// Functions should return EOF only to signal a graceful end of input.
+// If the EOF occurs unexpectedly in a structured data stream,
+// the appropriate error is either io.ErrUnexpectedEOF or some other error
+// giving more detail.
+var EOF Error = eofError(0)
+
+// Read reads up to len(b) bytes from the File.
+// It returns the number of bytes read and an Error, if any.
+// EOF is signaled by a zero count with err set to EOF.
+func (file *File) Read(b []byte) (n int, err Error) {
+	if file == nil {
+		return 0, EINVAL
+	}
+	n, e := file.read(b)
+	if n < 0 {
+		n = 0
+	}
+	if n == 0 && !iserror(e) {
+		return 0, EOF
+	}
+	if iserror(e) {
+		err = &PathError{"read", file.name, Errno(e)}
+	}
+	return n, err
+}
+
+// ReadAt reads len(b) bytes from the File starting at byte offset off.
+// It returns the number of bytes read and the Error, if any.
+// EOF is signaled by a zero count with err set to EOF.
+// ReadAt always returns a non-nil Error when n != len(b).
+func (file *File) ReadAt(b []byte, off int64) (n int, err Error) {
+	if file == nil {
+		return 0, EINVAL
+	}
+	for len(b) > 0 {
+		m, e := file.pread(b, off)
+		if m == 0 && !iserror(e) {
+			return n, EOF
+		}
+		if iserror(e) {
+			err = &PathError{"read", file.name, Errno(e)}
+			break
+		}
+		n += m
+		b = b[m:]
+		off += int64(m)
+	}
+	return
+}
+
+// Write writes len(b) bytes to the File.
+// It returns the number of bytes written and an Error, if any.
+// Write returns a non-nil Error when n != len(b).
+func (file *File) Write(b []byte) (n int, err Error) {
+	if file == nil {
+		return 0, EINVAL
+	}
+	n, e := file.write(b)
+	if n < 0 {
+		n = 0
+	}
+
+	epipecheck(file, e)
+
+	if iserror(e) {
+		err = &PathError{"write", file.name, Errno(e)}
+	}
+	return n, err
+}
+
+// WriteAt writes len(b) bytes to the File starting at byte offset off.
+// It returns the number of bytes written and an Error, if any.
+// WriteAt returns a non-nil Error when n != len(b).
+func (file *File) WriteAt(b []byte, off int64) (n int, err Error) {
+	if file == nil {
+		return 0, EINVAL
+	}
+	for len(b) > 0 {
+		m, e := file.pwrite(b, off)
+		if iserror(e) {
+			err = &PathError{"write", file.name, Errno(e)}
+			break
+		}
+		n += m
+		b = b[m:]
+		off += int64(m)
+	}
+	return
+}
+
+// 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 (file *File) Seek(offset int64, whence int) (ret int64, err Error) {
+	r, e := file.seek(offset, whence)
+	if !iserror(e) && file.dirinfo != nil && r != 0 {
+		e = syscall.EISDIR
+	}
+	if iserror(e) {
+		return 0, &PathError{"seek", file.name, Errno(e)}
+	}
+	return r, nil
+}
+
+// WriteString is like Write, but writes the contents of string s rather than
+// an array of bytes.
+func (file *File) WriteString(s string) (ret int, err Error) {
+	if file == nil {
+		return 0, EINVAL
+	}
+	return file.Write([]byte(s))
+}
+
+// Mkdir creates a new directory with the specified name and permission bits.
+// It returns an error, if any.
+func Mkdir(name string, perm uint32) Error {
+	e := syscall.Mkdir(name, perm)
+	if iserror(e) {
+		return &PathError{"mkdir", name, Errno(e)}
+	}
+	return nil
+}
+
+// Chdir changes the current working directory to the named directory.
+func Chdir(dir string) Error {
+	if e := syscall.Chdir(dir); iserror(e) {
+		return &PathError{"chdir", dir, Errno(e)}
+	}
+	return nil
+}
+
+// Chdir changes the current working directory to the file,
+// which must be a directory.
+func (f *File) Chdir() Error {
+	if e := syscall.Fchdir(f.fd); iserror(e) {
+		return &PathError{"chdir", f.name, Errno(e)}
+	}
+	return nil
+}
+
+// Open opens the named file for reading.  If successful, methods on
+// the returned file can be used for reading; the associated file
+// descriptor has mode O_RDONLY.
+// It returns the File and an Error, if any.
+func Open(name string) (file *File, err Error) {
+	return OpenFile(name, O_RDONLY, 0)
+}
+
+// Create creates the named file mode 0666 (before umask), truncating
+// it if it already exists.  If successful, methods on the returned
+// File can be used for I/O; the associated file descriptor has mode
+// O_RDWR.
+// It returns the File and an Error, if any.
+func Create(name string) (file *File, err Error) {
+	return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666)
+}
diff --git a/src/pkg/os/file_plan9.go b/src/pkg/os/file_plan9.go
new file mode 100644
index 000000000..1e94fb715
--- /dev/null
+++ b/src/pkg/os/file_plan9.go
@@ -0,0 +1,331 @@
+// Copyright 2011 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 (
+	"runtime"
+	"syscall"
+)
+
+// File represents an open file descriptor.
+type File struct {
+	fd      int
+	name    string
+	dirinfo *dirInfo // nil unless directory being read
+}
+
+// Fd returns the integer Unix file descriptor referencing the open file.
+func (file *File) Fd() int {
+	if file == nil {
+		return -1
+	}
+	return file.fd
+}
+
+// NewFile returns a new File with the given file descriptor and name.
+func NewFile(fd int, name string) *File {
+	if fd < 0 {
+		return nil
+	}
+	f := &File{fd: fd, name: name}
+	runtime.SetFinalizer(f, (*File).Close)
+	return f
+}
+
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	buf  [syscall.STATMAX]byte // buffer for directory I/O
+	nbuf int                   // length of buf; return value from Read
+	bufp int                   // location of next record in buf.
+}
+
+func epipecheck(file *File, e syscall.Error) {
+}
+
+// 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"
+
+// OpenFile is the generalized open call; most users will use Open
+// or Create instead.  It opens the named file with specified flag
+// (O_RDONLY etc.) and perm, (0666 etc.) if applicable.  If successful,
+// methods on the returned File can be used for I/O.
+// It returns the File and an Error, if any.
+func OpenFile(name string, flag int, perm uint32) (file *File, err Error) {
+	var (
+		fd     int
+		e      syscall.Error
+		create bool
+		excl   bool
+		trunc  bool
+		append bool
+	)
+
+	if flag&O_CREATE == O_CREATE {
+		flag = flag & ^O_CREATE
+		create = true
+	}
+	if flag&O_EXCL == O_EXCL {
+		excl = true
+	}
+	if flag&O_TRUNC == O_TRUNC {
+		trunc = true
+	}
+	// O_APPEND is emulated on Plan 9
+	if flag&O_APPEND == O_APPEND {
+		flag = flag &^ O_APPEND
+		append = true
+	}
+
+	syscall.ForkLock.RLock()
+	if (create && trunc) || excl {
+		fd, e = syscall.Create(name, flag, perm)
+	} else {
+		fd, e = syscall.Open(name, flag)
+		if e != nil && create {
+			var e1 syscall.Error
+			fd, e1 = syscall.Create(name, flag, perm)
+			if e1 == nil {
+				e = nil
+			}
+		}
+	}
+	syscall.ForkLock.RUnlock()
+
+	if e != nil {
+		return nil, &PathError{"open", name, e}
+	}
+
+	if append {
+		if _, e = syscall.Seek(fd, 0, SEEK_END); e != nil {
+			return nil, &PathError{"seek", name, e}
+		}
+	}
+
+	return NewFile(fd, name), nil
+}
+
+// Close closes the File, rendering it unusable for I/O.
+// It returns an Error, if any.
+func (file *File) Close() Error {
+	if file == nil || file.fd < 0 {
+		return Ebadfd
+	}
+	var err Error
+	syscall.ForkLock.RLock()
+	if e := syscall.Close(file.fd); e != nil {
+		err = &PathError{"close", file.name, e}
+	}
+	syscall.ForkLock.RUnlock()
+	file.fd = -1 // so it can't be closed again
+
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(file, nil)
+	return err
+}
+
+// Stat returns the FileInfo structure describing file.
+// It returns the FileInfo and an error, if any.
+func (f *File) Stat() (fi *FileInfo, err Error) {
+	d, err := dirstat(f)
+	if iserror(err) {
+		return nil, err
+	}
+	return fileInfoFromStat(new(FileInfo), d), err
+}
+
+// Truncate changes the size of the file.
+// It does not change the I/O offset.
+func (f *File) Truncate(size int64) Error {
+	var d Dir
+	d.Null()
+
+	d.Length = uint64(size)
+
+	if e := syscall.Fwstat(f.fd, pdir(nil, &d)); iserror(e) {
+		return &PathError{"truncate", f.name, e}
+	}
+	return nil
+}
+
+// Chmod changes the mode of the file to mode.
+func (f *File) Chmod(mode uint32) Error {
+	var d Dir
+	var mask = ^uint32(0777)
+
+	d.Null()
+	odir, e := dirstat(f)
+	if iserror(e) {
+		return &PathError{"chmod", f.name, e}
+	}
+
+	d.Mode = (odir.Mode & mask) | (mode &^ mask)
+	if e := syscall.Fwstat(f.fd, pdir(nil, &d)); iserror(e) {
+		return &PathError{"chmod", f.name, 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() (err Error) {
+	if f == nil {
+		return EINVAL
+	}
+
+	var d Dir
+	d.Null()
+
+	if e := syscall.Fwstat(f.fd, pdir(nil, &d)); iserror(e) {
+		return NewSyscallError("fsync", e)
+	}
+	return nil
+}
+
+// read reads up to len(b) bytes from the File.
+// It returns the number of bytes read and an error, if any.
+func (f *File) read(b []byte) (n int, err syscall.Error) {
+	return syscall.Read(f.fd, b)
+}
+
+// pread reads len(b) bytes from the File starting at byte offset off.
+// It returns the number of bytes read and the error, if any.
+// EOF is signaled by a zero count with err set to nil.
+func (f *File) pread(b []byte, off int64) (n int, err syscall.Error) {
+	return syscall.Pread(f.fd, b, off)
+}
+
+// write writes len(b) bytes to the File.
+// It returns the number of bytes written and an error, if any.
+func (f *File) write(b []byte) (n int, err syscall.Error) {
+	return syscall.Write(f.fd, b)
+}
+
+// pwrite writes len(b) bytes to the File starting at byte offset off.
+// It returns the number of bytes written and an error, if any.
+func (f *File) pwrite(b []byte, off int64) (n int, err syscall.Error) {
+	return syscall.Pwrite(f.fd, b, off)
+}
+
+// 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 syscall.Error) {
+	return syscall.Seek(f.fd, offset, whence)
+}
+
+// Truncate changes the size of the named file.
+// If the file is a symbolic link, it changes the size of the link's target.
+func Truncate(name string, size int64) Error {
+	var d Dir
+	d.Null()
+
+	d.Length = uint64(size)
+
+	if e := syscall.Wstat(name, pdir(nil, &d)); iserror(e) {
+		return &PathError{"truncate", name, e}
+	}
+	return nil
+}
+
+// Remove removes the named file or directory.
+func Remove(name string) Error {
+	if e := syscall.Remove(name); iserror(e) {
+		return &PathError{"remove", name, e}
+	}
+	return nil
+}
+
+// Rename renames a file.
+func Rename(oldname, newname string) Error {
+	var d Dir
+	d.Null()
+
+	d.Name = newname
+
+	if e := syscall.Wstat(oldname, pdir(nil, &d)); iserror(e) {
+		return &PathError{"rename", oldname, e}
+	}
+	return nil
+}
+
+// Chmod changes the mode of the named file to mode.
+func Chmod(name string, mode uint32) Error {
+	var d Dir
+	var mask = ^uint32(0777)
+
+	d.Null()
+	odir, e := dirstat(name)
+	if iserror(e) {
+		return &PathError{"chmod", name, e}
+	}
+
+	d.Mode = (odir.Mode & mask) | (mode &^ mask)
+	if e := syscall.Wstat(name, pdir(nil, &d)); iserror(e) {
+		return &PathError{"chmod", name, e}
+	}
+	return nil
+}
+
+// Chtimes changes the access and modification times of the named
+// file, similar to the Unix utime() or utimes() functions.
+//
+// The argument times are in nanoseconds, although the underlying
+// filesystem may truncate or round the values to a more
+// coarse time unit.
+func Chtimes(name string, atimeNs int64, mtimeNs int64) Error {
+	var d Dir
+	d.Null()
+
+	d.Atime = uint32(atimeNs / 1e9)
+	d.Mtime = uint32(mtimeNs / 1e9)
+
+	if e := syscall.Wstat(name, pdir(nil, &d)); iserror(e) {
+		return &PathError{"chtimes", name, e}
+	}
+	return nil
+}
+
+func Pipe() (r *File, w *File, err Error) {
+	var p [2]int
+
+	syscall.ForkLock.RLock()
+	if e := syscall.Pipe(p[0:]); iserror(e) {
+		syscall.ForkLock.RUnlock()
+		return nil, nil, NewSyscallError("pipe", e)
+	}
+	syscall.ForkLock.RUnlock()
+
+	return NewFile(p[0], "|0"), NewFile(p[1], "|1"), nil
+}
+
+// not supported on Plan 9
+
+// Link creates a hard link.
+func Link(oldname, newname string) Error {
+	return EPLAN9
+}
+
+func Symlink(oldname, newname string) Error {
+	return EPLAN9
+}
+
+func Readlink(name string) (string, Error) {
+	return "", EPLAN9
+}
+
+func Chown(name string, uid, gid int) Error {
+	return EPLAN9
+}
+
+func Lchown(name string, uid, gid int) Error {
+	return EPLAN9
+}
+
+func (f *File) Chown(uid, gid int) Error {
+	return EPLAN9
+}
diff --git a/src/pkg/os/file_posix.go b/src/pkg/os/file_posix.go
new file mode 100644
index 000000000..0791a0dc0
--- /dev/null
+++ b/src/pkg/os/file_posix.go
@@ -0,0 +1,226 @@
+// 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 (
+	"syscall"
+)
+
+func sigpipe() // implemented in package runtime
+
+func epipecheck(file *File, e int) {
+	if e == syscall.EPIPE {
+		file.nepipe++
+		if file.nepipe >= 10 {
+			sigpipe()
+		}
+	} else {
+		file.nepipe = 0
+	}
+}
+
+// Stat returns a FileInfo structure describing the named file and an error, if any.
+// If name names a valid symbolic link, the returned FileInfo describes
+// the file pointed at by the link and has fi.FollowedSymlink set to true.
+// If name names an invalid symbolic link, the returned FileInfo describes
+// the link itself and has fi.FollowedSymlink set to false.
+func Stat(name string) (fi *FileInfo, err Error) {
+	var lstat, stat syscall.Stat_t
+	e := syscall.Lstat(name, &lstat)
+	if iserror(e) {
+		return nil, &PathError{"stat", name, Errno(e)}
+	}
+	statp := &lstat
+	if lstat.Mode&syscall.S_IFMT == syscall.S_IFLNK {
+		e := syscall.Stat(name, &stat)
+		if !iserror(e) {
+			statp = &stat
+		}
+	}
+	return fileInfoFromStat(name, new(FileInfo), &lstat, statp), nil
+}
+
+// Lstat returns the FileInfo structure describing the named file and an
+// error, if any.  If the file is a symbolic link, the returned FileInfo
+// describes the symbolic link.  Lstat makes no attempt to follow the link.
+func Lstat(name string) (fi *FileInfo, err Error) {
+	var stat syscall.Stat_t
+	e := syscall.Lstat(name, &stat)
+	if iserror(e) {
+		return nil, &PathError{"lstat", name, Errno(e)}
+	}
+	return fileInfoFromStat(name, new(FileInfo), &stat, &stat), nil
+}
+
+// Remove removes the named file or directory.
+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 := syscall.Unlink(name)
+	if !iserror(e) {
+		return nil
+	}
+	e1 := syscall.Rmdir(name)
+	if !iserror(e1) {
+		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.
+	// For windows syscall.ENOTDIR is set
+	// to syscall.ERROR_DIRECTORY, hopefully it should
+	// do the trick.
+	if e1 != syscall.ENOTDIR {
+		e = e1
+	}
+	return &PathError{"remove", name, Errno(e)}
+}
+
+// LinkError records an error during a link or symlink or rename
+// system call and the paths that caused it.
+type LinkError struct {
+	Op    string
+	Old   string
+	New   string
+	Error Error
+}
+
+func (e *LinkError) String() string {
+	return e.Op + " " + e.Old + " " + e.New + ": " + e.Error.String()
+}
+
+// Link creates a hard link.
+func Link(oldname, newname string) Error {
+	e := syscall.Link(oldname, newname)
+	if iserror(e) {
+		return &LinkError{"link", oldname, newname, Errno(e)}
+	}
+	return nil
+}
+
+// Symlink creates a symbolic link.
+func Symlink(oldname, newname string) Error {
+	e := syscall.Symlink(oldname, newname)
+	if iserror(e) {
+		return &LinkError{"symlink", oldname, newname, Errno(e)}
+	}
+	return nil
+}
+
+// Readlink reads the contents of a symbolic link: the destination of
+// the link.  It returns the contents and an Error, if any.
+func Readlink(name string) (string, Error) {
+	for len := 128; ; len *= 2 {
+		b := make([]byte, len)
+		n, e := syscall.Readlink(name, b)
+		if iserror(e) {
+			return "", &PathError{"readlink", name, Errno(e)}
+		}
+		if n < len {
+			return string(b[0:n]), nil
+		}
+	}
+	// Silence 6g.
+	return "", nil
+}
+
+// Rename renames a file.
+func Rename(oldname, newname string) Error {
+	e := syscall.Rename(oldname, newname)
+	if iserror(e) {
+		return &LinkError{"rename", oldname, newname, Errno(e)}
+	}
+	return nil
+}
+
+// Chmod changes the mode of the named file to mode.
+// If the file is a symbolic link, it changes the mode of the link's target.
+func Chmod(name string, mode uint32) Error {
+	if e := syscall.Chmod(name, mode); iserror(e) {
+		return &PathError{"chmod", name, Errno(e)}
+	}
+	return nil
+}
+
+// Chmod changes the mode of the file to mode.
+func (f *File) Chmod(mode uint32) Error {
+	if e := syscall.Fchmod(f.fd, mode); iserror(e) {
+		return &PathError{"chmod", f.name, Errno(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.
+func Chown(name string, uid, gid int) Error {
+	if e := syscall.Chown(name, uid, gid); iserror(e) {
+		return &PathError{"chown", name, Errno(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.
+func Lchown(name string, uid, gid int) Error {
+	if e := syscall.Lchown(name, uid, gid); iserror(e) {
+		return &PathError{"lchown", name, Errno(e)}
+	}
+	return nil
+}
+
+// Chown changes the numeric uid and gid of the named file.
+func (f *File) Chown(uid, gid int) Error {
+	if e := syscall.Fchown(f.fd, uid, gid); iserror(e) {
+		return &PathError{"chown", f.name, Errno(e)}
+	}
+	return nil
+}
+
+// Truncate changes the size of the file.
+// It does not change the I/O offset.
+func (f *File) Truncate(size int64) Error {
+	if e := syscall.Ftruncate(f.fd, size); iserror(e) {
+		return &PathError{"truncate", f.name, Errno(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 (file *File) Sync() (err Error) {
+	if file == nil {
+		return EINVAL
+	}
+	if e := syscall.Fsync(file.fd); iserror(e) {
+		return NewSyscallError("fsync", e)
+	}
+	return nil
+}
+
+// Chtimes changes the access and modification times of the named
+// file, similar to the Unix utime() or utimes() functions.
+//
+// The argument times are in nanoseconds, although the underlying
+// filesystem may truncate or round the values to a more
+// coarse time unit.
+func Chtimes(name string, atime_ns int64, mtime_ns int64) Error {
+	var utimes [2]syscall.Timeval
+	utimes[0] = syscall.NsecToTimeval(atime_ns)
+	utimes[1] = syscall.NsecToTimeval(mtime_ns)
+	if e := syscall.Utimes(name, utimes[0:]); iserror(e) {
+		return &PathError{"chtimes", name, Errno(e)}
+	}
+	return nil
+}
diff --git a/src/pkg/os/file_unix.go b/src/pkg/os/file_unix.go
new file mode 100644
index 000000000..301c2f473
--- /dev/null
+++ b/src/pkg/os/file_unix.go
@@ -0,0 +1,208 @@
+// 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 (
+	"runtime"
+	"syscall"
+)
+
+// File represents an open file descriptor.
+type File struct {
+	fd      int
+	name    string
+	dirinfo *dirInfo // nil unless directory being read
+	nepipe  int      // number of consecutive EPIPE in Write
+}
+
+// Fd returns the integer Unix file descriptor referencing the open file.
+func (file *File) Fd() int {
+	if file == nil {
+		return -1
+	}
+	return file.fd
+}
+
+// NewFile returns a new File with the given file descriptor and name.
+func NewFile(fd int, name string) *File {
+	if fd < 0 {
+		return nil
+	}
+	f := &File{fd: fd, name: name}
+	runtime.SetFinalizer(f, (*File).Close)
+	return f
+}
+
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	buf  []byte // buffer for directory I/O
+	nbuf int    // length of buf; return value from Getdirentries
+	bufp int    // location of next record in buf.
+}
+
+// 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"
+
+// OpenFile is the generalized open call; most users will use Open
+// or Create instead.  It opens the named file with specified flag
+// (O_RDONLY etc.) and perm, (0666 etc.) if applicable.  If successful,
+// methods on the returned File can be used for I/O.
+// It returns the File and an Error, if any.
+func OpenFile(name string, flag int, perm uint32) (file *File, err Error) {
+	r, e := syscall.Open(name, flag|syscall.O_CLOEXEC, perm)
+	if e != 0 {
+		return nil, &PathError{"open", name, Errno(e)}
+	}
+
+	// There's a race here with fork/exec, which we are
+	// content to live with.  See ../syscall/exec.go
+	if syscall.O_CLOEXEC == 0 { // O_CLOEXEC not supported
+		syscall.CloseOnExec(r)
+	}
+
+	return NewFile(r, name), nil
+}
+
+// Close closes the File, rendering it unusable for I/O.
+// It returns an Error, if any.
+func (file *File) Close() Error {
+	if file == nil || file.fd < 0 {
+		return EINVAL
+	}
+	var err Error
+	if e := syscall.Close(file.fd); e != 0 {
+		err = &PathError{"close", file.name, Errno(e)}
+	}
+	file.fd = -1 // so it can't be closed again
+
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(file, nil)
+	return err
+}
+
+// Stat returns the FileInfo structure describing file.
+// It returns the FileInfo and an error, if any.
+func (file *File) Stat() (fi *FileInfo, err Error) {
+	var stat syscall.Stat_t
+	e := syscall.Fstat(file.fd, &stat)
+	if e != 0 {
+		return nil, &PathError{"stat", file.name, Errno(e)}
+	}
+	return fileInfoFromStat(file.name, new(FileInfo), &stat, &stat), nil
+}
+
+// Readdir reads the contents of the directory associated with file and
+// returns an array of up to n FileInfo structures, as would be returned
+// by Lstat, in directory order. Subsequent calls on the same file will yield
+// further FileInfos.
+//
+// If n > 0, Readdir returns at most n FileInfo structures. In this case, if
+// Readdir returns an empty slice, it will return a non-nil error
+// explaining why. At the end of a directory, the error is os.EOF.
+//
+// If n <= 0, Readdir returns all the FileInfo from the directory in
+// a single slice. In this case, if Readdir succeeds (reads all
+// the way to the end of the directory), it returns the slice and a
+// nil os.Error. If it encounters an error before the end of the
+// directory, Readdir returns the FileInfo read until that point
+// and a non-nil error.
+func (file *File) Readdir(n int) (fi []FileInfo, err Error) {
+	dirname := file.name
+	if dirname == "" {
+		dirname = "."
+	}
+	dirname += "/"
+	names, err := file.Readdirnames(n)
+	fi = make([]FileInfo, len(names))
+	for i, filename := range names {
+		fip, err := Lstat(dirname + filename)
+		if fip == nil || err != nil {
+			fi[i].Name = filename // rest is already zeroed out
+		} else {
+			fi[i] = *fip
+		}
+	}
+	return
+}
+
+// read reads up to len(b) bytes from the File.
+// It returns the number of bytes read and an error, if any.
+func (f *File) read(b []byte) (n int, err int) {
+	return syscall.Read(f.fd, b)
+}
+
+// pread reads len(b) bytes from the File starting at byte offset off.
+// It returns the number of bytes read and the error, if any.
+// EOF is signaled by a zero count with err set to 0.
+func (f *File) pread(b []byte, off int64) (n int, err int) {
+	return syscall.Pread(f.fd, b, off)
+}
+
+// write writes len(b) bytes to the File.
+// It returns the number of bytes written and an error, if any.
+func (f *File) write(b []byte) (n int, err int) {
+	return syscall.Write(f.fd, b)
+}
+
+// pwrite writes len(b) bytes to the File starting at byte offset off.
+// It returns the number of bytes written and an error, if any.
+func (f *File) pwrite(b []byte, off int64) (n int, err int) {
+	return syscall.Pwrite(f.fd, b, off)
+}
+
+// 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 int) {
+	return syscall.Seek(f.fd, offset, whence)
+}
+
+// Truncate changes the size of the named file.
+// If the file is a symbolic link, it changes the size of the link's target.
+func Truncate(name string, size int64) Error {
+	if e := syscall.Truncate(name, size); e != 0 {
+		return &PathError{"truncate", name, Errno(e)}
+	}
+	return nil
+}
+
+// basename removes trailing slashes and the leading directory name from path name
+func basename(name string) string {
+	i := len(name) - 1
+	// Remove trailing slashes
+	for ; i > 0 && name[i] == '/'; i-- {
+		name = name[:i]
+	}
+	// Remove leading directory name
+	for i--; i >= 0; i-- {
+		if name[i] == '/' {
+			name = name[i+1:]
+			break
+		}
+	}
+
+	return name
+}
+
+// Pipe returns a connected pair of Files; reads from r return bytes written to w.
+// It returns the files and an Error, if any.
+func Pipe() (r *File, w *File, err Error) {
+	var p [2]int
+
+	// See ../syscall/exec.go for description of lock.
+	syscall.ForkLock.RLock()
+	e := syscall.Pipe(p[0:])
+	if iserror(e) {
+		syscall.ForkLock.RUnlock()
+		return nil, nil, NewSyscallError("pipe", e)
+	}
+	syscall.CloseOnExec(p[0])
+	syscall.CloseOnExec(p[1])
+	syscall.ForkLock.RUnlock()
+
+	return NewFile(p[0], "|0"), NewFile(p[1], "|1"), nil
+}
diff --git a/src/pkg/os/file_windows.go b/src/pkg/os/file_windows.go
new file mode 100644
index 000000000..70dd6e241
--- /dev/null
+++ b/src/pkg/os/file_windows.go
@@ -0,0 +1,317 @@
+// 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 (
+	"runtime"
+	"sync"
+	"syscall"
+)
+
+// File represents an open file descriptor.
+type File struct {
+	fd      syscall.Handle
+	name    string
+	dirinfo *dirInfo   // nil unless directory being read
+	nepipe  int        // number of consecutive EPIPE in Write
+	l       sync.Mutex // used to implement windows pread/pwrite
+}
+
+// Fd returns the Windows handle referencing the open file.
+func (file *File) Fd() syscall.Handle {
+	if file == nil {
+		return syscall.InvalidHandle
+	}
+	return file.fd
+}
+
+// NewFile returns a new File with the given file descriptor and name.
+func NewFile(fd syscall.Handle, name string) *File {
+	if fd < 0 {
+		return nil
+	}
+	f := &File{fd: fd, name: name}
+	runtime.SetFinalizer(f, (*File).Close)
+	return f
+}
+
+// Auxiliary information if the File describes a directory
+type dirInfo struct {
+	stat         syscall.Stat_t
+	usefirststat bool
+}
+
+const DevNull = "NUL"
+
+func (file *File) isdir() bool { return file != nil && file.dirinfo != nil }
+
+func openFile(name string, flag int, perm uint32) (file *File, err Error) {
+	r, e := syscall.Open(name, flag|syscall.O_CLOEXEC, perm)
+	if e != 0 {
+		return nil, &PathError{"open", name, Errno(e)}
+	}
+
+	// There's a race here with fork/exec, which we are
+	// content to live with.  See ../syscall/exec.go
+	if syscall.O_CLOEXEC == 0 { // O_CLOEXEC not supported
+		syscall.CloseOnExec(r)
+	}
+
+	return NewFile(r, name), nil
+}
+
+func openDir(name string) (file *File, err Error) {
+	d := new(dirInfo)
+	r, e := syscall.FindFirstFile(syscall.StringToUTF16Ptr(name+"\\*"), &d.stat.Windata)
+	if e != 0 {
+		return nil, &PathError{"open", name, Errno(e)}
+	}
+	f := NewFile(r, name)
+	d.usefirststat = true
+	f.dirinfo = d
+	return f, nil
+}
+
+// OpenFile is the generalized open call; most users will use Open
+// or Create instead.  It opens the named file with specified flag
+// (O_RDONLY etc.) and perm, (0666 etc.) if applicable.  If successful,
+// methods on the returned File can be used for I/O.
+// It returns the File and an Error, if any.
+func OpenFile(name string, flag int, perm uint32) (file *File, err Error) {
+	// TODO(brainman): not sure about my logic of assuming it is dir first, then fall back to file
+	r, e := openDir(name)
+	if e == nil {
+		if flag&O_WRONLY != 0 || flag&O_RDWR != 0 {
+			r.Close()
+			return nil, &PathError{"open", name, EISDIR}
+		}
+		return r, nil
+	}
+	r, e = openFile(name, flag, perm)
+	if e == nil {
+		return r, nil
+	}
+	// Imitating Unix behavior by replacing syscall.ERROR_PATH_NOT_FOUND with
+	// os.ENOTDIR. Not sure if we should go into that.
+	if e2, ok := e.(*PathError); ok {
+		if e3, ok := e2.Error.(Errno); ok {
+			if e3 == Errno(syscall.ERROR_PATH_NOT_FOUND) {
+				return nil, &PathError{"open", name, ENOTDIR}
+			}
+		}
+	}
+	return nil, e
+}
+
+// Close closes the File, rendering it unusable for I/O.
+// It returns an Error, if any.
+func (file *File) Close() Error {
+	if file == nil || file.fd < 0 {
+		return EINVAL
+	}
+	var e int
+	if file.isdir() {
+		e = syscall.FindClose(syscall.Handle(file.fd))
+	} else {
+		e = syscall.CloseHandle(syscall.Handle(file.fd))
+	}
+	var err Error
+	if e != 0 {
+		err = &PathError{"close", file.name, Errno(e)}
+	}
+	file.fd = syscall.InvalidHandle // so it can't be closed again
+
+	// no need for a finalizer anymore
+	runtime.SetFinalizer(file, nil)
+	return err
+}
+
+func (file *File) statFile(name string) (fi *FileInfo, err Error) {
+	var stat syscall.ByHandleFileInformation
+	e := syscall.GetFileInformationByHandle(syscall.Handle(file.fd), &stat)
+	if e != 0 {
+		return nil, &PathError{"stat", file.name, Errno(e)}
+	}
+	return fileInfoFromByHandleInfo(new(FileInfo), file.name, &stat), nil
+}
+
+// Stat returns the FileInfo structure describing file.
+// It returns the FileInfo and an error, if any.
+func (file *File) Stat() (fi *FileInfo, err Error) {
+	if file == nil || file.fd < 0 {
+		return nil, EINVAL
+	}
+	if file.isdir() {
+		// I don't know any better way to do that for directory
+		return Stat(file.name)
+	}
+	return file.statFile(file.name)
+}
+
+// Readdir reads the contents of the directory associated with file and
+// returns an array of up to n FileInfo structures, as would be returned
+// by Lstat, in directory order. Subsequent calls on the same file will yield
+// further FileInfos.
+//
+// If n > 0, Readdir returns at most n FileInfo structures. In this case, if
+// Readdir returns an empty slice, it will return a non-nil error
+// explaining why. At the end of a directory, the error is os.EOF.
+//
+// If n <= 0, Readdir returns all the FileInfo from the directory in
+// a single slice. In this case, if Readdir succeeds (reads all
+// the way to the end of the directory), it returns the slice and a
+// nil os.Error. If it encounters an error before the end of the
+// directory, Readdir returns the FileInfo read until that point
+// and a non-nil error.
+func (file *File) Readdir(n int) (fi []FileInfo, err Error) {
+	if file == nil || file.fd < 0 {
+		return nil, EINVAL
+	}
+	if !file.isdir() {
+		return nil, &PathError{"Readdir", file.name, ENOTDIR}
+	}
+	di := file.dirinfo
+	wantAll := n <= 0
+	size := n
+	if wantAll {
+		n = -1
+		size = 100
+	}
+	fi = make([]FileInfo, 0, size) // Empty with room to grow.
+	for n != 0 {
+		if di.usefirststat {
+			di.usefirststat = false
+		} else {
+			e := syscall.FindNextFile(syscall.Handle(file.fd), &di.stat.Windata)
+			if e != 0 {
+				if e == syscall.ERROR_NO_MORE_FILES {
+					break
+				} else {
+					err = &PathError{"FindNextFile", file.name, Errno(e)}
+					if !wantAll {
+						fi = nil
+					}
+					return
+				}
+			}
+		}
+		var f FileInfo
+		fileInfoFromWin32finddata(&f, &di.stat.Windata)
+		if f.Name == "." || f.Name == ".." { // Useless names
+			continue
+		}
+		n--
+		fi = append(fi, f)
+	}
+	if !wantAll && len(fi) == 0 {
+		return fi, EOF
+	}
+	return fi, nil
+}
+
+// read reads up to len(b) bytes from the File.
+// It returns the number of bytes read and an error, if any.
+func (f *File) read(b []byte) (n int, err int) {
+	f.l.Lock()
+	defer f.l.Unlock()
+	return syscall.Read(f.fd, b)
+}
+
+// pread reads len(b) bytes from the File starting at byte offset off.
+// It returns the number of bytes read and the error, if any.
+// EOF is signaled by a zero count with err set to 0.
+func (f *File) pread(b []byte, off int64) (n int, err int) {
+	f.l.Lock()
+	defer f.l.Unlock()
+	curoffset, e := syscall.Seek(f.fd, 0, 1)
+	if e != 0 {
+		return 0, e
+	}
+	defer syscall.Seek(f.fd, curoffset, 0)
+	o := syscall.Overlapped{
+		OffsetHigh: uint32(off >> 32),
+		Offset:     uint32(off),
+	}
+	var done uint32
+	e = syscall.ReadFile(syscall.Handle(f.fd), b, &done, &o)
+	if e != 0 {
+		return 0, e
+	}
+	return int(done), 0
+}
+
+// write writes len(b) bytes to the File.
+// It returns the number of bytes written and an error, if any.
+func (f *File) write(b []byte) (n int, err int) {
+	f.l.Lock()
+	defer f.l.Unlock()
+	return syscall.Write(f.fd, b)
+}
+
+// pwrite writes len(b) bytes to the File starting at byte offset off.
+// It returns the number of bytes written and an error, if any.
+func (f *File) pwrite(b []byte, off int64) (n int, err int) {
+	f.l.Lock()
+	defer f.l.Unlock()
+	curoffset, e := syscall.Seek(f.fd, 0, 1)
+	if e != 0 {
+		return 0, e
+	}
+	defer syscall.Seek(f.fd, curoffset, 0)
+	o := syscall.Overlapped{
+		OffsetHigh: uint32(off >> 32),
+		Offset:     uint32(off),
+	}
+	var done uint32
+	e = syscall.WriteFile(syscall.Handle(f.fd), b, &done, &o)
+	if e != 0 {
+		return 0, e
+	}
+	return int(done), 0
+}
+
+// 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 int) {
+	f.l.Lock()
+	defer f.l.Unlock()
+	return syscall.Seek(f.fd, offset, whence)
+}
+
+// Truncate changes the size of the named file.
+// If the file is a symbolic link, it changes the size of the link's target.
+func Truncate(name string, size int64) Error {
+	f, e := OpenFile(name, O_WRONLY|O_CREATE, 0666)
+	if e != nil {
+		return e
+	}
+	defer f.Close()
+	e1 := f.Truncate(size)
+	if e1 != nil {
+		return e1
+	}
+	return nil
+}
+
+// Pipe returns a connected pair of Files; reads from r return bytes written to w.
+// It returns the files and an Error, if any.
+func Pipe() (r *File, w *File, err Error) {
+	var p [2]syscall.Handle
+
+	// See ../syscall/exec.go for description of lock.
+	syscall.ForkLock.RLock()
+	e := syscall.Pipe(p[0:])
+	if iserror(e) {
+		syscall.ForkLock.RUnlock()
+		return nil, nil, NewSyscallError("pipe", e)
+	}
+	syscall.CloseOnExec(p[0])
+	syscall.CloseOnExec(p[1])
+	syscall.ForkLock.RUnlock()
+
+	return NewFile(p[0], "|0"), NewFile(p[1], "|1"), nil
+}
diff --git a/src/pkg/os/getwd.go b/src/pkg/os/getwd.go
new file mode 100644
index 000000000..4c142ad3a
--- /dev/null
+++ b/src/pkg/os/getwd.go
@@ -0,0 +1,92 @@
+// 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 (
+	"syscall"
+)
+
+// Getwd returns a rooted path name corresponding to the
+// current directory.  If the current directory can be
+// reached via multiple paths (due to symbolic links),
+// Getwd may return any one of them.
+func Getwd() (string, Error) {
+	// If the operating system provides a Getwd call, use it.
+	if syscall.ImplementsGetwd {
+		s, e := syscall.Getwd()
+		return s, NewSyscallError("getwd", e)
+	}
+
+	// Otherwise, we're trying to find our way back to ".".
+	dot, err := Stat(".")
+	if err != nil {
+		return "", err
+	}
+
+	// Clumsy but widespread kludge:
+	// if $PWD is set and matches ".", use it.
+	pwd := Getenv("PWD")
+	if len(pwd) > 0 && pwd[0] == '/' {
+		d, err := Stat(pwd)
+		if err == nil && d.Dev == dot.Dev && d.Ino == dot.Ino {
+			return pwd, nil
+		}
+	}
+
+	// Root is a special case because it has no parent
+	// and ends in a slash.
+	root, err := Stat("/")
+	if err != nil {
+		// Can't stat root - no hope.
+		return "", err
+	}
+	if root.Dev == dot.Dev && root.Ino == dot.Ino {
+		return "/", nil
+	}
+
+	// General algorithm: find name in parent
+	// and then find name of parent.  Each iteration
+	// adds /name to the beginning of pwd.
+	pwd = ""
+	for parent := ".."; ; parent = "../" + parent {
+		if len(parent) >= 1024 { // Sanity check
+			return "", ENAMETOOLONG
+		}
+		fd, err := Open(parent)
+		if err != nil {
+			return "", err
+		}
+
+		for {
+			names, err := fd.Readdirnames(100)
+			if err != nil {
+				fd.Close()
+				return "", err
+			}
+			for _, name := range names {
+				d, _ := Lstat(parent + "/" + name)
+				if d.Dev == dot.Dev && d.Ino == dot.Ino {
+					pwd = "/" + name + pwd
+					goto Found
+				}
+			}
+		}
+		fd.Close()
+		return "", ENOENT
+
+	Found:
+		pd, err := fd.Stat()
+		if err != nil {
+			return "", err
+		}
+		fd.Close()
+		if pd.Dev == root.Dev && pd.Ino == root.Ino {
+			break
+		}
+		// Set up for next round.
+		dot = pd
+	}
+	return pwd, nil
+}
diff --git a/src/pkg/os/inotify/Makefile b/src/pkg/os/inotify/Makefile
new file mode 100644
index 000000000..90e18da57
--- /dev/null
+++ b/src/pkg/os/inotify/Makefile
@@ -0,0 +1,14 @@
+# Copyright 2010 The Go Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+include ../../../Make.inc
+
+TARG=os/inotify
+
+GOFILES_linux=\
+	inotify_linux.go\
+
+GOFILES+=$(GOFILES_$(GOOS))
+
+include ../../../Make.pkg
diff --git a/src/pkg/os/inotify/inotify_linux.go b/src/pkg/os/inotify/inotify_linux.go
new file mode 100644
index 000000000..99fa51622
--- /dev/null
+++ b/src/pkg/os/inotify/inotify_linux.go
@@ -0,0 +1,288 @@
+// Copyright 2010 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 inotify implements a wrapper for the Linux inotify system.
+
+Example:
+    watcher, err := inotify.NewWatcher()
+    if err != nil {
+        log.Fatal(err)
+    }
+    err = watcher.Watch("/tmp")
+    if err != nil {
+        log.Fatal(err)
+    }
+    for {
+        select {
+        case ev := <-watcher.Event:
+            log.Println("event:", ev)
+        case err := <-watcher.Error:
+            log.Println("error:", err)
+        }
+    }
+
+*/
+package inotify
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"syscall"
+	"unsafe"
+)
+
+type Event struct {
+	Mask   uint32 // Mask of events
+	Cookie uint32 // Unique cookie associating related events (for rename(2))
+	Name   string // File name (optional)
+}
+
+type watch struct {
+	wd    uint32 // Watch descriptor (as returned by the inotify_add_watch() syscall)
+	flags uint32 // inotify flags of this watch (see inotify(7) for the list of valid flags)
+}
+
+type Watcher struct {
+	fd       int               // File descriptor (as returned by the inotify_init() syscall)
+	watches  map[string]*watch // Map of inotify watches (key: path)
+	paths    map[int]string    // Map of watched paths (key: watch descriptor)
+	Error    chan os.Error     // Errors are sent on this channel
+	Event    chan *Event       // Events are returned on this channel
+	done     chan bool         // Channel for sending a "quit message" to the reader goroutine
+	isClosed bool              // Set to true when Close() is first called
+}
+
+// NewWatcher creates and returns a new inotify instance using inotify_init(2)
+func NewWatcher() (*Watcher, os.Error) {
+	fd, errno := syscall.InotifyInit()
+	if fd == -1 {
+		return nil, os.NewSyscallError("inotify_init", errno)
+	}
+	w := &Watcher{
+		fd:      fd,
+		watches: make(map[string]*watch),
+		paths:   make(map[int]string),
+		Event:   make(chan *Event),
+		Error:   make(chan os.Error),
+		done:    make(chan bool, 1),
+	}
+
+	go w.readEvents()
+	return w, nil
+}
+
+// Close closes an inotify watcher instance
+// It sends a message to the reader goroutine to quit and removes all watches
+// associated with the inotify instance
+func (w *Watcher) Close() os.Error {
+	if w.isClosed {
+		return nil
+	}
+	w.isClosed = true
+
+	// Send "quit" message to the reader goroutine
+	w.done <- true
+	for path := range w.watches {
+		w.RemoveWatch(path)
+	}
+
+	return nil
+}
+
+// AddWatch adds path to the watched file set.
+// The flags are interpreted as described in inotify_add_watch(2).
+func (w *Watcher) AddWatch(path string, flags uint32) os.Error {
+	if w.isClosed {
+		return os.NewError("inotify instance already closed")
+	}
+
+	watchEntry, found := w.watches[path]
+	if found {
+		watchEntry.flags |= flags
+		flags |= syscall.IN_MASK_ADD
+	}
+	wd, errno := syscall.InotifyAddWatch(w.fd, path, flags)
+	if wd == -1 {
+		return &os.PathError{"inotify_add_watch", path, os.Errno(errno)}
+	}
+
+	if !found {
+		w.watches[path] = &watch{wd: uint32(wd), flags: flags}
+		w.paths[wd] = path
+	}
+	return nil
+}
+
+// Watch adds path to the watched file set, watching all events.
+func (w *Watcher) Watch(path string) os.Error {
+	return w.AddWatch(path, IN_ALL_EVENTS)
+}
+
+// RemoveWatch removes path from the watched file set.
+func (w *Watcher) RemoveWatch(path string) os.Error {
+	watch, ok := w.watches[path]
+	if !ok {
+		return os.NewError(fmt.Sprintf("can't remove non-existent inotify watch for: %s", path))
+	}
+	success, errno := syscall.InotifyRmWatch(w.fd, watch.wd)
+	if success == -1 {
+		return os.NewSyscallError("inotify_rm_watch", errno)
+	}
+	w.watches[path] = nil, false
+	return nil
+}
+
+// readEvents reads from the inotify file descriptor, converts the
+// received events into Event objects and sends them via the Event channel
+func (w *Watcher) readEvents() {
+	var (
+		buf   [syscall.SizeofInotifyEvent * 4096]byte // Buffer for a maximum of 4096 raw events
+		n     int                                     // Number of bytes read with read()
+		errno int                                     // Syscall errno
+	)
+
+	for {
+		n, errno = syscall.Read(w.fd, buf[0:])
+		// See if there is a message on the "done" channel
+		var done bool
+		select {
+		case done = <-w.done:
+		default:
+		}
+
+		// If EOF or a "done" message is received
+		if n == 0 || done {
+			errno := syscall.Close(w.fd)
+			if errno == -1 {
+				w.Error <- os.NewSyscallError("close", errno)
+			}
+			close(w.Event)
+			close(w.Error)
+			return
+		}
+		if n < 0 {
+			w.Error <- os.NewSyscallError("read", errno)
+			continue
+		}
+		if n < syscall.SizeofInotifyEvent {
+			w.Error <- os.NewError("inotify: short read in readEvents()")
+			continue
+		}
+
+		var offset uint32 = 0
+		// We don't know how many events we just read into the buffer
+		// While the offset points to at least one whole event...
+		for offset <= uint32(n-syscall.SizeofInotifyEvent) {
+			// Point "raw" to the event in the buffer
+			raw := (*syscall.InotifyEvent)(unsafe.Pointer(&buf[offset]))
+			event := new(Event)
+			event.Mask = uint32(raw.Mask)
+			event.Cookie = uint32(raw.Cookie)
+			nameLen := uint32(raw.Len)
+			// If the event happened to the watched directory or the watched file, the kernel
+			// doesn't append the filename to the event, but we would like to always fill the
+			// the "Name" field with a valid filename. We retrieve the path of the watch from
+			// the "paths" map.
+			event.Name = w.paths[int(raw.Wd)]
+			if nameLen > 0 {
+				// Point "bytes" at the first byte of the filename
+				bytes := (*[syscall.PathMax]byte)(unsafe.Pointer(&buf[offset+syscall.SizeofInotifyEvent]))
+				// The filename is padded with NUL bytes. TrimRight() gets rid of those.
+				event.Name += "/" + strings.TrimRight(string(bytes[0:nameLen]), "\000")
+			}
+			// Send the event on the events channel
+			w.Event <- event
+
+			// Move to the next event in the buffer
+			offset += syscall.SizeofInotifyEvent + nameLen
+		}
+	}
+}
+
+// String formats the event e in the form
+// "filename: 0xEventMask = IN_ACCESS|IN_ATTRIB_|..."
+func (e *Event) String() string {
+	var events string = ""
+
+	m := e.Mask
+	for _, b := range eventBits {
+		if m&b.Value != 0 {
+			m &^= b.Value
+			events += "|" + b.Name
+		}
+	}
+
+	if m != 0 {
+		events += fmt.Sprintf("|%#x", m)
+	}
+	if len(events) > 0 {
+		events = " == " + events[1:]
+	}
+
+	return fmt.Sprintf("%q: %#x%s", e.Name, e.Mask, events)
+}
+
+const (
+	// Options for inotify_init() are not exported
+	// IN_CLOEXEC    uint32 = syscall.IN_CLOEXEC
+	// IN_NONBLOCK   uint32 = syscall.IN_NONBLOCK
+
+	// Options for AddWatch
+	IN_DONT_FOLLOW uint32 = syscall.IN_DONT_FOLLOW
+	IN_ONESHOT     uint32 = syscall.IN_ONESHOT
+	IN_ONLYDIR     uint32 = syscall.IN_ONLYDIR
+
+	// The "IN_MASK_ADD" option is not exported, as AddWatch
+	// adds it automatically, if there is already a watch for the given path
+	// IN_MASK_ADD      uint32 = syscall.IN_MASK_ADD
+
+	// Events
+	IN_ACCESS        uint32 = syscall.IN_ACCESS
+	IN_ALL_EVENTS    uint32 = syscall.IN_ALL_EVENTS
+	IN_ATTRIB        uint32 = syscall.IN_ATTRIB
+	IN_CLOSE         uint32 = syscall.IN_CLOSE
+	IN_CLOSE_NOWRITE uint32 = syscall.IN_CLOSE_NOWRITE
+	IN_CLOSE_WRITE   uint32 = syscall.IN_CLOSE_WRITE
+	IN_CREATE        uint32 = syscall.IN_CREATE
+	IN_DELETE        uint32 = syscall.IN_DELETE
+	IN_DELETE_SELF   uint32 = syscall.IN_DELETE_SELF
+	IN_MODIFY        uint32 = syscall.IN_MODIFY
+	IN_MOVE          uint32 = syscall.IN_MOVE
+	IN_MOVED_FROM    uint32 = syscall.IN_MOVED_FROM
+	IN_MOVED_TO      uint32 = syscall.IN_MOVED_TO
+	IN_MOVE_SELF     uint32 = syscall.IN_MOVE_SELF
+	IN_OPEN          uint32 = syscall.IN_OPEN
+
+	// Special events
+	IN_ISDIR      uint32 = syscall.IN_ISDIR
+	IN_IGNORED    uint32 = syscall.IN_IGNORED
+	IN_Q_OVERFLOW uint32 = syscall.IN_Q_OVERFLOW
+	IN_UNMOUNT    uint32 = syscall.IN_UNMOUNT
+)
+
+var eventBits = []struct {
+	Value uint32
+	Name  string
+}{
+	{IN_ACCESS, "IN_ACCESS"},
+	{IN_ATTRIB, "IN_ATTRIB"},
+	{IN_CLOSE, "IN_CLOSE"},
+	{IN_CLOSE_NOWRITE, "IN_CLOSE_NOWRITE"},
+	{IN_CLOSE_WRITE, "IN_CLOSE_WRITE"},
+	{IN_CREATE, "IN_CREATE"},
+	{IN_DELETE, "IN_DELETE"},
+	{IN_DELETE_SELF, "IN_DELETE_SELF"},
+	{IN_MODIFY, "IN_MODIFY"},
+	{IN_MOVE, "IN_MOVE"},
+	{IN_MOVED_FROM, "IN_MOVED_FROM"},
+	{IN_MOVED_TO, "IN_MOVED_TO"},
+	{IN_MOVE_SELF, "IN_MOVE_SELF"},
+	{IN_OPEN, "IN_OPEN"},
+	{IN_ISDIR, "IN_ISDIR"},
+	{IN_IGNORED, "IN_IGNORED"},
+	{IN_Q_OVERFLOW, "IN_Q_OVERFLOW"},
+	{IN_UNMOUNT, "IN_UNMOUNT"},
+}
diff --git a/src/pkg/os/inotify/inotify_linux_test.go b/src/pkg/os/inotify/inotify_linux_test.go
new file mode 100644
index 000000000..aa72604eb
--- /dev/null
+++ b/src/pkg/os/inotify/inotify_linux_test.go
@@ -0,0 +1,96 @@
+// Copyright 2010 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 inotify
+
+import (
+	"os"
+	"time"
+	"testing"
+)
+
+func TestInotifyEvents(t *testing.T) {
+	// Create an inotify watcher instance and initialize it
+	watcher, err := NewWatcher()
+	if err != nil {
+		t.Fatalf("NewWatcher() failed: %s", err)
+	}
+
+	// Add a watch for "_test"
+	err = watcher.Watch("_test")
+	if err != nil {
+		t.Fatalf("Watcher.Watch() failed: %s", err)
+	}
+
+	// Receive errors on the error channel on a separate goroutine
+	go func() {
+		for err := range watcher.Error {
+			t.Fatalf("error received: %s", err)
+		}
+	}()
+
+	const testFile string = "_test/TestInotifyEvents.testfile"
+
+	// Receive events on the event channel on a separate goroutine
+	eventstream := watcher.Event
+	var eventsReceived = 0
+	done := make(chan bool)
+	go func() {
+		for event := range eventstream {
+			// Only count relevant events
+			if event.Name == testFile {
+				eventsReceived++
+				t.Logf("event received: %s", event)
+			} else {
+				t.Logf("unexpected event received: %s", event)
+			}
+		}
+		done <- true
+	}()
+
+	// Create a file
+	// This should add at least one event to the inotify event queue
+	_, err = os.OpenFile(testFile, os.O_WRONLY|os.O_CREATE, 0666)
+	if err != nil {
+		t.Fatalf("creating test file failed: %s", err)
+	}
+
+	// We expect this event to be received almost immediately, but let's wait 1 s to be sure
+	time.Sleep(1000e6) // 1000 ms
+	if eventsReceived == 0 {
+		t.Fatal("inotify event hasn't been received after 1 second")
+	}
+
+	// Try closing the inotify instance
+	t.Log("calling Close()")
+	watcher.Close()
+	t.Log("waiting for the event channel to become closed...")
+	select {
+	case <-done:
+		t.Log("event channel closed")
+	case <-time.After(1e9):
+		t.Fatal("event stream was not closed after 1 second")
+	}
+}
+
+func TestInotifyClose(t *testing.T) {
+	watcher, _ := NewWatcher()
+	watcher.Close()
+
+	done := false
+	go func() {
+		watcher.Close()
+		done = true
+	}()
+
+	time.Sleep(50e6) // 50 ms
+	if !done {
+		t.Fatal("double Close() test failed: second Close() call didn't return")
+	}
+
+	err := watcher.Watch("_test")
+	if err == nil {
+		t.Fatal("expected error on Watch() after Close(), got nil")
+	}
+}
diff --git a/src/pkg/os/mkunixsignals.sh b/src/pkg/os/mkunixsignals.sh
new file mode 100755
index 000000000..4bbc43f3d
--- /dev/null
+++ b/src/pkg/os/mkunixsignals.sh
@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+# Copyright 2010 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.
+
+echo '// ./mkunix.sh' "$1"
+echo '// MACHINE GENERATED BY THE COMMAND ABOVE; DO NOT EDIT'
+echo
+
+cat <<EOH
+package os
+
+import (
+  "syscall"
+)
+
+var _ = syscall.Open  // in case there are zero signals
+
+const (
+EOH
+
+sed -n 's/^[ 	]*\(SIG[A-Z0-9][A-Z0-9]*\)[ 	].*/  \1 = UnixSignal(syscall.\1)/p' "$1"
+
+echo ")"
diff --git a/src/pkg/os/os_test.go b/src/pkg/os/os_test.go
new file mode 100644
index 000000000..4d60333df
--- /dev/null
+++ b/src/pkg/os/os_test.go
@@ -0,0 +1,1058 @@
+// 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_test
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	. "os"
+	"path/filepath"
+	"strings"
+	"syscall"
+	"testing"
+)
+
+var dot = []string{
+	"dir_unix.go",
+	"env_unix.go",
+	"error.go",
+	"file.go",
+	"os_test.go",
+	"time.go",
+	"types.go",
+	"stat_darwin.go",
+	"stat_linux.go",
+}
+
+type sysDir struct {
+	name  string
+	files []string
+}
+
+var sysdir = func() (sd *sysDir) {
+	switch syscall.OS {
+	case "windows":
+		sd = &sysDir{
+			Getenv("SystemRoot") + "\\system32\\drivers\\etc",
+			[]string{
+				"hosts",
+				"networks",
+				"protocol",
+				"services",
+			},
+		}
+	case "plan9":
+		sd = &sysDir{
+			"/lib/ndb",
+			[]string{
+				"common",
+				"local",
+			},
+		}
+	default:
+		sd = &sysDir{
+			"/etc",
+			[]string{
+				"group",
+				"hosts",
+				"passwd",
+			},
+		}
+	}
+	return
+}()
+
+func size(name string, t *testing.T) int64 {
+	file, err := Open(name)
+	defer file.Close()
+	if err != nil {
+		t.Fatal("open failed:", err)
+	}
+	var buf [100]byte
+	len := 0
+	for {
+		n, e := file.Read(buf[0:])
+		len += n
+		if e == EOF {
+			break
+		}
+		if e != nil {
+			t.Fatal("read failed:", err)
+		}
+	}
+	return int64(len)
+}
+
+func equal(name1, name2 string) (r bool) {
+	switch syscall.OS {
+	case "windows":
+		r = strings.ToLower(name1) == strings.ToLower(name2)
+	default:
+		r = name1 == name2
+	}
+	return
+}
+
+func newFile(testName string, t *testing.T) (f *File) {
+	// Use a local file system, not NFS.
+	// On Unix, override $TMPDIR in case the user
+	// has it set to an NFS-mounted directory.
+	dir := ""
+	if syscall.OS != "windows" {
+		dir = "/tmp"
+	}
+	f, err := ioutil.TempFile(dir, "_Go_"+testName)
+	if err != nil {
+		t.Fatalf("open %s: %s", testName, err)
+	}
+	return
+}
+
+var sfdir = sysdir.name
+var sfname = sysdir.files[0]
+
+func TestStat(t *testing.T) {
+	path := sfdir + "/" + sfname
+	dir, err := Stat(path)
+	if err != nil {
+		t.Fatal("stat failed:", err)
+	}
+	if !equal(sfname, dir.Name) {
+		t.Error("name should be ", sfname, "; is", dir.Name)
+	}
+	filesize := size(path, t)
+	if dir.Size != filesize {
+		t.Error("size should be", filesize, "; is", dir.Size)
+	}
+}
+
+func TestFstat(t *testing.T) {
+	path := sfdir + "/" + sfname
+	file, err1 := Open(path)
+	defer file.Close()
+	if err1 != nil {
+		t.Fatal("open failed:", err1)
+	}
+	dir, err2 := file.Stat()
+	if err2 != nil {
+		t.Fatal("fstat failed:", err2)
+	}
+	if !equal(sfname, dir.Name) {
+		t.Error("name should be ", sfname, "; is", dir.Name)
+	}
+	filesize := size(path, t)
+	if dir.Size != filesize {
+		t.Error("size should be", filesize, "; is", dir.Size)
+	}
+}
+
+func TestLstat(t *testing.T) {
+	path := sfdir + "/" + sfname
+	dir, err := Lstat(path)
+	if err != nil {
+		t.Fatal("lstat failed:", err)
+	}
+	if !equal(sfname, dir.Name) {
+		t.Error("name should be ", sfname, "; is", dir.Name)
+	}
+	filesize := size(path, t)
+	if dir.Size != filesize {
+		t.Error("size should be", filesize, "; is", dir.Size)
+	}
+}
+
+func testReaddirnames(dir string, contents []string, t *testing.T) {
+	file, err := Open(dir)
+	defer file.Close()
+	if err != nil {
+		t.Fatalf("open %q failed: %v", dir, err)
+	}
+	s, err2 := file.Readdirnames(-1)
+	if err2 != nil {
+		t.Fatalf("readdirnames %q failed: %v", dir, err2)
+	}
+	for _, m := range contents {
+		found := false
+		for _, n := range s {
+			if n == "." || n == ".." {
+				t.Errorf("got %s in directory", n)
+			}
+			if equal(m, n) {
+				if found {
+					t.Error("present twice:", m)
+				}
+				found = true
+			}
+		}
+		if !found {
+			t.Error("could not find", m)
+		}
+	}
+}
+
+func testReaddir(dir string, contents []string, t *testing.T) {
+	file, err := Open(dir)
+	defer file.Close()
+	if err != nil {
+		t.Fatalf("open %q failed: %v", dir, err)
+	}
+	s, err2 := file.Readdir(-1)
+	if err2 != nil {
+		t.Fatalf("readdir %q failed: %v", dir, err2)
+	}
+	for _, m := range contents {
+		found := false
+		for _, n := range s {
+			if equal(m, n.Name) {
+				if found {
+					t.Error("present twice:", m)
+				}
+				found = true
+			}
+		}
+		if !found {
+			t.Error("could not find", m)
+		}
+	}
+}
+
+func TestReaddirnames(t *testing.T) {
+	testReaddirnames(".", dot, t)
+	testReaddirnames(sysdir.name, sysdir.files, t)
+}
+
+func TestReaddir(t *testing.T) {
+	testReaddir(".", dot, t)
+	testReaddir(sysdir.name, sysdir.files, t)
+}
+
+// Read the directory one entry at a time.
+func smallReaddirnames(file *File, length int, t *testing.T) []string {
+	names := make([]string, length)
+	count := 0
+	for {
+		d, err := file.Readdirnames(1)
+		if err == EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("readdirnames %q failed: %v", file.Name(), err)
+		}
+		if len(d) == 0 {
+			t.Fatalf("readdirnames %q returned empty slice and no error", file.Name())
+		}
+		names[count] = d[0]
+		count++
+	}
+	return names[0:count]
+}
+
+// Check that reading a directory one entry at a time gives the same result
+// as reading it all at once.
+func TestReaddirnamesOneAtATime(t *testing.T) {
+	// big directory that doesn't change often.
+	dir := "/usr/bin"
+	switch syscall.OS {
+	case "windows":
+		dir = Getenv("SystemRoot") + "\\system32"
+	case "plan9":
+		dir = "/bin"
+	}
+	file, err := Open(dir)
+	defer file.Close()
+	if err != nil {
+		t.Fatalf("open %q failed: %v", dir, err)
+	}
+	all, err1 := file.Readdirnames(-1)
+	if err1 != nil {
+		t.Fatalf("readdirnames %q failed: %v", dir, err1)
+	}
+	file1, err2 := Open(dir)
+	if err2 != nil {
+		t.Fatalf("open %q failed: %v", dir, err2)
+	}
+	small := smallReaddirnames(file1, len(all)+100, t) // +100 in case we screw up
+	if len(small) < len(all) {
+		t.Fatalf("len(small) is %d, less than %d", len(small), len(all))
+	}
+	for i, n := range all {
+		if small[i] != n {
+			t.Errorf("small read %q mismatch: %v", small[i], n)
+		}
+	}
+}
+
+func TestReaddirNValues(t *testing.T) {
+	if testing.Short() {
+		t.Logf("test.short; skipping")
+		return
+	}
+	dir, err := ioutil.TempDir("", "")
+	if err != nil {
+		t.Fatalf("TempDir: %v", err)
+	}
+	defer RemoveAll(dir)
+	for i := 1; i <= 105; i++ {
+		f, err := Create(filepath.Join(dir, fmt.Sprintf("%d", i)))
+		if err != nil {
+			t.Fatalf("Create: %v", err)
+		}
+		f.Write([]byte(strings.Repeat("X", i)))
+		f.Close()
+	}
+
+	var d *File
+	openDir := func() {
+		var err Error
+		d, err = Open(dir)
+		if err != nil {
+			t.Fatalf("Open directory: %v", err)
+		}
+	}
+
+	readDirExpect := func(n, want int, wantErr Error) {
+		fi, err := d.Readdir(n)
+		if err != wantErr {
+			t.Fatalf("Readdir of %d got error %v, want %v", n, err, wantErr)
+		}
+		if g, e := len(fi), want; g != e {
+			t.Errorf("Readdir of %d got %d files, want %d", n, g, e)
+		}
+	}
+
+	readDirNamesExpect := func(n, want int, wantErr Error) {
+		fi, err := d.Readdirnames(n)
+		if err != wantErr {
+			t.Fatalf("Readdirnames of %d got error %v, want %v", n, err, wantErr)
+		}
+		if g, e := len(fi), want; g != e {
+			t.Errorf("Readdirnames of %d got %d files, want %d", n, g, e)
+		}
+	}
+
+	for _, fn := range []func(int, int, Error){readDirExpect, readDirNamesExpect} {
+		// Test the slurp case
+		openDir()
+		fn(0, 105, nil)
+		fn(0, 0, nil)
+		d.Close()
+
+		// Slurp with -1 instead
+		openDir()
+		fn(-1, 105, nil)
+		fn(-2, 0, nil)
+		fn(0, 0, nil)
+		d.Close()
+
+		// Test the bounded case
+		openDir()
+		fn(1, 1, nil)
+		fn(2, 2, nil)
+		fn(105, 102, nil) // and tests buffer >100 case
+		fn(3, 0, EOF)
+		d.Close()
+	}
+}
+
+func TestHardLink(t *testing.T) {
+	// Hardlinks are not supported under windows or Plan 9.
+	if syscall.OS == "windows" || syscall.OS == "plan9" {
+		return
+	}
+	from, to := "hardlinktestfrom", "hardlinktestto"
+	Remove(from) // Just in case.
+	file, err := Create(to)
+	if err != nil {
+		t.Fatalf("open %q failed: %v", to, err)
+	}
+	defer Remove(to)
+	if err = file.Close(); err != nil {
+		t.Errorf("close %q failed: %v", to, err)
+	}
+	err = Link(to, from)
+	if err != nil {
+		t.Fatalf("link %q, %q failed: %v", to, from, err)
+	}
+	defer Remove(from)
+	tostat, err := Stat(to)
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", to, err)
+	}
+	fromstat, err := Stat(from)
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", from, err)
+	}
+	if tostat.Dev != fromstat.Dev || tostat.Ino != fromstat.Ino {
+		t.Errorf("link %q, %q did not create hard link", to, from)
+	}
+}
+
+func TestSymLink(t *testing.T) {
+	// Symlinks are not supported under windows or Plan 9.
+	if syscall.OS == "windows" || syscall.OS == "plan9" {
+		return
+	}
+	from, to := "symlinktestfrom", "symlinktestto"
+	Remove(from) // Just in case.
+	file, err := Create(to)
+	if err != nil {
+		t.Fatalf("open %q failed: %v", to, err)
+	}
+	defer Remove(to)
+	if err = file.Close(); err != nil {
+		t.Errorf("close %q failed: %v", to, err)
+	}
+	err = Symlink(to, from)
+	if err != nil {
+		t.Fatalf("symlink %q, %q failed: %v", to, from, err)
+	}
+	defer Remove(from)
+	tostat, err := Stat(to)
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", to, err)
+	}
+	if tostat.FollowedSymlink {
+		t.Fatalf("stat %q claims to have followed a symlink", to)
+	}
+	fromstat, err := Stat(from)
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", from, err)
+	}
+	if tostat.Dev != fromstat.Dev || tostat.Ino != fromstat.Ino {
+		t.Errorf("symlink %q, %q did not create symlink", to, from)
+	}
+	fromstat, err = Lstat(from)
+	if err != nil {
+		t.Fatalf("lstat %q failed: %v", from, err)
+	}
+	if !fromstat.IsSymlink() {
+		t.Fatalf("symlink %q, %q did not create symlink", to, from)
+	}
+	fromstat, err = Stat(from)
+	if err != nil {
+		t.Fatalf("stat %q failed: %v", from, err)
+	}
+	if !fromstat.FollowedSymlink {
+		t.Fatalf("stat %q did not follow symlink", from)
+	}
+	s, err := Readlink(from)
+	if err != nil {
+		t.Fatalf("readlink %q failed: %v", from, err)
+	}
+	if s != to {
+		t.Fatalf("after symlink %q != %q", s, to)
+	}
+	file, err = Open(from)
+	if err != nil {
+		t.Fatalf("open %q failed: %v", from, err)
+	}
+	file.Close()
+}
+
+func TestLongSymlink(t *testing.T) {
+	// Symlinks are not supported under windows or Plan 9.
+	if syscall.OS == "windows" || syscall.OS == "plan9" {
+		return
+	}
+	s := "0123456789abcdef"
+	// Long, but not too long: a common limit is 255.
+	s = s + s + s + s + s + s + s + s + s + s + s + s + s + s + s
+	from := "longsymlinktestfrom"
+	Remove(from) // Just in case.
+	err := Symlink(s, from)
+	if err != nil {
+		t.Fatalf("symlink %q, %q failed: %v", s, from, err)
+	}
+	defer Remove(from)
+	r, err := Readlink(from)
+	if err != nil {
+		t.Fatalf("readlink %q failed: %v", from, err)
+	}
+	if r != s {
+		t.Fatalf("after symlink %q != %q", r, s)
+	}
+}
+
+func TestRename(t *testing.T) {
+	from, to := "renamefrom", "renameto"
+	Remove(to) // Just in case.
+	file, err := Create(from)
+	if err != nil {
+		t.Fatalf("open %q failed: %v", to, err)
+	}
+	if err = file.Close(); err != nil {
+		t.Errorf("close %q failed: %v", to, err)
+	}
+	err = Rename(from, to)
+	if err != nil {
+		t.Fatalf("rename %q, %q failed: %v", to, from, err)
+	}
+	defer Remove(to)
+	_, err = Stat(to)
+	if err != nil {
+		t.Errorf("stat %q failed: %v", to, err)
+	}
+}
+
+func exec(t *testing.T, dir, cmd string, args []string, expect string) {
+	r, w, err := Pipe()
+	if err != nil {
+		t.Fatalf("Pipe: %v", err)
+	}
+	attr := &ProcAttr{Dir: dir, Files: []*File{nil, w, Stderr}}
+	p, err := StartProcess(cmd, args, attr)
+	if err != nil {
+		t.Fatalf("StartProcess: %v", err)
+	}
+	defer p.Release()
+	w.Close()
+
+	var b bytes.Buffer
+	io.Copy(&b, r)
+	output := b.String()
+	// Accept /usr prefix because Solaris /bin is symlinked to /usr/bin.
+	if output != expect && output != "/usr"+expect {
+		t.Errorf("exec %q returned %q wanted %q",
+			strings.Join(append([]string{cmd}, args...), " "), output, expect)
+	}
+	p.Wait(0)
+}
+
+func TestStartProcess(t *testing.T) {
+	var dir, cmd, le string
+	var args []string
+	if syscall.OS == "windows" {
+		le = "\r\n"
+		cmd = Getenv("COMSPEC")
+		dir = Getenv("SystemRoot")
+		args = []string{"/c", "cd"}
+	} else {
+		le = "\n"
+		cmd = "/bin/pwd"
+		dir = "/"
+		args = []string{}
+	}
+	cmddir, cmdbase := filepath.Split(cmd)
+	args = append([]string{cmdbase}, args...)
+	// Test absolute executable path.
+	exec(t, dir, cmd, args, dir+le)
+	// Test relative executable path.
+	exec(t, cmddir, cmdbase, args, filepath.Clean(cmddir)+le)
+}
+
+func checkMode(t *testing.T, path string, mode uint32) {
+	dir, err := Stat(path)
+	if err != nil {
+		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
+	}
+	if dir.Mode&0777 != mode {
+		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode, mode)
+	}
+}
+
+func TestChmod(t *testing.T) {
+	// Chmod is not supported under windows.
+	if syscall.OS == "windows" {
+		return
+	}
+	f := newFile("TestChmod", t)
+	defer Remove(f.Name())
+	defer f.Close()
+
+	if err := Chmod(f.Name(), 0456); err != nil {
+		t.Fatalf("chmod %s 0456: %s", f.Name(), err)
+	}
+	checkMode(t, f.Name(), 0456)
+
+	if err := f.Chmod(0123); err != nil {
+		t.Fatalf("chmod %s 0123: %s", f.Name(), err)
+	}
+	checkMode(t, f.Name(), 0123)
+}
+
+func checkUidGid(t *testing.T, path string, uid, gid int) {
+	dir, err := Stat(path)
+	if err != nil {
+		t.Fatalf("Stat %q (looking for uid/gid %d/%d): %s", path, uid, gid, err)
+	}
+	if dir.Uid != uid {
+		t.Errorf("Stat %q: uid %d want %d", path, dir.Uid, uid)
+	}
+	if dir.Gid != gid {
+		t.Errorf("Stat %q: gid %d want %d", path, dir.Gid, gid)
+	}
+}
+
+func TestChown(t *testing.T) {
+	// Chown is not supported under windows or Plan 9.
+	// Plan9 provides a native ChownPlan9 version instead.
+	if syscall.OS == "windows" || syscall.OS == "plan9" {
+		return
+	}
+	// Use TempDir() to make sure we're on a local file system,
+	// so that the group ids returned by Getgroups will be allowed
+	// on the file.  On NFS, the Getgroups groups are
+	// basically useless.
+	f := newFile("TestChown", t)
+	defer Remove(f.Name())
+	defer f.Close()
+	dir, err := f.Stat()
+	if err != nil {
+		t.Fatalf("stat %s: %s", f.Name(), err)
+	}
+
+	// Can't change uid unless root, but can try
+	// changing the group id.  First try our current group.
+	gid := Getgid()
+	t.Log("gid:", gid)
+	if err = Chown(f.Name(), -1, gid); err != nil {
+		t.Fatalf("chown %s -1 %d: %s", f.Name(), gid, err)
+	}
+	checkUidGid(t, f.Name(), dir.Uid, gid)
+
+	// Then try all the auxiliary groups.
+	groups, err := Getgroups()
+	if err != nil {
+		t.Fatalf("getgroups: %s", err)
+	}
+	t.Log("groups: ", groups)
+	for _, g := range groups {
+		if err = Chown(f.Name(), -1, g); err != nil {
+			t.Fatalf("chown %s -1 %d: %s", f.Name(), g, err)
+		}
+		checkUidGid(t, f.Name(), dir.Uid, g)
+
+		// change back to gid to test fd.Chown
+		if err = f.Chown(-1, gid); err != nil {
+			t.Fatalf("fchown %s -1 %d: %s", f.Name(), gid, err)
+		}
+		checkUidGid(t, f.Name(), dir.Uid, gid)
+	}
+}
+
+func checkSize(t *testing.T, f *File, size int64) {
+	dir, err := f.Stat()
+	if err != nil {
+		t.Fatalf("Stat %q (looking for size %d): %s", f.Name(), size, err)
+	}
+	if dir.Size != size {
+		t.Errorf("Stat %q: size %d want %d", f.Name(), dir.Size, size)
+	}
+}
+
+func TestFTruncate(t *testing.T) {
+	f := newFile("TestFTruncate", t)
+	defer Remove(f.Name())
+	defer f.Close()
+
+	checkSize(t, f, 0)
+	f.Write([]byte("hello, world\n"))
+	checkSize(t, f, 13)
+	f.Truncate(10)
+	checkSize(t, f, 10)
+	f.Truncate(1024)
+	checkSize(t, f, 1024)
+	f.Truncate(0)
+	checkSize(t, f, 0)
+	f.Write([]byte("surprise!"))
+	checkSize(t, f, 13+9) // wrote at offset past where hello, world was.
+}
+
+func TestTruncate(t *testing.T) {
+	f := newFile("TestTruncate", t)
+	defer Remove(f.Name())
+	defer f.Close()
+
+	checkSize(t, f, 0)
+	f.Write([]byte("hello, world\n"))
+	checkSize(t, f, 13)
+	Truncate(f.Name(), 10)
+	checkSize(t, f, 10)
+	Truncate(f.Name(), 1024)
+	checkSize(t, f, 1024)
+	Truncate(f.Name(), 0)
+	checkSize(t, f, 0)
+	f.Write([]byte("surprise!"))
+	checkSize(t, f, 13+9) // wrote at offset past where hello, world was.
+}
+
+// Use TempDir() to make sure we're on a local file system,
+// so that timings are not distorted by latency and caching.
+// On NFS, timings can be off due to caching of meta-data on
+// NFS servers (Issue 848).
+func TestChtimes(t *testing.T) {
+	f := newFile("TestChtimes", t)
+	defer Remove(f.Name())
+	defer f.Close()
+
+	f.Write([]byte("hello, world\n"))
+	f.Close()
+
+	preStat, err := Stat(f.Name())
+	if err != nil {
+		t.Fatalf("Stat %s: %s", f.Name(), err)
+	}
+
+	// Move access and modification time back a second
+	const OneSecond = 1e9 // in nanoseconds
+	err = Chtimes(f.Name(), preStat.Atime_ns-OneSecond, preStat.Mtime_ns-OneSecond)
+	if err != nil {
+		t.Fatalf("Chtimes %s: %s", f.Name(), err)
+	}
+
+	postStat, err := Stat(f.Name())
+	if err != nil {
+		t.Fatalf("second Stat %s: %s", f.Name(), err)
+	}
+
+	/* Plan 9:
+		Mtime is the time of the last change of content.  Similarly, atime is set whenever the
+	    contents are accessed; also, it is set whenever mtime is set.
+	*/
+	if postStat.Atime_ns >= preStat.Atime_ns && syscall.OS != "plan9" {
+		t.Errorf("Atime_ns didn't go backwards; was=%d, after=%d",
+			preStat.Atime_ns,
+			postStat.Atime_ns)
+	}
+
+	if postStat.Mtime_ns >= preStat.Mtime_ns {
+		t.Errorf("Mtime_ns didn't go backwards; was=%d, after=%d",
+			preStat.Mtime_ns,
+			postStat.Mtime_ns)
+	}
+}
+
+func TestChdirAndGetwd(t *testing.T) {
+	// TODO(brainman): file.Chdir() is not implemented on windows.
+	if syscall.OS == "windows" {
+		return
+	}
+	fd, err := Open(".")
+	if err != nil {
+		t.Fatalf("Open .: %s", err)
+	}
+	// These are chosen carefully not to be symlinks on a Mac
+	// (unlike, say, /var, /etc, and /tmp).
+	dirs := []string{"/", "/usr/bin"}
+	// /usr/bin does not usually exist on Plan 9.
+	if syscall.OS == "plan9" {
+		dirs = []string{"/", "/usr"}
+	}
+	for mode := 0; mode < 2; mode++ {
+		for _, d := range dirs {
+			if mode == 0 {
+				err = Chdir(d)
+			} else {
+				fd1, err := Open(d)
+				if err != nil {
+					t.Errorf("Open %s: %s", d, err)
+					continue
+				}
+				err = fd1.Chdir()
+				fd1.Close()
+			}
+			pwd, err1 := Getwd()
+			err2 := fd.Chdir()
+			if err2 != nil {
+				// We changed the current directory and cannot go back.
+				// Don't let the tests continue; they'll scribble
+				// all over some other directory.
+				fmt.Fprintf(Stderr, "fchdir back to dot failed: %s\n", err2)
+				Exit(1)
+			}
+			if err != nil {
+				fd.Close()
+				t.Fatalf("Chdir %s: %s", d, err)
+			}
+			if err1 != nil {
+				fd.Close()
+				t.Fatalf("Getwd in %s: %s", d, err1)
+			}
+			if pwd != d {
+				fd.Close()
+				t.Fatalf("Getwd returned %q want %q", pwd, d)
+			}
+		}
+	}
+	fd.Close()
+}
+
+func TestTime(t *testing.T) {
+	// Just want to check that Time() is getting something.
+	// A common failure mode on Darwin is to get 0, 0,
+	// because it returns the time in registers instead of
+	// filling in the structure passed to the system call.
+	// Too bad the compiler doesn't know that
+	// 365.24*86400 is an integer.
+	sec, nsec, err := Time()
+	if sec < (2009-1970)*36524*864 {
+		t.Errorf("Time() = %d, %d, %s; not plausible", sec, nsec, err)
+	}
+}
+
+func TestSeek(t *testing.T) {
+	f := newFile("TestSeek", t)
+	defer Remove(f.Name())
+	defer f.Close()
+
+	const data = "hello, world\n"
+	io.WriteString(f, data)
+
+	type test struct {
+		in     int64
+		whence int
+		out    int64
+	}
+	var tests = []test{
+		{0, 1, int64(len(data))},
+		{0, 0, 0},
+		{5, 0, 5},
+		{0, 2, int64(len(data))},
+		{0, 0, 0},
+		{-1, 2, int64(len(data)) - 1},
+		{1 << 33, 0, 1 << 33},
+		{1 << 33, 2, 1<<33 + int64(len(data))},
+	}
+	for i, tt := range tests {
+		off, err := f.Seek(tt.in, tt.whence)
+		if off != tt.out || err != nil {
+			if e, ok := err.(*PathError); ok && e.Error == EINVAL && tt.out > 1<<32 {
+				// Reiserfs rejects the big seeks.
+				// http://code.google.com/p/go/issues/detail?id=91
+				break
+			}
+			t.Errorf("#%d: Seek(%v, %v) = %v, %v want %v, nil", i, tt.in, tt.whence, off, err, tt.out)
+		}
+	}
+}
+
+type openErrorTest struct {
+	path  string
+	mode  int
+	error Error
+}
+
+var openErrorTests = []openErrorTest{
+	{
+		sfdir + "/no-such-file",
+		O_RDONLY,
+		ENOENT,
+	},
+	{
+		sfdir,
+		O_WRONLY,
+		EISDIR,
+	},
+	{
+		sfdir + "/" + sfname + "/no-such-file",
+		O_WRONLY,
+		ENOTDIR,
+	},
+}
+
+func TestOpenError(t *testing.T) {
+	for _, tt := range openErrorTests {
+		f, err := OpenFile(tt.path, tt.mode, 0)
+		if err == nil {
+			t.Errorf("Open(%q, %d) succeeded", tt.path, tt.mode)
+			f.Close()
+			continue
+		}
+		perr, ok := err.(*PathError)
+		if !ok {
+			t.Errorf("Open(%q, %d) returns error of %T type; want *os.PathError", tt.path, tt.mode, err)
+		}
+		if perr.Error != tt.error {
+			if syscall.OS == "plan9" {
+				syscallErrStr := perr.Error.String()
+				expectedErrStr := strings.Replace(tt.error.String(), "file ", "", 1)
+				if !strings.HasSuffix(syscallErrStr, expectedErrStr) {
+					t.Errorf("Open(%q, %d) = _, %q; want suffix %q", tt.path, tt.mode, syscallErrStr, expectedErrStr)
+				}
+			} else {
+				t.Errorf("Open(%q, %d) = _, %q; want %q", tt.path, tt.mode, perr.Error.String(), tt.error.String())
+			}
+		}
+	}
+}
+
+func run(t *testing.T, cmd []string) string {
+	// Run /bin/hostname and collect output.
+	r, w, err := Pipe()
+	if err != nil {
+		t.Fatal(err)
+	}
+	p, err := StartProcess("/bin/hostname", []string{"hostname"}, &ProcAttr{Files: []*File{nil, w, Stderr}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer p.Release()
+	w.Close()
+
+	var b bytes.Buffer
+	io.Copy(&b, r)
+	_, err = p.Wait(0)
+	if err != nil {
+		t.Fatalf("run hostname Wait: %v", err)
+	}
+	err = p.Kill()
+	if err == nil {
+		t.Errorf("expected an error from Kill running 'hostname'")
+	}
+	output := b.String()
+	if n := len(output); n > 0 && output[n-1] == '\n' {
+		output = output[0 : n-1]
+	}
+	if output == "" {
+		t.Fatalf("%v produced no output", cmd)
+	}
+
+	return output
+}
+
+func TestHostname(t *testing.T) {
+	// There is no other way to fetch hostname on windows, but via winapi.
+	// On Plan 9 it is can be taken from #c/sysname as Hostname() does.
+	if syscall.OS == "windows" || syscall.OS == "plan9" {
+		return
+	}
+	// Check internal Hostname() against the output of /bin/hostname.
+	// Allow that the internal Hostname returns a Fully Qualified Domain Name
+	// and the /bin/hostname only returns the first component
+	hostname, err := Hostname()
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	want := run(t, []string{"/bin/hostname"})
+	if hostname != want {
+		i := strings.Index(hostname, ".")
+		if i < 0 || hostname[0:i] != want {
+			t.Errorf("Hostname() = %q, want %q", hostname, want)
+		}
+	}
+}
+
+func TestReadAt(t *testing.T) {
+	f := newFile("TestReadAt", t)
+	defer Remove(f.Name())
+	defer f.Close()
+
+	const data = "hello, world\n"
+	io.WriteString(f, data)
+
+	b := make([]byte, 5)
+	n, err := f.ReadAt(b, 7)
+	if err != nil || n != len(b) {
+		t.Fatalf("ReadAt 7: %d, %r", n, err)
+	}
+	if string(b) != "world" {
+		t.Fatalf("ReadAt 7: have %q want %q", string(b), "world")
+	}
+}
+
+func TestWriteAt(t *testing.T) {
+	f := newFile("TestWriteAt", t)
+	defer Remove(f.Name())
+	defer f.Close()
+
+	const data = "hello, world\n"
+	io.WriteString(f, data)
+
+	n, err := f.WriteAt([]byte("WORLD"), 7)
+	if err != nil || n != 5 {
+		t.Fatalf("WriteAt 7: %d, %v", n, err)
+	}
+
+	b, err := ioutil.ReadFile(f.Name())
+	if err != nil {
+		t.Fatalf("ReadFile %s: %v", f.Name(), err)
+	}
+	if string(b) != "hello, WORLD\n" {
+		t.Fatalf("after write: have %q want %q", string(b), "hello, WORLD\n")
+	}
+}
+
+func writeFile(t *testing.T, fname string, flag int, text string) string {
+	f, err := OpenFile(fname, flag, 0666)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	n, err := io.WriteString(f, text)
+	if err != nil {
+		t.Fatalf("WriteString: %d, %v", n, err)
+	}
+	f.Close()
+	data, err := ioutil.ReadFile(fname)
+	if err != nil {
+		t.Fatalf("ReadFile: %v", err)
+	}
+	return string(data)
+}
+
+func TestAppend(t *testing.T) {
+	const f = "append.txt"
+	defer Remove(f)
+	s := writeFile(t, f, O_CREATE|O_TRUNC|O_RDWR, "new")
+	if s != "new" {
+		t.Fatalf("writeFile: have %q want %q", s, "new")
+	}
+	s = writeFile(t, f, O_APPEND|O_RDWR, "|append")
+	if s != "new|append" {
+		t.Fatalf("writeFile: have %q want %q", s, "new|append")
+	}
+	s = writeFile(t, f, O_CREATE|O_APPEND|O_RDWR, "|append")
+	if s != "new|append|append" {
+		t.Fatalf("writeFile: have %q want %q", s, "new|append|append")
+	}
+	err := Remove(f)
+	if err != nil {
+		t.Fatalf("Remove: %v", err)
+	}
+	s = writeFile(t, f, O_CREATE|O_APPEND|O_RDWR, "new&append")
+	if s != "new&append" {
+		t.Fatalf("writeFile: after append have %q want %q", s, "new&append")
+	}
+	s = writeFile(t, f, O_CREATE|O_RDWR, "old")
+	if s != "old&append" {
+		t.Fatalf("writeFile: after create have %q want %q", s, "old&append")
+	}
+	s = writeFile(t, f, O_CREATE|O_TRUNC|O_RDWR, "new")
+	if s != "new" {
+		t.Fatalf("writeFile: after truncate have %q want %q", s, "new")
+	}
+}
+
+func TestStatDirWithTrailingSlash(t *testing.T) {
+	// Create new dir, in _test so it will get
+	// cleaned up by make if not by us.
+	path := "_test/_TestStatDirWithSlash_"
+	err := MkdirAll(path, 0777)
+	if err != nil {
+		t.Fatalf("MkdirAll %q: %s", path, err)
+	}
+	defer RemoveAll(path)
+
+	// Stat of path should succeed.
+	_, err = Stat(path)
+	if err != nil {
+		t.Fatal("stat failed:", err)
+	}
+
+	// Stat of path+"/" should succeed too.
+	_, err = Stat(path + "/")
+	if err != nil {
+		t.Fatal("stat failed:", err)
+	}
+}
+
+func TestNilWaitmsgString(t *testing.T) {
+	var w *Waitmsg
+	s := w.String()
+	if s != "<nil>" {
+		t.Errorf("(*Waitmsg)(nil).String() = %q, want %q", s, "<nil>")
+	}
+}
diff --git a/src/pkg/os/path.go b/src/pkg/os/path.go
new file mode 100644
index 000000000..a8dfce307
--- /dev/null
+++ b/src/pkg/os/path.go
@@ -0,0 +1,118 @@
+// 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
+
+// MkdirAll creates a directory named path,
+// along with any necessary parents, and returns nil,
+// or else returns an error.
+// The permission bits perm are used for all
+// directories that MkdirAll creates.
+// If path is already a directory, MkdirAll does nothing
+// and returns nil.
+func MkdirAll(path string, perm uint32) Error {
+	// If path exists, stop with success or error.
+	dir, err := Stat(path)
+	if err == nil {
+		if dir.IsDirectory() {
+			return nil
+		}
+		return &PathError{"mkdir", path, ENOTDIR}
+	}
+
+	// Doesn't already exist; make sure parent does.
+	i := len(path)
+	for i > 0 && IsPathSeparator(path[i-1]) { // Skip trailing path separator.
+		i--
+	}
+
+	j := i
+	for j > 0 && !IsPathSeparator(path[j-1]) { // Scan backward over element.
+		j--
+	}
+
+	if j > 1 {
+		// Create parent
+		err = MkdirAll(path[0:j-1], perm)
+		if err != nil {
+			return err
+		}
+	}
+
+	// Now parent exists, try to create.
+	err = Mkdir(path, perm)
+	if err != nil {
+		// Handle arguments like "foo/." by
+		// double-checking that directory doesn't exist.
+		dir, err1 := Lstat(path)
+		if err1 == nil && dir.IsDirectory() {
+			return nil
+		}
+		return err
+	}
+	return nil
+}
+
+// RemoveAll removes path and any children it contains.
+// It removes everything it can but returns the first error
+// it encounters.  If the path does not exist, RemoveAll
+// returns nil (no error).
+func RemoveAll(path string) Error {
+	// Simple case: if Remove works, we're done.
+	err := Remove(path)
+	if err == nil {
+		return nil
+	}
+
+	// Otherwise, is this a directory we need to recurse into?
+	dir, serr := Lstat(path)
+	if serr != nil {
+		if serr, ok := serr.(*PathError); ok && serr.Error == ENOENT {
+			return nil
+		}
+		return serr
+	}
+	if !dir.IsDirectory() {
+		// Not a directory; return the error from Remove.
+		return err
+	}
+
+	// Directory.
+	fd, err := Open(path)
+	if err != nil {
+		return err
+	}
+
+	// Remove contents & return first error.
+	err = nil
+	for {
+		names, err1 := fd.Readdirnames(100)
+		for _, name := range names {
+			err1 := RemoveAll(path + string(PathSeparator) + name)
+			if err == nil {
+				err = err1
+			}
+		}
+		if err1 == EOF {
+			break
+		}
+		// If Readdirnames returned an error, use it.
+		if err == nil {
+			err = err1
+		}
+		if len(names) == 0 {
+			break
+		}
+	}
+
+	// Close directory, because windows won't remove opened directory.
+	fd.Close()
+
+	// Remove directory.
+	err1 := Remove(path)
+	if err == nil {
+		err = err1
+	}
+	return err
+}
diff --git a/src/pkg/os/path_plan9.go b/src/pkg/os/path_plan9.go
new file mode 100644
index 000000000..3121b7bc7
--- /dev/null
+++ b/src/pkg/os/path_plan9.go
@@ -0,0 +1,15 @@
+// Copyright 2011 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
+
+const (
+	PathSeparator     = '/' // OS-specific path separator
+	PathListSeparator = 0   // OS-specific path list separator
+)
+
+// IsPathSeparator returns true if c is a directory separator character.
+func IsPathSeparator(c uint8) bool {
+	return PathSeparator == c
+}
diff --git a/src/pkg/os/path_test.go b/src/pkg/os/path_test.go
new file mode 100644
index 000000000..31acbaa43
--- /dev/null
+++ b/src/pkg/os/path_test.go
@@ -0,0 +1,208 @@
+// 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_test
+
+import (
+	. "os"
+	"path/filepath"
+	"testing"
+	"runtime"
+	"syscall"
+)
+
+func TestMkdirAll(t *testing.T) {
+	// Create new dir, in _test so it will get
+	// cleaned up by make if not by us.
+	path := "_test/_TestMkdirAll_/dir/./dir2"
+	err := MkdirAll(path, 0777)
+	if err != nil {
+		t.Fatalf("MkdirAll %q: %s", path, err)
+	}
+	defer RemoveAll("_test/_TestMkdirAll_")
+
+	// Already exists, should succeed.
+	err = MkdirAll(path, 0777)
+	if err != nil {
+		t.Fatalf("MkdirAll %q (second time): %s", path, err)
+	}
+
+	// Make file.
+	fpath := path + "/file"
+	f, err := Create(fpath)
+	if err != nil {
+		t.Fatalf("create %q: %s", fpath, err)
+	}
+	defer f.Close()
+
+	// Can't make directory named after file.
+	err = MkdirAll(fpath, 0777)
+	if err == nil {
+		t.Fatalf("MkdirAll %q: no error", fpath)
+	}
+	perr, ok := err.(*PathError)
+	if !ok {
+		t.Fatalf("MkdirAll %q returned %T, not *PathError", fpath, err)
+	}
+	if filepath.Clean(perr.Path) != filepath.Clean(fpath) {
+		t.Fatalf("MkdirAll %q returned wrong error path: %q not %q", fpath, filepath.Clean(perr.Path), filepath.Clean(fpath))
+	}
+
+	// Can't make subdirectory of file.
+	ffpath := fpath + "/subdir"
+	err = MkdirAll(ffpath, 0777)
+	if err == nil {
+		t.Fatalf("MkdirAll %q: no error", ffpath)
+	}
+	perr, ok = err.(*PathError)
+	if !ok {
+		t.Fatalf("MkdirAll %q returned %T, not *PathError", ffpath, err)
+	}
+	if filepath.Clean(perr.Path) != filepath.Clean(fpath) {
+		t.Fatalf("MkdirAll %q returned wrong error path: %q not %q", ffpath, filepath.Clean(perr.Path), filepath.Clean(fpath))
+	}
+
+	if syscall.OS == "windows" {
+		path := `_test\_TestMkdirAll_\dir\.\dir2\`
+		err := MkdirAll(path, 0777)
+		if err != nil {
+			t.Fatalf("MkdirAll %q: %s", path, err)
+		}
+	}
+}
+
+func TestRemoveAll(t *testing.T) {
+	// Work directory.
+	path := "_test/_TestRemoveAll_"
+	fpath := path + "/file"
+	dpath := path + "/dir"
+
+	// Make directory with 1 file and remove.
+	if err := MkdirAll(path, 0777); err != nil {
+		t.Fatalf("MkdirAll %q: %s", path, err)
+	}
+	fd, err := Create(fpath)
+	if err != nil {
+		t.Fatalf("create %q: %s", fpath, err)
+	}
+	fd.Close()
+	if err = RemoveAll(path); err != nil {
+		t.Fatalf("RemoveAll %q (first): %s", path, err)
+	}
+	if _, err := Lstat(path); err == nil {
+		t.Fatalf("Lstat %q succeeded after RemoveAll (first)", path)
+	}
+
+	// Make directory with file and subdirectory and remove.
+	if err = MkdirAll(dpath, 0777); err != nil {
+		t.Fatalf("MkdirAll %q: %s", dpath, err)
+	}
+	fd, err = Create(fpath)
+	if err != nil {
+		t.Fatalf("create %q: %s", fpath, err)
+	}
+	fd.Close()
+	fd, err = Create(dpath + "/file")
+	if err != nil {
+		t.Fatalf("create %q: %s", fpath, err)
+	}
+	fd.Close()
+	if err = RemoveAll(path); err != nil {
+		t.Fatalf("RemoveAll %q (second): %s", path, err)
+	}
+	if _, err := Lstat(path); err == nil {
+		t.Fatalf("Lstat %q succeeded after RemoveAll (second)", path)
+	}
+
+	// Determine if we should run the following test.
+	testit := true
+	if syscall.OS == "windows" {
+		// Chmod is not supported under windows.
+		testit = false
+	} else {
+		// Test fails as root.
+		testit = Getuid() != 0
+	}
+	if testit {
+		// Make directory with file and subdirectory and trigger error.
+		if err = MkdirAll(dpath, 0777); err != nil {
+			t.Fatalf("MkdirAll %q: %s", dpath, err)
+		}
+
+		for _, s := range []string{fpath, dpath + "/file1", path + "/zzz"} {
+			fd, err = Create(s)
+			if err != nil {
+				t.Fatalf("create %q: %s", s, err)
+			}
+			fd.Close()
+		}
+		if err = Chmod(dpath, 0); err != nil {
+			t.Fatalf("Chmod %q 0: %s", dpath, err)
+		}
+
+		// No error checking here: either RemoveAll
+		// will or won't be able to remove dpath;
+		// either way we want to see if it removes fpath
+		// and path/zzz.  Reasons why RemoveAll might
+		// succeed in removing dpath as well include:
+		//	* running as root
+		//	* running on a file system without permissions (FAT)
+		RemoveAll(path)
+		Chmod(dpath, 0777)
+
+		for _, s := range []string{fpath, path + "/zzz"} {
+			if _, err := Lstat(s); err == nil {
+				t.Fatalf("Lstat %q succeeded after partial RemoveAll", s)
+			}
+		}
+	}
+	if err = RemoveAll(path); err != nil {
+		t.Fatalf("RemoveAll %q after partial RemoveAll: %s", path, err)
+	}
+	if _, err := Lstat(path); err == nil {
+		t.Fatalf("Lstat %q succeeded after RemoveAll (final)", path)
+	}
+}
+
+func TestMkdirAllWithSymlink(t *testing.T) {
+	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
+		t.Log("Skipping test: symlinks don't exist under Windows/Plan 9")
+		return
+	}
+
+	err := Mkdir("_test/dir", 0755)
+	if err != nil {
+		t.Fatal(`Mkdir "_test/dir":`, err)
+	}
+	defer RemoveAll("_test/dir")
+
+	err = Symlink("dir", "_test/link")
+	if err != nil {
+		t.Fatal(`Symlink "dir", "_test/link":`, err)
+	}
+	defer RemoveAll("_test/link")
+
+	path := "_test/link/foo"
+	err = MkdirAll(path, 0755)
+	if err != nil {
+		t.Errorf("MkdirAll %q: %s", path, err)
+	}
+}
+
+func TestMkdirAllAtSlash(t *testing.T) {
+	if runtime.GOOS == "windows" || runtime.GOOS == "plan9" {
+		return
+	}
+	RemoveAll("/_go_os_test")
+	err := MkdirAll("/_go_os_test/dir", 0777)
+	if err != nil {
+		pathErr, ok := err.(*PathError)
+		// common for users not to be able to write to /
+		if ok && pathErr.Error == EACCES {
+			return
+		}
+		t.Fatalf(`MkdirAll "/_go_os_test/dir": %v`, err)
+	}
+	RemoveAll("/_go_os_test")
+}
diff --git a/src/pkg/os/path_unix.go b/src/pkg/os/path_unix.go
new file mode 100644
index 000000000..0d327cddd
--- /dev/null
+++ b/src/pkg/os/path_unix.go
@@ -0,0 +1,15 @@
+// Copyright 2011 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
+
+const (
+	PathSeparator     = '/' // OS-specific path separator
+	PathListSeparator = ':' // OS-specific path list separator
+)
+
+// IsPathSeparator returns true if c is a directory separator character.
+func IsPathSeparator(c uint8) bool {
+	return PathSeparator == c
+}
diff --git a/src/pkg/os/path_windows.go b/src/pkg/os/path_windows.go
new file mode 100644
index 000000000..61f2ca59f
--- /dev/null
+++ b/src/pkg/os/path_windows.go
@@ -0,0 +1,16 @@
+// Copyright 2011 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
+
+const (
+	PathSeparator     = '\\' // OS-specific path separator
+	PathListSeparator = ';'  // OS-specific path list separator
+)
+
+// IsPathSeparator returns true if c is a directory separator character.
+func IsPathSeparator(c uint8) bool {
+	// NOTE: Windows accept / as path separator.
+	return c == '\\' || c == '/'
+}
diff --git a/src/pkg/os/proc.go b/src/pkg/os/proc.go
new file mode 100644
index 000000000..dfe388f25
--- /dev/null
+++ b/src/pkg/os/proc.go
@@ -0,0 +1,34 @@
+// 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.
+
+// Process etc.
+
+package os
+
+import "syscall"
+
+var Args []string // provided by runtime
+var Envs []string // provided by runtime
+
+// Getuid returns the numeric user id of the caller.
+func Getuid() int { return syscall.Getuid() }
+
+// Geteuid returns the numeric effective user id of the caller.
+func Geteuid() int { return syscall.Geteuid() }
+
+// Getgid returns the numeric group id of the caller.
+func Getgid() int { return syscall.Getgid() }
+
+// Getegid returns the numeric effective group id of the caller.
+func Getegid() int { return syscall.Getegid() }
+
+// Getgroups returns a list of the numeric ids of groups that the caller belongs to.
+func Getgroups() ([]int, Error) {
+	gids, e := syscall.Getgroups()
+	return gids, NewSyscallError("getgroups", e)
+}
+
+// Exit causes the current program to exit with the given status code.
+// Conventionally, code zero indicates success, non-zero an error.
+func Exit(code int) { syscall.Exit(code) }
diff --git a/src/pkg/os/signal/Makefile b/src/pkg/os/signal/Makefile
new file mode 100644
index 000000000..26f58760e
--- /dev/null
+++ b/src/pkg/os/signal/Makefile
@@ -0,0 +1,11 @@
+# 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.
+
+include ../../../Make.inc
+
+TARG=os/signal
+GOFILES=\
+	signal.go\
+
+include ../../../Make.pkg
diff --git a/src/pkg/os/signal/signal.go b/src/pkg/os/signal/signal.go
new file mode 100644
index 000000000..520f3f8a9
--- /dev/null
+++ b/src/pkg/os/signal/signal.go
@@ -0,0 +1,33 @@
+// 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 signal implements operating system-independent signal handling.
+package signal
+
+import (
+	"os"
+	"runtime"
+)
+
+// Incoming is the global signal channel.
+// All signals received by the program will be delivered to this channel.
+var Incoming <-chan os.Signal
+
+func process(ch chan<- os.Signal) {
+	for {
+		var mask uint32 = runtime.Sigrecv()
+		for sig := uint(0); sig < 32; sig++ {
+			if mask&(1<<sig) != 0 {
+				ch <- os.UnixSignal(sig)
+			}
+		}
+	}
+}
+
+func init() {
+	runtime.Siginit()
+	ch := make(chan os.Signal) // Done here so Incoming can have type <-chan Signal
+	Incoming = ch
+	go process(ch)
+}
diff --git a/src/pkg/os/signal/signal_test.go b/src/pkg/os/signal/signal_test.go
new file mode 100644
index 000000000..00eb29578
--- /dev/null
+++ b/src/pkg/os/signal/signal_test.go
@@ -0,0 +1,20 @@
+// 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 signal
+
+import (
+	"os"
+	"syscall"
+	"testing"
+)
+
+func TestSignal(t *testing.T) {
+	// Send this process a SIGHUP.
+	syscall.Syscall(syscall.SYS_KILL, uintptr(syscall.Getpid()), syscall.SIGHUP, 0)
+
+	if sig := (<-Incoming).(os.UnixSignal); sig != os.SIGHUP {
+		t.Errorf("signal was %v, want %v", sig, os.SIGHUP)
+	}
+}
diff --git a/src/pkg/os/stat_darwin.go b/src/pkg/os/stat_darwin.go
new file mode 100644
index 000000000..0661a6d59
--- /dev/null
+++ b/src/pkg/os/stat_darwin.go
@@ -0,0 +1,32 @@
+// 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 "syscall"
+
+func isSymlink(stat *syscall.Stat_t) bool {
+	return stat.Mode&syscall.S_IFMT == syscall.S_IFLNK
+}
+
+func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *FileInfo {
+	fi.Dev = uint64(stat.Dev)
+	fi.Ino = stat.Ino
+	fi.Nlink = uint64(stat.Nlink)
+	fi.Mode = uint32(stat.Mode)
+	fi.Uid = int(stat.Uid)
+	fi.Gid = int(stat.Gid)
+	fi.Rdev = uint64(stat.Rdev)
+	fi.Size = stat.Size
+	fi.Blksize = int64(stat.Blksize)
+	fi.Blocks = stat.Blocks
+	fi.Atime_ns = syscall.TimespecToNsec(stat.Atimespec)
+	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtimespec)
+	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctimespec)
+	fi.Name = basename(name)
+	if isSymlink(lstat) && !isSymlink(stat) {
+		fi.FollowedSymlink = true
+	}
+	return fi
+}
diff --git a/src/pkg/os/stat_freebsd.go b/src/pkg/os/stat_freebsd.go
new file mode 100644
index 000000000..454165d4e
--- /dev/null
+++ b/src/pkg/os/stat_freebsd.go
@@ -0,0 +1,32 @@
+// 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 "syscall"
+
+func isSymlink(stat *syscall.Stat_t) bool {
+	return stat.Mode&syscall.S_IFMT == syscall.S_IFLNK
+}
+
+func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *FileInfo {
+	fi.Dev = uint64(stat.Dev)
+	fi.Ino = uint64(stat.Ino)
+	fi.Nlink = uint64(stat.Nlink)
+	fi.Mode = uint32(stat.Mode)
+	fi.Uid = int(stat.Uid)
+	fi.Gid = int(stat.Gid)
+	fi.Rdev = uint64(stat.Rdev)
+	fi.Size = int64(stat.Size)
+	fi.Blksize = int64(stat.Blksize)
+	fi.Blocks = stat.Blocks
+	fi.Atime_ns = syscall.TimespecToNsec(stat.Atimespec)
+	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtimespec)
+	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctimespec)
+	fi.Name = basename(name)
+	if isSymlink(lstat) && !isSymlink(stat) {
+		fi.FollowedSymlink = true
+	}
+	return fi
+}
diff --git a/src/pkg/os/stat_linux.go b/src/pkg/os/stat_linux.go
new file mode 100644
index 000000000..7a3cf794d
--- /dev/null
+++ b/src/pkg/os/stat_linux.go
@@ -0,0 +1,32 @@
+// 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 "syscall"
+
+func isSymlink(stat *syscall.Stat_t) bool {
+	return stat.Mode&syscall.S_IFMT == syscall.S_IFLNK
+}
+
+func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *FileInfo {
+	fi.Dev = stat.Dev
+	fi.Ino = stat.Ino
+	fi.Nlink = uint64(stat.Nlink)
+	fi.Mode = stat.Mode
+	fi.Uid = int(stat.Uid)
+	fi.Gid = int(stat.Gid)
+	fi.Rdev = stat.Rdev
+	fi.Size = stat.Size
+	fi.Blksize = int64(stat.Blksize)
+	fi.Blocks = stat.Blocks
+	fi.Atime_ns = syscall.TimespecToNsec(stat.Atim)
+	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtim)
+	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctim)
+	fi.Name = basename(name)
+	if isSymlink(lstat) && !isSymlink(stat) {
+		fi.FollowedSymlink = true
+	}
+	return fi
+}
diff --git a/src/pkg/os/stat_openbsd.go b/src/pkg/os/stat_openbsd.go
new file mode 100644
index 000000000..6d3a3813b
--- /dev/null
+++ b/src/pkg/os/stat_openbsd.go
@@ -0,0 +1,32 @@
+// 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 "syscall"
+
+func isSymlink(stat *syscall.Stat_t) bool {
+	return stat.Mode&syscall.S_IFMT == syscall.S_IFLNK
+}
+
+func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *FileInfo {
+	fi.Dev = uint64(stat.Dev)
+	fi.Ino = uint64(stat.Ino)
+	fi.Nlink = uint64(stat.Nlink)
+	fi.Mode = uint32(stat.Mode)
+	fi.Uid = int(stat.Uid)
+	fi.Gid = int(stat.Gid)
+	fi.Rdev = uint64(stat.Rdev)
+	fi.Size = int64(stat.Size)
+	fi.Blksize = int64(stat.Blksize)
+	fi.Blocks = stat.Blocks
+	fi.Atime_ns = syscall.TimespecToNsec(stat.Atim)
+	fi.Mtime_ns = syscall.TimespecToNsec(stat.Mtim)
+	fi.Ctime_ns = syscall.TimespecToNsec(stat.Ctim)
+	fi.Name = basename(name)
+	if isSymlink(lstat) && !isSymlink(stat) {
+		fi.FollowedSymlink = true
+	}
+	return fi
+}
diff --git a/src/pkg/os/stat_plan9.go b/src/pkg/os/stat_plan9.go
new file mode 100644
index 000000000..173a23f8b
--- /dev/null
+++ b/src/pkg/os/stat_plan9.go
@@ -0,0 +1,90 @@
+// Copyright 2011 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 "syscall"
+
+func fileInfoFromStat(fi *FileInfo, d *Dir) *FileInfo {
+	fi.Dev = uint64(d.Qid.Vers) | uint64(d.Qid.Type<<32)
+	fi.Ino = d.Qid.Path
+
+	fi.Mode = uint32(d.Mode) & 0777
+	if (d.Mode & syscall.DMDIR) == syscall.DMDIR {
+		fi.Mode |= syscall.S_IFDIR
+	} else {
+		fi.Mode |= syscall.S_IFREG
+	}
+
+	fi.Size = int64(d.Length)
+	fi.Atime_ns = 1e9 * int64(d.Atime)
+	fi.Mtime_ns = 1e9 * int64(d.Mtime)
+	fi.Name = d.Name
+	fi.FollowedSymlink = false
+	return fi
+}
+
+// arg is an open *File or a path string. 
+func dirstat(arg interface{}) (d *Dir, err Error) {
+	var name string
+	nd := syscall.STATFIXLEN + 16*4
+
+	for i := 0; i < 2; i++ { /* should work by the second try */
+		buf := make([]byte, nd)
+
+		var n int
+		var e syscall.Error
+
+		switch syscallArg := arg.(type) {
+		case *File:
+			name = syscallArg.name
+			n, e = syscall.Fstat(syscallArg.fd, buf)
+		case string:
+			name = syscallArg
+			n, e = syscall.Stat(name, buf)
+		}
+
+		if e != nil {
+			return nil, &PathError{"stat", name, e}
+		}
+
+		if n < syscall.STATFIXLEN {
+			return nil, &PathError{"stat", name, Eshortstat}
+		}
+
+		ntmp, _ := gbit16(buf)
+		nd = int(ntmp)
+
+		if nd <= n {
+			d, e := UnmarshalDir(buf[:n])
+
+			if e != nil {
+				return nil, &PathError{"stat", name, e}
+			}
+			return d, e
+		}
+	}
+
+	return nil, &PathError{"stat", name, Ebadstat}
+}
+
+// Stat returns a FileInfo structure describing the named file and an error, if any.
+func Stat(name string) (fi *FileInfo, err Error) {
+	d, err := dirstat(name)
+	if iserror(err) {
+		return nil, err
+	}
+	return fileInfoFromStat(new(FileInfo), d), err
+}
+
+// Lstat returns the FileInfo structure describing the named file and an
+// error, if any.  If the file is a symbolic link (though Plan 9 does not have symbolic links), 
+// the returned FileInfo describes the symbolic link.  Lstat makes no attempt to follow the link.
+func Lstat(name string) (fi *FileInfo, err Error) {
+	d, err := dirstat(name)
+	if iserror(err) {
+		return nil, err
+	}
+	return fileInfoFromStat(new(FileInfo), d), err
+}
diff --git a/src/pkg/os/stat_windows.go b/src/pkg/os/stat_windows.go
new file mode 100644
index 000000000..11088436a
--- /dev/null
+++ b/src/pkg/os/stat_windows.go
@@ -0,0 +1,46 @@
+// 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 "syscall"
+
+func fileInfoFromStat(name string, fi *FileInfo, lstat, stat *syscall.Stat_t) *FileInfo {
+	return fileInfoFromWin32finddata(fi, &stat.Windata)
+}
+
+func fileInfoFromWin32finddata(fi *FileInfo, d *syscall.Win32finddata) *FileInfo {
+	return setFileInfo(fi, string(syscall.UTF16ToString(d.FileName[0:])), d.FileAttributes, d.FileSizeHigh, d.FileSizeLow, d.CreationTime, d.LastAccessTime, d.LastWriteTime)
+}
+
+func fileInfoFromByHandleInfo(fi *FileInfo, name string, d *syscall.ByHandleFileInformation) *FileInfo {
+	for i := len(name) - 1; i >= 0; i-- {
+		if name[i] == '/' || name[i] == '\\' {
+			name = name[i+1:]
+			break
+		}
+	}
+	return setFileInfo(fi, name, d.FileAttributes, d.FileSizeHigh, d.FileSizeLow, d.CreationTime, d.LastAccessTime, d.LastWriteTime)
+}
+
+func setFileInfo(fi *FileInfo, name string, fa, sizehi, sizelo uint32, ctime, atime, wtime syscall.Filetime) *FileInfo {
+	fi.Mode = 0
+	if fa&syscall.FILE_ATTRIBUTE_DIRECTORY != 0 {
+		fi.Mode = fi.Mode | syscall.S_IFDIR
+	} else {
+		fi.Mode = fi.Mode | syscall.S_IFREG
+	}
+	if fa&syscall.FILE_ATTRIBUTE_READONLY != 0 {
+		fi.Mode = fi.Mode | 0444
+	} else {
+		fi.Mode = fi.Mode | 0666
+	}
+	fi.Size = int64(sizehi)<<32 + int64(sizelo)
+	fi.Name = name
+	fi.FollowedSymlink = false
+	fi.Atime_ns = atime.Nanoseconds()
+	fi.Mtime_ns = wtime.Nanoseconds()
+	fi.Ctime_ns = ctime.Nanoseconds()
+	return fi
+}
diff --git a/src/pkg/os/str.go b/src/pkg/os/str.go
new file mode 100644
index 000000000..8dc9e4747
--- /dev/null
+++ b/src/pkg/os/str.go
@@ -0,0 +1,20 @@
+// 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
+
+func itoa(val int) string { // do it here rather than with fmt to avoid dependency
+	if val < 0 {
+		return "-" + itoa(-val)
+	}
+	var buf [32]byte // big enough for int64
+	i := len(buf) - 1
+	for val >= 10 {
+		buf[i] = byte(val%10 + '0')
+		i--
+		val /= 10
+	}
+	buf[i] = byte(val + '0')
+	return string(buf[i:])
+}
diff --git a/src/pkg/os/sys_bsd.go b/src/pkg/os/sys_bsd.go
new file mode 100644
index 000000000..188993b69
--- /dev/null
+++ b/src/pkg/os/sys_bsd.go
@@ -0,0 +1,19 @@
+// 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.
+
+// os code shared between *BSD systems including OS X (Darwin)
+// and FreeBSD.
+
+package os
+
+import "syscall"
+
+func Hostname() (name string, err Error) {
+	var errno int
+	name, errno = syscall.Sysctl("kern.hostname")
+	if errno != 0 {
+		return "", NewSyscallError("sysctl kern.hostname", errno)
+	}
+	return name, nil
+}
diff --git a/src/pkg/os/sys_linux.go b/src/pkg/os/sys_linux.go
new file mode 100644
index 000000000..2accd6c1f
--- /dev/null
+++ b/src/pkg/os/sys_linux.go
@@ -0,0 +1,27 @@
+// 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.
+
+// Linux-specific
+
+package os
+
+// Hostname returns the host name reported by the kernel.
+func Hostname() (name string, err Error) {
+	f, err := Open("/proc/sys/kernel/hostname")
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	var buf [512]byte // Enough for a DNS name.
+	n, err := f.Read(buf[0:])
+	if err != nil {
+		return "", err
+	}
+
+	if n > 0 && buf[n-1] == '\n' {
+		n--
+	}
+	return string(buf[0:n]), nil
+}
diff --git a/src/pkg/os/sys_plan9.go b/src/pkg/os/sys_plan9.go
new file mode 100644
index 000000000..c24cde05e
--- /dev/null
+++ b/src/pkg/os/sys_plan9.go
@@ -0,0 +1,26 @@
+// Copyright 2011 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.
+
+// Plan 9-specific
+
+package os
+
+func Hostname() (name string, err Error) {
+	f, err := Open("#c/sysname")
+	if err != nil {
+		return "", err
+	}
+	defer f.Close()
+
+	var buf [128]byte
+	n, err := f.Read(buf[:len(buf)-1])
+
+	if err != nil {
+		return "", err
+	}
+	if n > 0 {
+		buf[n] = 0
+	}
+	return string(buf[0:n]), nil
+}
diff --git a/src/pkg/os/sys_windows.go b/src/pkg/os/sys_windows.go
new file mode 100644
index 000000000..a78798458
--- /dev/null
+++ b/src/pkg/os/sys_windows.go
@@ -0,0 +1,15 @@
+// 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 "syscall"
+
+func Hostname() (name string, err Error) {
+	s, e := syscall.ComputerName()
+	if e != 0 {
+		return "", NewSyscallError("ComputerName", e)
+	}
+	return s, nil
+}
diff --git a/src/pkg/os/time.go b/src/pkg/os/time.go
new file mode 100644
index 000000000..949574d19
--- /dev/null
+++ b/src/pkg/os/time.go
@@ -0,0 +1,19 @@
+// 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 "syscall"
+
+// Time returns the current time, in whole seconds and
+// fractional nanoseconds, plus an Error if any. The current
+// time is thus 1e9*sec+nsec, in nanoseconds.  The zero of
+// time is the Unix epoch.
+func Time() (sec int64, nsec int64, err Error) {
+	var tv syscall.Timeval
+	if e := syscall.Gettimeofday(&tv); iserror(e) {
+		return 0, 0, NewSyscallError("gettimeofday", e)
+	}
+	return int64(tv.Sec), int64(tv.Usec) * 1000, err
+}
diff --git a/src/pkg/os/types.go b/src/pkg/os/types.go
new file mode 100644
index 000000000..df57b59a3
--- /dev/null
+++ b/src/pkg/os/types.go
@@ -0,0 +1,56 @@
+// 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 "syscall"
+
+// An operating-system independent representation of Unix data structures.
+// OS-specific routines in this directory convert the OS-local versions to these.
+
+// 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, Fstat, and Lstat
+type FileInfo struct {
+	Dev             uint64 // device number of file system holding file.
+	Ino             uint64 // inode number.
+	Nlink           uint64 // number of hard links.
+	Mode            uint32 // permission and mode bits.
+	Uid             int    // user id of owner.
+	Gid             int    // group id of owner.
+	Rdev            uint64 // device type for special file.
+	Size            int64  // length in bytes.
+	Blksize         int64  // size of blocks, in bytes.
+	Blocks          int64  // number of blocks allocated for file.
+	Atime_ns        int64  // access time; nanoseconds since epoch.
+	Mtime_ns        int64  // modified time; nanoseconds since epoch.
+	Ctime_ns        int64  // status change time; nanoseconds since epoch.
+	Name            string // base name of the file name provided in Open, Stat, etc.
+	FollowedSymlink bool   // followed a symlink to get this information
+}
+
+// IsFifo reports whether the FileInfo describes a FIFO file.
+func (f *FileInfo) IsFifo() bool { return (f.Mode & syscall.S_IFMT) == syscall.S_IFIFO }
+
+// IsChar reports whether the FileInfo describes a character special file.
+func (f *FileInfo) IsChar() bool { return (f.Mode & syscall.S_IFMT) == syscall.S_IFCHR }
+
+// IsDirectory reports whether the FileInfo describes a directory.
+func (f *FileInfo) IsDirectory() bool { return (f.Mode & syscall.S_IFMT) == syscall.S_IFDIR }
+
+// IsBlock reports whether the FileInfo describes a block special file.
+func (f *FileInfo) IsBlock() bool { return (f.Mode & syscall.S_IFMT) == syscall.S_IFBLK }
+
+// IsRegular reports whether the FileInfo describes a regular file.
+func (f *FileInfo) IsRegular() bool { return (f.Mode & syscall.S_IFMT) == syscall.S_IFREG }
+
+// IsSymlink reports whether the FileInfo describes a symbolic link.
+func (f *FileInfo) IsSymlink() bool { return (f.Mode & syscall.S_IFMT) == syscall.S_IFLNK }
+
+// IsSocket reports whether the FileInfo describes a socket.
+func (f *FileInfo) IsSocket() bool { return (f.Mode & syscall.S_IFMT) == syscall.S_IFSOCK }
+
+// Permission returns the file permission bits.
+func (f *FileInfo) Permission() uint32 { return f.Mode & 0777 }
diff --git a/src/pkg/os/user/Makefile b/src/pkg/os/user/Makefile
new file mode 100644
index 000000000..aabb54995
--- /dev/null
+++ b/src/pkg/os/user/Makefile
@@ -0,0 +1,26 @@
+# Copyright 2011 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.
+
+include ../../../Make.inc
+
+TARG=os/user
+GOFILES=\
+	user.go\
+
+ifeq ($(CGO_ENABLED),1)
+CGOFILES_linux=\
+	lookup_unix.go
+CGOFILES_freebsd=\
+	lookup_unix.go
+CGOFILES_darwin=\
+	lookup_unix.go
+endif
+
+ifneq ($(CGOFILES_$(GOOS)),)
+CGOFILES+=$(CGOFILES_$(GOOS))
+else
+GOFILES+=lookup_stubs.go
+endif
+
+include ../../../Make.pkg
diff --git a/src/pkg/os/user/lookup_stubs.go b/src/pkg/os/user/lookup_stubs.go
new file mode 100644
index 000000000..2f08f70fd
--- /dev/null
+++ b/src/pkg/os/user/lookup_stubs.go
@@ -0,0 +1,19 @@
+// Copyright 2011 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 user
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+)
+
+func Lookup(username string) (*User, os.Error) {
+	return nil, fmt.Errorf("user: Lookup not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}
+
+func LookupId(int) (*User, os.Error) {
+	return nil, fmt.Errorf("user: LookupId not implemented on %s/%s", runtime.GOOS, runtime.GOARCH)
+}
diff --git a/src/pkg/os/user/lookup_unix.go b/src/pkg/os/user/lookup_unix.go
new file mode 100644
index 000000000..1b2c9e8c9
--- /dev/null
+++ b/src/pkg/os/user/lookup_unix.go
@@ -0,0 +1,108 @@
+// Copyright 2011 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 user
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"strings"
+	"unsafe"
+)
+
+/*
+#include <unistd.h>
+#include <sys/types.h>
+#include <pwd.h>
+#include <stdlib.h>
+
+static int mygetpwuid_r(int uid, struct passwd *pwd,
+	char *buf, size_t buflen, struct passwd **result) {
+ return getpwuid_r(uid, pwd, buf, buflen, result);
+}
+*/
+import "C"
+
+func init() {
+	implemented = true
+}
+
+// Lookup looks up a user by username. If the user cannot be found,
+// the returned error is of type UnknownUserError.
+func Lookup(username string) (*User, os.Error) {
+	return lookup(-1, username, true)
+}
+
+// LookupId looks up a user by userid. If the user cannot be found,
+// the returned error is of type UnknownUserIdError.
+func LookupId(uid int) (*User, os.Error) {
+	return lookup(uid, "", false)
+}
+
+func lookup(uid int, username string, lookupByName bool) (*User, os.Error) {
+	var pwd C.struct_passwd
+	var result *C.struct_passwd
+
+	var bufSize C.long
+	if runtime.GOOS == "freebsd" {
+		// FreeBSD doesn't have _SC_GETPW_R_SIZE_MAX
+		// and just returns -1.  So just use the same
+		// size that Linux returns
+		bufSize = 1024
+	} else {
+		bufSize = C.sysconf(C._SC_GETPW_R_SIZE_MAX)
+		if bufSize <= 0 || bufSize > 1<<20 {
+			return nil, fmt.Errorf("user: unreasonable _SC_GETPW_R_SIZE_MAX of %d", bufSize)
+		}
+	}
+	buf := C.malloc(C.size_t(bufSize))
+	defer C.free(buf)
+	var rv C.int
+	if lookupByName {
+		nameC := C.CString(username)
+		defer C.free(unsafe.Pointer(nameC))
+		rv = C.getpwnam_r(nameC,
+			&pwd,
+			(*C.char)(buf),
+			C.size_t(bufSize),
+			&result)
+		if rv != 0 {
+			return nil, fmt.Errorf("user: lookup username %s: %s", username, os.Errno(rv))
+		}
+		if result == nil {
+			return nil, UnknownUserError(username)
+		}
+	} else {
+		// mygetpwuid_r is a wrapper around getpwuid_r to
+		// to avoid using uid_t because C.uid_t(uid) for
+		// unknown reasons doesn't work on linux.
+		rv = C.mygetpwuid_r(C.int(uid),
+			&pwd,
+			(*C.char)(buf),
+			C.size_t(bufSize),
+			&result)
+		if rv != 0 {
+			return nil, fmt.Errorf("user: lookup userid %d: %s", uid, os.Errno(rv))
+		}
+		if result == nil {
+			return nil, UnknownUserIdError(uid)
+		}
+	}
+	u := &User{
+		Uid:      int(pwd.pw_uid),
+		Gid:      int(pwd.pw_gid),
+		Username: C.GoString(pwd.pw_name),
+		Name:     C.GoString(pwd.pw_gecos),
+		HomeDir:  C.GoString(pwd.pw_dir),
+	}
+	// The pw_gecos field isn't quite standardized.  Some docs
+	// say: "It is expected to be a comma separated list of
+	// personal data where the first item is the full name of the
+	// user."
+	if i := strings.Index(u.Name, ","); i >= 0 {
+		u.Name = u.Name[:i]
+	}
+	return u, nil
+}
diff --git a/src/pkg/os/user/user.go b/src/pkg/os/user/user.go
new file mode 100644
index 000000000..f71e11d8b
--- /dev/null
+++ b/src/pkg/os/user/user.go
@@ -0,0 +1,37 @@
+// Copyright 2011 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 user allows user account lookups by name or id.
+package user
+
+import (
+	"strconv"
+)
+
+var implemented = false // set to true by lookup_unix.go's init
+
+// User represents a user account.
+type User struct {
+	Uid      int // user id
+	Gid      int // primary group id
+	Username string
+	Name     string
+	HomeDir  string
+}
+
+// UnknownUserIdError is returned by LookupId when
+// a user cannot be found.
+type UnknownUserIdError int
+
+func (e UnknownUserIdError) String() string {
+	return "user: unknown userid " + strconv.Itoa(int(e))
+}
+
+// UnknownUserError is returned by Lookup when
+// a user cannot be found.
+type UnknownUserError string
+
+func (e UnknownUserError) String() string {
+	return "user: unknown user " + string(e)
+}
diff --git a/src/pkg/os/user/user_test.go b/src/pkg/os/user/user_test.go
new file mode 100644
index 000000000..59f15e4c6
--- /dev/null
+++ b/src/pkg/os/user/user_test.go
@@ -0,0 +1,61 @@
+// Copyright 2011 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 user
+
+import (
+	"os"
+	"reflect"
+	"runtime"
+	"syscall"
+	"testing"
+)
+
+func skip(t *testing.T) bool {
+	if !implemented {
+		t.Logf("user: not implemented; skipping tests")
+		return true
+	}
+
+	if runtime.GOOS == "linux" || runtime.GOOS == "freebsd" || runtime.GOOS == "darwin" {
+		return false
+	}
+
+	t.Logf("user: Lookup not implemented on %s; skipping test", runtime.GOOS)
+	return true
+}
+
+func TestLookup(t *testing.T) {
+	if skip(t) {
+		return
+	}
+
+	// Test LookupId on the current user
+	uid := syscall.Getuid()
+	u, err := LookupId(uid)
+	if err != nil {
+		t.Fatalf("LookupId: %v", err)
+	}
+	if e, g := uid, u.Uid; e != g {
+		t.Errorf("expected Uid of %d; got %d", e, g)
+	}
+	fi, err := os.Stat(u.HomeDir)
+	if err != nil || !fi.IsDirectory() {
+		t.Errorf("expected a valid HomeDir; stat(%q): err=%v, IsDirectory=%v", u.HomeDir, err, fi.IsDirectory())
+	}
+	if u.Username == "" {
+		t.Fatalf("didn't get a username")
+	}
+
+	// Test Lookup by username, using the username from LookupId
+	un, err := Lookup(u.Username)
+	if err != nil {
+		t.Fatalf("Lookup: %v", err)
+	}
+	if !reflect.DeepEqual(u, un) {
+		t.Errorf("Lookup by userid vs. name didn't match\n"+
+			"LookupId(%d): %#v\n"+
+			"Lookup(%q): %#v\n", uid, u, u.Username, un)
+	}
+}