Source file src/os/os_test.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package os_test
     6  
     7  import (
     8  	"bytes"
     9  	"errors"
    10  	"flag"
    11  	"fmt"
    12  	"internal/testenv"
    13  	"io"
    14  	"io/fs"
    15  	"log"
    16  	. "os"
    17  	"os/exec"
    18  	"path/filepath"
    19  	"runtime"
    20  	"runtime/debug"
    21  	"slices"
    22  	"strconv"
    23  	"strings"
    24  	"sync"
    25  	"syscall"
    26  	"testing"
    27  	"testing/fstest"
    28  	"time"
    29  )
    30  
    31  func TestMain(m *testing.M) {
    32  	if Getenv("GO_OS_TEST_DRAIN_STDIN") == "1" {
    33  		Stdout.Close()
    34  		io.Copy(io.Discard, Stdin)
    35  		Exit(0)
    36  	}
    37  
    38  	log.SetFlags(log.LstdFlags | log.Lshortfile)
    39  
    40  	Exit(m.Run())
    41  }
    42  
    43  var dot = []string{
    44  	"dir_unix.go",
    45  	"env.go",
    46  	"error.go",
    47  	"file.go",
    48  	"os_test.go",
    49  	"types.go",
    50  	"stat_darwin.go",
    51  	"stat_linux.go",
    52  }
    53  
    54  type sysDir struct {
    55  	name  string
    56  	files []string
    57  }
    58  
    59  var sysdir = func() *sysDir {
    60  	switch runtime.GOOS {
    61  	case "android":
    62  		return &sysDir{
    63  			"/system/lib",
    64  			[]string{
    65  				"libmedia.so",
    66  				"libpowermanager.so",
    67  			},
    68  		}
    69  	case "ios":
    70  		wd, err := syscall.Getwd()
    71  		if err != nil {
    72  			wd = err.Error()
    73  		}
    74  		sd := &sysDir{
    75  			filepath.Join(wd, "..", ".."),
    76  			[]string{
    77  				"ResourceRules.plist",
    78  				"Info.plist",
    79  			},
    80  		}
    81  		found := true
    82  		for _, f := range sd.files {
    83  			path := filepath.Join(sd.name, f)
    84  			if _, err := Stat(path); err != nil {
    85  				found = false
    86  				break
    87  			}
    88  		}
    89  		if found {
    90  			return sd
    91  		}
    92  		// In a self-hosted iOS build the above files might
    93  		// not exist. Look for system files instead below.
    94  	case "windows":
    95  		return &sysDir{
    96  			Getenv("SystemRoot") + "\\system32\\drivers\\etc",
    97  			[]string{
    98  				"networks",
    99  				"protocol",
   100  				"services",
   101  			},
   102  		}
   103  	case "plan9":
   104  		return &sysDir{
   105  			"/lib/ndb",
   106  			[]string{
   107  				"common",
   108  				"local",
   109  			},
   110  		}
   111  	case "wasip1":
   112  		// wasmtime has issues resolving symbolic links that are often present
   113  		// in directories like /etc/group below (e.g. private/etc/group on OSX).
   114  		// For this reason we use files in the Go source tree instead.
   115  		return &sysDir{
   116  			runtime.GOROOT(),
   117  			[]string{
   118  				"go.env",
   119  				"LICENSE",
   120  				"CONTRIBUTING.md",
   121  			},
   122  		}
   123  	}
   124  	return &sysDir{
   125  		"/etc",
   126  		[]string{
   127  			"group",
   128  			"hosts",
   129  			"passwd",
   130  		},
   131  	}
   132  }()
   133  
   134  func size(name string, t *testing.T) int64 {
   135  	file, err := Open(name)
   136  	if err != nil {
   137  		t.Fatal("open failed:", err)
   138  	}
   139  	defer func() {
   140  		if err := file.Close(); err != nil {
   141  			t.Error(err)
   142  		}
   143  	}()
   144  	n, err := io.Copy(io.Discard, file)
   145  	if err != nil {
   146  		t.Fatal(err)
   147  	}
   148  	return n
   149  }
   150  
   151  func equal(name1, name2 string) (r bool) {
   152  	switch runtime.GOOS {
   153  	case "windows":
   154  		r = strings.EqualFold(name1, name2)
   155  	default:
   156  		r = name1 == name2
   157  	}
   158  	return
   159  }
   160  
   161  func newFile(t *testing.T) (f *File) {
   162  	t.Helper()
   163  	f, err := CreateTemp("", "_Go_"+t.Name())
   164  	if err != nil {
   165  		t.Fatal(err)
   166  	}
   167  	t.Cleanup(func() {
   168  		if err := f.Close(); err != nil && !errors.Is(err, ErrClosed) {
   169  			t.Fatal(err)
   170  		}
   171  		if err := Remove(f.Name()); err != nil {
   172  			t.Fatal(err)
   173  		}
   174  	})
   175  	return
   176  }
   177  
   178  var sfdir = sysdir.name
   179  var sfname = sysdir.files[0]
   180  
   181  func TestStat(t *testing.T) {
   182  	t.Parallel()
   183  
   184  	path := sfdir + "/" + sfname
   185  	dir, err := Stat(path)
   186  	if err != nil {
   187  		t.Fatal("stat failed:", err)
   188  	}
   189  	if !equal(sfname, dir.Name()) {
   190  		t.Error("name should be ", sfname, "; is", dir.Name())
   191  	}
   192  	filesize := size(path, t)
   193  	if dir.Size() != filesize {
   194  		t.Error("size should be", filesize, "; is", dir.Size())
   195  	}
   196  }
   197  
   198  func TestStatError(t *testing.T) {
   199  	t.Chdir(t.TempDir())
   200  
   201  	path := "no-such-file"
   202  
   203  	fi, err := Stat(path)
   204  	if err == nil {
   205  		t.Fatal("got nil, want error")
   206  	}
   207  	if fi != nil {
   208  		t.Errorf("got %v, want nil", fi)
   209  	}
   210  	if perr, ok := err.(*PathError); !ok {
   211  		t.Errorf("got %T, want %T", err, perr)
   212  	}
   213  
   214  	testenv.MustHaveSymlink(t)
   215  
   216  	link := "symlink"
   217  	err = Symlink(path, link)
   218  	if err != nil {
   219  		t.Fatal(err)
   220  	}
   221  
   222  	fi, err = Stat(link)
   223  	if err == nil {
   224  		t.Fatal("got nil, want error")
   225  	}
   226  	if fi != nil {
   227  		t.Errorf("got %v, want nil", fi)
   228  	}
   229  	if perr, ok := err.(*PathError); !ok {
   230  		t.Errorf("got %T, want %T", err, perr)
   231  	}
   232  }
   233  
   234  func TestStatSymlinkLoop(t *testing.T) {
   235  	testenv.MustHaveSymlink(t)
   236  	t.Chdir(t.TempDir())
   237  
   238  	err := Symlink("x", "y")
   239  	if err != nil {
   240  		t.Fatal(err)
   241  	}
   242  	defer Remove("y")
   243  
   244  	err = Symlink("y", "x")
   245  	if err != nil {
   246  		t.Fatal(err)
   247  	}
   248  	defer Remove("x")
   249  
   250  	_, err = Stat("x")
   251  	if _, ok := err.(*fs.PathError); !ok {
   252  		t.Errorf("expected *PathError, got %T: %v\n", err, err)
   253  	}
   254  }
   255  
   256  func TestFstat(t *testing.T) {
   257  	t.Parallel()
   258  
   259  	path := sfdir + "/" + sfname
   260  	file, err1 := Open(path)
   261  	if err1 != nil {
   262  		t.Fatal("open failed:", err1)
   263  	}
   264  	defer file.Close()
   265  	dir, err2 := file.Stat()
   266  	if err2 != nil {
   267  		t.Fatal("fstat failed:", err2)
   268  	}
   269  	if !equal(sfname, dir.Name()) {
   270  		t.Error("name should be ", sfname, "; is", dir.Name())
   271  	}
   272  	filesize := size(path, t)
   273  	if dir.Size() != filesize {
   274  		t.Error("size should be", filesize, "; is", dir.Size())
   275  	}
   276  }
   277  
   278  func TestLstat(t *testing.T) {
   279  	t.Parallel()
   280  
   281  	path := sfdir + "/" + sfname
   282  	dir, err := Lstat(path)
   283  	if err != nil {
   284  		t.Fatal("lstat failed:", err)
   285  	}
   286  	if !equal(sfname, dir.Name()) {
   287  		t.Error("name should be ", sfname, "; is", dir.Name())
   288  	}
   289  	if dir.Mode()&ModeSymlink == 0 {
   290  		filesize := size(path, t)
   291  		if dir.Size() != filesize {
   292  			t.Error("size should be", filesize, "; is", dir.Size())
   293  		}
   294  	}
   295  }
   296  
   297  // Read with length 0 should not return EOF.
   298  func TestRead0(t *testing.T) {
   299  	t.Parallel()
   300  
   301  	path := sfdir + "/" + sfname
   302  	f, err := Open(path)
   303  	if err != nil {
   304  		t.Fatal("open failed:", err)
   305  	}
   306  	defer f.Close()
   307  
   308  	b := make([]byte, 0)
   309  	n, err := f.Read(b)
   310  	if n != 0 || err != nil {
   311  		t.Errorf("Read(0) = %d, %v, want 0, nil", n, err)
   312  	}
   313  	b = make([]byte, 100)
   314  	n, err = f.Read(b)
   315  	if n <= 0 || err != nil {
   316  		t.Errorf("Read(100) = %d, %v, want >0, nil", n, err)
   317  	}
   318  }
   319  
   320  // Reading a closed file should return ErrClosed error
   321  func TestReadClosed(t *testing.T) {
   322  	t.Parallel()
   323  
   324  	path := sfdir + "/" + sfname
   325  	file, err := Open(path)
   326  	if err != nil {
   327  		t.Fatal("open failed:", err)
   328  	}
   329  	file.Close() // close immediately
   330  
   331  	b := make([]byte, 100)
   332  	_, err = file.Read(b)
   333  
   334  	e, ok := err.(*PathError)
   335  	if !ok || e.Err != ErrClosed {
   336  		t.Fatalf("Read: got %T(%v), want %T(%v)", err, err, e, ErrClosed)
   337  	}
   338  }
   339  
   340  func testReaddirnames(dir string, contents []string) func(*testing.T) {
   341  	return func(t *testing.T) {
   342  		t.Parallel()
   343  
   344  		file, err := Open(dir)
   345  		if err != nil {
   346  			t.Fatalf("open %q failed: %v", dir, err)
   347  		}
   348  		defer file.Close()
   349  		s, err2 := file.Readdirnames(-1)
   350  		if err2 != nil {
   351  			t.Fatalf("Readdirnames %q failed: %v", dir, err2)
   352  		}
   353  		for _, m := range contents {
   354  			found := false
   355  			for _, n := range s {
   356  				if n == "." || n == ".." {
   357  					t.Errorf("got %q in directory", n)
   358  				}
   359  				if !equal(m, n) {
   360  					continue
   361  				}
   362  				if found {
   363  					t.Error("present twice:", m)
   364  				}
   365  				found = true
   366  			}
   367  			if !found {
   368  				t.Error("could not find", m)
   369  			}
   370  		}
   371  		if s == nil {
   372  			t.Error("Readdirnames returned nil instead of empty slice")
   373  		}
   374  	}
   375  }
   376  
   377  func testReaddir(dir string, contents []string) func(*testing.T) {
   378  	return func(t *testing.T) {
   379  		t.Parallel()
   380  
   381  		file, err := Open(dir)
   382  		if err != nil {
   383  			t.Fatalf("open %q failed: %v", dir, err)
   384  		}
   385  		defer file.Close()
   386  		s, err2 := file.Readdir(-1)
   387  		if err2 != nil {
   388  			t.Fatalf("Readdir %q failed: %v", dir, err2)
   389  		}
   390  		for _, m := range contents {
   391  			found := false
   392  			for _, n := range s {
   393  				if n.Name() == "." || n.Name() == ".." {
   394  					t.Errorf("got %q in directory", n.Name())
   395  				}
   396  				if !equal(m, n.Name()) {
   397  					continue
   398  				}
   399  				if found {
   400  					t.Error("present twice:", m)
   401  				}
   402  				found = true
   403  			}
   404  			if !found {
   405  				t.Error("could not find", m)
   406  			}
   407  		}
   408  		if s == nil {
   409  			t.Error("Readdir returned nil instead of empty slice")
   410  		}
   411  	}
   412  }
   413  
   414  func testReadDir(dir string, contents []string) func(*testing.T) {
   415  	return func(t *testing.T) {
   416  		t.Parallel()
   417  
   418  		file, err := Open(dir)
   419  		if err != nil {
   420  			t.Fatalf("open %q failed: %v", dir, err)
   421  		}
   422  		defer file.Close()
   423  		s, err2 := file.ReadDir(-1)
   424  		if err2 != nil {
   425  			t.Fatalf("ReadDir %q failed: %v", dir, err2)
   426  		}
   427  		for _, m := range contents {
   428  			found := false
   429  			for _, n := range s {
   430  				if n.Name() == "." || n.Name() == ".." {
   431  					t.Errorf("got %q in directory", n)
   432  				}
   433  				if !equal(m, n.Name()) {
   434  					continue
   435  				}
   436  				if found {
   437  					t.Error("present twice:", m)
   438  				}
   439  				found = true
   440  				lstat, err := Lstat(dir + "/" + m)
   441  				if err != nil {
   442  					t.Fatal(err)
   443  				}
   444  				if n.IsDir() != lstat.IsDir() {
   445  					t.Errorf("%s: IsDir=%v, want %v", m, n.IsDir(), lstat.IsDir())
   446  				}
   447  				if n.Type() != lstat.Mode().Type() {
   448  					t.Errorf("%s: IsDir=%v, want %v", m, n.Type(), lstat.Mode().Type())
   449  				}
   450  				info, err := n.Info()
   451  				if err != nil {
   452  					t.Errorf("%s: Info: %v", m, err)
   453  					continue
   454  				}
   455  				if !SameFile(info, lstat) {
   456  					t.Errorf("%s: Info: SameFile(info, lstat) = false", m)
   457  				}
   458  			}
   459  			if !found {
   460  				t.Error("could not find", m)
   461  			}
   462  		}
   463  		if s == nil {
   464  			t.Error("ReadDir returned nil instead of empty slice")
   465  		}
   466  	}
   467  }
   468  
   469  func TestFileReaddirnames(t *testing.T) {
   470  	t.Parallel()
   471  
   472  	t.Run(".", testReaddirnames(".", dot))
   473  	t.Run("sysdir", testReaddirnames(sysdir.name, sysdir.files))
   474  	t.Run("TempDir", testReaddirnames(t.TempDir(), nil))
   475  }
   476  
   477  func TestFileReaddir(t *testing.T) {
   478  	t.Parallel()
   479  
   480  	t.Run(".", testReaddir(".", dot))
   481  	t.Run("sysdir", testReaddir(sysdir.name, sysdir.files))
   482  	t.Run("TempDir", testReaddir(t.TempDir(), nil))
   483  }
   484  
   485  func TestFileReadDir(t *testing.T) {
   486  	t.Parallel()
   487  
   488  	t.Run(".", testReadDir(".", dot))
   489  	t.Run("sysdir", testReadDir(sysdir.name, sysdir.files))
   490  	t.Run("TempDir", testReadDir(t.TempDir(), nil))
   491  }
   492  
   493  func benchmarkReaddirname(path string, b *testing.B) {
   494  	var nentries int
   495  	for i := 0; i < b.N; i++ {
   496  		f, err := Open(path)
   497  		if err != nil {
   498  			b.Fatalf("open %q failed: %v", path, err)
   499  		}
   500  		ns, err := f.Readdirnames(-1)
   501  		f.Close()
   502  		if err != nil {
   503  			b.Fatalf("readdirnames %q failed: %v", path, err)
   504  		}
   505  		nentries = len(ns)
   506  	}
   507  	b.Logf("benchmarkReaddirname %q: %d entries", path, nentries)
   508  }
   509  
   510  func benchmarkReaddir(path string, b *testing.B) {
   511  	var nentries int
   512  	for i := 0; i < b.N; i++ {
   513  		f, err := Open(path)
   514  		if err != nil {
   515  			b.Fatalf("open %q failed: %v", path, err)
   516  		}
   517  		fs, err := f.Readdir(-1)
   518  		f.Close()
   519  		if err != nil {
   520  			b.Fatalf("readdir %q failed: %v", path, err)
   521  		}
   522  		nentries = len(fs)
   523  	}
   524  	b.Logf("benchmarkReaddir %q: %d entries", path, nentries)
   525  }
   526  
   527  func benchmarkReadDir(path string, b *testing.B) {
   528  	var nentries int
   529  	for i := 0; i < b.N; i++ {
   530  		f, err := Open(path)
   531  		if err != nil {
   532  			b.Fatalf("open %q failed: %v", path, err)
   533  		}
   534  		fs, err := f.ReadDir(-1)
   535  		f.Close()
   536  		if err != nil {
   537  			b.Fatalf("readdir %q failed: %v", path, err)
   538  		}
   539  		nentries = len(fs)
   540  	}
   541  	b.Logf("benchmarkReadDir %q: %d entries", path, nentries)
   542  }
   543  
   544  func BenchmarkReaddirname(b *testing.B) {
   545  	benchmarkReaddirname(".", b)
   546  }
   547  
   548  func BenchmarkReaddir(b *testing.B) {
   549  	benchmarkReaddir(".", b)
   550  }
   551  
   552  func BenchmarkReadDir(b *testing.B) {
   553  	benchmarkReadDir(".", b)
   554  }
   555  
   556  func benchmarkStat(b *testing.B, path string) {
   557  	b.ResetTimer()
   558  	for i := 0; i < b.N; i++ {
   559  		_, err := Stat(path)
   560  		if err != nil {
   561  			b.Fatalf("Stat(%q) failed: %v", path, err)
   562  		}
   563  	}
   564  }
   565  
   566  func benchmarkLstat(b *testing.B, path string) {
   567  	b.ResetTimer()
   568  	for i := 0; i < b.N; i++ {
   569  		_, err := Lstat(path)
   570  		if err != nil {
   571  			b.Fatalf("Lstat(%q) failed: %v", path, err)
   572  		}
   573  	}
   574  }
   575  
   576  func BenchmarkStatDot(b *testing.B) {
   577  	benchmarkStat(b, ".")
   578  }
   579  
   580  func BenchmarkStatFile(b *testing.B) {
   581  	benchmarkStat(b, filepath.Join(runtime.GOROOT(), "src/os/os_test.go"))
   582  }
   583  
   584  func BenchmarkStatDir(b *testing.B) {
   585  	benchmarkStat(b, filepath.Join(runtime.GOROOT(), "src/os"))
   586  }
   587  
   588  func BenchmarkLstatDot(b *testing.B) {
   589  	benchmarkLstat(b, ".")
   590  }
   591  
   592  func BenchmarkLstatFile(b *testing.B) {
   593  	benchmarkLstat(b, filepath.Join(runtime.GOROOT(), "src/os/os_test.go"))
   594  }
   595  
   596  func BenchmarkLstatDir(b *testing.B) {
   597  	benchmarkLstat(b, filepath.Join(runtime.GOROOT(), "src/os"))
   598  }
   599  
   600  // Read the directory one entry at a time.
   601  func smallReaddirnames(file *File, length int, t *testing.T) []string {
   602  	names := make([]string, length)
   603  	count := 0
   604  	for {
   605  		d, err := file.Readdirnames(1)
   606  		if err == io.EOF {
   607  			break
   608  		}
   609  		if err != nil {
   610  			t.Fatalf("readdirnames %q failed: %v", file.Name(), err)
   611  		}
   612  		if len(d) == 0 {
   613  			t.Fatalf("readdirnames %q returned empty slice and no error", file.Name())
   614  		}
   615  		names[count] = d[0]
   616  		count++
   617  	}
   618  	return names[0:count]
   619  }
   620  
   621  // Check that reading a directory one entry at a time gives the same result
   622  // as reading it all at once.
   623  func TestReaddirnamesOneAtATime(t *testing.T) {
   624  	t.Parallel()
   625  
   626  	// big directory that doesn't change often.
   627  	dir := "/usr/bin"
   628  	switch runtime.GOOS {
   629  	case "android":
   630  		dir = "/system/bin"
   631  	case "ios", "wasip1":
   632  		wd, err := Getwd()
   633  		if err != nil {
   634  			t.Fatal(err)
   635  		}
   636  		dir = wd
   637  	case "plan9":
   638  		dir = "/bin"
   639  	case "windows":
   640  		dir = Getenv("SystemRoot") + "\\system32"
   641  	}
   642  	file, err := Open(dir)
   643  	if err != nil {
   644  		t.Fatalf("open %q failed: %v", dir, err)
   645  	}
   646  	defer file.Close()
   647  	all, err1 := file.Readdirnames(-1)
   648  	if err1 != nil {
   649  		t.Fatalf("readdirnames %q failed: %v", dir, err1)
   650  	}
   651  	file1, err2 := Open(dir)
   652  	if err2 != nil {
   653  		t.Fatalf("open %q failed: %v", dir, err2)
   654  	}
   655  	defer file1.Close()
   656  	small := smallReaddirnames(file1, len(all)+100, t) // +100 in case we screw up
   657  	if len(small) < len(all) {
   658  		t.Fatalf("len(small) is %d, less than %d", len(small), len(all))
   659  	}
   660  	for i, n := range all {
   661  		if small[i] != n {
   662  			t.Errorf("small read %q mismatch: %v", small[i], n)
   663  		}
   664  	}
   665  }
   666  
   667  func TestReaddirNValues(t *testing.T) {
   668  	if testing.Short() {
   669  		t.Skip("test.short; skipping")
   670  	}
   671  	t.Parallel()
   672  
   673  	dir := t.TempDir()
   674  	for i := 1; i <= 105; i++ {
   675  		f, err := Create(filepath.Join(dir, fmt.Sprintf("%d", i)))
   676  		if err != nil {
   677  			t.Fatalf("Create: %v", err)
   678  		}
   679  		f.Write([]byte(strings.Repeat("X", i)))
   680  		f.Close()
   681  	}
   682  
   683  	var d *File
   684  	openDir := func() {
   685  		var err error
   686  		d, err = Open(dir)
   687  		if err != nil {
   688  			t.Fatalf("Open directory: %v", err)
   689  		}
   690  	}
   691  
   692  	readdirExpect := func(n, want int, wantErr error) {
   693  		t.Helper()
   694  		fi, err := d.Readdir(n)
   695  		if err != wantErr {
   696  			t.Fatalf("Readdir of %d got error %v, want %v", n, err, wantErr)
   697  		}
   698  		if g, e := len(fi), want; g != e {
   699  			t.Errorf("Readdir of %d got %d files, want %d", n, g, e)
   700  		}
   701  	}
   702  
   703  	readDirExpect := func(n, want int, wantErr error) {
   704  		t.Helper()
   705  		de, err := d.ReadDir(n)
   706  		if err != wantErr {
   707  			t.Fatalf("ReadDir of %d got error %v, want %v", n, err, wantErr)
   708  		}
   709  		if g, e := len(de), want; g != e {
   710  			t.Errorf("ReadDir of %d got %d files, want %d", n, g, e)
   711  		}
   712  	}
   713  
   714  	readdirnamesExpect := func(n, want int, wantErr error) {
   715  		t.Helper()
   716  		fi, err := d.Readdirnames(n)
   717  		if err != wantErr {
   718  			t.Fatalf("Readdirnames of %d got error %v, want %v", n, err, wantErr)
   719  		}
   720  		if g, e := len(fi), want; g != e {
   721  			t.Errorf("Readdirnames of %d got %d files, want %d", n, g, e)
   722  		}
   723  	}
   724  
   725  	for _, fn := range []func(int, int, error){readdirExpect, readdirnamesExpect, readDirExpect} {
   726  		// Test the slurp case
   727  		openDir()
   728  		fn(0, 105, nil)
   729  		fn(0, 0, nil)
   730  		d.Close()
   731  
   732  		// Slurp with -1 instead
   733  		openDir()
   734  		fn(-1, 105, nil)
   735  		fn(-2, 0, nil)
   736  		fn(0, 0, nil)
   737  		d.Close()
   738  
   739  		// Test the bounded case
   740  		openDir()
   741  		fn(1, 1, nil)
   742  		fn(2, 2, nil)
   743  		fn(105, 102, nil) // and tests buffer >100 case
   744  		fn(3, 0, io.EOF)
   745  		d.Close()
   746  	}
   747  }
   748  
   749  func touch(t *testing.T, name string) {
   750  	f, err := Create(name)
   751  	if err != nil {
   752  		t.Fatal(err)
   753  	}
   754  	if err := f.Close(); err != nil {
   755  		t.Fatal(err)
   756  	}
   757  }
   758  
   759  func TestReaddirStatFailures(t *testing.T) {
   760  	switch runtime.GOOS {
   761  	case "windows", "plan9":
   762  		// Windows and Plan 9 already do this correctly,
   763  		// but are structured with different syscalls such
   764  		// that they don't use Lstat, so the hook below for
   765  		// testing it wouldn't work.
   766  		t.Skipf("skipping test on %v", runtime.GOOS)
   767  	}
   768  
   769  	var xerr error // error to return for x
   770  	*LstatP = func(path string) (FileInfo, error) {
   771  		if xerr != nil && strings.HasSuffix(path, "x") {
   772  			return nil, xerr
   773  		}
   774  		return Lstat(path)
   775  	}
   776  	defer func() { *LstatP = Lstat }()
   777  
   778  	dir := t.TempDir()
   779  	touch(t, filepath.Join(dir, "good1"))
   780  	touch(t, filepath.Join(dir, "x")) // will disappear or have an error
   781  	touch(t, filepath.Join(dir, "good2"))
   782  	readDir := func() ([]FileInfo, error) {
   783  		d, err := Open(dir)
   784  		if err != nil {
   785  			t.Fatal(err)
   786  		}
   787  		defer d.Close()
   788  		return d.Readdir(-1)
   789  	}
   790  	mustReadDir := func(testName string) []FileInfo {
   791  		fis, err := readDir()
   792  		if err != nil {
   793  			t.Fatalf("%s: Readdir: %v", testName, err)
   794  		}
   795  		return fis
   796  	}
   797  	names := func(fis []FileInfo) []string {
   798  		s := make([]string, len(fis))
   799  		for i, fi := range fis {
   800  			s[i] = fi.Name()
   801  		}
   802  		slices.Sort(s)
   803  		return s
   804  	}
   805  
   806  	if got, want := names(mustReadDir("initial readdir")),
   807  		[]string{"good1", "good2", "x"}; !slices.Equal(got, want) {
   808  		t.Errorf("initial readdir got %q; want %q", got, want)
   809  	}
   810  
   811  	xerr = ErrNotExist
   812  	if got, want := names(mustReadDir("with x disappearing")),
   813  		[]string{"good1", "good2"}; !slices.Equal(got, want) {
   814  		t.Errorf("with x disappearing, got %q; want %q", got, want)
   815  	}
   816  
   817  	xerr = errors.New("some real error")
   818  	if _, err := readDir(); err != xerr {
   819  		t.Errorf("with a non-ErrNotExist error, got error %v; want %v", err, xerr)
   820  	}
   821  }
   822  
   823  // Readdir on a regular file should fail.
   824  func TestReaddirOfFile(t *testing.T) {
   825  	t.Parallel()
   826  
   827  	f, err := CreateTemp(t.TempDir(), "_Go_ReaddirOfFile")
   828  	if err != nil {
   829  		t.Fatal(err)
   830  	}
   831  	f.Write([]byte("foo"))
   832  	f.Close()
   833  	reg, err := Open(f.Name())
   834  	if err != nil {
   835  		t.Fatal(err)
   836  	}
   837  	defer reg.Close()
   838  
   839  	names, err := reg.Readdirnames(-1)
   840  	if err == nil {
   841  		t.Error("Readdirnames succeeded; want non-nil error")
   842  	}
   843  	if pe, ok := errors.AsType[*PathError](err); !ok || pe.Path != f.Name() {
   844  		t.Errorf("Readdirnames returned %q; want a PathError with path %q", err, f.Name())
   845  	}
   846  	if len(names) > 0 {
   847  		t.Errorf("unexpected dir names in regular file: %q", names)
   848  	}
   849  }
   850  
   851  func TestHardLink(t *testing.T) {
   852  	testMaybeRooted(t, testHardLink)
   853  }
   854  func testHardLink(t *testing.T, root *Root) {
   855  	testenv.MustHaveLink(t)
   856  
   857  	var (
   858  		create = Create
   859  		link   = Link
   860  		stat   = Stat
   861  		op     = "link"
   862  	)
   863  	if root != nil {
   864  		create = root.Create
   865  		link = root.Link
   866  		stat = root.Stat
   867  		op = "linkat"
   868  	}
   869  
   870  	from, to := "hardlinktestfrom", "hardlinktestto"
   871  	file, err := create(to)
   872  	if err != nil {
   873  		t.Fatalf("open %q failed: %v", to, err)
   874  	}
   875  	if err = file.Close(); err != nil {
   876  		t.Errorf("close %q failed: %v", to, err)
   877  	}
   878  	err = link(to, from)
   879  	if err != nil {
   880  		t.Fatalf("link %q, %q failed: %v", to, from, err)
   881  	}
   882  
   883  	none := "hardlinktestnone"
   884  	err = link(none, none)
   885  	// Check the returned error is well-formed.
   886  	if lerr, ok := err.(*LinkError); !ok || lerr.Error() == "" {
   887  		t.Errorf("link %q, %q failed to return a valid error", none, none)
   888  	}
   889  
   890  	tostat, err := stat(to)
   891  	if err != nil {
   892  		t.Fatalf("stat %q failed: %v", to, err)
   893  	}
   894  	fromstat, err := stat(from)
   895  	if err != nil {
   896  		t.Fatalf("stat %q failed: %v", from, err)
   897  	}
   898  	if !SameFile(tostat, fromstat) {
   899  		t.Errorf("link %q, %q did not create hard link", to, from)
   900  	}
   901  	// We should not be able to perform the same Link() a second time
   902  	err = link(to, from)
   903  	switch err := err.(type) {
   904  	case *LinkError:
   905  		if err.Op != op {
   906  			t.Errorf("Link(%q, %q) err.Op = %q; want %q", to, from, err.Op, op)
   907  		}
   908  		if err.Old != to {
   909  			t.Errorf("Link(%q, %q) err.Old = %q; want %q", to, from, err.Old, to)
   910  		}
   911  		if err.New != from {
   912  			t.Errorf("Link(%q, %q) err.New = %q; want %q", to, from, err.New, from)
   913  		}
   914  		if !IsExist(err.Err) {
   915  			t.Errorf("Link(%q, %q) err.Err = %q; want %q", to, from, err.Err, "file exists error")
   916  		}
   917  	case nil:
   918  		t.Errorf("link %q, %q: expected error, got nil", from, to)
   919  	default:
   920  		t.Errorf("link %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
   921  	}
   922  }
   923  
   924  func TestSymlink(t *testing.T) {
   925  	testMaybeRooted(t, testSymlink)
   926  }
   927  func testSymlink(t *testing.T, root *Root) {
   928  	testenv.MustHaveSymlink(t)
   929  
   930  	var (
   931  		create   = Create
   932  		open     = Open
   933  		symlink  = Symlink
   934  		stat     = Stat
   935  		lstat    = Lstat
   936  		readlink = Readlink
   937  	)
   938  	if root != nil {
   939  		create = root.Create
   940  		open = root.Open
   941  		symlink = root.Symlink
   942  		stat = root.Stat
   943  		lstat = root.Lstat
   944  		readlink = root.Readlink
   945  	}
   946  
   947  	from, to := "symlinktestfrom", "symlinktestto"
   948  	file, err := create(to)
   949  	if err != nil {
   950  		t.Fatalf("Create(%q) failed: %v", to, err)
   951  	}
   952  	if err = file.Close(); err != nil {
   953  		t.Errorf("Close(%q) failed: %v", to, err)
   954  	}
   955  	err = symlink(to, from)
   956  	if err != nil {
   957  		t.Fatalf("Symlink(%q, %q) failed: %v", to, from, err)
   958  	}
   959  	tostat, err := lstat(to)
   960  	if err != nil {
   961  		t.Fatalf("Lstat(%q) failed: %v", to, err)
   962  	}
   963  	if tostat.Mode()&ModeSymlink != 0 {
   964  		t.Fatalf("Lstat(%q).Mode()&ModeSymlink = %v, want 0", to, tostat.Mode()&ModeSymlink)
   965  	}
   966  	fromstat, err := stat(from)
   967  	if err != nil {
   968  		t.Fatalf("Stat(%q) failed: %v", from, err)
   969  	}
   970  	if !SameFile(tostat, fromstat) {
   971  		t.Errorf("Symlink(%q, %q) did not create symlink", to, from)
   972  	}
   973  	fromstat, err = lstat(from)
   974  	if err != nil {
   975  		t.Fatalf("Lstat(%q) failed: %v", from, err)
   976  	}
   977  	if fromstat.Mode()&ModeSymlink == 0 {
   978  		t.Fatalf("Lstat(%q).Mode()&ModeSymlink = 0, want %v", from, ModeSymlink)
   979  	}
   980  	fromstat, err = stat(from)
   981  	if err != nil {
   982  		t.Fatalf("Stat(%q) failed: %v", from, err)
   983  	}
   984  	if fromstat.Name() != from {
   985  		t.Errorf("Stat(%q).Name() = %q, want %q", from, fromstat.Name(), from)
   986  	}
   987  	if fromstat.Mode()&ModeSymlink != 0 {
   988  		t.Fatalf("Stat(%q).Mode()&ModeSymlink = %v, want 0", from, fromstat.Mode()&ModeSymlink)
   989  	}
   990  	s, err := readlink(from)
   991  	if err != nil {
   992  		t.Fatalf("Readlink(%q) failed: %v", from, err)
   993  	}
   994  	if s != to {
   995  		t.Fatalf("Readlink(%q) = %q, want %q", from, s, to)
   996  	}
   997  	file, err = open(from)
   998  	if err != nil {
   999  		t.Fatalf("Open(%q) failed: %v", from, err)
  1000  	}
  1001  	file.Close()
  1002  }
  1003  
  1004  func TestLongSymlink(t *testing.T) {
  1005  	testenv.MustHaveSymlink(t)
  1006  	t.Chdir(t.TempDir())
  1007  
  1008  	s := "0123456789abcdef"
  1009  	// Long, but not too long: a common limit is 255.
  1010  	s = s + s + s + s + s + s + s + s + s + s + s + s + s + s + s
  1011  	from := "longsymlinktestfrom"
  1012  	err := Symlink(s, from)
  1013  	if err != nil {
  1014  		t.Fatalf("symlink %q, %q failed: %v", s, from, err)
  1015  	}
  1016  	r, err := Readlink(from)
  1017  	if err != nil {
  1018  		t.Fatalf("readlink %q failed: %v", from, err)
  1019  	}
  1020  	if r != s {
  1021  		t.Fatalf("after symlink %q != %q", r, s)
  1022  	}
  1023  }
  1024  
  1025  func TestRename(t *testing.T) {
  1026  	t.Chdir(t.TempDir())
  1027  	from, to := "renamefrom", "renameto"
  1028  
  1029  	file, err := Create(from)
  1030  	if err != nil {
  1031  		t.Fatalf("open %q failed: %v", from, err)
  1032  	}
  1033  	if err = file.Close(); err != nil {
  1034  		t.Errorf("close %q failed: %v", from, err)
  1035  	}
  1036  	err = Rename(from, to)
  1037  	if err != nil {
  1038  		t.Fatalf("rename %q, %q failed: %v", to, from, err)
  1039  	}
  1040  	_, err = Stat(to)
  1041  	if err != nil {
  1042  		t.Errorf("stat %q failed: %v", to, err)
  1043  	}
  1044  }
  1045  
  1046  func TestRenameOverwriteDest(t *testing.T) {
  1047  	t.Chdir(t.TempDir())
  1048  	from, to := "renamefrom", "renameto"
  1049  
  1050  	toData := []byte("to")
  1051  	fromData := []byte("from")
  1052  
  1053  	err := WriteFile(to, toData, 0777)
  1054  	if err != nil {
  1055  		t.Fatalf("write file %q failed: %v", to, err)
  1056  	}
  1057  
  1058  	err = WriteFile(from, fromData, 0777)
  1059  	if err != nil {
  1060  		t.Fatalf("write file %q failed: %v", from, err)
  1061  	}
  1062  	err = Rename(from, to)
  1063  	if err != nil {
  1064  		t.Fatalf("rename %q, %q failed: %v", to, from, err)
  1065  	}
  1066  
  1067  	_, err = Stat(from)
  1068  	if err == nil {
  1069  		t.Errorf("from file %q still exists", from)
  1070  	}
  1071  	if err != nil && !IsNotExist(err) {
  1072  		t.Fatalf("stat from: %v", err)
  1073  	}
  1074  	toFi, err := Stat(to)
  1075  	if err != nil {
  1076  		t.Fatalf("stat %q failed: %v", to, err)
  1077  	}
  1078  	if toFi.Size() != int64(len(fromData)) {
  1079  		t.Errorf(`"to" size = %d; want %d (old "from" size)`, toFi.Size(), len(fromData))
  1080  	}
  1081  }
  1082  
  1083  func TestRenameFailed(t *testing.T) {
  1084  	t.Chdir(t.TempDir())
  1085  	from, to := "renamefrom", "renameto"
  1086  
  1087  	err := Rename(from, to)
  1088  	switch err := err.(type) {
  1089  	case *LinkError:
  1090  		if err.Op != "rename" {
  1091  			t.Errorf("rename %q, %q: err.Op: want %q, got %q", from, to, "rename", err.Op)
  1092  		}
  1093  		if err.Old != from {
  1094  			t.Errorf("rename %q, %q: err.Old: want %q, got %q", from, to, from, err.Old)
  1095  		}
  1096  		if err.New != to {
  1097  			t.Errorf("rename %q, %q: err.New: want %q, got %q", from, to, to, err.New)
  1098  		}
  1099  	case nil:
  1100  		t.Errorf("rename %q, %q: expected error, got nil", from, to)
  1101  	default:
  1102  		t.Errorf("rename %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
  1103  	}
  1104  }
  1105  
  1106  func TestRenameNotExisting(t *testing.T) {
  1107  	t.Chdir(t.TempDir())
  1108  	from, to := "doesnt-exist", "dest"
  1109  
  1110  	Mkdir(to, 0777)
  1111  
  1112  	if err := Rename(from, to); !IsNotExist(err) {
  1113  		t.Errorf("Rename(%q, %q) = %v; want an IsNotExist error", from, to, err)
  1114  	}
  1115  }
  1116  
  1117  func TestRenameToDirFailed(t *testing.T) {
  1118  	t.Chdir(t.TempDir())
  1119  	from, to := "renamefrom", "renameto"
  1120  
  1121  	Mkdir(from, 0777)
  1122  	Mkdir(to, 0777)
  1123  
  1124  	err := Rename(from, to)
  1125  	switch err := err.(type) {
  1126  	case *LinkError:
  1127  		if err.Op != "rename" {
  1128  			t.Errorf("rename %q, %q: err.Op: want %q, got %q", from, to, "rename", err.Op)
  1129  		}
  1130  		if err.Old != from {
  1131  			t.Errorf("rename %q, %q: err.Old: want %q, got %q", from, to, from, err.Old)
  1132  		}
  1133  		if err.New != to {
  1134  			t.Errorf("rename %q, %q: err.New: want %q, got %q", from, to, to, err.New)
  1135  		}
  1136  	case nil:
  1137  		t.Errorf("rename %q, %q: expected error, got nil", from, to)
  1138  	default:
  1139  		t.Errorf("rename %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
  1140  	}
  1141  }
  1142  
  1143  func TestRenameCaseDifference(pt *testing.T) {
  1144  	from, to := "renameFROM", "RENAMEfrom"
  1145  	tests := []struct {
  1146  		name   string
  1147  		create func() error
  1148  	}{
  1149  		{"dir", func() error {
  1150  			return Mkdir(from, 0777)
  1151  		}},
  1152  		{"file", func() error {
  1153  			fd, err := Create(from)
  1154  			if err != nil {
  1155  				return err
  1156  			}
  1157  			return fd.Close()
  1158  		}},
  1159  	}
  1160  
  1161  	for _, test := range tests {
  1162  		pt.Run(test.name, func(t *testing.T) {
  1163  			t.Chdir(t.TempDir())
  1164  
  1165  			if err := test.create(); err != nil {
  1166  				t.Fatalf("failed to create test file: %s", err)
  1167  			}
  1168  
  1169  			if _, err := Stat(to); err != nil {
  1170  				// Sanity check that the underlying filesystem is not case sensitive.
  1171  				if IsNotExist(err) {
  1172  					t.Skipf("case sensitive filesystem")
  1173  				}
  1174  				t.Fatalf("stat %q, got: %q", to, err)
  1175  			}
  1176  
  1177  			if err := Rename(from, to); err != nil {
  1178  				t.Fatalf("unexpected error when renaming from %q to %q: %s", from, to, err)
  1179  			}
  1180  
  1181  			fd, err := Open(".")
  1182  			if err != nil {
  1183  				t.Fatalf("Open .: %s", err)
  1184  			}
  1185  
  1186  			// Stat does not return the real case of the file (it returns what the called asked for)
  1187  			// So we have to use readdir to get the real name of the file.
  1188  			dirNames, err := fd.Readdirnames(-1)
  1189  			fd.Close()
  1190  			if err != nil {
  1191  				t.Fatalf("readdirnames: %s", err)
  1192  			}
  1193  
  1194  			if dirNamesLen := len(dirNames); dirNamesLen != 1 {
  1195  				t.Fatalf("unexpected dirNames len, got %q, want %q", dirNamesLen, 1)
  1196  			}
  1197  
  1198  			if dirNames[0] != to {
  1199  				t.Errorf("unexpected name, got %q, want %q", dirNames[0], to)
  1200  			}
  1201  		})
  1202  	}
  1203  }
  1204  
  1205  func testStartProcess(dir, cmd string, args []string, expect string) func(t *testing.T) {
  1206  	return func(t *testing.T) {
  1207  		t.Parallel()
  1208  
  1209  		r, w, err := Pipe()
  1210  		if err != nil {
  1211  			t.Fatalf("Pipe: %v", err)
  1212  		}
  1213  		defer r.Close()
  1214  		attr := &ProcAttr{Dir: dir, Files: []*File{nil, w, Stderr}}
  1215  		p, err := StartProcess(cmd, args, attr)
  1216  		if err != nil {
  1217  			t.Fatalf("StartProcess: %v", err)
  1218  		}
  1219  		w.Close()
  1220  
  1221  		var b strings.Builder
  1222  		io.Copy(&b, r)
  1223  		output := b.String()
  1224  
  1225  		fi1, _ := Stat(strings.TrimSpace(output))
  1226  		fi2, _ := Stat(expect)
  1227  		if !SameFile(fi1, fi2) {
  1228  			t.Errorf("exec %q returned %q wanted %q",
  1229  				strings.Join(append([]string{cmd}, args...), " "), output, expect)
  1230  		}
  1231  		p.Wait()
  1232  	}
  1233  }
  1234  
  1235  func TestStartProcess(t *testing.T) {
  1236  	testenv.MustHaveExec(t)
  1237  	t.Parallel()
  1238  
  1239  	var dir, cmd string
  1240  	var args []string
  1241  	switch runtime.GOOS {
  1242  	case "android":
  1243  		t.Skip("android doesn't have /bin/pwd")
  1244  	case "windows":
  1245  		cmd = Getenv("COMSPEC")
  1246  		dir = Getenv("SystemRoot")
  1247  		args = []string{"/c", "cd"}
  1248  	default:
  1249  		var err error
  1250  		cmd, err = exec.LookPath("pwd")
  1251  		if err != nil {
  1252  			t.Fatalf("Can't find pwd: %v", err)
  1253  		}
  1254  		dir = "/"
  1255  		args = []string{}
  1256  		t.Logf("Testing with %v", cmd)
  1257  	}
  1258  	cmddir, cmdbase := filepath.Split(cmd)
  1259  	args = append([]string{cmdbase}, args...)
  1260  	t.Run("absolute", testStartProcess(dir, cmd, args, dir))
  1261  	t.Run("relative", testStartProcess(cmddir, cmdbase, args, cmddir))
  1262  }
  1263  
  1264  func checkMode(t *testing.T, path string, mode FileMode) {
  1265  	dir, err := Stat(path)
  1266  	if err != nil {
  1267  		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
  1268  	}
  1269  	if dir.Mode()&ModePerm != mode {
  1270  		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode(), mode)
  1271  	}
  1272  }
  1273  
  1274  func TestChmod(t *testing.T) {
  1275  	// Chmod is not supported on wasip1.
  1276  	if runtime.GOOS == "wasip1" {
  1277  		t.Skip("Chmod is not supported on " + runtime.GOOS)
  1278  	}
  1279  	t.Parallel()
  1280  
  1281  	f := newFile(t)
  1282  	// Creation mode is read write
  1283  
  1284  	fm := FileMode(0456)
  1285  	if runtime.GOOS == "windows" {
  1286  		fm = FileMode(0444) // read-only file
  1287  	}
  1288  	if err := Chmod(f.Name(), fm); err != nil {
  1289  		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
  1290  	}
  1291  	checkMode(t, f.Name(), fm)
  1292  
  1293  	fm = FileMode(0123)
  1294  	if runtime.GOOS == "windows" {
  1295  		fm = FileMode(0666) // read-write file
  1296  	}
  1297  	if err := f.Chmod(fm); err != nil {
  1298  		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
  1299  	}
  1300  	checkMode(t, f.Name(), fm)
  1301  }
  1302  
  1303  func checkSize(t *testing.T, f *File, size int64) {
  1304  	t.Helper()
  1305  	dir, err := f.Stat()
  1306  	if err != nil {
  1307  		t.Fatalf("Stat %q (looking for size %d): %s", f.Name(), size, err)
  1308  	}
  1309  	if dir.Size() != size {
  1310  		t.Errorf("Stat %q: size %d want %d", f.Name(), dir.Size(), size)
  1311  	}
  1312  }
  1313  
  1314  func TestFTruncate(t *testing.T) {
  1315  	t.Parallel()
  1316  
  1317  	f := newFile(t)
  1318  
  1319  	checkSize(t, f, 0)
  1320  	f.Write([]byte("hello, world\n"))
  1321  	checkSize(t, f, 13)
  1322  	f.Truncate(10)
  1323  	checkSize(t, f, 10)
  1324  	f.Truncate(1024)
  1325  	checkSize(t, f, 1024)
  1326  	f.Truncate(0)
  1327  	checkSize(t, f, 0)
  1328  	_, err := f.Write([]byte("surprise!"))
  1329  	if err == nil {
  1330  		checkSize(t, f, 13+9) // wrote at offset past where hello, world was.
  1331  	}
  1332  }
  1333  
  1334  func TestTruncate(t *testing.T) {
  1335  	t.Parallel()
  1336  
  1337  	f := newFile(t)
  1338  
  1339  	checkSize(t, f, 0)
  1340  	f.Write([]byte("hello, world\n"))
  1341  	checkSize(t, f, 13)
  1342  	Truncate(f.Name(), 10)
  1343  	checkSize(t, f, 10)
  1344  	Truncate(f.Name(), 1024)
  1345  	checkSize(t, f, 1024)
  1346  	Truncate(f.Name(), 0)
  1347  	checkSize(t, f, 0)
  1348  	_, err := f.Write([]byte("surprise!"))
  1349  	if err == nil {
  1350  		checkSize(t, f, 13+9) // wrote at offset past where hello, world was.
  1351  	}
  1352  }
  1353  
  1354  func TestTruncateNonexistentFile(t *testing.T) {
  1355  	t.Parallel()
  1356  
  1357  	assertPathError := func(t testing.TB, path string, err error) {
  1358  		t.Helper()
  1359  		if pe, ok := err.(*PathError); !ok || !IsNotExist(err) || pe.Path != path {
  1360  			t.Errorf("got error: %v\nwant an ErrNotExist PathError with path %q", err, path)
  1361  		}
  1362  	}
  1363  
  1364  	path := filepath.Join(t.TempDir(), "nonexistent")
  1365  
  1366  	err := Truncate(path, 1)
  1367  	assertPathError(t, path, err)
  1368  
  1369  	// Truncate shouldn't create any new file.
  1370  	_, err = Stat(path)
  1371  	assertPathError(t, path, err)
  1372  }
  1373  
  1374  var hasNoatime = sync.OnceValue(func() bool {
  1375  	// A sloppy way to check if noatime flag is set (as all filesystems are
  1376  	// checked, not just the one we're interested in). A correct way
  1377  	// would be to use statvfs syscall and check if flags has ST_NOATIME,
  1378  	// but the syscall is OS-specific and is not even wired into Go stdlib.
  1379  	//
  1380  	// Only used on NetBSD (which ignores explicit atime updates with noatime).
  1381  	if runtime.GOOS != "netbsd" {
  1382  		return false
  1383  	}
  1384  	mounts, _ := ReadFile("/proc/mounts")
  1385  	return bytes.Contains(mounts, []byte("noatime"))
  1386  })
  1387  
  1388  func TestChtimes(t *testing.T) {
  1389  	t.Parallel()
  1390  
  1391  	f := newFile(t)
  1392  	// This should be an empty file (see #68687, #68663).
  1393  	f.Close()
  1394  
  1395  	testChtimes(t, f.Name())
  1396  }
  1397  
  1398  func TestChtimesOmit(t *testing.T) {
  1399  	t.Parallel()
  1400  
  1401  	testChtimesOmit(t, true, false)
  1402  	testChtimesOmit(t, false, true)
  1403  	testChtimesOmit(t, true, true)
  1404  	testChtimesOmit(t, false, false) // Same as TestChtimes.
  1405  }
  1406  
  1407  func testChtimesOmit(t *testing.T, omitAt, omitMt bool) {
  1408  	t.Logf("omit atime: %v, mtime: %v", omitAt, omitMt)
  1409  	file := newFile(t)
  1410  	// This should be an empty file (see #68687, #68663).
  1411  	name := file.Name()
  1412  	err := file.Close()
  1413  	if err != nil {
  1414  		t.Error(err)
  1415  	}
  1416  	fs, err := Stat(name)
  1417  	if err != nil {
  1418  		t.Fatal(err)
  1419  	}
  1420  
  1421  	wantAtime := Atime(fs)
  1422  	wantMtime := fs.ModTime()
  1423  	switch runtime.GOOS {
  1424  	case "js":
  1425  		wantAtime = wantAtime.Truncate(time.Second)
  1426  		wantMtime = wantMtime.Truncate(time.Second)
  1427  	}
  1428  
  1429  	var setAtime, setMtime time.Time // Zero value means omit.
  1430  	if !omitAt {
  1431  		wantAtime = wantAtime.Add(-1 * time.Second)
  1432  		setAtime = wantAtime
  1433  	}
  1434  	if !omitMt {
  1435  		wantMtime = wantMtime.Add(-1 * time.Second)
  1436  		setMtime = wantMtime
  1437  	}
  1438  
  1439  	// Change the times accordingly.
  1440  	if err := Chtimes(name, setAtime, setMtime); err != nil {
  1441  		t.Error(err)
  1442  	}
  1443  
  1444  	// Verify the expectations.
  1445  	fs, err = Stat(name)
  1446  	if err != nil {
  1447  		t.Error(err)
  1448  	}
  1449  	gotAtime := Atime(fs)
  1450  	gotMtime := fs.ModTime()
  1451  
  1452  	// TODO: remove the dragonfly omitAt && omitMt exceptions below once the
  1453  	// fix (https://github.com/DragonFlyBSD/DragonFlyBSD/commit/c7c71870ed0)
  1454  	// is available generally and on CI runners.
  1455  	if !gotAtime.Equal(wantAtime) {
  1456  		errormsg := fmt.Sprintf("atime mismatch, got: %q, want: %q", gotAtime, wantAtime)
  1457  		switch runtime.GOOS {
  1458  		case "plan9":
  1459  			// Mtime is the time of the last change of content.
  1460  			// Similarly, atime is set whenever the contents are
  1461  			// accessed; also, it is set whenever mtime is set.
  1462  		case "dragonfly":
  1463  			if omitAt && omitMt {
  1464  				t.Log(errormsg)
  1465  				t.Log("Known DragonFly BSD issue (won't work when both times are omitted); ignoring.")
  1466  			} else {
  1467  				// Assume hammer2 fs; https://www.dragonflybsd.org/hammer/ says:
  1468  				// > Because HAMMER2 is a block copy-on-write filesystem,
  1469  				// > the "atime" field is not supported and will typically
  1470  				// > just reflect local system in-memory caches or mtime.
  1471  				//
  1472  				// TODO: if only can CI define TMPDIR to point to a tmpfs
  1473  				// (e.g. /var/run/shm), this exception can be removed.
  1474  				t.Log(errormsg)
  1475  				t.Log("Known DragonFly BSD issue (atime not supported on hammer2); ignoring.")
  1476  			}
  1477  		case "netbsd":
  1478  			if !omitAt && hasNoatime() {
  1479  				t.Log(errormsg)
  1480  				t.Log("Known NetBSD issue (atime not changed on fs mounted with noatime); ignoring.")
  1481  			} else {
  1482  				t.Error(errormsg)
  1483  			}
  1484  		default:
  1485  			t.Error(errormsg)
  1486  		}
  1487  	}
  1488  	if !gotMtime.Equal(wantMtime) {
  1489  		errormsg := fmt.Sprintf("mtime mismatch, got: %q, want: %q", gotMtime, wantMtime)
  1490  		switch runtime.GOOS {
  1491  		case "dragonfly":
  1492  			if omitAt && omitMt {
  1493  				t.Log(errormsg)
  1494  				t.Log("Known DragonFly BSD issue (won't work when both times are omitted); ignoring.")
  1495  			} else {
  1496  				t.Error(errormsg)
  1497  			}
  1498  		default:
  1499  			t.Error(errormsg)
  1500  		}
  1501  	}
  1502  }
  1503  
  1504  func TestChtimesDir(t *testing.T) {
  1505  	t.Parallel()
  1506  
  1507  	testChtimes(t, t.TempDir())
  1508  }
  1509  
  1510  func testChtimes(t *testing.T, name string) {
  1511  	st, err := Stat(name)
  1512  	if err != nil {
  1513  		t.Fatalf("Stat %s: %s", name, err)
  1514  	}
  1515  	preStat := st
  1516  
  1517  	// Move access and modification time back a second
  1518  	at := Atime(preStat)
  1519  	mt := preStat.ModTime()
  1520  	err = Chtimes(name, at.Add(-time.Second), mt.Add(-time.Second))
  1521  	if err != nil {
  1522  		t.Fatalf("Chtimes %s: %s", name, err)
  1523  	}
  1524  
  1525  	st, err = Stat(name)
  1526  	if err != nil {
  1527  		t.Fatalf("second Stat %s: %s", name, err)
  1528  	}
  1529  	postStat := st
  1530  
  1531  	pat := Atime(postStat)
  1532  	pmt := postStat.ModTime()
  1533  	if !pat.Before(at) {
  1534  		errormsg := fmt.Sprintf("AccessTime didn't go backwards; was=%v, after=%v", at, pat)
  1535  		switch runtime.GOOS {
  1536  		case "plan9":
  1537  			// Mtime is the time of the last change of
  1538  			// content.  Similarly, atime is set whenever
  1539  			// the contents are accessed; also, it is set
  1540  			// whenever mtime is set.
  1541  		case "netbsd":
  1542  			if hasNoatime() {
  1543  				t.Log(errormsg)
  1544  				t.Log("Known NetBSD issue (atime not changed on fs mounted with noatime); ignoring.")
  1545  			} else {
  1546  				t.Error(errormsg)
  1547  			}
  1548  		default:
  1549  			t.Error(errormsg)
  1550  		}
  1551  	}
  1552  
  1553  	if !pmt.Before(mt) {
  1554  		t.Errorf("ModTime didn't go backwards; was=%v, after=%v", mt, pmt)
  1555  	}
  1556  }
  1557  
  1558  func TestChtimesToUnixZero(t *testing.T) {
  1559  	file := newFile(t)
  1560  	fn := file.Name()
  1561  	if _, err := file.Write([]byte("hi")); err != nil {
  1562  		t.Fatal(err)
  1563  	}
  1564  	if err := file.Close(); err != nil {
  1565  		t.Fatal(err)
  1566  	}
  1567  
  1568  	unixZero := time.Unix(0, 0)
  1569  	if err := Chtimes(fn, unixZero, unixZero); err != nil {
  1570  		t.Fatalf("Chtimes failed: %v", err)
  1571  	}
  1572  
  1573  	st, err := Stat(fn)
  1574  	if err != nil {
  1575  		t.Fatal(err)
  1576  	}
  1577  
  1578  	if mt := st.ModTime(); mt != unixZero {
  1579  		t.Errorf("mtime is %v, want %v", mt, unixZero)
  1580  	}
  1581  }
  1582  
  1583  func TestFileChdir(t *testing.T) {
  1584  	wd, err := Getwd()
  1585  	if err != nil {
  1586  		t.Fatalf("Getwd: %s", err)
  1587  	}
  1588  	t.Chdir(".") // Ensure wd is restored after the test.
  1589  
  1590  	fd, err := Open(".")
  1591  	if err != nil {
  1592  		t.Fatalf("Open .: %s", err)
  1593  	}
  1594  	defer fd.Close()
  1595  
  1596  	if err := Chdir("/"); err != nil {
  1597  		t.Fatalf("Chdir /: %s", err)
  1598  	}
  1599  
  1600  	if err := fd.Chdir(); err != nil {
  1601  		t.Fatalf("fd.Chdir: %s", err)
  1602  	}
  1603  
  1604  	wdNew, err := Getwd()
  1605  	if err != nil {
  1606  		t.Fatalf("Getwd: %s", err)
  1607  	}
  1608  
  1609  	wdInfo, err := fd.Stat()
  1610  	if err != nil {
  1611  		t.Fatal(err)
  1612  	}
  1613  	newInfo, err := Stat(wdNew)
  1614  	if err != nil {
  1615  		t.Fatal(err)
  1616  	}
  1617  	if !SameFile(wdInfo, newInfo) {
  1618  		t.Fatalf("fd.Chdir failed: got %s, want %s", wdNew, wd)
  1619  	}
  1620  }
  1621  
  1622  func TestChdirAndGetwd(t *testing.T) {
  1623  	t.Chdir(t.TempDir()) // Ensure wd is restored after the test.
  1624  
  1625  	// These are chosen carefully not to be symlinks on a Mac
  1626  	// (unlike, say, /var, /etc), except /tmp, which we handle below.
  1627  	dirs := []string{"/", "/usr/bin", "/tmp"}
  1628  	// /usr/bin does not usually exist on Plan 9 or Android.
  1629  	switch runtime.GOOS {
  1630  	case "android":
  1631  		dirs = []string{"/system/bin"}
  1632  	case "plan9":
  1633  		dirs = []string{"/", "/usr"}
  1634  	case "ios", "windows", "wasip1":
  1635  		dirs = nil
  1636  		for _, dir := range []string{t.TempDir(), t.TempDir()} {
  1637  			// Expand symlinks so path equality tests work.
  1638  			dir, err := filepath.EvalSymlinks(dir)
  1639  			if err != nil {
  1640  				t.Fatalf("EvalSymlinks: %v", err)
  1641  			}
  1642  			dirs = append(dirs, dir)
  1643  		}
  1644  	}
  1645  	for mode := 0; mode < 2; mode++ {
  1646  		for _, d := range dirs {
  1647  			var err error
  1648  			if mode == 0 {
  1649  				err = Chdir(d)
  1650  			} else {
  1651  				fd1, err1 := Open(d)
  1652  				if err1 != nil {
  1653  					t.Errorf("Open %s: %s", d, err1)
  1654  					continue
  1655  				}
  1656  				err = fd1.Chdir()
  1657  				fd1.Close()
  1658  			}
  1659  			if d == "/tmp" {
  1660  				Setenv("PWD", "/tmp")
  1661  			}
  1662  			pwd, err1 := Getwd()
  1663  			if err != nil {
  1664  				t.Fatalf("Chdir %s: %s", d, err)
  1665  			}
  1666  			if err1 != nil {
  1667  				t.Fatalf("Getwd in %s: %s", d, err1)
  1668  			}
  1669  			if !equal(pwd, d) {
  1670  				t.Fatalf("Getwd returned %q want %q", pwd, d)
  1671  			}
  1672  		}
  1673  	}
  1674  }
  1675  
  1676  // Test that Chdir+Getwd is program-wide.
  1677  func TestProgWideChdir(t *testing.T) {
  1678  	const N = 10
  1679  	var wg sync.WaitGroup
  1680  	hold := make(chan struct{})
  1681  	done := make(chan struct{})
  1682  
  1683  	d := t.TempDir()
  1684  	t.Chdir(d)
  1685  
  1686  	// Note the deferred Wait must be called after the deferred close(done),
  1687  	// to ensure the N goroutines have been released even if the main goroutine
  1688  	// calls Fatalf. It must be called before the Chdir back to the original
  1689  	// directory, and before the deferred deletion implied by TempDir,
  1690  	// so as not to interfere while the N goroutines are still running.
  1691  	defer wg.Wait()
  1692  	defer close(done)
  1693  
  1694  	for i := 0; i < N; i++ {
  1695  		wg.Add(1)
  1696  		go func(i int) {
  1697  			defer wg.Done()
  1698  			// Lock half the goroutines in their own operating system
  1699  			// thread to exercise more scheduler possibilities.
  1700  			if i%2 == 1 {
  1701  				// On Plan 9, after calling LockOSThread, the goroutines
  1702  				// run on different processes which don't share the working
  1703  				// directory. This used to be an issue because Go expects
  1704  				// the working directory to be program-wide.
  1705  				// See issue 9428.
  1706  				runtime.LockOSThread()
  1707  			}
  1708  			select {
  1709  			case <-done:
  1710  				return
  1711  			case <-hold:
  1712  			}
  1713  			// Getwd might be wrong
  1714  			f0, err := Stat(".")
  1715  			if err != nil {
  1716  				t.Error(err)
  1717  				return
  1718  			}
  1719  			pwd, err := Getwd()
  1720  			if err != nil {
  1721  				t.Errorf("Getwd: %v", err)
  1722  				return
  1723  			}
  1724  			if pwd != d {
  1725  				t.Errorf("Getwd() = %q, want %q", pwd, d)
  1726  				return
  1727  			}
  1728  			f1, err := Stat(pwd)
  1729  			if err != nil {
  1730  				t.Error(err)
  1731  				return
  1732  			}
  1733  			if !SameFile(f0, f1) {
  1734  				t.Errorf(`Samefile(Stat("."), Getwd()) reports false (%s != %s)`, f0.Name(), f1.Name())
  1735  				return
  1736  			}
  1737  		}(i)
  1738  	}
  1739  	var err error
  1740  	if err = Chdir(d); err != nil {
  1741  		t.Fatalf("Chdir: %v", err)
  1742  	}
  1743  	// OS X sets TMPDIR to a symbolic link.
  1744  	// So we resolve our working directory again before the test.
  1745  	d, err = Getwd()
  1746  	if err != nil {
  1747  		t.Fatalf("Getwd: %v", err)
  1748  	}
  1749  	close(hold)
  1750  	wg.Wait()
  1751  }
  1752  
  1753  func TestSeek(t *testing.T) {
  1754  	t.Parallel()
  1755  
  1756  	f := newFile(t)
  1757  
  1758  	const data = "hello, world\n"
  1759  	io.WriteString(f, data)
  1760  
  1761  	type test struct {
  1762  		in     int64
  1763  		whence int
  1764  		out    int64
  1765  	}
  1766  	var tests = []test{
  1767  		{0, io.SeekCurrent, int64(len(data))},
  1768  		{0, io.SeekStart, 0},
  1769  		{5, io.SeekStart, 5},
  1770  		{0, io.SeekEnd, int64(len(data))},
  1771  		{0, io.SeekStart, 0},
  1772  		{-1, io.SeekEnd, int64(len(data)) - 1},
  1773  		{1 << 33, io.SeekStart, 1 << 33},
  1774  		{1 << 33, io.SeekEnd, 1<<33 + int64(len(data))},
  1775  
  1776  		// Issue 21681, Windows 4G-1, etc:
  1777  		{1<<32 - 1, io.SeekStart, 1<<32 - 1},
  1778  		{0, io.SeekCurrent, 1<<32 - 1},
  1779  		{2<<32 - 1, io.SeekStart, 2<<32 - 1},
  1780  		{0, io.SeekCurrent, 2<<32 - 1},
  1781  	}
  1782  	for i, tt := range tests {
  1783  		off, err := f.Seek(tt.in, tt.whence)
  1784  		if off != tt.out || err != nil {
  1785  			t.Errorf("#%d: Seek(%v, %v) = %v, %v want %v, nil", i, tt.in, tt.whence, off, err, tt.out)
  1786  		}
  1787  	}
  1788  }
  1789  
  1790  func TestSeekError(t *testing.T) {
  1791  	switch runtime.GOOS {
  1792  	case "js", "plan9", "wasip1":
  1793  		t.Skipf("skipping test on %v", runtime.GOOS)
  1794  	}
  1795  	t.Parallel()
  1796  
  1797  	r, w, err := Pipe()
  1798  	if err != nil {
  1799  		t.Fatal(err)
  1800  	}
  1801  	_, err = r.Seek(0, 0)
  1802  	if err == nil {
  1803  		t.Fatal("Seek on pipe should fail")
  1804  	}
  1805  	if perr, ok := err.(*PathError); !ok || perr.Err != syscall.ESPIPE {
  1806  		t.Errorf("Seek returned error %v, want &PathError{Err: syscall.ESPIPE}", err)
  1807  	}
  1808  	_, err = w.Seek(0, 0)
  1809  	if err == nil {
  1810  		t.Fatal("Seek on pipe should fail")
  1811  	}
  1812  	if perr, ok := err.(*PathError); !ok || perr.Err != syscall.ESPIPE {
  1813  		t.Errorf("Seek returned error %v, want &PathError{Err: syscall.ESPIPE}", err)
  1814  	}
  1815  }
  1816  
  1817  func TestOpenError(t *testing.T) {
  1818  	t.Parallel()
  1819  	dir := makefs(t, []string{
  1820  		"is-a-file",
  1821  		"is-a-dir/",
  1822  	})
  1823  	t.Run("NoRoot", func(t *testing.T) { testOpenError(t, dir, false) })
  1824  	t.Run("InRoot", func(t *testing.T) { testOpenError(t, dir, true) })
  1825  }
  1826  func testOpenError(t *testing.T, dir string, rooted bool) {
  1827  	t.Parallel()
  1828  	var r *Root
  1829  	if rooted {
  1830  		var err error
  1831  		r, err = OpenRoot(dir)
  1832  		if err != nil {
  1833  			t.Fatal(err)
  1834  		}
  1835  		defer r.Close()
  1836  	}
  1837  	for _, tt := range []struct {
  1838  		path  string
  1839  		mode  int
  1840  		error error
  1841  	}{{
  1842  		"no-such-file",
  1843  		O_RDONLY,
  1844  		syscall.ENOENT,
  1845  	}, {
  1846  		"is-a-dir",
  1847  		O_WRONLY,
  1848  		syscall.EISDIR,
  1849  	}, {
  1850  		"is-a-file/no-such-file",
  1851  		O_WRONLY,
  1852  		syscall.ENOTDIR,
  1853  	}} {
  1854  		var f *File
  1855  		var err error
  1856  		var name string
  1857  		if rooted {
  1858  			name = fmt.Sprintf("Root(%q).OpenFile(%q, %d)", dir, tt.path, tt.mode)
  1859  			f, err = r.OpenFile(tt.path, tt.mode, 0)
  1860  		} else {
  1861  			path := filepath.Join(dir, tt.path)
  1862  			name = fmt.Sprintf("OpenFile(%q, %d)", path, tt.mode)
  1863  			f, err = OpenFile(path, tt.mode, 0)
  1864  		}
  1865  		if err == nil {
  1866  			t.Errorf("%v succeeded", name)
  1867  			f.Close()
  1868  			continue
  1869  		}
  1870  		perr, ok := err.(*PathError)
  1871  		if !ok {
  1872  			t.Errorf("%v returns error of %T type; want *PathError", name, err)
  1873  		}
  1874  		if perr.Err != tt.error {
  1875  			if runtime.GOOS == "plan9" {
  1876  				syscallErrStr := perr.Err.Error()
  1877  				expectedErrStr := strings.Replace(tt.error.Error(), "file ", "", 1)
  1878  				if !strings.HasSuffix(syscallErrStr, expectedErrStr) {
  1879  					// Some Plan 9 file servers incorrectly return
  1880  					// EPERM or EACCES rather than EISDIR when a directory is
  1881  					// opened for write.
  1882  					if tt.error == syscall.EISDIR &&
  1883  						(strings.HasSuffix(syscallErrStr, syscall.EPERM.Error()) ||
  1884  							strings.HasSuffix(syscallErrStr, syscall.EACCES.Error())) {
  1885  						continue
  1886  					}
  1887  					t.Errorf("%v = _, %q; want suffix %q", name, syscallErrStr, expectedErrStr)
  1888  				}
  1889  				continue
  1890  			}
  1891  			if runtime.GOOS == "dragonfly" {
  1892  				// DragonFly incorrectly returns EACCES rather
  1893  				// EISDIR when a directory is opened for write.
  1894  				if tt.error == syscall.EISDIR && perr.Err == syscall.EACCES {
  1895  					continue
  1896  				}
  1897  			}
  1898  			t.Errorf("%v = _, %q; want %q", name, perr.Err.Error(), tt.error.Error())
  1899  		}
  1900  	}
  1901  }
  1902  
  1903  func TestOpenNoName(t *testing.T) {
  1904  	f, err := Open("")
  1905  	if err == nil {
  1906  		f.Close()
  1907  		t.Fatal(`Open("") succeeded`)
  1908  	}
  1909  }
  1910  
  1911  func runBinHostname(t *testing.T) string {
  1912  	// Run /bin/hostname and collect output.
  1913  	r, w, err := Pipe()
  1914  	if err != nil {
  1915  		t.Fatal(err)
  1916  	}
  1917  	defer r.Close()
  1918  
  1919  	path, err := exec.LookPath("hostname")
  1920  	if err != nil {
  1921  		if errors.Is(err, exec.ErrNotFound) {
  1922  			t.Skip("skipping test; test requires hostname but it does not exist")
  1923  		}
  1924  		t.Fatal(err)
  1925  	}
  1926  
  1927  	argv := []string{"hostname"}
  1928  	if runtime.GOOS == "aix" {
  1929  		argv = []string{"hostname", "-s"}
  1930  	}
  1931  	p, err := StartProcess(path, argv, &ProcAttr{Files: []*File{nil, w, Stderr}})
  1932  	if err != nil {
  1933  		t.Fatal(err)
  1934  	}
  1935  	w.Close()
  1936  
  1937  	var b strings.Builder
  1938  	io.Copy(&b, r)
  1939  	_, err = p.Wait()
  1940  	if err != nil {
  1941  		t.Fatalf("run hostname Wait: %v", err)
  1942  	}
  1943  	err = p.Kill()
  1944  	if err == nil {
  1945  		t.Errorf("expected an error from Kill running 'hostname'")
  1946  	}
  1947  	output := b.String()
  1948  	if n := len(output); n > 0 && output[n-1] == '\n' {
  1949  		output = output[0 : n-1]
  1950  	}
  1951  	if output == "" {
  1952  		t.Fatalf("/bin/hostname produced no output")
  1953  	}
  1954  
  1955  	return output
  1956  }
  1957  
  1958  func testWindowsHostname(t *testing.T, hostname string) {
  1959  	cmd := testenv.Command(t, "hostname")
  1960  	out, err := cmd.Output()
  1961  	if err != nil {
  1962  		t.Fatalf("Failed to execute hostname command: %v %s", err, out)
  1963  	}
  1964  	want := strings.Trim(string(out), "\r\n")
  1965  	if hostname != want {
  1966  		t.Fatalf("Hostname() = %q != system hostname of %q", hostname, want)
  1967  	}
  1968  }
  1969  
  1970  func TestHostname(t *testing.T) {
  1971  	t.Parallel()
  1972  
  1973  	hostname, err := Hostname()
  1974  	if err != nil {
  1975  		t.Fatal(err)
  1976  	}
  1977  	if hostname == "" {
  1978  		t.Fatal("Hostname returned empty string and no error")
  1979  	}
  1980  	if strings.Contains(hostname, "\x00") {
  1981  		t.Fatalf("unexpected zero byte in hostname: %q", hostname)
  1982  	}
  1983  
  1984  	// There is no other way to fetch hostname on windows, but via winapi.
  1985  	// On Plan 9 it can be taken from #c/sysname as Hostname() does.
  1986  	switch runtime.GOOS {
  1987  	case "android", "plan9":
  1988  		// No /bin/hostname to verify against.
  1989  		return
  1990  	case "windows":
  1991  		testWindowsHostname(t, hostname)
  1992  		return
  1993  	}
  1994  
  1995  	testenv.MustHaveExec(t)
  1996  
  1997  	// Check internal Hostname() against the output of /bin/hostname.
  1998  	// Allow that the internal Hostname returns a Fully Qualified Domain Name
  1999  	// and the /bin/hostname only returns the first component
  2000  	want := runBinHostname(t)
  2001  	if hostname != want {
  2002  		host, _, ok := strings.Cut(hostname, ".")
  2003  		if !ok || host != want {
  2004  			t.Errorf("Hostname() = %q, want %q", hostname, want)
  2005  		}
  2006  	}
  2007  }
  2008  
  2009  func TestReadAt(t *testing.T) {
  2010  	t.Parallel()
  2011  
  2012  	f := newFile(t)
  2013  
  2014  	const data = "hello, world\n"
  2015  	io.WriteString(f, data)
  2016  
  2017  	b := make([]byte, 5)
  2018  	n, err := f.ReadAt(b, 7)
  2019  	if err != nil || n != len(b) {
  2020  		t.Fatalf("ReadAt 7: %d, %v", n, err)
  2021  	}
  2022  	if string(b) != "world" {
  2023  		t.Fatalf("ReadAt 7: have %q want %q", string(b), "world")
  2024  	}
  2025  }
  2026  
  2027  // Verify that ReadAt doesn't affect seek offset.
  2028  // In the Plan 9 kernel, there used to be a bug in the implementation of
  2029  // the pread syscall, where the channel offset was erroneously updated after
  2030  // calling pread on a file.
  2031  func TestReadAtOffset(t *testing.T) {
  2032  	t.Parallel()
  2033  
  2034  	f := newFile(t)
  2035  
  2036  	const data = "hello, world\n"
  2037  	io.WriteString(f, data)
  2038  
  2039  	f.Seek(0, 0)
  2040  	b := make([]byte, 5)
  2041  
  2042  	n, err := f.ReadAt(b, 7)
  2043  	if err != nil || n != len(b) {
  2044  		t.Fatalf("ReadAt 7: %d, %v", n, err)
  2045  	}
  2046  	if string(b) != "world" {
  2047  		t.Fatalf("ReadAt 7: have %q want %q", string(b), "world")
  2048  	}
  2049  
  2050  	n, err = f.Read(b)
  2051  	if err != nil || n != len(b) {
  2052  		t.Fatalf("Read: %d, %v", n, err)
  2053  	}
  2054  	if string(b) != "hello" {
  2055  		t.Fatalf("Read: have %q want %q", string(b), "hello")
  2056  	}
  2057  }
  2058  
  2059  // Verify that ReadAt doesn't allow negative offset.
  2060  func TestReadAtNegativeOffset(t *testing.T) {
  2061  	t.Parallel()
  2062  
  2063  	f := newFile(t)
  2064  
  2065  	const data = "hello, world\n"
  2066  	io.WriteString(f, data)
  2067  
  2068  	f.Seek(0, 0)
  2069  	b := make([]byte, 5)
  2070  
  2071  	n, err := f.ReadAt(b, -10)
  2072  
  2073  	const wantsub = "negative offset"
  2074  	if !strings.Contains(fmt.Sprint(err), wantsub) || n != 0 {
  2075  		t.Errorf("ReadAt(-10) = %v, %v; want 0, ...%q...", n, err, wantsub)
  2076  	}
  2077  }
  2078  
  2079  func TestWriteAt(t *testing.T) {
  2080  	t.Parallel()
  2081  
  2082  	f := newFile(t)
  2083  
  2084  	const data = "hello, world"
  2085  	io.WriteString(f, data)
  2086  
  2087  	n, err := f.WriteAt([]byte("WOR"), 7)
  2088  	if err != nil || n != 3 {
  2089  		t.Fatalf("WriteAt 7: %d, %v", n, err)
  2090  	}
  2091  	n, err = io.WriteString(f, "!") // test that WriteAt doesn't change the file offset
  2092  	if err != nil || n != 1 {
  2093  		t.Fatal(err)
  2094  	}
  2095  
  2096  	got, err := ReadFile(f.Name())
  2097  	if err != nil {
  2098  		t.Fatalf("ReadFile %s: %v", f.Name(), err)
  2099  	}
  2100  	want := "hello, WORld!"
  2101  	if string(got) != want {
  2102  		t.Fatalf("after write: have %q want %q", string(got), want)
  2103  	}
  2104  }
  2105  
  2106  func TestWriteAtConcurrent(t *testing.T) {
  2107  	t.Parallel()
  2108  
  2109  	f := newFile(t)
  2110  	io.WriteString(f, "0000000000")
  2111  
  2112  	var wg sync.WaitGroup
  2113  	for i := range 10 {
  2114  		wg.Add(1)
  2115  		go func() {
  2116  			defer wg.Done()
  2117  			n, err := f.WriteAt([]byte(strconv.Itoa(i)), int64(i))
  2118  			if err != nil || n != 1 {
  2119  				t.Errorf("WriteAt %d: %d, %v", i, n, err)
  2120  			}
  2121  			n, err = io.WriteString(f, "!") // test that WriteAt doesn't change the file offset
  2122  			if err != nil || n != 1 {
  2123  				t.Error(err)
  2124  			}
  2125  		}()
  2126  	}
  2127  	wg.Wait()
  2128  
  2129  	got, err := ReadFile(f.Name())
  2130  	if err != nil {
  2131  		t.Fatalf("ReadFile %s: %v", f.Name(), err)
  2132  	}
  2133  	want := "0123456789!!!!!!!!!!"
  2134  	if string(got) != want {
  2135  		t.Fatalf("after write: have %q want %q", string(got), want)
  2136  	}
  2137  }
  2138  
  2139  // Verify that WriteAt doesn't allow negative offset.
  2140  func TestWriteAtNegativeOffset(t *testing.T) {
  2141  	t.Parallel()
  2142  
  2143  	f := newFile(t)
  2144  
  2145  	n, err := f.WriteAt([]byte("WORLD"), -10)
  2146  
  2147  	const wantsub = "negative offset"
  2148  	if !strings.Contains(fmt.Sprint(err), wantsub) || n != 0 {
  2149  		t.Errorf("WriteAt(-10) = %v, %v; want 0, ...%q...", n, err, wantsub)
  2150  	}
  2151  }
  2152  
  2153  // Verify that WriteAt doesn't work in append mode.
  2154  func TestWriteAtInAppendMode(t *testing.T) {
  2155  	t.Chdir(t.TempDir())
  2156  	f, err := OpenFile("write_at_in_append_mode.txt", O_APPEND|O_CREATE, 0666)
  2157  	if err != nil {
  2158  		t.Fatalf("OpenFile: %v", err)
  2159  	}
  2160  	defer f.Close()
  2161  
  2162  	_, err = f.WriteAt([]byte(""), 1)
  2163  	if err != ErrWriteAtInAppendMode {
  2164  		t.Fatalf("f.WriteAt returned %v, expected %v", err, ErrWriteAtInAppendMode)
  2165  	}
  2166  }
  2167  
  2168  func writeFile(t *testing.T, r *Root, fname string, flag int, text string) string {
  2169  	t.Helper()
  2170  	var f *File
  2171  	var err error
  2172  	if r == nil {
  2173  		f, err = OpenFile(fname, flag, 0666)
  2174  	} else {
  2175  		f, err = r.OpenFile(fname, flag, 0666)
  2176  	}
  2177  	if err != nil {
  2178  		t.Fatalf("Open: %v", err)
  2179  	}
  2180  	n, err := io.WriteString(f, text)
  2181  	if err != nil {
  2182  		t.Fatalf("WriteString: %d, %v", n, err)
  2183  	}
  2184  	f.Close()
  2185  	data, err := ReadFile(fname)
  2186  	if err != nil {
  2187  		t.Fatalf("ReadFile: %v", err)
  2188  	}
  2189  	return string(data)
  2190  }
  2191  
  2192  func TestAppend(t *testing.T) {
  2193  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  2194  		const f = "append.txt"
  2195  		s := writeFile(t, r, f, O_CREATE|O_TRUNC|O_RDWR, "new")
  2196  		if s != "new" {
  2197  			t.Fatalf("writeFile: have %q want %q", s, "new")
  2198  		}
  2199  		s = writeFile(t, r, f, O_APPEND|O_RDWR, "|append")
  2200  		if s != "new|append" {
  2201  			t.Fatalf("writeFile: have %q want %q", s, "new|append")
  2202  		}
  2203  		s = writeFile(t, r, f, O_CREATE|O_APPEND|O_RDWR, "|append")
  2204  		if s != "new|append|append" {
  2205  			t.Fatalf("writeFile: have %q want %q", s, "new|append|append")
  2206  		}
  2207  		err := Remove(f)
  2208  		if err != nil {
  2209  			t.Fatalf("Remove: %v", err)
  2210  		}
  2211  		s = writeFile(t, r, f, O_CREATE|O_APPEND|O_RDWR, "new&append")
  2212  		if s != "new&append" {
  2213  			t.Fatalf("writeFile: after append have %q want %q", s, "new&append")
  2214  		}
  2215  		s = writeFile(t, r, f, O_CREATE|O_RDWR, "old")
  2216  		if s != "old&append" {
  2217  			t.Fatalf("writeFile: after create have %q want %q", s, "old&append")
  2218  		}
  2219  		s = writeFile(t, r, f, O_CREATE|O_TRUNC|O_RDWR, "new")
  2220  		if s != "new" {
  2221  			t.Fatalf("writeFile: after truncate have %q want %q", s, "new")
  2222  		}
  2223  	})
  2224  }
  2225  
  2226  // TestFilePermissions tests setting Unix permission bits on file creation.
  2227  func TestFilePermissions(t *testing.T) {
  2228  	if Getuid() == 0 {
  2229  		t.Skip("skipping test when running as root")
  2230  	}
  2231  	for _, test := range []struct {
  2232  		name string
  2233  		mode FileMode
  2234  	}{
  2235  		{"r", 0o444},
  2236  		{"w", 0o222},
  2237  		{"rw", 0o666},
  2238  	} {
  2239  		t.Run(test.name, func(t *testing.T) {
  2240  			switch runtime.GOOS {
  2241  			case "windows":
  2242  				if test.mode&0444 == 0 {
  2243  					t.Skip("write-only files not supported on " + runtime.GOOS)
  2244  				}
  2245  			case "wasip1":
  2246  				t.Skip("file permissions not supported on " + runtime.GOOS)
  2247  			}
  2248  			testMaybeRooted(t, func(t *testing.T, r *Root) {
  2249  				const filename = "f"
  2250  				var f *File
  2251  				var err error
  2252  				if r == nil {
  2253  					f, err = OpenFile(filename, O_RDWR|O_CREATE|O_EXCL, test.mode)
  2254  				} else {
  2255  					f, err = r.OpenFile(filename, O_RDWR|O_CREATE|O_EXCL, test.mode)
  2256  				}
  2257  				if err != nil {
  2258  					t.Fatal(err)
  2259  				}
  2260  				f.Close()
  2261  				b, err := ReadFile(filename)
  2262  				if test.mode&0o444 != 0 {
  2263  					if err != nil {
  2264  						t.Errorf("ReadFile = %v; want success", err)
  2265  					}
  2266  				} else {
  2267  					if err == nil {
  2268  						t.Errorf("ReadFile = %q, <nil>; want failure", string(b))
  2269  					}
  2270  				}
  2271  				_, err = Stat(filename)
  2272  				if err != nil {
  2273  					t.Errorf("Stat = %v; want success", err)
  2274  				}
  2275  				err = WriteFile(filename, nil, 0666)
  2276  				if test.mode&0o222 != 0 {
  2277  					if err != nil {
  2278  						t.Errorf("WriteFile = %v; want success", err)
  2279  						b, err := ReadFile(filename)
  2280  						t.Errorf("ReadFile: %v", err)
  2281  						t.Errorf("file contents: %q", b)
  2282  					}
  2283  				} else {
  2284  					if err == nil {
  2285  						t.Errorf("WriteFile(%q) = <nil>; want failure", filename)
  2286  						st, err := Stat(filename)
  2287  						if err == nil {
  2288  							t.Errorf("mode: %s", st.Mode())
  2289  						}
  2290  						b, err := ReadFile(filename)
  2291  						t.Errorf("ReadFile: %v", err)
  2292  						t.Errorf("file contents: %q", b)
  2293  					}
  2294  				}
  2295  			})
  2296  		})
  2297  	}
  2298  
  2299  }
  2300  
  2301  func TestOpenFileCreateExclDanglingSymlink(t *testing.T) {
  2302  	testenv.MustHaveSymlink(t)
  2303  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  2304  		const link = "link"
  2305  		if err := Symlink("does_not_exist", link); err != nil {
  2306  			t.Fatal(err)
  2307  		}
  2308  		var f *File
  2309  		var err error
  2310  		if r == nil {
  2311  			f, err = OpenFile(link, O_WRONLY|O_CREATE|O_EXCL, 0o444)
  2312  		} else {
  2313  			f, err = r.OpenFile(link, O_WRONLY|O_CREATE|O_EXCL, 0o444)
  2314  		}
  2315  		if err == nil {
  2316  			f.Close()
  2317  		}
  2318  		if !errors.Is(err, ErrExist) {
  2319  			t.Errorf("OpenFile of a dangling symlink with O_CREATE|O_EXCL = %v, want ErrExist", err)
  2320  		}
  2321  		if _, err := Stat(link); err == nil {
  2322  			t.Errorf("OpenFile of a dangling symlink with O_CREATE|O_EXCL created a file")
  2323  		}
  2324  	})
  2325  }
  2326  
  2327  // TestFileRDWRFlags tests the O_RDONLY, O_WRONLY, and O_RDWR flags.
  2328  func TestFileRDWRFlags(t *testing.T) {
  2329  	for _, test := range []struct {
  2330  		name string
  2331  		flag int
  2332  	}{
  2333  		{"O_RDONLY", O_RDONLY},
  2334  		{"O_WRONLY", O_WRONLY},
  2335  		{"O_RDWR", O_RDWR},
  2336  	} {
  2337  		t.Run(test.name, func(t *testing.T) {
  2338  			testMaybeRooted(t, func(t *testing.T, r *Root) {
  2339  				const filename = "f"
  2340  				content := []byte("content")
  2341  				if err := WriteFile(filename, content, 0666); err != nil {
  2342  					t.Fatal(err)
  2343  				}
  2344  				var f *File
  2345  				var err error
  2346  				if r == nil {
  2347  					f, err = OpenFile(filename, test.flag, 0)
  2348  				} else {
  2349  					f, err = r.OpenFile(filename, test.flag, 0)
  2350  				}
  2351  				if err != nil {
  2352  					t.Fatal(err)
  2353  				}
  2354  				defer f.Close()
  2355  				got, err := io.ReadAll(f)
  2356  				if test.flag == O_WRONLY {
  2357  					if err == nil {
  2358  						t.Errorf("read file: %q, %v; want error", got, err)
  2359  					}
  2360  				} else {
  2361  					if err != nil || !bytes.Equal(got, content) {
  2362  						t.Errorf("read file: %q, %v; want %q, <nil>", got, err, content)
  2363  					}
  2364  				}
  2365  				if _, err := f.Seek(0, 0); err != nil {
  2366  					t.Fatalf("f.Seek: %v", err)
  2367  				}
  2368  				newcontent := []byte("CONTENT")
  2369  				_, err = f.Write(newcontent)
  2370  				if test.flag == O_RDONLY {
  2371  					if err == nil {
  2372  						t.Errorf("write file: succeeded, want error")
  2373  					}
  2374  				} else {
  2375  					if err != nil {
  2376  						t.Errorf("write file: %v, want success", err)
  2377  					}
  2378  				}
  2379  				f.Close()
  2380  				got, err = ReadFile(filename)
  2381  				if err != nil {
  2382  					t.Fatal(err)
  2383  				}
  2384  				want := content
  2385  				if test.flag != O_RDONLY {
  2386  					want = newcontent
  2387  				}
  2388  				if !bytes.Equal(got, want) {
  2389  					t.Fatalf("after write, file contains %q, want %q", got, want)
  2390  				}
  2391  			})
  2392  		})
  2393  	}
  2394  }
  2395  
  2396  func TestStatDirWithTrailingSlash(t *testing.T) {
  2397  	t.Parallel()
  2398  
  2399  	// Create new temporary directory and arrange to clean it up.
  2400  	path := t.TempDir()
  2401  
  2402  	// Stat of path should succeed.
  2403  	if _, err := Stat(path); err != nil {
  2404  		t.Fatalf("stat %s failed: %s", path, err)
  2405  	}
  2406  
  2407  	// Stat of path+"/" should succeed too.
  2408  	path += "/"
  2409  	if _, err := Stat(path); err != nil {
  2410  		t.Fatalf("stat %s failed: %s", path, err)
  2411  	}
  2412  }
  2413  
  2414  func TestNilProcessStateString(t *testing.T) {
  2415  	var ps *ProcessState
  2416  	s := ps.String()
  2417  	if s != "<nil>" {
  2418  		t.Errorf("(*ProcessState)(nil).String() = %q, want %q", s, "<nil>")
  2419  	}
  2420  }
  2421  
  2422  func TestSameFile(t *testing.T) {
  2423  	t.Chdir(t.TempDir())
  2424  	fa, err := Create("a")
  2425  	if err != nil {
  2426  		t.Fatalf("Create(a): %v", err)
  2427  	}
  2428  	fa.Close()
  2429  	fb, err := Create("b")
  2430  	if err != nil {
  2431  		t.Fatalf("Create(b): %v", err)
  2432  	}
  2433  	fb.Close()
  2434  
  2435  	ia1, err := Stat("a")
  2436  	if err != nil {
  2437  		t.Fatalf("Stat(a): %v", err)
  2438  	}
  2439  	ia2, err := Stat("a")
  2440  	if err != nil {
  2441  		t.Fatalf("Stat(a): %v", err)
  2442  	}
  2443  	if !SameFile(ia1, ia2) {
  2444  		t.Errorf("files should be same")
  2445  	}
  2446  
  2447  	ib, err := Stat("b")
  2448  	if err != nil {
  2449  		t.Fatalf("Stat(b): %v", err)
  2450  	}
  2451  	if SameFile(ia1, ib) {
  2452  		t.Errorf("files should be different")
  2453  	}
  2454  }
  2455  
  2456  func testDevNullFileInfo(t *testing.T, statname, devNullName string, fi FileInfo) {
  2457  	pre := fmt.Sprintf("%s(%q): ", statname, devNullName)
  2458  	if fi.Size() != 0 {
  2459  		t.Errorf(pre+"wrong file size have %d want 0", fi.Size())
  2460  	}
  2461  	if fi.Mode()&ModeDevice == 0 {
  2462  		t.Errorf(pre+"wrong file mode %q: ModeDevice is not set", fi.Mode())
  2463  	}
  2464  	if fi.Mode()&ModeCharDevice == 0 {
  2465  		t.Errorf(pre+"wrong file mode %q: ModeCharDevice is not set", fi.Mode())
  2466  	}
  2467  	if fi.Mode().IsRegular() {
  2468  		t.Errorf(pre+"wrong file mode %q: IsRegular returns true", fi.Mode())
  2469  	}
  2470  }
  2471  
  2472  func testDevNullFile(t *testing.T, devNullName string) {
  2473  	f, err := Open(devNullName)
  2474  	if err != nil {
  2475  		t.Fatalf("Open(%s): %v", devNullName, err)
  2476  	}
  2477  	defer f.Close()
  2478  
  2479  	fi, err := f.Stat()
  2480  	if err != nil {
  2481  		t.Fatalf("Stat(%s): %v", devNullName, err)
  2482  	}
  2483  	testDevNullFileInfo(t, "f.Stat", devNullName, fi)
  2484  
  2485  	fi, err = Stat(devNullName)
  2486  	if err != nil {
  2487  		t.Fatalf("Stat(%s): %v", devNullName, err)
  2488  	}
  2489  	testDevNullFileInfo(t, "Stat", devNullName, fi)
  2490  }
  2491  
  2492  func TestDevNullFile(t *testing.T) {
  2493  	t.Parallel()
  2494  
  2495  	testDevNullFile(t, DevNull)
  2496  	if runtime.GOOS == "windows" {
  2497  		testDevNullFile(t, "./nul")
  2498  		testDevNullFile(t, "//./nul")
  2499  	}
  2500  }
  2501  
  2502  var testLargeWrite = flag.Bool("large_write", false, "run TestLargeWriteToConsole test that floods console with output")
  2503  
  2504  func TestLargeWriteToConsole(t *testing.T) {
  2505  	if !*testLargeWrite {
  2506  		t.Skip("skipping console-flooding test; enable with -large_write")
  2507  	}
  2508  	b := make([]byte, 32000)
  2509  	for i := range b {
  2510  		b[i] = '.'
  2511  	}
  2512  	b[len(b)-1] = '\n'
  2513  	n, err := Stdout.Write(b)
  2514  	if err != nil {
  2515  		t.Fatalf("Write to os.Stdout failed: %v", err)
  2516  	}
  2517  	if n != len(b) {
  2518  		t.Errorf("Write to os.Stdout should return %d; got %d", len(b), n)
  2519  	}
  2520  	n, err = Stderr.Write(b)
  2521  	if err != nil {
  2522  		t.Fatalf("Write to os.Stderr failed: %v", err)
  2523  	}
  2524  	if n != len(b) {
  2525  		t.Errorf("Write to os.Stderr should return %d; got %d", len(b), n)
  2526  	}
  2527  }
  2528  
  2529  func TestStatDirModeExec(t *testing.T) {
  2530  	if runtime.GOOS == "wasip1" {
  2531  		t.Skip("Chmod is not supported on " + runtime.GOOS)
  2532  	}
  2533  	t.Parallel()
  2534  
  2535  	const mode = 0111
  2536  
  2537  	path := t.TempDir()
  2538  	if err := Chmod(path, 0777); err != nil {
  2539  		t.Fatalf("Chmod %q 0777: %v", path, err)
  2540  	}
  2541  
  2542  	dir, err := Stat(path)
  2543  	if err != nil {
  2544  		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
  2545  	}
  2546  	if dir.Mode()&mode != mode {
  2547  		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode()&mode, mode)
  2548  	}
  2549  }
  2550  
  2551  func TestStatStdin(t *testing.T) {
  2552  	switch runtime.GOOS {
  2553  	case "android", "plan9":
  2554  		t.Skipf("%s doesn't have /bin/sh", runtime.GOOS)
  2555  	}
  2556  
  2557  	if Getenv("GO_WANT_HELPER_PROCESS") == "1" {
  2558  		st, err := Stdin.Stat()
  2559  		if err != nil {
  2560  			t.Fatalf("Stat failed: %v", err)
  2561  		}
  2562  		fmt.Println(st.Mode() & ModeNamedPipe)
  2563  		Exit(0)
  2564  	}
  2565  
  2566  	t.Parallel()
  2567  	exe := testenv.Executable(t)
  2568  
  2569  	fi, err := Stdin.Stat()
  2570  	if err != nil {
  2571  		t.Fatal(err)
  2572  	}
  2573  	switch mode := fi.Mode(); {
  2574  	case mode&ModeCharDevice != 0 && mode&ModeDevice != 0:
  2575  	case mode&ModeNamedPipe != 0:
  2576  	default:
  2577  		t.Fatalf("unexpected Stdin mode (%v), want ModeCharDevice or ModeNamedPipe", mode)
  2578  	}
  2579  
  2580  	cmd := testenv.Command(t, exe, "-test.run=^TestStatStdin$")
  2581  	cmd = testenv.CleanCmdEnv(cmd)
  2582  	cmd.Env = append(cmd.Env, "GO_WANT_HELPER_PROCESS=1")
  2583  	// This will make standard input a pipe.
  2584  	cmd.Stdin = strings.NewReader("output")
  2585  
  2586  	output, err := cmd.CombinedOutput()
  2587  	if err != nil {
  2588  		t.Fatalf("Failed to spawn child process: %v %q", err, string(output))
  2589  	}
  2590  
  2591  	// result will be like "prw-rw-rw"
  2592  	if len(output) < 1 || output[0] != 'p' {
  2593  		t.Fatalf("Child process reports stdin is not pipe '%v'", string(output))
  2594  	}
  2595  }
  2596  
  2597  func TestStatRelativeSymlink(t *testing.T) {
  2598  	testenv.MustHaveSymlink(t)
  2599  	t.Parallel()
  2600  
  2601  	tmpdir := t.TempDir()
  2602  	target := filepath.Join(tmpdir, "target")
  2603  	f, err := Create(target)
  2604  	if err != nil {
  2605  		t.Fatal(err)
  2606  	}
  2607  	defer f.Close()
  2608  
  2609  	st, err := f.Stat()
  2610  	if err != nil {
  2611  		t.Fatal(err)
  2612  	}
  2613  
  2614  	link := filepath.Join(tmpdir, "link")
  2615  	err = Symlink(filepath.Base(target), link)
  2616  	if err != nil {
  2617  		t.Fatal(err)
  2618  	}
  2619  
  2620  	st1, err := Stat(link)
  2621  	if err != nil {
  2622  		t.Fatal(err)
  2623  	}
  2624  
  2625  	if !SameFile(st, st1) {
  2626  		t.Error("Stat doesn't follow relative symlink")
  2627  	}
  2628  
  2629  	if runtime.GOOS == "windows" {
  2630  		Remove(link)
  2631  		err = Symlink(target[len(filepath.VolumeName(target)):], link)
  2632  		if err != nil {
  2633  			t.Fatal(err)
  2634  		}
  2635  
  2636  		st1, err := Stat(link)
  2637  		if err != nil {
  2638  			t.Fatal(err)
  2639  		}
  2640  
  2641  		if !SameFile(st, st1) {
  2642  			t.Error("Stat doesn't follow relative symlink")
  2643  		}
  2644  	}
  2645  }
  2646  
  2647  func TestReadAtEOF(t *testing.T) {
  2648  	t.Parallel()
  2649  
  2650  	f := newFile(t)
  2651  
  2652  	_, err := f.ReadAt(make([]byte, 10), 0)
  2653  	switch err {
  2654  	case io.EOF:
  2655  		// all good
  2656  	case nil:
  2657  		t.Fatalf("ReadAt succeeded")
  2658  	default:
  2659  		t.Fatalf("ReadAt failed: %s", err)
  2660  	}
  2661  }
  2662  
  2663  func TestLongPath(t *testing.T) {
  2664  	t.Parallel()
  2665  
  2666  	tmpdir := t.TempDir()
  2667  
  2668  	// Test the boundary of 247 and fewer bytes (normal) and 248 and more bytes (adjusted).
  2669  	sizes := []int{247, 248, 249, 400}
  2670  	for len(tmpdir) < 400 {
  2671  		tmpdir += "/dir3456789"
  2672  	}
  2673  	for _, sz := range sizes {
  2674  		t.Run(fmt.Sprintf("length=%d", sz), func(t *testing.T) {
  2675  			sizedTempDir := tmpdir[:sz-1] + "x" // Ensure it does not end with a slash.
  2676  
  2677  			// The various sized runs are for this call to trigger the boundary
  2678  			// condition.
  2679  			if err := MkdirAll(sizedTempDir, 0755); err != nil {
  2680  				t.Fatalf("MkdirAll failed: %v", err)
  2681  			}
  2682  			data := []byte("hello world\n")
  2683  			if err := WriteFile(sizedTempDir+"/foo.txt", data, 0644); err != nil {
  2684  				t.Fatalf("os.WriteFile() failed: %v", err)
  2685  			}
  2686  			if err := Rename(sizedTempDir+"/foo.txt", sizedTempDir+"/bar.txt"); err != nil {
  2687  				t.Fatalf("Rename failed: %v", err)
  2688  			}
  2689  			mtime := time.Now().Truncate(time.Minute)
  2690  			if err := Chtimes(sizedTempDir+"/bar.txt", mtime, mtime); err != nil {
  2691  				t.Fatalf("Chtimes failed: %v", err)
  2692  			}
  2693  			names := []string{"bar.txt"}
  2694  			if testenv.HasSymlink() {
  2695  				if err := Symlink(sizedTempDir+"/bar.txt", sizedTempDir+"/symlink.txt"); err != nil {
  2696  					t.Fatalf("Symlink failed: %v", err)
  2697  				}
  2698  				names = append(names, "symlink.txt")
  2699  			}
  2700  			if testenv.HasLink() {
  2701  				if err := Link(sizedTempDir+"/bar.txt", sizedTempDir+"/link.txt"); err != nil {
  2702  					t.Fatalf("Link failed: %v", err)
  2703  				}
  2704  				names = append(names, "link.txt")
  2705  			}
  2706  			for _, wantSize := range []int64{int64(len(data)), 0} {
  2707  				for _, name := range names {
  2708  					path := sizedTempDir + "/" + name
  2709  					dir, err := Stat(path)
  2710  					if err != nil {
  2711  						t.Fatalf("Stat(%q) failed: %v", path, err)
  2712  					}
  2713  					filesize := size(path, t)
  2714  					if dir.Size() != filesize || filesize != wantSize {
  2715  						t.Errorf("Size(%q) is %d, len(ReadFile()) is %d, want %d", path, dir.Size(), filesize, wantSize)
  2716  					}
  2717  					if runtime.GOOS != "wasip1" { // Chmod is not supported on wasip1
  2718  						err = Chmod(path, dir.Mode())
  2719  						if err != nil {
  2720  							t.Fatalf("Chmod(%q) failed: %v", path, err)
  2721  						}
  2722  					}
  2723  				}
  2724  				if err := Truncate(sizedTempDir+"/bar.txt", 0); err != nil {
  2725  					t.Fatalf("Truncate failed: %v", err)
  2726  				}
  2727  			}
  2728  		})
  2729  	}
  2730  }
  2731  
  2732  func testKillProcess(t *testing.T, processKiller func(p *Process)) {
  2733  	t.Parallel()
  2734  
  2735  	// Re-exec the test binary to start a process that hangs until stdin is closed.
  2736  	cmd := testenv.Command(t, testenv.Executable(t))
  2737  	cmd.Env = append(cmd.Environ(), "GO_OS_TEST_DRAIN_STDIN=1")
  2738  	stdout, err := cmd.StdoutPipe()
  2739  	if err != nil {
  2740  		t.Fatal(err)
  2741  	}
  2742  	stdin, err := cmd.StdinPipe()
  2743  	if err != nil {
  2744  		t.Fatal(err)
  2745  	}
  2746  	err = cmd.Start()
  2747  	if err != nil {
  2748  		t.Fatalf("Failed to start test process: %v", err)
  2749  	}
  2750  
  2751  	defer func() {
  2752  		if err := cmd.Wait(); err == nil {
  2753  			t.Errorf("Test process succeeded, but expected to fail")
  2754  		}
  2755  		stdin.Close() // Keep stdin alive until the process has finished dying.
  2756  	}()
  2757  
  2758  	// Wait for the process to be started.
  2759  	// (It will close its stdout when it reaches TestMain.)
  2760  	io.Copy(io.Discard, stdout)
  2761  
  2762  	processKiller(cmd.Process)
  2763  }
  2764  
  2765  func TestKillStartProcess(t *testing.T) {
  2766  	testKillProcess(t, func(p *Process) {
  2767  		err := p.Kill()
  2768  		if err != nil {
  2769  			t.Fatalf("Failed to kill test process: %v", err)
  2770  		}
  2771  	})
  2772  }
  2773  
  2774  func TestGetppid(t *testing.T) {
  2775  	if runtime.GOOS == "plan9" {
  2776  		// TODO: golang.org/issue/8206
  2777  		t.Skipf("skipping test on plan9; see issue 8206")
  2778  	}
  2779  
  2780  	if Getenv("GO_WANT_HELPER_PROCESS") == "1" {
  2781  		fmt.Print(Getppid())
  2782  		Exit(0)
  2783  	}
  2784  
  2785  	t.Parallel()
  2786  
  2787  	cmd := testenv.Command(t, testenv.Executable(t), "-test.run=^TestGetppid$")
  2788  	cmd.Env = append(Environ(), "GO_WANT_HELPER_PROCESS=1")
  2789  
  2790  	// verify that Getppid() from the forked process reports our process id
  2791  	output, err := cmd.CombinedOutput()
  2792  	if err != nil {
  2793  		t.Fatalf("Failed to spawn child process: %v %q", err, string(output))
  2794  	}
  2795  
  2796  	childPpid := string(output)
  2797  	ourPid := fmt.Sprintf("%d", Getpid())
  2798  	if childPpid != ourPid {
  2799  		t.Fatalf("Child process reports parent process id '%v', expected '%v'", childPpid, ourPid)
  2800  	}
  2801  }
  2802  
  2803  func TestKillFindProcess(t *testing.T) {
  2804  	testKillProcess(t, func(p *Process) {
  2805  		p2, err := FindProcess(p.Pid)
  2806  		if err != nil {
  2807  			t.Fatalf("Failed to find test process: %v", err)
  2808  		}
  2809  		err = p2.Kill()
  2810  		if err != nil {
  2811  			t.Fatalf("Failed to kill test process: %v", err)
  2812  		}
  2813  	})
  2814  }
  2815  
  2816  var nilFileMethodTests = []struct {
  2817  	name string
  2818  	f    func(*File) error
  2819  }{
  2820  	{"Chdir", func(f *File) error { return f.Chdir() }},
  2821  	{"Close", func(f *File) error { return f.Close() }},
  2822  	{"Chmod", func(f *File) error { return f.Chmod(0) }},
  2823  	{"Chown", func(f *File) error { return f.Chown(0, 0) }},
  2824  	{"Read", func(f *File) error { _, err := f.Read(make([]byte, 0)); return err }},
  2825  	{"ReadAt", func(f *File) error { _, err := f.ReadAt(make([]byte, 0), 0); return err }},
  2826  	{"Readdir", func(f *File) error { _, err := f.Readdir(1); return err }},
  2827  	{"Readdirnames", func(f *File) error { _, err := f.Readdirnames(1); return err }},
  2828  	{"Seek", func(f *File) error { _, err := f.Seek(0, io.SeekStart); return err }},
  2829  	{"Stat", func(f *File) error { _, err := f.Stat(); return err }},
  2830  	{"Sync", func(f *File) error { return f.Sync() }},
  2831  	{"Truncate", func(f *File) error { return f.Truncate(0) }},
  2832  	{"Write", func(f *File) error { _, err := f.Write(make([]byte, 0)); return err }},
  2833  	{"WriteAt", func(f *File) error { _, err := f.WriteAt(make([]byte, 0), 0); return err }},
  2834  	{"WriteString", func(f *File) error { _, err := f.WriteString(""); return err }},
  2835  }
  2836  
  2837  // Test that all File methods give ErrInvalid if the receiver is nil.
  2838  func TestNilFileMethods(t *testing.T) {
  2839  	t.Parallel()
  2840  
  2841  	for _, tt := range nilFileMethodTests {
  2842  		var file *File
  2843  		got := tt.f(file)
  2844  		if got != ErrInvalid {
  2845  			t.Errorf("%v should fail when f is nil; got %v", tt.name, got)
  2846  		}
  2847  	}
  2848  }
  2849  
  2850  func mkdirTree(t *testing.T, root string, level, max int) {
  2851  	if level >= max {
  2852  		return
  2853  	}
  2854  	level++
  2855  	for i := 'a'; i < 'c'; i++ {
  2856  		dir := filepath.Join(root, string(i))
  2857  		if err := Mkdir(dir, 0700); err != nil {
  2858  			t.Fatal(err)
  2859  		}
  2860  		mkdirTree(t, dir, level, max)
  2861  	}
  2862  }
  2863  
  2864  // Test that simultaneous RemoveAll do not report an error.
  2865  // As long as it gets removed, we should be happy.
  2866  func TestRemoveAllRace(t *testing.T) {
  2867  	if runtime.GOOS == "windows" {
  2868  		// Windows has very strict rules about things like
  2869  		// removing directories while someone else has
  2870  		// them open. The racing doesn't work out nicely
  2871  		// like it does on Unix.
  2872  		t.Skip("skipping on windows")
  2873  	}
  2874  	if runtime.GOOS == "dragonfly" {
  2875  		testenv.SkipFlaky(t, 52301)
  2876  	}
  2877  
  2878  	n := runtime.GOMAXPROCS(16)
  2879  	defer runtime.GOMAXPROCS(n)
  2880  	root := t.TempDir()
  2881  	mkdirTree(t, root, 1, 6)
  2882  	hold := make(chan struct{})
  2883  	var wg sync.WaitGroup
  2884  	for i := 0; i < 4; i++ {
  2885  		wg.Add(1)
  2886  		go func() {
  2887  			defer wg.Done()
  2888  			<-hold
  2889  			err := RemoveAll(root)
  2890  			if err != nil {
  2891  				t.Errorf("unexpected error: %T, %q", err, err)
  2892  			}
  2893  		}()
  2894  	}
  2895  	close(hold) // let workers race to remove root
  2896  	wg.Wait()
  2897  }
  2898  
  2899  // Test that reading from a pipe doesn't use up a thread.
  2900  func TestPipeThreads(t *testing.T) {
  2901  	switch runtime.GOOS {
  2902  	case "aix":
  2903  		t.Skip("skipping on aix; issue 70131")
  2904  	case "illumos", "solaris":
  2905  		t.Skip("skipping on Solaris and illumos; issue 19111")
  2906  	case "windows":
  2907  		t.Skip("skipping on Windows; issue 19098")
  2908  	case "plan9":
  2909  		t.Skip("skipping on Plan 9; does not support runtime poller")
  2910  	case "js":
  2911  		t.Skip("skipping on js; no support for os.Pipe")
  2912  	case "wasip1":
  2913  		t.Skip("skipping on wasip1; no support for os.Pipe")
  2914  	}
  2915  
  2916  	threads := 100
  2917  
  2918  	r := make([]*File, threads)
  2919  	w := make([]*File, threads)
  2920  	for i := 0; i < threads; i++ {
  2921  		rp, wp, err := Pipe()
  2922  		if err != nil {
  2923  			for j := 0; j < i; j++ {
  2924  				r[j].Close()
  2925  				w[j].Close()
  2926  			}
  2927  			t.Fatal(err)
  2928  		}
  2929  		r[i] = rp
  2930  		w[i] = wp
  2931  	}
  2932  
  2933  	defer debug.SetMaxThreads(debug.SetMaxThreads(threads / 2))
  2934  
  2935  	creading := make(chan bool, threads)
  2936  	cdone := make(chan bool, threads)
  2937  	for i := 0; i < threads; i++ {
  2938  		go func(i int) {
  2939  			var b [1]byte
  2940  			creading <- true
  2941  			if _, err := r[i].Read(b[:]); err != nil {
  2942  				t.Error(err)
  2943  			}
  2944  			if err := r[i].Close(); err != nil {
  2945  				t.Error(err)
  2946  			}
  2947  			cdone <- true
  2948  		}(i)
  2949  	}
  2950  
  2951  	for i := 0; i < threads; i++ {
  2952  		<-creading
  2953  	}
  2954  
  2955  	// If we are still alive, it means that the 100 goroutines did
  2956  	// not require 100 threads.
  2957  
  2958  	for i := 0; i < threads; i++ {
  2959  		if _, err := w[i].Write([]byte{0}); err != nil {
  2960  			t.Error(err)
  2961  		}
  2962  		if err := w[i].Close(); err != nil {
  2963  			t.Error(err)
  2964  		}
  2965  		<-cdone
  2966  	}
  2967  }
  2968  
  2969  func testDoubleCloseError(path string) func(*testing.T) {
  2970  	return func(t *testing.T) {
  2971  		t.Parallel()
  2972  
  2973  		file, err := Open(path)
  2974  		if err != nil {
  2975  			t.Fatal(err)
  2976  		}
  2977  		if err := file.Close(); err != nil {
  2978  			t.Fatalf("unexpected error from Close: %v", err)
  2979  		}
  2980  		if err := file.Close(); err == nil {
  2981  			t.Error("second Close did not fail")
  2982  		} else if pe, ok := err.(*PathError); !ok {
  2983  			t.Errorf("second Close: got %T, want %T", err, pe)
  2984  		} else if pe.Err != ErrClosed {
  2985  			t.Errorf("second Close: got %q, want %q", pe.Err, ErrClosed)
  2986  		} else {
  2987  			t.Logf("second close returned expected error %q", err)
  2988  		}
  2989  	}
  2990  }
  2991  
  2992  func TestDoubleCloseError(t *testing.T) {
  2993  	t.Parallel()
  2994  	t.Run("file", testDoubleCloseError(filepath.Join(sfdir, sfname)))
  2995  	t.Run("dir", testDoubleCloseError(sfdir))
  2996  }
  2997  
  2998  func TestUserCacheDir(t *testing.T) {
  2999  	t.Parallel()
  3000  
  3001  	dir, err := UserCacheDir()
  3002  	if err != nil {
  3003  		t.Skipf("skipping: %v", err)
  3004  	}
  3005  	if dir == "" {
  3006  		t.Fatalf("UserCacheDir returned %q; want non-empty path or error", dir)
  3007  	}
  3008  
  3009  	fi, err := Stat(dir)
  3010  	if err != nil {
  3011  		if IsNotExist(err) {
  3012  			t.Log(err)
  3013  			return
  3014  		}
  3015  		t.Fatal(err)
  3016  	}
  3017  	if !fi.IsDir() {
  3018  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3019  	}
  3020  }
  3021  
  3022  func TestUserCacheDirXDGConfigDirEnvVar(t *testing.T) {
  3023  	switch runtime.GOOS {
  3024  	case "windows", "darwin", "plan9":
  3025  		t.Skip("$XDG_CACHE_HOME is effective only on Unix systems")
  3026  	}
  3027  
  3028  	wd, err := Getwd()
  3029  	if err != nil {
  3030  		t.Fatal(err)
  3031  	}
  3032  	t.Setenv("XDG_CACHE_HOME", wd)
  3033  
  3034  	dir, err := UserCacheDir()
  3035  	if err != nil {
  3036  		t.Fatal(err)
  3037  	}
  3038  	if dir != wd {
  3039  		t.Fatalf("UserCacheDir returned %q; want the value of $XDG_CACHE_HOME %q", dir, wd)
  3040  	}
  3041  
  3042  	t.Setenv("XDG_CACHE_HOME", "some-dir")
  3043  	_, err = UserCacheDir()
  3044  	if err == nil {
  3045  		t.Fatal("UserCacheDir succeeded though $XDG_CACHE_HOME contains a relative path")
  3046  	}
  3047  }
  3048  
  3049  func TestUserConfigDir(t *testing.T) {
  3050  	t.Parallel()
  3051  
  3052  	dir, err := UserConfigDir()
  3053  	if err != nil {
  3054  		t.Skipf("skipping: %v", err)
  3055  	}
  3056  	if dir == "" {
  3057  		t.Fatalf("UserConfigDir returned %q; want non-empty path or error", dir)
  3058  	}
  3059  
  3060  	fi, err := Stat(dir)
  3061  	if err != nil {
  3062  		if IsNotExist(err) {
  3063  			t.Log(err)
  3064  			return
  3065  		}
  3066  		t.Fatal(err)
  3067  	}
  3068  	if !fi.IsDir() {
  3069  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3070  	}
  3071  }
  3072  
  3073  func TestUserConfigDirXDGConfigDirEnvVar(t *testing.T) {
  3074  	switch runtime.GOOS {
  3075  	case "windows", "darwin", "plan9":
  3076  		t.Skip("$XDG_CONFIG_HOME is effective only on Unix systems")
  3077  	}
  3078  
  3079  	wd, err := Getwd()
  3080  	if err != nil {
  3081  		t.Fatal(err)
  3082  	}
  3083  	t.Setenv("XDG_CONFIG_HOME", wd)
  3084  
  3085  	dir, err := UserConfigDir()
  3086  	if err != nil {
  3087  		t.Fatal(err)
  3088  	}
  3089  	if dir != wd {
  3090  		t.Fatalf("UserConfigDir returned %q; want the value of $XDG_CONFIG_HOME %q", dir, wd)
  3091  	}
  3092  
  3093  	t.Setenv("XDG_CONFIG_HOME", "some-dir")
  3094  	_, err = UserConfigDir()
  3095  	if err == nil {
  3096  		t.Fatal("UserConfigDir succeeded though $XDG_CONFIG_HOME contains a relative path")
  3097  	}
  3098  }
  3099  
  3100  func TestUserHomeDir(t *testing.T) {
  3101  	t.Parallel()
  3102  
  3103  	dir, err := UserHomeDir()
  3104  	if dir == "" && err == nil {
  3105  		t.Fatal("UserHomeDir returned an empty string but no error")
  3106  	}
  3107  	if err != nil {
  3108  		// UserHomeDir may return a non-nil error if the environment variable
  3109  		// for the home directory is empty or unset in the environment.
  3110  		t.Skipf("skipping: %v", err)
  3111  	}
  3112  
  3113  	fi, err := Stat(dir)
  3114  	if err != nil {
  3115  		if IsNotExist(err) {
  3116  			// The user's home directory has a well-defined location, but does not
  3117  			// exist. (Maybe nothing has written to it yet? That could happen, for
  3118  			// example, on minimal VM images used for CI testing.)
  3119  			t.Log(err)
  3120  			return
  3121  		}
  3122  		t.Fatal(err)
  3123  	}
  3124  	if !fi.IsDir() {
  3125  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3126  	}
  3127  }
  3128  
  3129  func TestDirSeek(t *testing.T) {
  3130  	t.Parallel()
  3131  
  3132  	wd, err := Getwd()
  3133  	if err != nil {
  3134  		t.Fatal(err)
  3135  	}
  3136  	f, err := Open(wd)
  3137  	if err != nil {
  3138  		t.Fatal(err)
  3139  	}
  3140  	dirnames1, err := f.Readdirnames(0)
  3141  	if err != nil {
  3142  		t.Fatal(err)
  3143  	}
  3144  
  3145  	ret, err := f.Seek(0, 0)
  3146  	if err != nil {
  3147  		t.Fatal(err)
  3148  	}
  3149  	if ret != 0 {
  3150  		t.Fatalf("seek result not zero: %d", ret)
  3151  	}
  3152  
  3153  	dirnames2, err := f.Readdirnames(0)
  3154  	if err != nil {
  3155  		t.Fatal(err)
  3156  	}
  3157  
  3158  	if len(dirnames1) != len(dirnames2) {
  3159  		t.Fatalf("listings have different lengths: %d and %d\n", len(dirnames1), len(dirnames2))
  3160  	}
  3161  	for i, n1 := range dirnames1 {
  3162  		n2 := dirnames2[i]
  3163  		if n1 != n2 {
  3164  			t.Fatalf("different name i=%d n1=%s n2=%s\n", i, n1, n2)
  3165  		}
  3166  	}
  3167  }
  3168  
  3169  func TestReaddirSmallSeek(t *testing.T) {
  3170  	// See issue 37161. Read only one entry from a directory,
  3171  	// seek to the beginning, and read again. We should not see
  3172  	// duplicate entries.
  3173  	t.Parallel()
  3174  
  3175  	wd, err := Getwd()
  3176  	if err != nil {
  3177  		t.Fatal(err)
  3178  	}
  3179  	df, err := Open(filepath.Join(wd, "testdata", "issue37161"))
  3180  	if err != nil {
  3181  		t.Fatal(err)
  3182  	}
  3183  	names1, err := df.Readdirnames(1)
  3184  	if err != nil {
  3185  		t.Fatal(err)
  3186  	}
  3187  	if _, err = df.Seek(0, 0); err != nil {
  3188  		t.Fatal(err)
  3189  	}
  3190  	names2, err := df.Readdirnames(0)
  3191  	if err != nil {
  3192  		t.Fatal(err)
  3193  	}
  3194  	if len(names2) != 3 {
  3195  		t.Fatalf("first names: %v, second names: %v", names1, names2)
  3196  	}
  3197  }
  3198  
  3199  // isDeadlineExceeded reports whether err is or wraps ErrDeadlineExceeded.
  3200  // We also check that the error has a Timeout method that returns true.
  3201  func isDeadlineExceeded(err error) bool {
  3202  	if !IsTimeout(err) {
  3203  		return false
  3204  	}
  3205  	if !errors.Is(err, ErrDeadlineExceeded) {
  3206  		return false
  3207  	}
  3208  	return true
  3209  }
  3210  
  3211  // Test that opening a file does not change its permissions.  Issue 38225.
  3212  func TestOpenFileKeepsPermissions(t *testing.T) {
  3213  	t.Run("OpenFile", func(t *testing.T) {
  3214  		testOpenFileKeepsPermissions(t, OpenFile)
  3215  	})
  3216  	t.Run("RootOpenFile", func(t *testing.T) {
  3217  		testOpenFileKeepsPermissions(t, func(name string, flag int, perm FileMode) (*File, error) {
  3218  			dir, file := filepath.Split(name)
  3219  			r, err := OpenRoot(dir)
  3220  			if err != nil {
  3221  				return nil, err
  3222  			}
  3223  			defer r.Close()
  3224  			return r.OpenFile(file, flag, perm)
  3225  		})
  3226  	})
  3227  }
  3228  func testOpenFileKeepsPermissions(t *testing.T, openf func(name string, flag int, perm FileMode) (*File, error)) {
  3229  	t.Parallel()
  3230  
  3231  	dir := t.TempDir()
  3232  	name := filepath.Join(dir, "x")
  3233  	f, err := Create(name)
  3234  	if err != nil {
  3235  		t.Fatal(err)
  3236  	}
  3237  	if err := f.Close(); err != nil {
  3238  		t.Error(err)
  3239  	}
  3240  	f, err = openf(name, O_WRONLY|O_CREATE|O_TRUNC, 0)
  3241  	if err != nil {
  3242  		t.Fatal(err)
  3243  	}
  3244  	if fi, err := f.Stat(); err != nil {
  3245  		t.Error(err)
  3246  	} else if fi.Mode()&0222 == 0 {
  3247  		t.Errorf("f.Stat.Mode after OpenFile is %v, should be writable", fi.Mode())
  3248  	}
  3249  	if err := f.Close(); err != nil {
  3250  		t.Error(err)
  3251  	}
  3252  	if fi, err := Stat(name); err != nil {
  3253  		t.Error(err)
  3254  	} else if fi.Mode()&0222 == 0 {
  3255  		t.Errorf("Stat after OpenFile is %v, should be writable", fi.Mode())
  3256  	}
  3257  }
  3258  
  3259  func forceMFTUpdateOnWindows(t *testing.T, path string) {
  3260  	t.Helper()
  3261  
  3262  	if runtime.GOOS != "windows" {
  3263  		return
  3264  	}
  3265  
  3266  	// On Windows, we force the MFT to update by reading the actual metadata from GetFileInformationByHandle and then
  3267  	// explicitly setting that. Otherwise it might get out of sync with FindFirstFile. See golang.org/issues/42637.
  3268  	if err := filepath.WalkDir(path, func(path string, d fs.DirEntry, err error) error {
  3269  		if err != nil {
  3270  			t.Fatal(err)
  3271  		}
  3272  		info, err := d.Info()
  3273  		if err != nil {
  3274  			t.Fatal(err)
  3275  		}
  3276  		stat, err := Stat(path) // This uses GetFileInformationByHandle internally.
  3277  		if err != nil {
  3278  			t.Fatal(err)
  3279  		}
  3280  		if stat.ModTime() == info.ModTime() {
  3281  			return nil
  3282  		}
  3283  		if err := Chtimes(path, stat.ModTime(), stat.ModTime()); err != nil {
  3284  			t.Log(err) // We only log, not die, in case the test directory is not writable.
  3285  		}
  3286  		return nil
  3287  	}); err != nil {
  3288  		t.Fatal(err)
  3289  	}
  3290  }
  3291  
  3292  func TestDirFS(t *testing.T) {
  3293  	t.Parallel()
  3294  	testDirFS(t, DirFS("./testdata/dirfs"))
  3295  }
  3296  
  3297  func TestRootDirFS(t *testing.T) {
  3298  	t.Parallel()
  3299  	r, err := OpenRoot("./testdata/dirfs")
  3300  	if err != nil {
  3301  		t.Fatal(err)
  3302  	}
  3303  	defer r.Close()
  3304  	testDirFS(t, r.FS())
  3305  }
  3306  
  3307  func testDirFS(t *testing.T, fsys fs.FS) {
  3308  	forceMFTUpdateOnWindows(t, "./testdata/dirfs")
  3309  
  3310  	if err := fstest.TestFS(fsys, "a", "b", "dir/x"); err != nil {
  3311  		t.Fatal(err)
  3312  	}
  3313  
  3314  	rdfs, ok := fsys.(fs.ReadDirFS)
  3315  	if !ok {
  3316  		t.Error("expected DirFS result to implement fs.ReadDirFS")
  3317  	}
  3318  	if _, err := rdfs.ReadDir("nonexistent"); err == nil {
  3319  		t.Error("fs.ReadDir of nonexistent directory succeeded")
  3320  	}
  3321  
  3322  	// Test that the error message does not contain a backslash,
  3323  	// and does not contain the DirFS argument.
  3324  	const nonesuch = "dir/nonesuch"
  3325  	_, err := fsys.Open(nonesuch)
  3326  	if err == nil {
  3327  		t.Error("fs.Open of nonexistent file succeeded")
  3328  	} else {
  3329  		if !strings.Contains(err.Error(), nonesuch) {
  3330  			t.Errorf("error %q does not contain %q", err, nonesuch)
  3331  		}
  3332  		if strings.Contains(err.(*PathError).Path, "testdata") {
  3333  			t.Errorf("error %q contains %q", err, "testdata")
  3334  		}
  3335  	}
  3336  
  3337  	// Test that Open does not accept backslash as separator.
  3338  	d := DirFS(".")
  3339  	_, err = d.Open(`testdata\dirfs`)
  3340  	if err == nil {
  3341  		t.Fatalf(`Open testdata\dirfs succeeded`)
  3342  	}
  3343  
  3344  	// Test that Open does not open Windows device files.
  3345  	_, err = d.Open(`NUL`)
  3346  	if err == nil {
  3347  		t.Errorf(`Open NUL succeeded`)
  3348  	}
  3349  }
  3350  
  3351  func TestDirFSRootDir(t *testing.T) {
  3352  	t.Parallel()
  3353  
  3354  	cwd, err := Getwd()
  3355  	if err != nil {
  3356  		t.Fatal(err)
  3357  	}
  3358  	cwd = cwd[len(filepath.VolumeName(cwd)):] // trim volume prefix (C:) on Windows
  3359  	cwd = filepath.ToSlash(cwd)               // convert \ to /
  3360  	cwd = strings.TrimPrefix(cwd, "/")        // trim leading /
  3361  
  3362  	// Test that Open can open a path starting at /.
  3363  	d := DirFS("/")
  3364  	f, err := d.Open(cwd + "/testdata/dirfs/a")
  3365  	if err != nil {
  3366  		t.Fatal(err)
  3367  	}
  3368  	f.Close()
  3369  }
  3370  
  3371  func TestDirFSEmptyDir(t *testing.T) {
  3372  	t.Parallel()
  3373  
  3374  	d := DirFS("")
  3375  	cwd, _ := Getwd()
  3376  	for _, path := range []string{
  3377  		"testdata/dirfs/a",                          // not DirFS(".")
  3378  		filepath.ToSlash(cwd) + "/testdata/dirfs/a", // not DirFS("/")
  3379  	} {
  3380  		_, err := d.Open(path)
  3381  		if err == nil {
  3382  			t.Fatalf(`DirFS("").Open(%q) succeeded`, path)
  3383  		}
  3384  	}
  3385  }
  3386  
  3387  func TestDirFSPathsValid(t *testing.T) {
  3388  	if runtime.GOOS == "windows" {
  3389  		t.Skipf("skipping on Windows")
  3390  	}
  3391  	t.Parallel()
  3392  
  3393  	d := t.TempDir()
  3394  	if err := WriteFile(filepath.Join(d, "control.txt"), []byte(string("Hello, world!")), 0644); err != nil {
  3395  		t.Fatal(err)
  3396  	}
  3397  	if err := WriteFile(filepath.Join(d, `e:xperi\ment.txt`), []byte(string("Hello, colon and backslash!")), 0644); err != nil {
  3398  		t.Fatal(err)
  3399  	}
  3400  
  3401  	fsys := DirFS(d)
  3402  	err := fs.WalkDir(fsys, ".", func(path string, e fs.DirEntry, err error) error {
  3403  		if fs.ValidPath(e.Name()) {
  3404  			t.Logf("%q ok", e.Name())
  3405  		} else {
  3406  			t.Errorf("%q INVALID", e.Name())
  3407  		}
  3408  		return nil
  3409  	})
  3410  	if err != nil {
  3411  		t.Fatal(err)
  3412  	}
  3413  }
  3414  
  3415  func TestReadFileProc(t *testing.T) {
  3416  	t.Parallel()
  3417  
  3418  	// Linux files in /proc report 0 size,
  3419  	// but then if ReadFile reads just a single byte at offset 0,
  3420  	// the read at offset 1 returns EOF instead of more data.
  3421  	// ReadFile has a minimum read size of 512 to work around this,
  3422  	// but test explicitly that it's working.
  3423  	name := "/proc/sys/fs/pipe-max-size"
  3424  	if _, err := Stat(name); err != nil {
  3425  		t.Skip(err)
  3426  	}
  3427  	data, err := ReadFile(name)
  3428  	if err != nil {
  3429  		t.Fatal(err)
  3430  	}
  3431  	if len(data) == 0 || data[len(data)-1] != '\n' {
  3432  		t.Fatalf("read %s: not newline-terminated: %q", name, data)
  3433  	}
  3434  }
  3435  
  3436  func TestDirFSReadFileProc(t *testing.T) {
  3437  	t.Parallel()
  3438  
  3439  	fsys := DirFS("/")
  3440  	name := "proc/sys/fs/pipe-max-size"
  3441  	if _, err := fs.Stat(fsys, name); err != nil {
  3442  		t.Skip()
  3443  	}
  3444  	data, err := fs.ReadFile(fsys, name)
  3445  	if err != nil {
  3446  		t.Fatal(err)
  3447  	}
  3448  	if len(data) == 0 || data[len(data)-1] != '\n' {
  3449  		t.Fatalf("read %s: not newline-terminated: %q", name, data)
  3450  	}
  3451  }
  3452  
  3453  func TestWriteStringAlloc(t *testing.T) {
  3454  	if runtime.GOOS == "js" {
  3455  		t.Skip("js allocates a lot during File.WriteString")
  3456  	}
  3457  	d := t.TempDir()
  3458  	f, err := Create(filepath.Join(d, "whiteboard.txt"))
  3459  	if err != nil {
  3460  		t.Fatal(err)
  3461  	}
  3462  	defer f.Close()
  3463  	allocs := testing.AllocsPerRun(100, func() {
  3464  		f.WriteString("I will not allocate when passed a string longer than 32 bytes.\n")
  3465  	})
  3466  	if allocs != 0 {
  3467  		t.Errorf("expected 0 allocs for File.WriteString, got %v", allocs)
  3468  	}
  3469  }
  3470  
  3471  // Test that it's OK to have parallel I/O and Close on a pipe.
  3472  func TestPipeIOCloseRace(t *testing.T) {
  3473  	// Skip on wasm, which doesn't have pipes.
  3474  	if runtime.GOOS == "js" || runtime.GOOS == "wasip1" {
  3475  		t.Skipf("skipping on %s: no pipes", runtime.GOOS)
  3476  	}
  3477  	t.Parallel()
  3478  
  3479  	r, w, err := Pipe()
  3480  	if err != nil {
  3481  		t.Fatal(err)
  3482  	}
  3483  
  3484  	var wg sync.WaitGroup
  3485  	wg.Add(3)
  3486  
  3487  	go func() {
  3488  		defer wg.Done()
  3489  		for {
  3490  			n, err := w.Write([]byte("hi"))
  3491  			if err != nil {
  3492  				// We look at error strings as the
  3493  				// expected errors are OS-specific.
  3494  				switch {
  3495  				case errors.Is(err, ErrClosed),
  3496  					strings.Contains(err.Error(), "broken pipe"),
  3497  					strings.Contains(err.Error(), "pipe is being closed"),
  3498  					strings.Contains(err.Error(), "hungup channel"):
  3499  					// Ignore an expected error.
  3500  				default:
  3501  					// Unexpected error.
  3502  					t.Error(err)
  3503  				}
  3504  				return
  3505  			}
  3506  			if n != 2 {
  3507  				t.Errorf("wrote %d bytes, expected 2", n)
  3508  				return
  3509  			}
  3510  		}
  3511  	}()
  3512  
  3513  	go func() {
  3514  		defer wg.Done()
  3515  		for {
  3516  			var buf [2]byte
  3517  			n, err := r.Read(buf[:])
  3518  			if err != nil {
  3519  				if err != io.EOF && !errors.Is(err, ErrClosed) {
  3520  					t.Error(err)
  3521  				}
  3522  				return
  3523  			}
  3524  			if n != 2 {
  3525  				t.Errorf("read %d bytes, want 2", n)
  3526  			}
  3527  		}
  3528  	}()
  3529  
  3530  	go func() {
  3531  		defer wg.Done()
  3532  
  3533  		// Let the other goroutines start. This is just to get
  3534  		// a better test, the test will still pass if they
  3535  		// don't start.
  3536  		time.Sleep(time.Millisecond)
  3537  
  3538  		if err := r.Close(); err != nil {
  3539  			t.Error(err)
  3540  		}
  3541  		if err := w.Close(); err != nil {
  3542  			t.Error(err)
  3543  		}
  3544  	}()
  3545  
  3546  	wg.Wait()
  3547  }
  3548  
  3549  // Test that it's OK to call Close concurrently on a pipe.
  3550  func TestPipeCloseRace(t *testing.T) {
  3551  	// Skip on wasm, which doesn't have pipes.
  3552  	if runtime.GOOS == "js" || runtime.GOOS == "wasip1" {
  3553  		t.Skipf("skipping on %s: no pipes", runtime.GOOS)
  3554  	}
  3555  	t.Parallel()
  3556  
  3557  	r, w, err := Pipe()
  3558  	if err != nil {
  3559  		t.Fatal(err)
  3560  	}
  3561  	var wg sync.WaitGroup
  3562  	c := make(chan error, 4)
  3563  	f := func() {
  3564  		defer wg.Done()
  3565  		c <- r.Close()
  3566  		c <- w.Close()
  3567  	}
  3568  	wg.Add(2)
  3569  	go f()
  3570  	go f()
  3571  	nils, errs := 0, 0
  3572  	for i := 0; i < 4; i++ {
  3573  		err := <-c
  3574  		if err == nil {
  3575  			nils++
  3576  		} else {
  3577  			errs++
  3578  		}
  3579  	}
  3580  	if nils != 2 || errs != 2 {
  3581  		t.Errorf("got nils %d errs %d, want 2 2", nils, errs)
  3582  	}
  3583  }
  3584  
  3585  func TestRandomLen(t *testing.T) {
  3586  	for range 5 {
  3587  		dir, err := MkdirTemp(t.TempDir(), "*")
  3588  		if err != nil {
  3589  			t.Fatal(err)
  3590  		}
  3591  		base := filepath.Base(dir)
  3592  		if len(base) > 10 {
  3593  			t.Errorf("MkdirTemp returned len %d: %s", len(base), base)
  3594  		}
  3595  	}
  3596  	for range 5 {
  3597  		f, err := CreateTemp(t.TempDir(), "*")
  3598  		if err != nil {
  3599  			t.Fatal(err)
  3600  		}
  3601  		base := filepath.Base(f.Name())
  3602  		f.Close()
  3603  		if len(base) > 10 {
  3604  			t.Errorf("CreateTemp returned len %d: %s", len(base), base)
  3605  		}
  3606  	}
  3607  }
  3608  
  3609  func TestCopyFS(t *testing.T) {
  3610  	t.Parallel()
  3611  
  3612  	// Test with disk filesystem.
  3613  	forceMFTUpdateOnWindows(t, "./testdata/dirfs")
  3614  	fsys := DirFS("./testdata/dirfs")
  3615  	tmpDir := t.TempDir()
  3616  	if err := CopyFS(tmpDir, fsys); err != nil {
  3617  		t.Fatal("CopyFS:", err)
  3618  	}
  3619  	forceMFTUpdateOnWindows(t, tmpDir)
  3620  	tmpFsys := DirFS(tmpDir)
  3621  	if err := fstest.TestFS(tmpFsys, "a", "b", "dir/x"); err != nil {
  3622  		t.Fatal("TestFS:", err)
  3623  	}
  3624  	if err := verifyCopyFS(t, fsys, tmpFsys); err != nil {
  3625  		t.Fatal("comparing two directories:", err)
  3626  	}
  3627  
  3628  	// Test whether CopyFS disallows copying for disk filesystem when there is any
  3629  	// existing file in the destination directory.
  3630  	if err := CopyFS(tmpDir, fsys); !errors.Is(err, fs.ErrExist) {
  3631  		t.Errorf("CopyFS should have failed and returned error when there is"+
  3632  			"any existing file in the destination directory (in disk filesystem), "+
  3633  			"got: %v, expected any error that indicates <file exists>", err)
  3634  	}
  3635  
  3636  	// Test with memory filesystem.
  3637  	fsys = fstest.MapFS{
  3638  		"william":    {Data: []byte("Shakespeare\n")},
  3639  		"carl":       {Data: []byte("Gauss\n")},
  3640  		"daVinci":    {Data: []byte("Leonardo\n")},
  3641  		"einstein":   {Data: []byte("Albert\n")},
  3642  		"dir/newton": {Data: []byte("Sir Isaac\n")},
  3643  	}
  3644  	tmpDir = t.TempDir()
  3645  	if err := CopyFS(tmpDir, fsys); err != nil {
  3646  		t.Fatal("CopyFS:", err)
  3647  	}
  3648  	forceMFTUpdateOnWindows(t, tmpDir)
  3649  	tmpFsys = DirFS(tmpDir)
  3650  	if err := fstest.TestFS(tmpFsys, "william", "carl", "daVinci", "einstein", "dir/newton"); err != nil {
  3651  		t.Fatal("TestFS:", err)
  3652  	}
  3653  	if err := verifyCopyFS(t, fsys, tmpFsys); err != nil {
  3654  		t.Fatal("comparing two directories:", err)
  3655  	}
  3656  
  3657  	// Test whether CopyFS disallows copying for memory filesystem when there is any
  3658  	// existing file in the destination directory.
  3659  	if err := CopyFS(tmpDir, fsys); !errors.Is(err, fs.ErrExist) {
  3660  		t.Errorf("CopyFS should have failed and returned error when there is"+
  3661  			"any existing file in the destination directory (in memory filesystem), "+
  3662  			"got: %v, expected any error that indicates <file exists>", err)
  3663  	}
  3664  }
  3665  
  3666  // verifyCopyFS checks the content and permission of each file inside copied FS to ensure
  3667  // the copied files satisfy the convention stipulated in CopyFS.
  3668  func verifyCopyFS(t *testing.T, originFS, copiedFS fs.FS) error {
  3669  	testDir := filepath.Join(t.TempDir(), "test")
  3670  	// umask doesn't apply to the wasip and windows and there is no general way to get masked perm,
  3671  	// so create a dir and a file to compare the permission after umask if any
  3672  	if err := Mkdir(testDir, ModePerm); err != nil {
  3673  		return fmt.Errorf("mkdir %q failed: %v", testDir, err)
  3674  	}
  3675  	dirStat, err := Stat(testDir)
  3676  	if err != nil {
  3677  		return fmt.Errorf("stat dir %q failed: %v", testDir, err)
  3678  	}
  3679  	wantDirMode := dirStat.Mode()
  3680  
  3681  	f, err := Create(filepath.Join(testDir, "tmp"))
  3682  	if err != nil {
  3683  		return fmt.Errorf("open %q failed: %v", filepath.Join(testDir, "tmp"), err)
  3684  	}
  3685  	defer f.Close()
  3686  	wantFileRWStat, err := f.Stat()
  3687  	if err != nil {
  3688  		return fmt.Errorf("stat file %q failed: %v", f.Name(), err)
  3689  	}
  3690  	wantFileRWMode := wantFileRWStat.Mode()
  3691  
  3692  	return fs.WalkDir(originFS, ".", func(path string, d fs.DirEntry, err error) error {
  3693  		if d.IsDir() {
  3694  			// the dir . is not the dir created by CopyFS so skip checking its permission
  3695  			if d.Name() == "." {
  3696  				return nil
  3697  			}
  3698  
  3699  			dinfo, err := fs.Stat(copiedFS, path)
  3700  			if err != nil {
  3701  				return err
  3702  			}
  3703  
  3704  			if dinfo.Mode() != wantDirMode {
  3705  				return fmt.Errorf("dir %q mode is %v, want %v",
  3706  					d.Name(), dinfo.Mode(), wantDirMode)
  3707  			}
  3708  			return nil
  3709  		}
  3710  
  3711  		fInfo, err := originFS.Open(path)
  3712  		if err != nil {
  3713  			return err
  3714  		}
  3715  		defer fInfo.Close()
  3716  		copiedInfo, err := copiedFS.Open(path)
  3717  		if err != nil {
  3718  			return err
  3719  		}
  3720  		defer copiedInfo.Close()
  3721  
  3722  		// verify the file contents are the same
  3723  		data, err := io.ReadAll(fInfo)
  3724  		if err != nil {
  3725  			return err
  3726  		}
  3727  		newData, err := io.ReadAll(copiedInfo)
  3728  		if err != nil {
  3729  			return err
  3730  		}
  3731  		if !bytes.Equal(data, newData) {
  3732  			return fmt.Errorf("file %q content is %s, want %s", path, newData, data)
  3733  		}
  3734  
  3735  		fStat, err := fInfo.Stat()
  3736  		if err != nil {
  3737  			return err
  3738  		}
  3739  		copiedStat, err := copiedInfo.Stat()
  3740  		if err != nil {
  3741  			return err
  3742  		}
  3743  
  3744  		// check whether the execute permission is inherited from original FS
  3745  
  3746  		if copiedStat.Mode()&0111&wantFileRWMode != fStat.Mode()&0111&wantFileRWMode {
  3747  			return fmt.Errorf("file %q execute mode is %v, want %v",
  3748  				path, copiedStat.Mode()&0111, fStat.Mode()&0111)
  3749  		}
  3750  
  3751  		rwMode := copiedStat.Mode() &^ 0111 // unset the executable permission from file mode
  3752  		if rwMode != wantFileRWMode {
  3753  			return fmt.Errorf("file %q rw mode is %v, want %v",
  3754  				path, rwMode, wantFileRWStat.Mode())
  3755  		}
  3756  		return nil
  3757  	})
  3758  }
  3759  
  3760  func TestCopyFSWithSymlinks(t *testing.T) {
  3761  	// Test it with absolute and relative symlinks that point inside and outside the tree.
  3762  	testenv.MustHaveSymlink(t)
  3763  
  3764  	// Create a directory and file outside.
  3765  	tmpDir := t.TempDir()
  3766  	outsideDir := filepath.Join(tmpDir, "copyfs_out")
  3767  	if err := Mkdir(outsideDir, 0755); err != nil {
  3768  		t.Fatalf("Mkdir: %v", err)
  3769  	}
  3770  	outsideFile := filepath.Join(outsideDir, "file.out.txt")
  3771  
  3772  	if err := WriteFile(outsideFile, []byte("Testing CopyFS outside"), 0644); err != nil {
  3773  		t.Fatalf("WriteFile: %v", err)
  3774  	}
  3775  
  3776  	// Create a directory and file inside.
  3777  	insideDir := filepath.Join(tmpDir, "copyfs_in")
  3778  	if err := Mkdir(insideDir, 0755); err != nil {
  3779  		t.Fatalf("Mkdir: %v", err)
  3780  	}
  3781  	insideFile := filepath.Join(insideDir, "file.in.txt")
  3782  	if err := WriteFile(insideFile, []byte("Testing CopyFS inside"), 0644); err != nil {
  3783  		t.Fatalf("WriteFile: %v", err)
  3784  	}
  3785  
  3786  	// Create directories for symlinks.
  3787  	linkInDir := filepath.Join(insideDir, "in_symlinks")
  3788  	if err := Mkdir(linkInDir, 0755); err != nil {
  3789  		t.Fatalf("Mkdir: %v", err)
  3790  	}
  3791  	linkOutDir := filepath.Join(insideDir, "out_symlinks")
  3792  	if err := Mkdir(linkOutDir, 0755); err != nil {
  3793  		t.Fatalf("Mkdir: %v", err)
  3794  	}
  3795  
  3796  	// First, we create the absolute symlink pointing outside.
  3797  	outLinkFile := filepath.Join(linkOutDir, "file.abs.out.link")
  3798  	if err := Symlink(outsideFile, outLinkFile); err != nil {
  3799  		t.Fatalf("Symlink: %v", err)
  3800  	}
  3801  
  3802  	// Then, we create the relative symlink pointing outside.
  3803  	relOutsideFile, err := filepath.Rel(filepath.Join(linkOutDir, "."), outsideFile)
  3804  	if err != nil {
  3805  		t.Fatalf("filepath.Rel: %v", err)
  3806  	}
  3807  	relOutLinkFile := filepath.Join(linkOutDir, "file.rel.out.link")
  3808  	if err := Symlink(relOutsideFile, relOutLinkFile); err != nil {
  3809  		t.Fatalf("Symlink: %v", err)
  3810  	}
  3811  
  3812  	// Last, we create the relative symlink pointing inside.
  3813  	relInsideFile, err := filepath.Rel(filepath.Join(linkInDir, "."), insideFile)
  3814  	if err != nil {
  3815  		t.Fatalf("filepath.Rel: %v", err)
  3816  	}
  3817  	relInLinkFile := filepath.Join(linkInDir, "file.rel.in.link")
  3818  	if err := Symlink(relInsideFile, relInLinkFile); err != nil {
  3819  		t.Fatalf("Symlink: %v", err)
  3820  	}
  3821  
  3822  	// Copy the directory tree and verify.
  3823  	forceMFTUpdateOnWindows(t, insideDir)
  3824  	fsys := DirFS(insideDir)
  3825  	tmpDupDir := filepath.Join(tmpDir, "copyfs_dup")
  3826  	if err := Mkdir(tmpDupDir, 0755); err != nil {
  3827  		t.Fatalf("Mkdir: %v", err)
  3828  	}
  3829  
  3830  	if err := CopyFS(tmpDupDir, fsys); err != nil {
  3831  		t.Fatalf("CopyFS: %v", err)
  3832  	}
  3833  
  3834  	forceMFTUpdateOnWindows(t, tmpDupDir)
  3835  	tmpFsys := DirFS(tmpDupDir)
  3836  	if err := fstest.TestFS(tmpFsys, "file.in.txt", "out_symlinks/file.abs.out.link", "out_symlinks/file.rel.out.link", "in_symlinks/file.rel.in.link"); err != nil {
  3837  		t.Fatal("TestFS:", err)
  3838  	}
  3839  	if err := fs.WalkDir(fsys, ".", func(path string, d fs.DirEntry, err error) error {
  3840  		if d.IsDir() {
  3841  			return nil
  3842  		}
  3843  
  3844  		fi, err := d.Info()
  3845  		if err != nil {
  3846  			return err
  3847  		}
  3848  		if filepath.Ext(path) == ".link" {
  3849  			if fi.Mode()&ModeSymlink == 0 {
  3850  				return errors.New("original file " + path + " should be a symlink")
  3851  			}
  3852  			tmpfi, err := fs.Stat(tmpFsys, path)
  3853  			if err != nil {
  3854  				return err
  3855  			}
  3856  			if tmpfi.Mode()&ModeSymlink != 0 {
  3857  				return errors.New("copied file " + path + " should not be a symlink")
  3858  			}
  3859  		}
  3860  
  3861  		data, err := fs.ReadFile(fsys, path)
  3862  		if err != nil {
  3863  			return err
  3864  		}
  3865  		newData, err := fs.ReadFile(tmpFsys, path)
  3866  		if err != nil {
  3867  			return err
  3868  		}
  3869  		if !bytes.Equal(data, newData) {
  3870  			return errors.New("file " + path + " contents differ")
  3871  		}
  3872  
  3873  		var target string
  3874  		switch fileName := filepath.Base(path); fileName {
  3875  		case "file.abs.out.link", "file.rel.out.link":
  3876  			target = outsideFile
  3877  		case "file.rel.in.link":
  3878  			target = insideFile
  3879  		}
  3880  		if len(target) > 0 {
  3881  			targetData, err := ReadFile(target)
  3882  			if err != nil {
  3883  				return err
  3884  			}
  3885  			if !bytes.Equal(targetData, newData) {
  3886  				return errors.New("file " + path + " contents differ from target")
  3887  			}
  3888  		}
  3889  
  3890  		return nil
  3891  	}); err != nil {
  3892  		t.Fatal("comparing two directories:", err)
  3893  	}
  3894  }
  3895  
  3896  func TestAppendDoesntOverwrite(t *testing.T) {
  3897  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  3898  		name := "file"
  3899  		if err := WriteFile(name, []byte("hello"), 0666); err != nil {
  3900  			t.Fatal(err)
  3901  		}
  3902  		var f *File
  3903  		var err error
  3904  		if r == nil {
  3905  			f, err = OpenFile(name, O_APPEND|O_WRONLY, 0)
  3906  		} else {
  3907  			f, err = r.OpenFile(name, O_APPEND|O_WRONLY, 0)
  3908  		}
  3909  		if err != nil {
  3910  			t.Fatal(err)
  3911  		}
  3912  		if _, err := f.Write([]byte(" world")); err != nil {
  3913  			f.Close()
  3914  			t.Fatal(err)
  3915  		}
  3916  		if err := f.Close(); err != nil {
  3917  			t.Fatal(err)
  3918  		}
  3919  		got, err := ReadFile(name)
  3920  		if err != nil {
  3921  			t.Fatal(err)
  3922  		}
  3923  		want := "hello world"
  3924  		if string(got) != want {
  3925  			t.Fatalf("got %q, want %q", got, want)
  3926  		}
  3927  	})
  3928  }
  3929  
  3930  func TestRemoveReadOnlyFile(t *testing.T) {
  3931  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  3932  		if err := WriteFile("file", []byte("1"), 0); err != nil {
  3933  			t.Fatal(err)
  3934  		}
  3935  		var err error
  3936  		if r == nil {
  3937  			err = Remove("file")
  3938  		} else {
  3939  			err = r.Remove("file")
  3940  		}
  3941  		if err != nil {
  3942  			t.Fatalf("Remove read-only file: %v", err)
  3943  		}
  3944  		if _, err := Stat("file"); !IsNotExist(err) {
  3945  			t.Fatalf("Stat read-only file after removal: %v (want IsNotExist)", err)
  3946  		}
  3947  	})
  3948  }
  3949  
  3950  func TestOpenFileDevNull(t *testing.T) {
  3951  	// See https://go.dev/issue/71752.
  3952  	t.Parallel()
  3953  
  3954  	f, err := OpenFile(DevNull, O_WRONLY|O_CREATE|O_TRUNC, 0o644)
  3955  	if err != nil {
  3956  		t.Fatalf("OpenFile(DevNull): %v", err)
  3957  	}
  3958  	f.Close()
  3959  }
  3960  
  3961  func TestReadFileContents(t *testing.T) {
  3962  	type readStep struct {
  3963  		bufSize int   // non-zero to check length of buf to Read
  3964  		retN    int   // result of Read call
  3965  		retErr  error // error result of Read call
  3966  	}
  3967  	errFoo := errors.New("foo")
  3968  	tests := []struct {
  3969  		name     string
  3970  		statSize int64 // size of file to read, per stat (may be 0 for /proc files)
  3971  		wantSize int   // wanted length of []byte from readFileContents
  3972  		wantErr  error // wanted error from readFileContents
  3973  		reads    []readStep
  3974  	}{
  3975  		{
  3976  			name:     "big-file",
  3977  			statSize: 2000,
  3978  			wantSize: 2000,
  3979  			reads: []readStep{
  3980  				{bufSize: 2001, retN: 21, retErr: nil},
  3981  				{bufSize: 1980, retN: 1979, retErr: io.EOF},
  3982  			},
  3983  		},
  3984  		{
  3985  			name:     "small-file",
  3986  			statSize: 100,
  3987  			wantSize: 100,
  3988  			reads: []readStep{
  3989  				{bufSize: 512, retN: 100, retErr: io.EOF},
  3990  			},
  3991  		},
  3992  		{
  3993  			name:     "returning-error",
  3994  			statSize: 1000,
  3995  			wantSize: 50,
  3996  			wantErr:  errFoo,
  3997  			reads: []readStep{
  3998  				{bufSize: 1001, retN: 25, retErr: nil},
  3999  				{retN: 25, retErr: errFoo},
  4000  			},
  4001  		},
  4002  		{
  4003  			name:     "proc-file",
  4004  			statSize: 0,
  4005  			wantSize: 1023,
  4006  			reads: []readStep{
  4007  				{bufSize: 512, retN: 512, retErr: nil},
  4008  				{retN: 511, retErr: io.EOF},
  4009  			},
  4010  		},
  4011  		{
  4012  			name:     "plan9-iproute-file", // Issue 72080
  4013  			statSize: 0,
  4014  			wantSize: 1032,
  4015  			reads: []readStep{
  4016  				{bufSize: 512, retN: 511, retErr: nil},
  4017  				{retN: 511, retErr: nil},
  4018  				{retN: 10, retErr: io.EOF},
  4019  			},
  4020  		},
  4021  	}
  4022  	for _, tt := range tests {
  4023  		t.Run(tt.name, func(t *testing.T) {
  4024  			remain := tt.reads
  4025  			i := -1
  4026  			got, err := ExportReadFileContents(tt.statSize, func(buf []byte) (int, error) {
  4027  				i++
  4028  				t.Logf("read[%d] with buf size %d", i, len(buf))
  4029  				if len(remain) == 0 {
  4030  					t.Fatalf("unexpected read of length %d after %d expected reads", len(buf), len(tt.reads))
  4031  				}
  4032  				if tt.statSize == 0 && len(buf) < 512 {
  4033  					// Issue 72080: readFileContents should not do /proc reads with buffers
  4034  					// smaller than 512.
  4035  					t.Fatalf("read[%d] with buf size %d; want at least 512 for 0-sized file", i, len(buf))
  4036  				}
  4037  				step := remain[0]
  4038  				remain = remain[1:]
  4039  				if step.bufSize != 0 && len(buf) != step.bufSize {
  4040  					t.Fatalf("read[%d] has buffer size %d; want %d", i, len(buf), step.bufSize)
  4041  				}
  4042  				return step.retN, step.retErr
  4043  			})
  4044  			if len(remain) > 0 {
  4045  				t.Fatalf("expected %d reads, got %d", len(tt.reads), i+1)
  4046  			}
  4047  			if fmt.Sprint(err) != fmt.Sprint(tt.wantErr) {
  4048  				t.Errorf("got error %v; want %v", err, tt.wantErr)
  4049  			}
  4050  			if len(got) != tt.wantSize {
  4051  				t.Errorf("got size %d; want %d", len(got), tt.wantSize)
  4052  			}
  4053  		})
  4054  	}
  4055  }
  4056  

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