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  	var pe *PathError
   844  	if !errors.As(err, &pe) || pe.Path != f.Name() {
   845  		t.Errorf("Readdirnames returned %q; want a PathError with path %q", err, f.Name())
   846  	}
   847  	if len(names) > 0 {
   848  		t.Errorf("unexpected dir names in regular file: %q", names)
   849  	}
   850  }
   851  
   852  func TestHardLink(t *testing.T) {
   853  	testMaybeRooted(t, testHardLink)
   854  }
   855  func testHardLink(t *testing.T, root *Root) {
   856  	testenv.MustHaveLink(t)
   857  
   858  	var (
   859  		create = Create
   860  		link   = Link
   861  		stat   = Stat
   862  		op     = "link"
   863  	)
   864  	if root != nil {
   865  		create = root.Create
   866  		link = root.Link
   867  		stat = root.Stat
   868  		op = "linkat"
   869  	}
   870  
   871  	from, to := "hardlinktestfrom", "hardlinktestto"
   872  	file, err := create(to)
   873  	if err != nil {
   874  		t.Fatalf("open %q failed: %v", to, err)
   875  	}
   876  	if err = file.Close(); err != nil {
   877  		t.Errorf("close %q failed: %v", to, err)
   878  	}
   879  	err = link(to, from)
   880  	if err != nil {
   881  		t.Fatalf("link %q, %q failed: %v", to, from, err)
   882  	}
   883  
   884  	none := "hardlinktestnone"
   885  	err = link(none, none)
   886  	// Check the returned error is well-formed.
   887  	if lerr, ok := err.(*LinkError); !ok || lerr.Error() == "" {
   888  		t.Errorf("link %q, %q failed to return a valid error", none, none)
   889  	}
   890  
   891  	tostat, err := stat(to)
   892  	if err != nil {
   893  		t.Fatalf("stat %q failed: %v", to, err)
   894  	}
   895  	fromstat, err := stat(from)
   896  	if err != nil {
   897  		t.Fatalf("stat %q failed: %v", from, err)
   898  	}
   899  	if !SameFile(tostat, fromstat) {
   900  		t.Errorf("link %q, %q did not create hard link", to, from)
   901  	}
   902  	// We should not be able to perform the same Link() a second time
   903  	err = link(to, from)
   904  	switch err := err.(type) {
   905  	case *LinkError:
   906  		if err.Op != op {
   907  			t.Errorf("Link(%q, %q) err.Op = %q; want %q", to, from, err.Op, op)
   908  		}
   909  		if err.Old != to {
   910  			t.Errorf("Link(%q, %q) err.Old = %q; want %q", to, from, err.Old, to)
   911  		}
   912  		if err.New != from {
   913  			t.Errorf("Link(%q, %q) err.New = %q; want %q", to, from, err.New, from)
   914  		}
   915  		if !IsExist(err.Err) {
   916  			t.Errorf("Link(%q, %q) err.Err = %q; want %q", to, from, err.Err, "file exists error")
   917  		}
   918  	case nil:
   919  		t.Errorf("link %q, %q: expected error, got nil", from, to)
   920  	default:
   921  		t.Errorf("link %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
   922  	}
   923  }
   924  
   925  func TestSymlink(t *testing.T) {
   926  	testMaybeRooted(t, testSymlink)
   927  }
   928  func testSymlink(t *testing.T, root *Root) {
   929  	testenv.MustHaveSymlink(t)
   930  
   931  	var (
   932  		create   = Create
   933  		open     = Open
   934  		symlink  = Symlink
   935  		stat     = Stat
   936  		lstat    = Lstat
   937  		readlink = Readlink
   938  	)
   939  	if root != nil {
   940  		create = root.Create
   941  		open = root.Open
   942  		symlink = root.Symlink
   943  		stat = root.Stat
   944  		lstat = root.Lstat
   945  		readlink = root.Readlink
   946  	}
   947  
   948  	from, to := "symlinktestfrom", "symlinktestto"
   949  	file, err := create(to)
   950  	if err != nil {
   951  		t.Fatalf("Create(%q) failed: %v", to, err)
   952  	}
   953  	if err = file.Close(); err != nil {
   954  		t.Errorf("Close(%q) failed: %v", to, err)
   955  	}
   956  	err = symlink(to, from)
   957  	if err != nil {
   958  		t.Fatalf("Symlink(%q, %q) failed: %v", to, from, err)
   959  	}
   960  	tostat, err := lstat(to)
   961  	if err != nil {
   962  		t.Fatalf("Lstat(%q) failed: %v", to, err)
   963  	}
   964  	if tostat.Mode()&ModeSymlink != 0 {
   965  		t.Fatalf("Lstat(%q).Mode()&ModeSymlink = %v, want 0", to, tostat.Mode()&ModeSymlink)
   966  	}
   967  	fromstat, err := stat(from)
   968  	if err != nil {
   969  		t.Fatalf("Stat(%q) failed: %v", from, err)
   970  	}
   971  	if !SameFile(tostat, fromstat) {
   972  		t.Errorf("Symlink(%q, %q) did not create symlink", to, from)
   973  	}
   974  	fromstat, err = lstat(from)
   975  	if err != nil {
   976  		t.Fatalf("Lstat(%q) failed: %v", from, err)
   977  	}
   978  	if fromstat.Mode()&ModeSymlink == 0 {
   979  		t.Fatalf("Lstat(%q).Mode()&ModeSymlink = 0, want %v", from, ModeSymlink)
   980  	}
   981  	fromstat, err = stat(from)
   982  	if err != nil {
   983  		t.Fatalf("Stat(%q) failed: %v", from, err)
   984  	}
   985  	if fromstat.Name() != from {
   986  		t.Errorf("Stat(%q).Name() = %q, want %q", from, fromstat.Name(), from)
   987  	}
   988  	if fromstat.Mode()&ModeSymlink != 0 {
   989  		t.Fatalf("Stat(%q).Mode()&ModeSymlink = %v, want 0", from, fromstat.Mode()&ModeSymlink)
   990  	}
   991  	s, err := readlink(from)
   992  	if err != nil {
   993  		t.Fatalf("Readlink(%q) failed: %v", from, err)
   994  	}
   995  	if s != to {
   996  		t.Fatalf("Readlink(%q) = %q, want %q", from, s, to)
   997  	}
   998  	file, err = open(from)
   999  	if err != nil {
  1000  		t.Fatalf("Open(%q) failed: %v", from, err)
  1001  	}
  1002  	file.Close()
  1003  }
  1004  
  1005  func TestLongSymlink(t *testing.T) {
  1006  	testenv.MustHaveSymlink(t)
  1007  	t.Chdir(t.TempDir())
  1008  
  1009  	s := "0123456789abcdef"
  1010  	// Long, but not too long: a common limit is 255.
  1011  	s = s + s + s + s + s + s + s + s + s + s + s + s + s + s + s
  1012  	from := "longsymlinktestfrom"
  1013  	err := Symlink(s, from)
  1014  	if err != nil {
  1015  		t.Fatalf("symlink %q, %q failed: %v", s, from, err)
  1016  	}
  1017  	r, err := Readlink(from)
  1018  	if err != nil {
  1019  		t.Fatalf("readlink %q failed: %v", from, err)
  1020  	}
  1021  	if r != s {
  1022  		t.Fatalf("after symlink %q != %q", r, s)
  1023  	}
  1024  }
  1025  
  1026  func TestRename(t *testing.T) {
  1027  	t.Chdir(t.TempDir())
  1028  	from, to := "renamefrom", "renameto"
  1029  
  1030  	file, err := Create(from)
  1031  	if err != nil {
  1032  		t.Fatalf("open %q failed: %v", from, err)
  1033  	}
  1034  	if err = file.Close(); err != nil {
  1035  		t.Errorf("close %q failed: %v", from, err)
  1036  	}
  1037  	err = Rename(from, to)
  1038  	if err != nil {
  1039  		t.Fatalf("rename %q, %q failed: %v", to, from, err)
  1040  	}
  1041  	_, err = Stat(to)
  1042  	if err != nil {
  1043  		t.Errorf("stat %q failed: %v", to, err)
  1044  	}
  1045  }
  1046  
  1047  func TestRenameOverwriteDest(t *testing.T) {
  1048  	t.Chdir(t.TempDir())
  1049  	from, to := "renamefrom", "renameto"
  1050  
  1051  	toData := []byte("to")
  1052  	fromData := []byte("from")
  1053  
  1054  	err := WriteFile(to, toData, 0777)
  1055  	if err != nil {
  1056  		t.Fatalf("write file %q failed: %v", to, err)
  1057  	}
  1058  
  1059  	err = WriteFile(from, fromData, 0777)
  1060  	if err != nil {
  1061  		t.Fatalf("write file %q failed: %v", from, err)
  1062  	}
  1063  	err = Rename(from, to)
  1064  	if err != nil {
  1065  		t.Fatalf("rename %q, %q failed: %v", to, from, err)
  1066  	}
  1067  
  1068  	_, err = Stat(from)
  1069  	if err == nil {
  1070  		t.Errorf("from file %q still exists", from)
  1071  	}
  1072  	if err != nil && !IsNotExist(err) {
  1073  		t.Fatalf("stat from: %v", err)
  1074  	}
  1075  	toFi, err := Stat(to)
  1076  	if err != nil {
  1077  		t.Fatalf("stat %q failed: %v", to, err)
  1078  	}
  1079  	if toFi.Size() != int64(len(fromData)) {
  1080  		t.Errorf(`"to" size = %d; want %d (old "from" size)`, toFi.Size(), len(fromData))
  1081  	}
  1082  }
  1083  
  1084  func TestRenameFailed(t *testing.T) {
  1085  	t.Chdir(t.TempDir())
  1086  	from, to := "renamefrom", "renameto"
  1087  
  1088  	err := Rename(from, to)
  1089  	switch err := err.(type) {
  1090  	case *LinkError:
  1091  		if err.Op != "rename" {
  1092  			t.Errorf("rename %q, %q: err.Op: want %q, got %q", from, to, "rename", err.Op)
  1093  		}
  1094  		if err.Old != from {
  1095  			t.Errorf("rename %q, %q: err.Old: want %q, got %q", from, to, from, err.Old)
  1096  		}
  1097  		if err.New != to {
  1098  			t.Errorf("rename %q, %q: err.New: want %q, got %q", from, to, to, err.New)
  1099  		}
  1100  	case nil:
  1101  		t.Errorf("rename %q, %q: expected error, got nil", from, to)
  1102  	default:
  1103  		t.Errorf("rename %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
  1104  	}
  1105  }
  1106  
  1107  func TestRenameNotExisting(t *testing.T) {
  1108  	t.Chdir(t.TempDir())
  1109  	from, to := "doesnt-exist", "dest"
  1110  
  1111  	Mkdir(to, 0777)
  1112  
  1113  	if err := Rename(from, to); !IsNotExist(err) {
  1114  		t.Errorf("Rename(%q, %q) = %v; want an IsNotExist error", from, to, err)
  1115  	}
  1116  }
  1117  
  1118  func TestRenameToDirFailed(t *testing.T) {
  1119  	t.Chdir(t.TempDir())
  1120  	from, to := "renamefrom", "renameto"
  1121  
  1122  	Mkdir(from, 0777)
  1123  	Mkdir(to, 0777)
  1124  
  1125  	err := Rename(from, to)
  1126  	switch err := err.(type) {
  1127  	case *LinkError:
  1128  		if err.Op != "rename" {
  1129  			t.Errorf("rename %q, %q: err.Op: want %q, got %q", from, to, "rename", err.Op)
  1130  		}
  1131  		if err.Old != from {
  1132  			t.Errorf("rename %q, %q: err.Old: want %q, got %q", from, to, from, err.Old)
  1133  		}
  1134  		if err.New != to {
  1135  			t.Errorf("rename %q, %q: err.New: want %q, got %q", from, to, to, err.New)
  1136  		}
  1137  	case nil:
  1138  		t.Errorf("rename %q, %q: expected error, got nil", from, to)
  1139  	default:
  1140  		t.Errorf("rename %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
  1141  	}
  1142  }
  1143  
  1144  func TestRenameCaseDifference(pt *testing.T) {
  1145  	from, to := "renameFROM", "RENAMEfrom"
  1146  	tests := []struct {
  1147  		name   string
  1148  		create func() error
  1149  	}{
  1150  		{"dir", func() error {
  1151  			return Mkdir(from, 0777)
  1152  		}},
  1153  		{"file", func() error {
  1154  			fd, err := Create(from)
  1155  			if err != nil {
  1156  				return err
  1157  			}
  1158  			return fd.Close()
  1159  		}},
  1160  	}
  1161  
  1162  	for _, test := range tests {
  1163  		pt.Run(test.name, func(t *testing.T) {
  1164  			t.Chdir(t.TempDir())
  1165  
  1166  			if err := test.create(); err != nil {
  1167  				t.Fatalf("failed to create test file: %s", err)
  1168  			}
  1169  
  1170  			if _, err := Stat(to); err != nil {
  1171  				// Sanity check that the underlying filesystem is not case sensitive.
  1172  				if IsNotExist(err) {
  1173  					t.Skipf("case sensitive filesystem")
  1174  				}
  1175  				t.Fatalf("stat %q, got: %q", to, err)
  1176  			}
  1177  
  1178  			if err := Rename(from, to); err != nil {
  1179  				t.Fatalf("unexpected error when renaming from %q to %q: %s", from, to, err)
  1180  			}
  1181  
  1182  			fd, err := Open(".")
  1183  			if err != nil {
  1184  				t.Fatalf("Open .: %s", err)
  1185  			}
  1186  
  1187  			// Stat does not return the real case of the file (it returns what the called asked for)
  1188  			// So we have to use readdir to get the real name of the file.
  1189  			dirNames, err := fd.Readdirnames(-1)
  1190  			fd.Close()
  1191  			if err != nil {
  1192  				t.Fatalf("readdirnames: %s", err)
  1193  			}
  1194  
  1195  			if dirNamesLen := len(dirNames); dirNamesLen != 1 {
  1196  				t.Fatalf("unexpected dirNames len, got %q, want %q", dirNamesLen, 1)
  1197  			}
  1198  
  1199  			if dirNames[0] != to {
  1200  				t.Errorf("unexpected name, got %q, want %q", dirNames[0], to)
  1201  			}
  1202  		})
  1203  	}
  1204  }
  1205  
  1206  func testStartProcess(dir, cmd string, args []string, expect string) func(t *testing.T) {
  1207  	return func(t *testing.T) {
  1208  		t.Parallel()
  1209  
  1210  		r, w, err := Pipe()
  1211  		if err != nil {
  1212  			t.Fatalf("Pipe: %v", err)
  1213  		}
  1214  		defer r.Close()
  1215  		attr := &ProcAttr{Dir: dir, Files: []*File{nil, w, Stderr}}
  1216  		p, err := StartProcess(cmd, args, attr)
  1217  		if err != nil {
  1218  			t.Fatalf("StartProcess: %v", err)
  1219  		}
  1220  		w.Close()
  1221  
  1222  		var b strings.Builder
  1223  		io.Copy(&b, r)
  1224  		output := b.String()
  1225  
  1226  		fi1, _ := Stat(strings.TrimSpace(output))
  1227  		fi2, _ := Stat(expect)
  1228  		if !SameFile(fi1, fi2) {
  1229  			t.Errorf("exec %q returned %q wanted %q",
  1230  				strings.Join(append([]string{cmd}, args...), " "), output, expect)
  1231  		}
  1232  		p.Wait()
  1233  	}
  1234  }
  1235  
  1236  func TestStartProcess(t *testing.T) {
  1237  	testenv.MustHaveExec(t)
  1238  	t.Parallel()
  1239  
  1240  	var dir, cmd string
  1241  	var args []string
  1242  	switch runtime.GOOS {
  1243  	case "android":
  1244  		t.Skip("android doesn't have /bin/pwd")
  1245  	case "windows":
  1246  		cmd = Getenv("COMSPEC")
  1247  		dir = Getenv("SystemRoot")
  1248  		args = []string{"/c", "cd"}
  1249  	default:
  1250  		var err error
  1251  		cmd, err = exec.LookPath("pwd")
  1252  		if err != nil {
  1253  			t.Fatalf("Can't find pwd: %v", err)
  1254  		}
  1255  		dir = "/"
  1256  		args = []string{}
  1257  		t.Logf("Testing with %v", cmd)
  1258  	}
  1259  	cmddir, cmdbase := filepath.Split(cmd)
  1260  	args = append([]string{cmdbase}, args...)
  1261  	t.Run("absolute", testStartProcess(dir, cmd, args, dir))
  1262  	t.Run("relative", testStartProcess(cmddir, cmdbase, args, cmddir))
  1263  }
  1264  
  1265  func checkMode(t *testing.T, path string, mode FileMode) {
  1266  	dir, err := Stat(path)
  1267  	if err != nil {
  1268  		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
  1269  	}
  1270  	if dir.Mode()&ModePerm != mode {
  1271  		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode(), mode)
  1272  	}
  1273  }
  1274  
  1275  func TestChmod(t *testing.T) {
  1276  	// Chmod is not supported on wasip1.
  1277  	if runtime.GOOS == "wasip1" {
  1278  		t.Skip("Chmod is not supported on " + runtime.GOOS)
  1279  	}
  1280  	t.Parallel()
  1281  
  1282  	f := newFile(t)
  1283  	// Creation mode is read write
  1284  
  1285  	fm := FileMode(0456)
  1286  	if runtime.GOOS == "windows" {
  1287  		fm = FileMode(0444) // read-only file
  1288  	}
  1289  	if err := Chmod(f.Name(), fm); err != nil {
  1290  		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
  1291  	}
  1292  	checkMode(t, f.Name(), fm)
  1293  
  1294  	fm = FileMode(0123)
  1295  	if runtime.GOOS == "windows" {
  1296  		fm = FileMode(0666) // read-write file
  1297  	}
  1298  	if err := f.Chmod(fm); err != nil {
  1299  		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
  1300  	}
  1301  	checkMode(t, f.Name(), fm)
  1302  }
  1303  
  1304  func checkSize(t *testing.T, f *File, size int64) {
  1305  	t.Helper()
  1306  	dir, err := f.Stat()
  1307  	if err != nil {
  1308  		t.Fatalf("Stat %q (looking for size %d): %s", f.Name(), size, err)
  1309  	}
  1310  	if dir.Size() != size {
  1311  		t.Errorf("Stat %q: size %d want %d", f.Name(), dir.Size(), size)
  1312  	}
  1313  }
  1314  
  1315  func TestFTruncate(t *testing.T) {
  1316  	t.Parallel()
  1317  
  1318  	f := newFile(t)
  1319  
  1320  	checkSize(t, f, 0)
  1321  	f.Write([]byte("hello, world\n"))
  1322  	checkSize(t, f, 13)
  1323  	f.Truncate(10)
  1324  	checkSize(t, f, 10)
  1325  	f.Truncate(1024)
  1326  	checkSize(t, f, 1024)
  1327  	f.Truncate(0)
  1328  	checkSize(t, f, 0)
  1329  	_, err := f.Write([]byte("surprise!"))
  1330  	if err == nil {
  1331  		checkSize(t, f, 13+9) // wrote at offset past where hello, world was.
  1332  	}
  1333  }
  1334  
  1335  func TestTruncate(t *testing.T) {
  1336  	t.Parallel()
  1337  
  1338  	f := newFile(t)
  1339  
  1340  	checkSize(t, f, 0)
  1341  	f.Write([]byte("hello, world\n"))
  1342  	checkSize(t, f, 13)
  1343  	Truncate(f.Name(), 10)
  1344  	checkSize(t, f, 10)
  1345  	Truncate(f.Name(), 1024)
  1346  	checkSize(t, f, 1024)
  1347  	Truncate(f.Name(), 0)
  1348  	checkSize(t, f, 0)
  1349  	_, err := f.Write([]byte("surprise!"))
  1350  	if err == nil {
  1351  		checkSize(t, f, 13+9) // wrote at offset past where hello, world was.
  1352  	}
  1353  }
  1354  
  1355  func TestTruncateNonexistentFile(t *testing.T) {
  1356  	t.Parallel()
  1357  
  1358  	assertPathError := func(t testing.TB, path string, err error) {
  1359  		t.Helper()
  1360  		if pe, ok := err.(*PathError); !ok || !IsNotExist(err) || pe.Path != path {
  1361  			t.Errorf("got error: %v\nwant an ErrNotExist PathError with path %q", err, path)
  1362  		}
  1363  	}
  1364  
  1365  	path := filepath.Join(t.TempDir(), "nonexistent")
  1366  
  1367  	err := Truncate(path, 1)
  1368  	assertPathError(t, path, err)
  1369  
  1370  	// Truncate shouldn't create any new file.
  1371  	_, err = Stat(path)
  1372  	assertPathError(t, path, err)
  1373  }
  1374  
  1375  var hasNoatime = sync.OnceValue(func() bool {
  1376  	// A sloppy way to check if noatime flag is set (as all filesystems are
  1377  	// checked, not just the one we're interested in). A correct way
  1378  	// would be to use statvfs syscall and check if flags has ST_NOATIME,
  1379  	// but the syscall is OS-specific and is not even wired into Go stdlib.
  1380  	//
  1381  	// Only used on NetBSD (which ignores explicit atime updates with noatime).
  1382  	if runtime.GOOS != "netbsd" {
  1383  		return false
  1384  	}
  1385  	mounts, _ := ReadFile("/proc/mounts")
  1386  	return bytes.Contains(mounts, []byte("noatime"))
  1387  })
  1388  
  1389  func TestChtimes(t *testing.T) {
  1390  	t.Parallel()
  1391  
  1392  	f := newFile(t)
  1393  	// This should be an empty file (see #68687, #68663).
  1394  	f.Close()
  1395  
  1396  	testChtimes(t, f.Name())
  1397  }
  1398  
  1399  func TestChtimesOmit(t *testing.T) {
  1400  	t.Parallel()
  1401  
  1402  	testChtimesOmit(t, true, false)
  1403  	testChtimesOmit(t, false, true)
  1404  	testChtimesOmit(t, true, true)
  1405  	testChtimesOmit(t, false, false) // Same as TestChtimes.
  1406  }
  1407  
  1408  func testChtimesOmit(t *testing.T, omitAt, omitMt bool) {
  1409  	t.Logf("omit atime: %v, mtime: %v", omitAt, omitMt)
  1410  	file := newFile(t)
  1411  	// This should be an empty file (see #68687, #68663).
  1412  	name := file.Name()
  1413  	err := file.Close()
  1414  	if err != nil {
  1415  		t.Error(err)
  1416  	}
  1417  	fs, err := Stat(name)
  1418  	if err != nil {
  1419  		t.Fatal(err)
  1420  	}
  1421  
  1422  	wantAtime := Atime(fs)
  1423  	wantMtime := fs.ModTime()
  1424  	switch runtime.GOOS {
  1425  	case "js":
  1426  		wantAtime = wantAtime.Truncate(time.Second)
  1427  		wantMtime = wantMtime.Truncate(time.Second)
  1428  	}
  1429  
  1430  	var setAtime, setMtime time.Time // Zero value means omit.
  1431  	if !omitAt {
  1432  		wantAtime = wantAtime.Add(-1 * time.Second)
  1433  		setAtime = wantAtime
  1434  	}
  1435  	if !omitMt {
  1436  		wantMtime = wantMtime.Add(-1 * time.Second)
  1437  		setMtime = wantMtime
  1438  	}
  1439  
  1440  	// Change the times accordingly.
  1441  	if err := Chtimes(name, setAtime, setMtime); err != nil {
  1442  		t.Error(err)
  1443  	}
  1444  
  1445  	// Verify the expectations.
  1446  	fs, err = Stat(name)
  1447  	if err != nil {
  1448  		t.Error(err)
  1449  	}
  1450  	gotAtime := Atime(fs)
  1451  	gotMtime := fs.ModTime()
  1452  
  1453  	// TODO: remove the dragonfly omitAt && omitMt exceptions below once the
  1454  	// fix (https://github.com/DragonFlyBSD/DragonFlyBSD/commit/c7c71870ed0)
  1455  	// is available generally and on CI runners.
  1456  	if !gotAtime.Equal(wantAtime) {
  1457  		errormsg := fmt.Sprintf("atime mismatch, got: %q, want: %q", gotAtime, wantAtime)
  1458  		switch runtime.GOOS {
  1459  		case "plan9":
  1460  			// Mtime is the time of the last change of content.
  1461  			// Similarly, atime is set whenever the contents are
  1462  			// accessed; also, it is set whenever mtime is set.
  1463  		case "dragonfly":
  1464  			if omitAt && omitMt {
  1465  				t.Log(errormsg)
  1466  				t.Log("Known DragonFly BSD issue (won't work when both times are omitted); ignoring.")
  1467  			} else {
  1468  				// Assume hammer2 fs; https://www.dragonflybsd.org/hammer/ says:
  1469  				// > Because HAMMER2 is a block copy-on-write filesystem,
  1470  				// > the "atime" field is not supported and will typically
  1471  				// > just reflect local system in-memory caches or mtime.
  1472  				//
  1473  				// TODO: if only can CI define TMPDIR to point to a tmpfs
  1474  				// (e.g. /var/run/shm), this exception can be removed.
  1475  				t.Log(errormsg)
  1476  				t.Log("Known DragonFly BSD issue (atime not supported on hammer2); ignoring.")
  1477  			}
  1478  		case "netbsd":
  1479  			if !omitAt && hasNoatime() {
  1480  				t.Log(errormsg)
  1481  				t.Log("Known NetBSD issue (atime not changed on fs mounted with noatime); ignoring.")
  1482  			} else {
  1483  				t.Error(errormsg)
  1484  			}
  1485  		default:
  1486  			t.Error(errormsg)
  1487  		}
  1488  	}
  1489  	if !gotMtime.Equal(wantMtime) {
  1490  		errormsg := fmt.Sprintf("mtime mismatch, got: %q, want: %q", gotMtime, wantMtime)
  1491  		switch runtime.GOOS {
  1492  		case "dragonfly":
  1493  			if omitAt && omitMt {
  1494  				t.Log(errormsg)
  1495  				t.Log("Known DragonFly BSD issue (won't work when both times are omitted); ignoring.")
  1496  			} else {
  1497  				t.Error(errormsg)
  1498  			}
  1499  		default:
  1500  			t.Error(errormsg)
  1501  		}
  1502  	}
  1503  }
  1504  
  1505  func TestChtimesDir(t *testing.T) {
  1506  	t.Parallel()
  1507  
  1508  	testChtimes(t, t.TempDir())
  1509  }
  1510  
  1511  func testChtimes(t *testing.T, name string) {
  1512  	st, err := Stat(name)
  1513  	if err != nil {
  1514  		t.Fatalf("Stat %s: %s", name, err)
  1515  	}
  1516  	preStat := st
  1517  
  1518  	// Move access and modification time back a second
  1519  	at := Atime(preStat)
  1520  	mt := preStat.ModTime()
  1521  	err = Chtimes(name, at.Add(-time.Second), mt.Add(-time.Second))
  1522  	if err != nil {
  1523  		t.Fatalf("Chtimes %s: %s", name, err)
  1524  	}
  1525  
  1526  	st, err = Stat(name)
  1527  	if err != nil {
  1528  		t.Fatalf("second Stat %s: %s", name, err)
  1529  	}
  1530  	postStat := st
  1531  
  1532  	pat := Atime(postStat)
  1533  	pmt := postStat.ModTime()
  1534  	if !pat.Before(at) {
  1535  		errormsg := fmt.Sprintf("AccessTime didn't go backwards; was=%v, after=%v", at, pat)
  1536  		switch runtime.GOOS {
  1537  		case "plan9":
  1538  			// Mtime is the time of the last change of
  1539  			// content.  Similarly, atime is set whenever
  1540  			// the contents are accessed; also, it is set
  1541  			// whenever mtime is set.
  1542  		case "netbsd":
  1543  			if hasNoatime() {
  1544  				t.Log(errormsg)
  1545  				t.Log("Known NetBSD issue (atime not changed on fs mounted with noatime); ignoring.")
  1546  			} else {
  1547  				t.Error(errormsg)
  1548  			}
  1549  		default:
  1550  			t.Error(errormsg)
  1551  		}
  1552  	}
  1553  
  1554  	if !pmt.Before(mt) {
  1555  		t.Errorf("ModTime didn't go backwards; was=%v, after=%v", mt, pmt)
  1556  	}
  1557  }
  1558  
  1559  func TestChtimesToUnixZero(t *testing.T) {
  1560  	file := newFile(t)
  1561  	fn := file.Name()
  1562  	if _, err := file.Write([]byte("hi")); err != nil {
  1563  		t.Fatal(err)
  1564  	}
  1565  	if err := file.Close(); err != nil {
  1566  		t.Fatal(err)
  1567  	}
  1568  
  1569  	unixZero := time.Unix(0, 0)
  1570  	if err := Chtimes(fn, unixZero, unixZero); err != nil {
  1571  		t.Fatalf("Chtimes failed: %v", err)
  1572  	}
  1573  
  1574  	st, err := Stat(fn)
  1575  	if err != nil {
  1576  		t.Fatal(err)
  1577  	}
  1578  
  1579  	if mt := st.ModTime(); mt != unixZero {
  1580  		t.Errorf("mtime is %v, want %v", mt, unixZero)
  1581  	}
  1582  }
  1583  
  1584  func TestFileChdir(t *testing.T) {
  1585  	wd, err := Getwd()
  1586  	if err != nil {
  1587  		t.Fatalf("Getwd: %s", err)
  1588  	}
  1589  	t.Chdir(".") // Ensure wd is restored after the test.
  1590  
  1591  	fd, err := Open(".")
  1592  	if err != nil {
  1593  		t.Fatalf("Open .: %s", err)
  1594  	}
  1595  	defer fd.Close()
  1596  
  1597  	if err := Chdir("/"); err != nil {
  1598  		t.Fatalf("Chdir /: %s", err)
  1599  	}
  1600  
  1601  	if err := fd.Chdir(); err != nil {
  1602  		t.Fatalf("fd.Chdir: %s", err)
  1603  	}
  1604  
  1605  	wdNew, err := Getwd()
  1606  	if err != nil {
  1607  		t.Fatalf("Getwd: %s", err)
  1608  	}
  1609  
  1610  	wdInfo, err := fd.Stat()
  1611  	if err != nil {
  1612  		t.Fatal(err)
  1613  	}
  1614  	newInfo, err := Stat(wdNew)
  1615  	if err != nil {
  1616  		t.Fatal(err)
  1617  	}
  1618  	if !SameFile(wdInfo, newInfo) {
  1619  		t.Fatalf("fd.Chdir failed: got %s, want %s", wdNew, wd)
  1620  	}
  1621  }
  1622  
  1623  func TestChdirAndGetwd(t *testing.T) {
  1624  	t.Chdir(t.TempDir()) // Ensure wd is restored after the test.
  1625  
  1626  	// These are chosen carefully not to be symlinks on a Mac
  1627  	// (unlike, say, /var, /etc), except /tmp, which we handle below.
  1628  	dirs := []string{"/", "/usr/bin", "/tmp"}
  1629  	// /usr/bin does not usually exist on Plan 9 or Android.
  1630  	switch runtime.GOOS {
  1631  	case "android":
  1632  		dirs = []string{"/system/bin"}
  1633  	case "plan9":
  1634  		dirs = []string{"/", "/usr"}
  1635  	case "ios", "windows", "wasip1":
  1636  		dirs = nil
  1637  		for _, dir := range []string{t.TempDir(), t.TempDir()} {
  1638  			// Expand symlinks so path equality tests work.
  1639  			dir, err := filepath.EvalSymlinks(dir)
  1640  			if err != nil {
  1641  				t.Fatalf("EvalSymlinks: %v", err)
  1642  			}
  1643  			dirs = append(dirs, dir)
  1644  		}
  1645  	}
  1646  	for mode := 0; mode < 2; mode++ {
  1647  		for _, d := range dirs {
  1648  			var err error
  1649  			if mode == 0 {
  1650  				err = Chdir(d)
  1651  			} else {
  1652  				fd1, err1 := Open(d)
  1653  				if err1 != nil {
  1654  					t.Errorf("Open %s: %s", d, err1)
  1655  					continue
  1656  				}
  1657  				err = fd1.Chdir()
  1658  				fd1.Close()
  1659  			}
  1660  			if d == "/tmp" {
  1661  				Setenv("PWD", "/tmp")
  1662  			}
  1663  			pwd, err1 := Getwd()
  1664  			if err != nil {
  1665  				t.Fatalf("Chdir %s: %s", d, err)
  1666  			}
  1667  			if err1 != nil {
  1668  				t.Fatalf("Getwd in %s: %s", d, err1)
  1669  			}
  1670  			if !equal(pwd, d) {
  1671  				t.Fatalf("Getwd returned %q want %q", pwd, d)
  1672  			}
  1673  		}
  1674  	}
  1675  }
  1676  
  1677  // Test that Chdir+Getwd is program-wide.
  1678  func TestProgWideChdir(t *testing.T) {
  1679  	const N = 10
  1680  	var wg sync.WaitGroup
  1681  	hold := make(chan struct{})
  1682  	done := make(chan struct{})
  1683  
  1684  	d := t.TempDir()
  1685  	t.Chdir(d)
  1686  
  1687  	// Note the deferred Wait must be called after the deferred close(done),
  1688  	// to ensure the N goroutines have been released even if the main goroutine
  1689  	// calls Fatalf. It must be called before the Chdir back to the original
  1690  	// directory, and before the deferred deletion implied by TempDir,
  1691  	// so as not to interfere while the N goroutines are still running.
  1692  	defer wg.Wait()
  1693  	defer close(done)
  1694  
  1695  	for i := 0; i < N; i++ {
  1696  		wg.Add(1)
  1697  		go func(i int) {
  1698  			defer wg.Done()
  1699  			// Lock half the goroutines in their own operating system
  1700  			// thread to exercise more scheduler possibilities.
  1701  			if i%2 == 1 {
  1702  				// On Plan 9, after calling LockOSThread, the goroutines
  1703  				// run on different processes which don't share the working
  1704  				// directory. This used to be an issue because Go expects
  1705  				// the working directory to be program-wide.
  1706  				// See issue 9428.
  1707  				runtime.LockOSThread()
  1708  			}
  1709  			select {
  1710  			case <-done:
  1711  				return
  1712  			case <-hold:
  1713  			}
  1714  			// Getwd might be wrong
  1715  			f0, err := Stat(".")
  1716  			if err != nil {
  1717  				t.Error(err)
  1718  				return
  1719  			}
  1720  			pwd, err := Getwd()
  1721  			if err != nil {
  1722  				t.Errorf("Getwd: %v", err)
  1723  				return
  1724  			}
  1725  			if pwd != d {
  1726  				t.Errorf("Getwd() = %q, want %q", pwd, d)
  1727  				return
  1728  			}
  1729  			f1, err := Stat(pwd)
  1730  			if err != nil {
  1731  				t.Error(err)
  1732  				return
  1733  			}
  1734  			if !SameFile(f0, f1) {
  1735  				t.Errorf(`Samefile(Stat("."), Getwd()) reports false (%s != %s)`, f0.Name(), f1.Name())
  1736  				return
  1737  			}
  1738  		}(i)
  1739  	}
  1740  	var err error
  1741  	if err = Chdir(d); err != nil {
  1742  		t.Fatalf("Chdir: %v", err)
  1743  	}
  1744  	// OS X sets TMPDIR to a symbolic link.
  1745  	// So we resolve our working directory again before the test.
  1746  	d, err = Getwd()
  1747  	if err != nil {
  1748  		t.Fatalf("Getwd: %v", err)
  1749  	}
  1750  	close(hold)
  1751  	wg.Wait()
  1752  }
  1753  
  1754  func TestSeek(t *testing.T) {
  1755  	t.Parallel()
  1756  
  1757  	f := newFile(t)
  1758  
  1759  	const data = "hello, world\n"
  1760  	io.WriteString(f, data)
  1761  
  1762  	type test struct {
  1763  		in     int64
  1764  		whence int
  1765  		out    int64
  1766  	}
  1767  	var tests = []test{
  1768  		{0, io.SeekCurrent, int64(len(data))},
  1769  		{0, io.SeekStart, 0},
  1770  		{5, io.SeekStart, 5},
  1771  		{0, io.SeekEnd, int64(len(data))},
  1772  		{0, io.SeekStart, 0},
  1773  		{-1, io.SeekEnd, int64(len(data)) - 1},
  1774  		{1 << 33, io.SeekStart, 1 << 33},
  1775  		{1 << 33, io.SeekEnd, 1<<33 + int64(len(data))},
  1776  
  1777  		// Issue 21681, Windows 4G-1, etc:
  1778  		{1<<32 - 1, io.SeekStart, 1<<32 - 1},
  1779  		{0, io.SeekCurrent, 1<<32 - 1},
  1780  		{2<<32 - 1, io.SeekStart, 2<<32 - 1},
  1781  		{0, io.SeekCurrent, 2<<32 - 1},
  1782  	}
  1783  	for i, tt := range tests {
  1784  		off, err := f.Seek(tt.in, tt.whence)
  1785  		if off != tt.out || err != nil {
  1786  			t.Errorf("#%d: Seek(%v, %v) = %v, %v want %v, nil", i, tt.in, tt.whence, off, err, tt.out)
  1787  		}
  1788  	}
  1789  }
  1790  
  1791  func TestSeekError(t *testing.T) {
  1792  	switch runtime.GOOS {
  1793  	case "js", "plan9", "wasip1":
  1794  		t.Skipf("skipping test on %v", runtime.GOOS)
  1795  	}
  1796  	t.Parallel()
  1797  
  1798  	r, w, err := Pipe()
  1799  	if err != nil {
  1800  		t.Fatal(err)
  1801  	}
  1802  	_, err = r.Seek(0, 0)
  1803  	if err == nil {
  1804  		t.Fatal("Seek on pipe should fail")
  1805  	}
  1806  	if perr, ok := err.(*PathError); !ok || perr.Err != syscall.ESPIPE {
  1807  		t.Errorf("Seek returned error %v, want &PathError{Err: syscall.ESPIPE}", err)
  1808  	}
  1809  	_, err = w.Seek(0, 0)
  1810  	if err == nil {
  1811  		t.Fatal("Seek on pipe should fail")
  1812  	}
  1813  	if perr, ok := err.(*PathError); !ok || perr.Err != syscall.ESPIPE {
  1814  		t.Errorf("Seek returned error %v, want &PathError{Err: syscall.ESPIPE}", err)
  1815  	}
  1816  }
  1817  
  1818  func TestOpenError(t *testing.T) {
  1819  	t.Parallel()
  1820  	dir := makefs(t, []string{
  1821  		"is-a-file",
  1822  		"is-a-dir/",
  1823  	})
  1824  	t.Run("NoRoot", func(t *testing.T) { testOpenError(t, dir, false) })
  1825  	t.Run("InRoot", func(t *testing.T) { testOpenError(t, dir, true) })
  1826  }
  1827  func testOpenError(t *testing.T, dir string, rooted bool) {
  1828  	t.Parallel()
  1829  	var r *Root
  1830  	if rooted {
  1831  		var err error
  1832  		r, err = OpenRoot(dir)
  1833  		if err != nil {
  1834  			t.Fatal(err)
  1835  		}
  1836  		defer r.Close()
  1837  	}
  1838  	for _, tt := range []struct {
  1839  		path  string
  1840  		mode  int
  1841  		error error
  1842  	}{{
  1843  		"no-such-file",
  1844  		O_RDONLY,
  1845  		syscall.ENOENT,
  1846  	}, {
  1847  		"is-a-dir",
  1848  		O_WRONLY,
  1849  		syscall.EISDIR,
  1850  	}, {
  1851  		"is-a-file/no-such-file",
  1852  		O_WRONLY,
  1853  		syscall.ENOTDIR,
  1854  	}} {
  1855  		var f *File
  1856  		var err error
  1857  		var name string
  1858  		if rooted {
  1859  			name = fmt.Sprintf("Root(%q).OpenFile(%q, %d)", dir, tt.path, tt.mode)
  1860  			f, err = r.OpenFile(tt.path, tt.mode, 0)
  1861  		} else {
  1862  			path := filepath.Join(dir, tt.path)
  1863  			name = fmt.Sprintf("OpenFile(%q, %d)", path, tt.mode)
  1864  			f, err = OpenFile(path, tt.mode, 0)
  1865  		}
  1866  		if err == nil {
  1867  			t.Errorf("%v succeeded", name)
  1868  			f.Close()
  1869  			continue
  1870  		}
  1871  		perr, ok := err.(*PathError)
  1872  		if !ok {
  1873  			t.Errorf("%v returns error of %T type; want *PathError", name, err)
  1874  		}
  1875  		if perr.Err != tt.error {
  1876  			if runtime.GOOS == "plan9" {
  1877  				syscallErrStr := perr.Err.Error()
  1878  				expectedErrStr := strings.Replace(tt.error.Error(), "file ", "", 1)
  1879  				if !strings.HasSuffix(syscallErrStr, expectedErrStr) {
  1880  					// Some Plan 9 file servers incorrectly return
  1881  					// EPERM or EACCES rather than EISDIR when a directory is
  1882  					// opened for write.
  1883  					if tt.error == syscall.EISDIR &&
  1884  						(strings.HasSuffix(syscallErrStr, syscall.EPERM.Error()) ||
  1885  							strings.HasSuffix(syscallErrStr, syscall.EACCES.Error())) {
  1886  						continue
  1887  					}
  1888  					t.Errorf("%v = _, %q; want suffix %q", name, syscallErrStr, expectedErrStr)
  1889  				}
  1890  				continue
  1891  			}
  1892  			if runtime.GOOS == "dragonfly" {
  1893  				// DragonFly incorrectly returns EACCES rather
  1894  				// EISDIR when a directory is opened for write.
  1895  				if tt.error == syscall.EISDIR && perr.Err == syscall.EACCES {
  1896  					continue
  1897  				}
  1898  			}
  1899  			t.Errorf("%v = _, %q; want %q", name, perr.Err.Error(), tt.error.Error())
  1900  		}
  1901  	}
  1902  }
  1903  
  1904  func TestOpenNoName(t *testing.T) {
  1905  	f, err := Open("")
  1906  	if err == nil {
  1907  		f.Close()
  1908  		t.Fatal(`Open("") succeeded`)
  1909  	}
  1910  }
  1911  
  1912  func runBinHostname(t *testing.T) string {
  1913  	// Run /bin/hostname and collect output.
  1914  	r, w, err := Pipe()
  1915  	if err != nil {
  1916  		t.Fatal(err)
  1917  	}
  1918  	defer r.Close()
  1919  
  1920  	path, err := exec.LookPath("hostname")
  1921  	if err != nil {
  1922  		if errors.Is(err, exec.ErrNotFound) {
  1923  			t.Skip("skipping test; test requires hostname but it does not exist")
  1924  		}
  1925  		t.Fatal(err)
  1926  	}
  1927  
  1928  	argv := []string{"hostname"}
  1929  	if runtime.GOOS == "aix" {
  1930  		argv = []string{"hostname", "-s"}
  1931  	}
  1932  	p, err := StartProcess(path, argv, &ProcAttr{Files: []*File{nil, w, Stderr}})
  1933  	if err != nil {
  1934  		t.Fatal(err)
  1935  	}
  1936  	w.Close()
  1937  
  1938  	var b strings.Builder
  1939  	io.Copy(&b, r)
  1940  	_, err = p.Wait()
  1941  	if err != nil {
  1942  		t.Fatalf("run hostname Wait: %v", err)
  1943  	}
  1944  	err = p.Kill()
  1945  	if err == nil {
  1946  		t.Errorf("expected an error from Kill running 'hostname'")
  1947  	}
  1948  	output := b.String()
  1949  	if n := len(output); n > 0 && output[n-1] == '\n' {
  1950  		output = output[0 : n-1]
  1951  	}
  1952  	if output == "" {
  1953  		t.Fatalf("/bin/hostname produced no output")
  1954  	}
  1955  
  1956  	return output
  1957  }
  1958  
  1959  func testWindowsHostname(t *testing.T, hostname string) {
  1960  	cmd := testenv.Command(t, "hostname")
  1961  	out, err := cmd.Output()
  1962  	if err != nil {
  1963  		t.Fatalf("Failed to execute hostname command: %v %s", err, out)
  1964  	}
  1965  	want := strings.Trim(string(out), "\r\n")
  1966  	if hostname != want {
  1967  		t.Fatalf("Hostname() = %q != system hostname of %q", hostname, want)
  1968  	}
  1969  }
  1970  
  1971  func TestHostname(t *testing.T) {
  1972  	t.Parallel()
  1973  
  1974  	hostname, err := Hostname()
  1975  	if err != nil {
  1976  		t.Fatal(err)
  1977  	}
  1978  	if hostname == "" {
  1979  		t.Fatal("Hostname returned empty string and no error")
  1980  	}
  1981  	if strings.Contains(hostname, "\x00") {
  1982  		t.Fatalf("unexpected zero byte in hostname: %q", hostname)
  1983  	}
  1984  
  1985  	// There is no other way to fetch hostname on windows, but via winapi.
  1986  	// On Plan 9 it can be taken from #c/sysname as Hostname() does.
  1987  	switch runtime.GOOS {
  1988  	case "android", "plan9":
  1989  		// No /bin/hostname to verify against.
  1990  		return
  1991  	case "windows":
  1992  		testWindowsHostname(t, hostname)
  1993  		return
  1994  	}
  1995  
  1996  	testenv.MustHaveExec(t)
  1997  
  1998  	// Check internal Hostname() against the output of /bin/hostname.
  1999  	// Allow that the internal Hostname returns a Fully Qualified Domain Name
  2000  	// and the /bin/hostname only returns the first component
  2001  	want := runBinHostname(t)
  2002  	if hostname != want {
  2003  		host, _, ok := strings.Cut(hostname, ".")
  2004  		if !ok || host != want {
  2005  			t.Errorf("Hostname() = %q, want %q", hostname, want)
  2006  		}
  2007  	}
  2008  }
  2009  
  2010  func TestReadAt(t *testing.T) {
  2011  	t.Parallel()
  2012  
  2013  	f := newFile(t)
  2014  
  2015  	const data = "hello, world\n"
  2016  	io.WriteString(f, data)
  2017  
  2018  	b := make([]byte, 5)
  2019  	n, err := f.ReadAt(b, 7)
  2020  	if err != nil || n != len(b) {
  2021  		t.Fatalf("ReadAt 7: %d, %v", n, err)
  2022  	}
  2023  	if string(b) != "world" {
  2024  		t.Fatalf("ReadAt 7: have %q want %q", string(b), "world")
  2025  	}
  2026  }
  2027  
  2028  // Verify that ReadAt doesn't affect seek offset.
  2029  // In the Plan 9 kernel, there used to be a bug in the implementation of
  2030  // the pread syscall, where the channel offset was erroneously updated after
  2031  // calling pread on a file.
  2032  func TestReadAtOffset(t *testing.T) {
  2033  	t.Parallel()
  2034  
  2035  	f := newFile(t)
  2036  
  2037  	const data = "hello, world\n"
  2038  	io.WriteString(f, data)
  2039  
  2040  	f.Seek(0, 0)
  2041  	b := make([]byte, 5)
  2042  
  2043  	n, err := f.ReadAt(b, 7)
  2044  	if err != nil || n != len(b) {
  2045  		t.Fatalf("ReadAt 7: %d, %v", n, err)
  2046  	}
  2047  	if string(b) != "world" {
  2048  		t.Fatalf("ReadAt 7: have %q want %q", string(b), "world")
  2049  	}
  2050  
  2051  	n, err = f.Read(b)
  2052  	if err != nil || n != len(b) {
  2053  		t.Fatalf("Read: %d, %v", n, err)
  2054  	}
  2055  	if string(b) != "hello" {
  2056  		t.Fatalf("Read: have %q want %q", string(b), "hello")
  2057  	}
  2058  }
  2059  
  2060  // Verify that ReadAt doesn't allow negative offset.
  2061  func TestReadAtNegativeOffset(t *testing.T) {
  2062  	t.Parallel()
  2063  
  2064  	f := newFile(t)
  2065  
  2066  	const data = "hello, world\n"
  2067  	io.WriteString(f, data)
  2068  
  2069  	f.Seek(0, 0)
  2070  	b := make([]byte, 5)
  2071  
  2072  	n, err := f.ReadAt(b, -10)
  2073  
  2074  	const wantsub = "negative offset"
  2075  	if !strings.Contains(fmt.Sprint(err), wantsub) || n != 0 {
  2076  		t.Errorf("ReadAt(-10) = %v, %v; want 0, ...%q...", n, err, wantsub)
  2077  	}
  2078  }
  2079  
  2080  func TestWriteAt(t *testing.T) {
  2081  	t.Parallel()
  2082  
  2083  	f := newFile(t)
  2084  
  2085  	const data = "hello, world"
  2086  	io.WriteString(f, data)
  2087  
  2088  	n, err := f.WriteAt([]byte("WOR"), 7)
  2089  	if err != nil || n != 3 {
  2090  		t.Fatalf("WriteAt 7: %d, %v", n, err)
  2091  	}
  2092  	n, err = io.WriteString(f, "!") // test that WriteAt doesn't change the file offset
  2093  	if err != nil || n != 1 {
  2094  		t.Fatal(err)
  2095  	}
  2096  
  2097  	got, err := ReadFile(f.Name())
  2098  	if err != nil {
  2099  		t.Fatalf("ReadFile %s: %v", f.Name(), err)
  2100  	}
  2101  	want := "hello, WORld!"
  2102  	if string(got) != want {
  2103  		t.Fatalf("after write: have %q want %q", string(got), want)
  2104  	}
  2105  }
  2106  
  2107  func TestWriteAtConcurrent(t *testing.T) {
  2108  	t.Parallel()
  2109  
  2110  	f := newFile(t)
  2111  	io.WriteString(f, "0000000000")
  2112  
  2113  	var wg sync.WaitGroup
  2114  	for i := range 10 {
  2115  		wg.Add(1)
  2116  		go func() {
  2117  			defer wg.Done()
  2118  			n, err := f.WriteAt([]byte(strconv.Itoa(i)), int64(i))
  2119  			if err != nil || n != 1 {
  2120  				t.Errorf("WriteAt %d: %d, %v", i, n, err)
  2121  			}
  2122  			n, err = io.WriteString(f, "!") // test that WriteAt doesn't change the file offset
  2123  			if err != nil || n != 1 {
  2124  				t.Error(err)
  2125  			}
  2126  		}()
  2127  	}
  2128  	wg.Wait()
  2129  
  2130  	got, err := ReadFile(f.Name())
  2131  	if err != nil {
  2132  		t.Fatalf("ReadFile %s: %v", f.Name(), err)
  2133  	}
  2134  	want := "0123456789!!!!!!!!!!"
  2135  	if string(got) != want {
  2136  		t.Fatalf("after write: have %q want %q", string(got), want)
  2137  	}
  2138  }
  2139  
  2140  // Verify that WriteAt doesn't allow negative offset.
  2141  func TestWriteAtNegativeOffset(t *testing.T) {
  2142  	t.Parallel()
  2143  
  2144  	f := newFile(t)
  2145  
  2146  	n, err := f.WriteAt([]byte("WORLD"), -10)
  2147  
  2148  	const wantsub = "negative offset"
  2149  	if !strings.Contains(fmt.Sprint(err), wantsub) || n != 0 {
  2150  		t.Errorf("WriteAt(-10) = %v, %v; want 0, ...%q...", n, err, wantsub)
  2151  	}
  2152  }
  2153  
  2154  // Verify that WriteAt doesn't work in append mode.
  2155  func TestWriteAtInAppendMode(t *testing.T) {
  2156  	t.Chdir(t.TempDir())
  2157  	f, err := OpenFile("write_at_in_append_mode.txt", O_APPEND|O_CREATE, 0666)
  2158  	if err != nil {
  2159  		t.Fatalf("OpenFile: %v", err)
  2160  	}
  2161  	defer f.Close()
  2162  
  2163  	_, err = f.WriteAt([]byte(""), 1)
  2164  	if err != ErrWriteAtInAppendMode {
  2165  		t.Fatalf("f.WriteAt returned %v, expected %v", err, ErrWriteAtInAppendMode)
  2166  	}
  2167  }
  2168  
  2169  func writeFile(t *testing.T, r *Root, fname string, flag int, text string) string {
  2170  	t.Helper()
  2171  	var f *File
  2172  	var err error
  2173  	if r == nil {
  2174  		f, err = OpenFile(fname, flag, 0666)
  2175  	} else {
  2176  		f, err = r.OpenFile(fname, flag, 0666)
  2177  	}
  2178  	if err != nil {
  2179  		t.Fatalf("Open: %v", err)
  2180  	}
  2181  	n, err := io.WriteString(f, text)
  2182  	if err != nil {
  2183  		t.Fatalf("WriteString: %d, %v", n, err)
  2184  	}
  2185  	f.Close()
  2186  	data, err := ReadFile(fname)
  2187  	if err != nil {
  2188  		t.Fatalf("ReadFile: %v", err)
  2189  	}
  2190  	return string(data)
  2191  }
  2192  
  2193  func TestAppend(t *testing.T) {
  2194  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  2195  		const f = "append.txt"
  2196  		s := writeFile(t, r, f, O_CREATE|O_TRUNC|O_RDWR, "new")
  2197  		if s != "new" {
  2198  			t.Fatalf("writeFile: have %q want %q", s, "new")
  2199  		}
  2200  		s = writeFile(t, r, f, O_APPEND|O_RDWR, "|append")
  2201  		if s != "new|append" {
  2202  			t.Fatalf("writeFile: have %q want %q", s, "new|append")
  2203  		}
  2204  		s = writeFile(t, r, f, O_CREATE|O_APPEND|O_RDWR, "|append")
  2205  		if s != "new|append|append" {
  2206  			t.Fatalf("writeFile: have %q want %q", s, "new|append|append")
  2207  		}
  2208  		err := Remove(f)
  2209  		if err != nil {
  2210  			t.Fatalf("Remove: %v", err)
  2211  		}
  2212  		s = writeFile(t, r, f, O_CREATE|O_APPEND|O_RDWR, "new&append")
  2213  		if s != "new&append" {
  2214  			t.Fatalf("writeFile: after append have %q want %q", s, "new&append")
  2215  		}
  2216  		s = writeFile(t, r, f, O_CREATE|O_RDWR, "old")
  2217  		if s != "old&append" {
  2218  			t.Fatalf("writeFile: after create have %q want %q", s, "old&append")
  2219  		}
  2220  		s = writeFile(t, r, f, O_CREATE|O_TRUNC|O_RDWR, "new")
  2221  		if s != "new" {
  2222  			t.Fatalf("writeFile: after truncate have %q want %q", s, "new")
  2223  		}
  2224  	})
  2225  }
  2226  
  2227  // TestFilePermissions tests setting Unix permission bits on file creation.
  2228  func TestFilePermissions(t *testing.T) {
  2229  	if Getuid() == 0 {
  2230  		t.Skip("skipping test when running as root")
  2231  	}
  2232  	for _, test := range []struct {
  2233  		name string
  2234  		mode FileMode
  2235  	}{
  2236  		{"r", 0o444},
  2237  		{"w", 0o222},
  2238  		{"rw", 0o666},
  2239  	} {
  2240  		t.Run(test.name, func(t *testing.T) {
  2241  			switch runtime.GOOS {
  2242  			case "windows":
  2243  				if test.mode&0444 == 0 {
  2244  					t.Skip("write-only files not supported on " + runtime.GOOS)
  2245  				}
  2246  			case "wasip1":
  2247  				t.Skip("file permissions not supported on " + runtime.GOOS)
  2248  			}
  2249  			testMaybeRooted(t, func(t *testing.T, r *Root) {
  2250  				const filename = "f"
  2251  				var f *File
  2252  				var err error
  2253  				if r == nil {
  2254  					f, err = OpenFile(filename, O_RDWR|O_CREATE|O_EXCL, test.mode)
  2255  				} else {
  2256  					f, err = r.OpenFile(filename, O_RDWR|O_CREATE|O_EXCL, test.mode)
  2257  				}
  2258  				if err != nil {
  2259  					t.Fatal(err)
  2260  				}
  2261  				f.Close()
  2262  				b, err := ReadFile(filename)
  2263  				if test.mode&0o444 != 0 {
  2264  					if err != nil {
  2265  						t.Errorf("ReadFile = %v; want success", err)
  2266  					}
  2267  				} else {
  2268  					if err == nil {
  2269  						t.Errorf("ReadFile = %q, <nil>; want failure", string(b))
  2270  					}
  2271  				}
  2272  				_, err = Stat(filename)
  2273  				if err != nil {
  2274  					t.Errorf("Stat = %v; want success", err)
  2275  				}
  2276  				err = WriteFile(filename, nil, 0666)
  2277  				if test.mode&0o222 != 0 {
  2278  					if err != nil {
  2279  						t.Errorf("WriteFile = %v; want success", err)
  2280  						b, err := ReadFile(filename)
  2281  						t.Errorf("ReadFile: %v", err)
  2282  						t.Errorf("file contents: %q", b)
  2283  					}
  2284  				} else {
  2285  					if err == nil {
  2286  						t.Errorf("WriteFile(%q) = <nil>; want failure", filename)
  2287  						st, err := Stat(filename)
  2288  						if err == nil {
  2289  							t.Errorf("mode: %s", st.Mode())
  2290  						}
  2291  						b, err := ReadFile(filename)
  2292  						t.Errorf("ReadFile: %v", err)
  2293  						t.Errorf("file contents: %q", b)
  2294  					}
  2295  				}
  2296  			})
  2297  		})
  2298  	}
  2299  
  2300  }
  2301  
  2302  func TestOpenFileCreateExclDanglingSymlink(t *testing.T) {
  2303  	testenv.MustHaveSymlink(t)
  2304  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  2305  		const link = "link"
  2306  		if err := Symlink("does_not_exist", link); err != nil {
  2307  			t.Fatal(err)
  2308  		}
  2309  		var f *File
  2310  		var err error
  2311  		if r == nil {
  2312  			f, err = OpenFile(link, O_WRONLY|O_CREATE|O_EXCL, 0o444)
  2313  		} else {
  2314  			f, err = r.OpenFile(link, O_WRONLY|O_CREATE|O_EXCL, 0o444)
  2315  		}
  2316  		if err == nil {
  2317  			f.Close()
  2318  		}
  2319  		if !errors.Is(err, ErrExist) {
  2320  			t.Errorf("OpenFile of a dangling symlink with O_CREATE|O_EXCL = %v, want ErrExist", err)
  2321  		}
  2322  		if _, err := Stat(link); err == nil {
  2323  			t.Errorf("OpenFile of a dangling symlink with O_CREATE|O_EXCL created a file")
  2324  		}
  2325  	})
  2326  }
  2327  
  2328  // TestFileRDWRFlags tests the O_RDONLY, O_WRONLY, and O_RDWR flags.
  2329  func TestFileRDWRFlags(t *testing.T) {
  2330  	for _, test := range []struct {
  2331  		name string
  2332  		flag int
  2333  	}{
  2334  		{"O_RDONLY", O_RDONLY},
  2335  		{"O_WRONLY", O_WRONLY},
  2336  		{"O_RDWR", O_RDWR},
  2337  	} {
  2338  		t.Run(test.name, func(t *testing.T) {
  2339  			testMaybeRooted(t, func(t *testing.T, r *Root) {
  2340  				const filename = "f"
  2341  				content := []byte("content")
  2342  				if err := WriteFile(filename, content, 0666); err != nil {
  2343  					t.Fatal(err)
  2344  				}
  2345  				var f *File
  2346  				var err error
  2347  				if r == nil {
  2348  					f, err = OpenFile(filename, test.flag, 0)
  2349  				} else {
  2350  					f, err = r.OpenFile(filename, test.flag, 0)
  2351  				}
  2352  				if err != nil {
  2353  					t.Fatal(err)
  2354  				}
  2355  				defer f.Close()
  2356  				got, err := io.ReadAll(f)
  2357  				if test.flag == O_WRONLY {
  2358  					if err == nil {
  2359  						t.Errorf("read file: %q, %v; want error", got, err)
  2360  					}
  2361  				} else {
  2362  					if err != nil || !bytes.Equal(got, content) {
  2363  						t.Errorf("read file: %q, %v; want %q, <nil>", got, err, content)
  2364  					}
  2365  				}
  2366  				if _, err := f.Seek(0, 0); err != nil {
  2367  					t.Fatalf("f.Seek: %v", err)
  2368  				}
  2369  				newcontent := []byte("CONTENT")
  2370  				_, err = f.Write(newcontent)
  2371  				if test.flag == O_RDONLY {
  2372  					if err == nil {
  2373  						t.Errorf("write file: succeeded, want error")
  2374  					}
  2375  				} else {
  2376  					if err != nil {
  2377  						t.Errorf("write file: %v, want success", err)
  2378  					}
  2379  				}
  2380  				f.Close()
  2381  				got, err = ReadFile(filename)
  2382  				if err != nil {
  2383  					t.Fatal(err)
  2384  				}
  2385  				want := content
  2386  				if test.flag != O_RDONLY {
  2387  					want = newcontent
  2388  				}
  2389  				if !bytes.Equal(got, want) {
  2390  					t.Fatalf("after write, file contains %q, want %q", got, want)
  2391  				}
  2392  			})
  2393  		})
  2394  	}
  2395  }
  2396  
  2397  func TestStatDirWithTrailingSlash(t *testing.T) {
  2398  	t.Parallel()
  2399  
  2400  	// Create new temporary directory and arrange to clean it up.
  2401  	path := t.TempDir()
  2402  
  2403  	// Stat of path should succeed.
  2404  	if _, err := Stat(path); err != nil {
  2405  		t.Fatalf("stat %s failed: %s", path, err)
  2406  	}
  2407  
  2408  	// Stat of path+"/" should succeed too.
  2409  	path += "/"
  2410  	if _, err := Stat(path); err != nil {
  2411  		t.Fatalf("stat %s failed: %s", path, err)
  2412  	}
  2413  }
  2414  
  2415  func TestNilProcessStateString(t *testing.T) {
  2416  	var ps *ProcessState
  2417  	s := ps.String()
  2418  	if s != "<nil>" {
  2419  		t.Errorf("(*ProcessState)(nil).String() = %q, want %q", s, "<nil>")
  2420  	}
  2421  }
  2422  
  2423  func TestSameFile(t *testing.T) {
  2424  	t.Chdir(t.TempDir())
  2425  	fa, err := Create("a")
  2426  	if err != nil {
  2427  		t.Fatalf("Create(a): %v", err)
  2428  	}
  2429  	fa.Close()
  2430  	fb, err := Create("b")
  2431  	if err != nil {
  2432  		t.Fatalf("Create(b): %v", err)
  2433  	}
  2434  	fb.Close()
  2435  
  2436  	ia1, err := Stat("a")
  2437  	if err != nil {
  2438  		t.Fatalf("Stat(a): %v", err)
  2439  	}
  2440  	ia2, err := Stat("a")
  2441  	if err != nil {
  2442  		t.Fatalf("Stat(a): %v", err)
  2443  	}
  2444  	if !SameFile(ia1, ia2) {
  2445  		t.Errorf("files should be same")
  2446  	}
  2447  
  2448  	ib, err := Stat("b")
  2449  	if err != nil {
  2450  		t.Fatalf("Stat(b): %v", err)
  2451  	}
  2452  	if SameFile(ia1, ib) {
  2453  		t.Errorf("files should be different")
  2454  	}
  2455  }
  2456  
  2457  func testDevNullFileInfo(t *testing.T, statname, devNullName string, fi FileInfo) {
  2458  	pre := fmt.Sprintf("%s(%q): ", statname, devNullName)
  2459  	if fi.Size() != 0 {
  2460  		t.Errorf(pre+"wrong file size have %d want 0", fi.Size())
  2461  	}
  2462  	if fi.Mode()&ModeDevice == 0 {
  2463  		t.Errorf(pre+"wrong file mode %q: ModeDevice is not set", fi.Mode())
  2464  	}
  2465  	if fi.Mode()&ModeCharDevice == 0 {
  2466  		t.Errorf(pre+"wrong file mode %q: ModeCharDevice is not set", fi.Mode())
  2467  	}
  2468  	if fi.Mode().IsRegular() {
  2469  		t.Errorf(pre+"wrong file mode %q: IsRegular returns true", fi.Mode())
  2470  	}
  2471  }
  2472  
  2473  func testDevNullFile(t *testing.T, devNullName string) {
  2474  	f, err := Open(devNullName)
  2475  	if err != nil {
  2476  		t.Fatalf("Open(%s): %v", devNullName, err)
  2477  	}
  2478  	defer f.Close()
  2479  
  2480  	fi, err := f.Stat()
  2481  	if err != nil {
  2482  		t.Fatalf("Stat(%s): %v", devNullName, err)
  2483  	}
  2484  	testDevNullFileInfo(t, "f.Stat", devNullName, fi)
  2485  
  2486  	fi, err = Stat(devNullName)
  2487  	if err != nil {
  2488  		t.Fatalf("Stat(%s): %v", devNullName, err)
  2489  	}
  2490  	testDevNullFileInfo(t, "Stat", devNullName, fi)
  2491  }
  2492  
  2493  func TestDevNullFile(t *testing.T) {
  2494  	t.Parallel()
  2495  
  2496  	testDevNullFile(t, DevNull)
  2497  	if runtime.GOOS == "windows" {
  2498  		testDevNullFile(t, "./nul")
  2499  		testDevNullFile(t, "//./nul")
  2500  	}
  2501  }
  2502  
  2503  var testLargeWrite = flag.Bool("large_write", false, "run TestLargeWriteToConsole test that floods console with output")
  2504  
  2505  func TestLargeWriteToConsole(t *testing.T) {
  2506  	if !*testLargeWrite {
  2507  		t.Skip("skipping console-flooding test; enable with -large_write")
  2508  	}
  2509  	b := make([]byte, 32000)
  2510  	for i := range b {
  2511  		b[i] = '.'
  2512  	}
  2513  	b[len(b)-1] = '\n'
  2514  	n, err := Stdout.Write(b)
  2515  	if err != nil {
  2516  		t.Fatalf("Write to os.Stdout failed: %v", err)
  2517  	}
  2518  	if n != len(b) {
  2519  		t.Errorf("Write to os.Stdout should return %d; got %d", len(b), n)
  2520  	}
  2521  	n, err = Stderr.Write(b)
  2522  	if err != nil {
  2523  		t.Fatalf("Write to os.Stderr failed: %v", err)
  2524  	}
  2525  	if n != len(b) {
  2526  		t.Errorf("Write to os.Stderr should return %d; got %d", len(b), n)
  2527  	}
  2528  }
  2529  
  2530  func TestStatDirModeExec(t *testing.T) {
  2531  	if runtime.GOOS == "wasip1" {
  2532  		t.Skip("Chmod is not supported on " + runtime.GOOS)
  2533  	}
  2534  	t.Parallel()
  2535  
  2536  	const mode = 0111
  2537  
  2538  	path := t.TempDir()
  2539  	if err := Chmod(path, 0777); err != nil {
  2540  		t.Fatalf("Chmod %q 0777: %v", path, err)
  2541  	}
  2542  
  2543  	dir, err := Stat(path)
  2544  	if err != nil {
  2545  		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
  2546  	}
  2547  	if dir.Mode()&mode != mode {
  2548  		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode()&mode, mode)
  2549  	}
  2550  }
  2551  
  2552  func TestStatStdin(t *testing.T) {
  2553  	switch runtime.GOOS {
  2554  	case "android", "plan9":
  2555  		t.Skipf("%s doesn't have /bin/sh", runtime.GOOS)
  2556  	}
  2557  
  2558  	if Getenv("GO_WANT_HELPER_PROCESS") == "1" {
  2559  		st, err := Stdin.Stat()
  2560  		if err != nil {
  2561  			t.Fatalf("Stat failed: %v", err)
  2562  		}
  2563  		fmt.Println(st.Mode() & ModeNamedPipe)
  2564  		Exit(0)
  2565  	}
  2566  
  2567  	t.Parallel()
  2568  	exe := testenv.Executable(t)
  2569  
  2570  	fi, err := Stdin.Stat()
  2571  	if err != nil {
  2572  		t.Fatal(err)
  2573  	}
  2574  	switch mode := fi.Mode(); {
  2575  	case mode&ModeCharDevice != 0 && mode&ModeDevice != 0:
  2576  	case mode&ModeNamedPipe != 0:
  2577  	default:
  2578  		t.Fatalf("unexpected Stdin mode (%v), want ModeCharDevice or ModeNamedPipe", mode)
  2579  	}
  2580  
  2581  	cmd := testenv.Command(t, exe, "-test.run=^TestStatStdin$")
  2582  	cmd = testenv.CleanCmdEnv(cmd)
  2583  	cmd.Env = append(cmd.Env, "GO_WANT_HELPER_PROCESS=1")
  2584  	// This will make standard input a pipe.
  2585  	cmd.Stdin = strings.NewReader("output")
  2586  
  2587  	output, err := cmd.CombinedOutput()
  2588  	if err != nil {
  2589  		t.Fatalf("Failed to spawn child process: %v %q", err, string(output))
  2590  	}
  2591  
  2592  	// result will be like "prw-rw-rw"
  2593  	if len(output) < 1 || output[0] != 'p' {
  2594  		t.Fatalf("Child process reports stdin is not pipe '%v'", string(output))
  2595  	}
  2596  }
  2597  
  2598  func TestStatRelativeSymlink(t *testing.T) {
  2599  	testenv.MustHaveSymlink(t)
  2600  	t.Parallel()
  2601  
  2602  	tmpdir := t.TempDir()
  2603  	target := filepath.Join(tmpdir, "target")
  2604  	f, err := Create(target)
  2605  	if err != nil {
  2606  		t.Fatal(err)
  2607  	}
  2608  	defer f.Close()
  2609  
  2610  	st, err := f.Stat()
  2611  	if err != nil {
  2612  		t.Fatal(err)
  2613  	}
  2614  
  2615  	link := filepath.Join(tmpdir, "link")
  2616  	err = Symlink(filepath.Base(target), link)
  2617  	if err != nil {
  2618  		t.Fatal(err)
  2619  	}
  2620  
  2621  	st1, err := Stat(link)
  2622  	if err != nil {
  2623  		t.Fatal(err)
  2624  	}
  2625  
  2626  	if !SameFile(st, st1) {
  2627  		t.Error("Stat doesn't follow relative symlink")
  2628  	}
  2629  
  2630  	if runtime.GOOS == "windows" {
  2631  		Remove(link)
  2632  		err = Symlink(target[len(filepath.VolumeName(target)):], link)
  2633  		if err != nil {
  2634  			t.Fatal(err)
  2635  		}
  2636  
  2637  		st1, err := Stat(link)
  2638  		if err != nil {
  2639  			t.Fatal(err)
  2640  		}
  2641  
  2642  		if !SameFile(st, st1) {
  2643  			t.Error("Stat doesn't follow relative symlink")
  2644  		}
  2645  	}
  2646  }
  2647  
  2648  func TestReadAtEOF(t *testing.T) {
  2649  	t.Parallel()
  2650  
  2651  	f := newFile(t)
  2652  
  2653  	_, err := f.ReadAt(make([]byte, 10), 0)
  2654  	switch err {
  2655  	case io.EOF:
  2656  		// all good
  2657  	case nil:
  2658  		t.Fatalf("ReadAt succeeded")
  2659  	default:
  2660  		t.Fatalf("ReadAt failed: %s", err)
  2661  	}
  2662  }
  2663  
  2664  func TestLongPath(t *testing.T) {
  2665  	t.Parallel()
  2666  
  2667  	tmpdir := t.TempDir()
  2668  
  2669  	// Test the boundary of 247 and fewer bytes (normal) and 248 and more bytes (adjusted).
  2670  	sizes := []int{247, 248, 249, 400}
  2671  	for len(tmpdir) < 400 {
  2672  		tmpdir += "/dir3456789"
  2673  	}
  2674  	for _, sz := range sizes {
  2675  		t.Run(fmt.Sprintf("length=%d", sz), func(t *testing.T) {
  2676  			sizedTempDir := tmpdir[:sz-1] + "x" // Ensure it does not end with a slash.
  2677  
  2678  			// The various sized runs are for this call to trigger the boundary
  2679  			// condition.
  2680  			if err := MkdirAll(sizedTempDir, 0755); err != nil {
  2681  				t.Fatalf("MkdirAll failed: %v", err)
  2682  			}
  2683  			data := []byte("hello world\n")
  2684  			if err := WriteFile(sizedTempDir+"/foo.txt", data, 0644); err != nil {
  2685  				t.Fatalf("os.WriteFile() failed: %v", err)
  2686  			}
  2687  			if err := Rename(sizedTempDir+"/foo.txt", sizedTempDir+"/bar.txt"); err != nil {
  2688  				t.Fatalf("Rename failed: %v", err)
  2689  			}
  2690  			mtime := time.Now().Truncate(time.Minute)
  2691  			if err := Chtimes(sizedTempDir+"/bar.txt", mtime, mtime); err != nil {
  2692  				t.Fatalf("Chtimes failed: %v", err)
  2693  			}
  2694  			names := []string{"bar.txt"}
  2695  			if testenv.HasSymlink() {
  2696  				if err := Symlink(sizedTempDir+"/bar.txt", sizedTempDir+"/symlink.txt"); err != nil {
  2697  					t.Fatalf("Symlink failed: %v", err)
  2698  				}
  2699  				names = append(names, "symlink.txt")
  2700  			}
  2701  			if testenv.HasLink() {
  2702  				if err := Link(sizedTempDir+"/bar.txt", sizedTempDir+"/link.txt"); err != nil {
  2703  					t.Fatalf("Link failed: %v", err)
  2704  				}
  2705  				names = append(names, "link.txt")
  2706  			}
  2707  			for _, wantSize := range []int64{int64(len(data)), 0} {
  2708  				for _, name := range names {
  2709  					path := sizedTempDir + "/" + name
  2710  					dir, err := Stat(path)
  2711  					if err != nil {
  2712  						t.Fatalf("Stat(%q) failed: %v", path, err)
  2713  					}
  2714  					filesize := size(path, t)
  2715  					if dir.Size() != filesize || filesize != wantSize {
  2716  						t.Errorf("Size(%q) is %d, len(ReadFile()) is %d, want %d", path, dir.Size(), filesize, wantSize)
  2717  					}
  2718  					if runtime.GOOS != "wasip1" { // Chmod is not supported on wasip1
  2719  						err = Chmod(path, dir.Mode())
  2720  						if err != nil {
  2721  							t.Fatalf("Chmod(%q) failed: %v", path, err)
  2722  						}
  2723  					}
  2724  				}
  2725  				if err := Truncate(sizedTempDir+"/bar.txt", 0); err != nil {
  2726  					t.Fatalf("Truncate failed: %v", err)
  2727  				}
  2728  			}
  2729  		})
  2730  	}
  2731  }
  2732  
  2733  func testKillProcess(t *testing.T, processKiller func(p *Process)) {
  2734  	t.Parallel()
  2735  
  2736  	// Re-exec the test binary to start a process that hangs until stdin is closed.
  2737  	cmd := testenv.Command(t, testenv.Executable(t))
  2738  	cmd.Env = append(cmd.Environ(), "GO_OS_TEST_DRAIN_STDIN=1")
  2739  	stdout, err := cmd.StdoutPipe()
  2740  	if err != nil {
  2741  		t.Fatal(err)
  2742  	}
  2743  	stdin, err := cmd.StdinPipe()
  2744  	if err != nil {
  2745  		t.Fatal(err)
  2746  	}
  2747  	err = cmd.Start()
  2748  	if err != nil {
  2749  		t.Fatalf("Failed to start test process: %v", err)
  2750  	}
  2751  
  2752  	defer func() {
  2753  		if err := cmd.Wait(); err == nil {
  2754  			t.Errorf("Test process succeeded, but expected to fail")
  2755  		}
  2756  		stdin.Close() // Keep stdin alive until the process has finished dying.
  2757  	}()
  2758  
  2759  	// Wait for the process to be started.
  2760  	// (It will close its stdout when it reaches TestMain.)
  2761  	io.Copy(io.Discard, stdout)
  2762  
  2763  	processKiller(cmd.Process)
  2764  }
  2765  
  2766  func TestKillStartProcess(t *testing.T) {
  2767  	testKillProcess(t, func(p *Process) {
  2768  		err := p.Kill()
  2769  		if err != nil {
  2770  			t.Fatalf("Failed to kill test process: %v", err)
  2771  		}
  2772  	})
  2773  }
  2774  
  2775  func TestGetppid(t *testing.T) {
  2776  	if runtime.GOOS == "plan9" {
  2777  		// TODO: golang.org/issue/8206
  2778  		t.Skipf("skipping test on plan9; see issue 8206")
  2779  	}
  2780  
  2781  	if Getenv("GO_WANT_HELPER_PROCESS") == "1" {
  2782  		fmt.Print(Getppid())
  2783  		Exit(0)
  2784  	}
  2785  
  2786  	t.Parallel()
  2787  
  2788  	cmd := testenv.Command(t, testenv.Executable(t), "-test.run=^TestGetppid$")
  2789  	cmd.Env = append(Environ(), "GO_WANT_HELPER_PROCESS=1")
  2790  
  2791  	// verify that Getppid() from the forked process reports our process id
  2792  	output, err := cmd.CombinedOutput()
  2793  	if err != nil {
  2794  		t.Fatalf("Failed to spawn child process: %v %q", err, string(output))
  2795  	}
  2796  
  2797  	childPpid := string(output)
  2798  	ourPid := fmt.Sprintf("%d", Getpid())
  2799  	if childPpid != ourPid {
  2800  		t.Fatalf("Child process reports parent process id '%v', expected '%v'", childPpid, ourPid)
  2801  	}
  2802  }
  2803  
  2804  func TestKillFindProcess(t *testing.T) {
  2805  	testKillProcess(t, func(p *Process) {
  2806  		p2, err := FindProcess(p.Pid)
  2807  		if err != nil {
  2808  			t.Fatalf("Failed to find test process: %v", err)
  2809  		}
  2810  		err = p2.Kill()
  2811  		if err != nil {
  2812  			t.Fatalf("Failed to kill test process: %v", err)
  2813  		}
  2814  	})
  2815  }
  2816  
  2817  var nilFileMethodTests = []struct {
  2818  	name string
  2819  	f    func(*File) error
  2820  }{
  2821  	{"Chdir", func(f *File) error { return f.Chdir() }},
  2822  	{"Close", func(f *File) error { return f.Close() }},
  2823  	{"Chmod", func(f *File) error { return f.Chmod(0) }},
  2824  	{"Chown", func(f *File) error { return f.Chown(0, 0) }},
  2825  	{"Read", func(f *File) error { _, err := f.Read(make([]byte, 0)); return err }},
  2826  	{"ReadAt", func(f *File) error { _, err := f.ReadAt(make([]byte, 0), 0); return err }},
  2827  	{"Readdir", func(f *File) error { _, err := f.Readdir(1); return err }},
  2828  	{"Readdirnames", func(f *File) error { _, err := f.Readdirnames(1); return err }},
  2829  	{"Seek", func(f *File) error { _, err := f.Seek(0, io.SeekStart); return err }},
  2830  	{"Stat", func(f *File) error { _, err := f.Stat(); return err }},
  2831  	{"Sync", func(f *File) error { return f.Sync() }},
  2832  	{"Truncate", func(f *File) error { return f.Truncate(0) }},
  2833  	{"Write", func(f *File) error { _, err := f.Write(make([]byte, 0)); return err }},
  2834  	{"WriteAt", func(f *File) error { _, err := f.WriteAt(make([]byte, 0), 0); return err }},
  2835  	{"WriteString", func(f *File) error { _, err := f.WriteString(""); return err }},
  2836  }
  2837  
  2838  // Test that all File methods give ErrInvalid if the receiver is nil.
  2839  func TestNilFileMethods(t *testing.T) {
  2840  	t.Parallel()
  2841  
  2842  	for _, tt := range nilFileMethodTests {
  2843  		var file *File
  2844  		got := tt.f(file)
  2845  		if got != ErrInvalid {
  2846  			t.Errorf("%v should fail when f is nil; got %v", tt.name, got)
  2847  		}
  2848  	}
  2849  }
  2850  
  2851  func mkdirTree(t *testing.T, root string, level, max int) {
  2852  	if level >= max {
  2853  		return
  2854  	}
  2855  	level++
  2856  	for i := 'a'; i < 'c'; i++ {
  2857  		dir := filepath.Join(root, string(i))
  2858  		if err := Mkdir(dir, 0700); err != nil {
  2859  			t.Fatal(err)
  2860  		}
  2861  		mkdirTree(t, dir, level, max)
  2862  	}
  2863  }
  2864  
  2865  // Test that simultaneous RemoveAll do not report an error.
  2866  // As long as it gets removed, we should be happy.
  2867  func TestRemoveAllRace(t *testing.T) {
  2868  	if runtime.GOOS == "windows" {
  2869  		// Windows has very strict rules about things like
  2870  		// removing directories while someone else has
  2871  		// them open. The racing doesn't work out nicely
  2872  		// like it does on Unix.
  2873  		t.Skip("skipping on windows")
  2874  	}
  2875  	if runtime.GOOS == "dragonfly" {
  2876  		testenv.SkipFlaky(t, 52301)
  2877  	}
  2878  
  2879  	n := runtime.GOMAXPROCS(16)
  2880  	defer runtime.GOMAXPROCS(n)
  2881  	root := t.TempDir()
  2882  	mkdirTree(t, root, 1, 6)
  2883  	hold := make(chan struct{})
  2884  	var wg sync.WaitGroup
  2885  	for i := 0; i < 4; i++ {
  2886  		wg.Add(1)
  2887  		go func() {
  2888  			defer wg.Done()
  2889  			<-hold
  2890  			err := RemoveAll(root)
  2891  			if err != nil {
  2892  				t.Errorf("unexpected error: %T, %q", err, err)
  2893  			}
  2894  		}()
  2895  	}
  2896  	close(hold) // let workers race to remove root
  2897  	wg.Wait()
  2898  }
  2899  
  2900  // Test that reading from a pipe doesn't use up a thread.
  2901  func TestPipeThreads(t *testing.T) {
  2902  	switch runtime.GOOS {
  2903  	case "aix":
  2904  		t.Skip("skipping on aix; issue 70131")
  2905  	case "illumos", "solaris":
  2906  		t.Skip("skipping on Solaris and illumos; issue 19111")
  2907  	case "windows":
  2908  		t.Skip("skipping on Windows; issue 19098")
  2909  	case "plan9":
  2910  		t.Skip("skipping on Plan 9; does not support runtime poller")
  2911  	case "js":
  2912  		t.Skip("skipping on js; no support for os.Pipe")
  2913  	case "wasip1":
  2914  		t.Skip("skipping on wasip1; no support for os.Pipe")
  2915  	}
  2916  
  2917  	threads := 100
  2918  
  2919  	r := make([]*File, threads)
  2920  	w := make([]*File, threads)
  2921  	for i := 0; i < threads; i++ {
  2922  		rp, wp, err := Pipe()
  2923  		if err != nil {
  2924  			for j := 0; j < i; j++ {
  2925  				r[j].Close()
  2926  				w[j].Close()
  2927  			}
  2928  			t.Fatal(err)
  2929  		}
  2930  		r[i] = rp
  2931  		w[i] = wp
  2932  	}
  2933  
  2934  	defer debug.SetMaxThreads(debug.SetMaxThreads(threads / 2))
  2935  
  2936  	creading := make(chan bool, threads)
  2937  	cdone := make(chan bool, threads)
  2938  	for i := 0; i < threads; i++ {
  2939  		go func(i int) {
  2940  			var b [1]byte
  2941  			creading <- true
  2942  			if _, err := r[i].Read(b[:]); err != nil {
  2943  				t.Error(err)
  2944  			}
  2945  			if err := r[i].Close(); err != nil {
  2946  				t.Error(err)
  2947  			}
  2948  			cdone <- true
  2949  		}(i)
  2950  	}
  2951  
  2952  	for i := 0; i < threads; i++ {
  2953  		<-creading
  2954  	}
  2955  
  2956  	// If we are still alive, it means that the 100 goroutines did
  2957  	// not require 100 threads.
  2958  
  2959  	for i := 0; i < threads; i++ {
  2960  		if _, err := w[i].Write([]byte{0}); err != nil {
  2961  			t.Error(err)
  2962  		}
  2963  		if err := w[i].Close(); err != nil {
  2964  			t.Error(err)
  2965  		}
  2966  		<-cdone
  2967  	}
  2968  }
  2969  
  2970  func testDoubleCloseError(path string) func(*testing.T) {
  2971  	return func(t *testing.T) {
  2972  		t.Parallel()
  2973  
  2974  		file, err := Open(path)
  2975  		if err != nil {
  2976  			t.Fatal(err)
  2977  		}
  2978  		if err := file.Close(); err != nil {
  2979  			t.Fatalf("unexpected error from Close: %v", err)
  2980  		}
  2981  		if err := file.Close(); err == nil {
  2982  			t.Error("second Close did not fail")
  2983  		} else if pe, ok := err.(*PathError); !ok {
  2984  			t.Errorf("second Close: got %T, want %T", err, pe)
  2985  		} else if pe.Err != ErrClosed {
  2986  			t.Errorf("second Close: got %q, want %q", pe.Err, ErrClosed)
  2987  		} else {
  2988  			t.Logf("second close returned expected error %q", err)
  2989  		}
  2990  	}
  2991  }
  2992  
  2993  func TestDoubleCloseError(t *testing.T) {
  2994  	t.Parallel()
  2995  	t.Run("file", testDoubleCloseError(filepath.Join(sfdir, sfname)))
  2996  	t.Run("dir", testDoubleCloseError(sfdir))
  2997  }
  2998  
  2999  func TestUserCacheDir(t *testing.T) {
  3000  	t.Parallel()
  3001  
  3002  	dir, err := UserCacheDir()
  3003  	if err != nil {
  3004  		t.Skipf("skipping: %v", err)
  3005  	}
  3006  	if dir == "" {
  3007  		t.Fatalf("UserCacheDir returned %q; want non-empty path or error", dir)
  3008  	}
  3009  
  3010  	fi, err := Stat(dir)
  3011  	if err != nil {
  3012  		if IsNotExist(err) {
  3013  			t.Log(err)
  3014  			return
  3015  		}
  3016  		t.Fatal(err)
  3017  	}
  3018  	if !fi.IsDir() {
  3019  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3020  	}
  3021  }
  3022  
  3023  func TestUserCacheDirXDGConfigDirEnvVar(t *testing.T) {
  3024  	switch runtime.GOOS {
  3025  	case "windows", "darwin", "plan9":
  3026  		t.Skip("$XDG_CACHE_HOME is effective only on Unix systems")
  3027  	}
  3028  
  3029  	wd, err := Getwd()
  3030  	if err != nil {
  3031  		t.Fatal(err)
  3032  	}
  3033  	t.Setenv("XDG_CACHE_HOME", wd)
  3034  
  3035  	dir, err := UserCacheDir()
  3036  	if err != nil {
  3037  		t.Fatal(err)
  3038  	}
  3039  	if dir != wd {
  3040  		t.Fatalf("UserCacheDir returned %q; want the value of $XDG_CACHE_HOME %q", dir, wd)
  3041  	}
  3042  
  3043  	t.Setenv("XDG_CACHE_HOME", "some-dir")
  3044  	_, err = UserCacheDir()
  3045  	if err == nil {
  3046  		t.Fatal("UserCacheDir succeeded though $XDG_CACHE_HOME contains a relative path")
  3047  	}
  3048  }
  3049  
  3050  func TestUserConfigDir(t *testing.T) {
  3051  	t.Parallel()
  3052  
  3053  	dir, err := UserConfigDir()
  3054  	if err != nil {
  3055  		t.Skipf("skipping: %v", err)
  3056  	}
  3057  	if dir == "" {
  3058  		t.Fatalf("UserConfigDir returned %q; want non-empty path or error", dir)
  3059  	}
  3060  
  3061  	fi, err := Stat(dir)
  3062  	if err != nil {
  3063  		if IsNotExist(err) {
  3064  			t.Log(err)
  3065  			return
  3066  		}
  3067  		t.Fatal(err)
  3068  	}
  3069  	if !fi.IsDir() {
  3070  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3071  	}
  3072  }
  3073  
  3074  func TestUserConfigDirXDGConfigDirEnvVar(t *testing.T) {
  3075  	switch runtime.GOOS {
  3076  	case "windows", "darwin", "plan9":
  3077  		t.Skip("$XDG_CONFIG_HOME is effective only on Unix systems")
  3078  	}
  3079  
  3080  	wd, err := Getwd()
  3081  	if err != nil {
  3082  		t.Fatal(err)
  3083  	}
  3084  	t.Setenv("XDG_CONFIG_HOME", wd)
  3085  
  3086  	dir, err := UserConfigDir()
  3087  	if err != nil {
  3088  		t.Fatal(err)
  3089  	}
  3090  	if dir != wd {
  3091  		t.Fatalf("UserConfigDir returned %q; want the value of $XDG_CONFIG_HOME %q", dir, wd)
  3092  	}
  3093  
  3094  	t.Setenv("XDG_CONFIG_HOME", "some-dir")
  3095  	_, err = UserConfigDir()
  3096  	if err == nil {
  3097  		t.Fatal("UserConfigDir succeeded though $XDG_CONFIG_HOME contains a relative path")
  3098  	}
  3099  }
  3100  
  3101  func TestUserHomeDir(t *testing.T) {
  3102  	t.Parallel()
  3103  
  3104  	dir, err := UserHomeDir()
  3105  	if dir == "" && err == nil {
  3106  		t.Fatal("UserHomeDir returned an empty string but no error")
  3107  	}
  3108  	if err != nil {
  3109  		// UserHomeDir may return a non-nil error if the environment variable
  3110  		// for the home directory is empty or unset in the environment.
  3111  		t.Skipf("skipping: %v", err)
  3112  	}
  3113  
  3114  	fi, err := Stat(dir)
  3115  	if err != nil {
  3116  		if IsNotExist(err) {
  3117  			// The user's home directory has a well-defined location, but does not
  3118  			// exist. (Maybe nothing has written to it yet? That could happen, for
  3119  			// example, on minimal VM images used for CI testing.)
  3120  			t.Log(err)
  3121  			return
  3122  		}
  3123  		t.Fatal(err)
  3124  	}
  3125  	if !fi.IsDir() {
  3126  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3127  	}
  3128  }
  3129  
  3130  func TestDirSeek(t *testing.T) {
  3131  	t.Parallel()
  3132  
  3133  	wd, err := Getwd()
  3134  	if err != nil {
  3135  		t.Fatal(err)
  3136  	}
  3137  	f, err := Open(wd)
  3138  	if err != nil {
  3139  		t.Fatal(err)
  3140  	}
  3141  	dirnames1, err := f.Readdirnames(0)
  3142  	if err != nil {
  3143  		t.Fatal(err)
  3144  	}
  3145  
  3146  	ret, err := f.Seek(0, 0)
  3147  	if err != nil {
  3148  		t.Fatal(err)
  3149  	}
  3150  	if ret != 0 {
  3151  		t.Fatalf("seek result not zero: %d", ret)
  3152  	}
  3153  
  3154  	dirnames2, err := f.Readdirnames(0)
  3155  	if err != nil {
  3156  		t.Fatal(err)
  3157  	}
  3158  
  3159  	if len(dirnames1) != len(dirnames2) {
  3160  		t.Fatalf("listings have different lengths: %d and %d\n", len(dirnames1), len(dirnames2))
  3161  	}
  3162  	for i, n1 := range dirnames1 {
  3163  		n2 := dirnames2[i]
  3164  		if n1 != n2 {
  3165  			t.Fatalf("different name i=%d n1=%s n2=%s\n", i, n1, n2)
  3166  		}
  3167  	}
  3168  }
  3169  
  3170  func TestReaddirSmallSeek(t *testing.T) {
  3171  	// See issue 37161. Read only one entry from a directory,
  3172  	// seek to the beginning, and read again. We should not see
  3173  	// duplicate entries.
  3174  	t.Parallel()
  3175  
  3176  	wd, err := Getwd()
  3177  	if err != nil {
  3178  		t.Fatal(err)
  3179  	}
  3180  	df, err := Open(filepath.Join(wd, "testdata", "issue37161"))
  3181  	if err != nil {
  3182  		t.Fatal(err)
  3183  	}
  3184  	names1, err := df.Readdirnames(1)
  3185  	if err != nil {
  3186  		t.Fatal(err)
  3187  	}
  3188  	if _, err = df.Seek(0, 0); err != nil {
  3189  		t.Fatal(err)
  3190  	}
  3191  	names2, err := df.Readdirnames(0)
  3192  	if err != nil {
  3193  		t.Fatal(err)
  3194  	}
  3195  	if len(names2) != 3 {
  3196  		t.Fatalf("first names: %v, second names: %v", names1, names2)
  3197  	}
  3198  }
  3199  
  3200  // isDeadlineExceeded reports whether err is or wraps ErrDeadlineExceeded.
  3201  // We also check that the error has a Timeout method that returns true.
  3202  func isDeadlineExceeded(err error) bool {
  3203  	if !IsTimeout(err) {
  3204  		return false
  3205  	}
  3206  	if !errors.Is(err, ErrDeadlineExceeded) {
  3207  		return false
  3208  	}
  3209  	return true
  3210  }
  3211  
  3212  // Test that opening a file does not change its permissions.  Issue 38225.
  3213  func TestOpenFileKeepsPermissions(t *testing.T) {
  3214  	t.Run("OpenFile", func(t *testing.T) {
  3215  		testOpenFileKeepsPermissions(t, OpenFile)
  3216  	})
  3217  	t.Run("RootOpenFile", func(t *testing.T) {
  3218  		testOpenFileKeepsPermissions(t, func(name string, flag int, perm FileMode) (*File, error) {
  3219  			dir, file := filepath.Split(name)
  3220  			r, err := OpenRoot(dir)
  3221  			if err != nil {
  3222  				return nil, err
  3223  			}
  3224  			defer r.Close()
  3225  			return r.OpenFile(file, flag, perm)
  3226  		})
  3227  	})
  3228  }
  3229  func testOpenFileKeepsPermissions(t *testing.T, openf func(name string, flag int, perm FileMode) (*File, error)) {
  3230  	t.Parallel()
  3231  
  3232  	dir := t.TempDir()
  3233  	name := filepath.Join(dir, "x")
  3234  	f, err := Create(name)
  3235  	if err != nil {
  3236  		t.Fatal(err)
  3237  	}
  3238  	if err := f.Close(); err != nil {
  3239  		t.Error(err)
  3240  	}
  3241  	f, err = openf(name, O_WRONLY|O_CREATE|O_TRUNC, 0)
  3242  	if err != nil {
  3243  		t.Fatal(err)
  3244  	}
  3245  	if fi, err := f.Stat(); err != nil {
  3246  		t.Error(err)
  3247  	} else if fi.Mode()&0222 == 0 {
  3248  		t.Errorf("f.Stat.Mode after OpenFile is %v, should be writable", fi.Mode())
  3249  	}
  3250  	if err := f.Close(); err != nil {
  3251  		t.Error(err)
  3252  	}
  3253  	if fi, err := Stat(name); err != nil {
  3254  		t.Error(err)
  3255  	} else if fi.Mode()&0222 == 0 {
  3256  		t.Errorf("Stat after OpenFile is %v, should be writable", fi.Mode())
  3257  	}
  3258  }
  3259  
  3260  func forceMFTUpdateOnWindows(t *testing.T, path string) {
  3261  	t.Helper()
  3262  
  3263  	if runtime.GOOS != "windows" {
  3264  		return
  3265  	}
  3266  
  3267  	// On Windows, we force the MFT to update by reading the actual metadata from GetFileInformationByHandle and then
  3268  	// explicitly setting that. Otherwise it might get out of sync with FindFirstFile. See golang.org/issues/42637.
  3269  	if err := filepath.WalkDir(path, func(path string, d fs.DirEntry, err error) error {
  3270  		if err != nil {
  3271  			t.Fatal(err)
  3272  		}
  3273  		info, err := d.Info()
  3274  		if err != nil {
  3275  			t.Fatal(err)
  3276  		}
  3277  		stat, err := Stat(path) // This uses GetFileInformationByHandle internally.
  3278  		if err != nil {
  3279  			t.Fatal(err)
  3280  		}
  3281  		if stat.ModTime() == info.ModTime() {
  3282  			return nil
  3283  		}
  3284  		if err := Chtimes(path, stat.ModTime(), stat.ModTime()); err != nil {
  3285  			t.Log(err) // We only log, not die, in case the test directory is not writable.
  3286  		}
  3287  		return nil
  3288  	}); err != nil {
  3289  		t.Fatal(err)
  3290  	}
  3291  }
  3292  
  3293  func TestDirFS(t *testing.T) {
  3294  	t.Parallel()
  3295  	testDirFS(t, DirFS("./testdata/dirfs"))
  3296  }
  3297  
  3298  func TestRootDirFS(t *testing.T) {
  3299  	t.Parallel()
  3300  	r, err := OpenRoot("./testdata/dirfs")
  3301  	if err != nil {
  3302  		t.Fatal(err)
  3303  	}
  3304  	defer r.Close()
  3305  	testDirFS(t, r.FS())
  3306  }
  3307  
  3308  func testDirFS(t *testing.T, fsys fs.FS) {
  3309  	forceMFTUpdateOnWindows(t, "./testdata/dirfs")
  3310  
  3311  	if err := fstest.TestFS(fsys, "a", "b", "dir/x"); err != nil {
  3312  		t.Fatal(err)
  3313  	}
  3314  
  3315  	rdfs, ok := fsys.(fs.ReadDirFS)
  3316  	if !ok {
  3317  		t.Error("expected DirFS result to implement fs.ReadDirFS")
  3318  	}
  3319  	if _, err := rdfs.ReadDir("nonexistent"); err == nil {
  3320  		t.Error("fs.ReadDir of nonexistent directory succeeded")
  3321  	}
  3322  
  3323  	// Test that the error message does not contain a backslash,
  3324  	// and does not contain the DirFS argument.
  3325  	const nonesuch = "dir/nonesuch"
  3326  	_, err := fsys.Open(nonesuch)
  3327  	if err == nil {
  3328  		t.Error("fs.Open of nonexistent file succeeded")
  3329  	} else {
  3330  		if !strings.Contains(err.Error(), nonesuch) {
  3331  			t.Errorf("error %q does not contain %q", err, nonesuch)
  3332  		}
  3333  		if strings.Contains(err.(*PathError).Path, "testdata") {
  3334  			t.Errorf("error %q contains %q", err, "testdata")
  3335  		}
  3336  	}
  3337  
  3338  	// Test that Open does not accept backslash as separator.
  3339  	d := DirFS(".")
  3340  	_, err = d.Open(`testdata\dirfs`)
  3341  	if err == nil {
  3342  		t.Fatalf(`Open testdata\dirfs succeeded`)
  3343  	}
  3344  
  3345  	// Test that Open does not open Windows device files.
  3346  	_, err = d.Open(`NUL`)
  3347  	if err == nil {
  3348  		t.Errorf(`Open NUL succeeded`)
  3349  	}
  3350  }
  3351  
  3352  func TestDirFSRootDir(t *testing.T) {
  3353  	t.Parallel()
  3354  
  3355  	cwd, err := Getwd()
  3356  	if err != nil {
  3357  		t.Fatal(err)
  3358  	}
  3359  	cwd = cwd[len(filepath.VolumeName(cwd)):] // trim volume prefix (C:) on Windows
  3360  	cwd = filepath.ToSlash(cwd)               // convert \ to /
  3361  	cwd = strings.TrimPrefix(cwd, "/")        // trim leading /
  3362  
  3363  	// Test that Open can open a path starting at /.
  3364  	d := DirFS("/")
  3365  	f, err := d.Open(cwd + "/testdata/dirfs/a")
  3366  	if err != nil {
  3367  		t.Fatal(err)
  3368  	}
  3369  	f.Close()
  3370  }
  3371  
  3372  func TestDirFSEmptyDir(t *testing.T) {
  3373  	t.Parallel()
  3374  
  3375  	d := DirFS("")
  3376  	cwd, _ := Getwd()
  3377  	for _, path := range []string{
  3378  		"testdata/dirfs/a",                          // not DirFS(".")
  3379  		filepath.ToSlash(cwd) + "/testdata/dirfs/a", // not DirFS("/")
  3380  	} {
  3381  		_, err := d.Open(path)
  3382  		if err == nil {
  3383  			t.Fatalf(`DirFS("").Open(%q) succeeded`, path)
  3384  		}
  3385  	}
  3386  }
  3387  
  3388  func TestDirFSPathsValid(t *testing.T) {
  3389  	if runtime.GOOS == "windows" {
  3390  		t.Skipf("skipping on Windows")
  3391  	}
  3392  	t.Parallel()
  3393  
  3394  	d := t.TempDir()
  3395  	if err := WriteFile(filepath.Join(d, "control.txt"), []byte(string("Hello, world!")), 0644); err != nil {
  3396  		t.Fatal(err)
  3397  	}
  3398  	if err := WriteFile(filepath.Join(d, `e:xperi\ment.txt`), []byte(string("Hello, colon and backslash!")), 0644); err != nil {
  3399  		t.Fatal(err)
  3400  	}
  3401  
  3402  	fsys := DirFS(d)
  3403  	err := fs.WalkDir(fsys, ".", func(path string, e fs.DirEntry, err error) error {
  3404  		if fs.ValidPath(e.Name()) {
  3405  			t.Logf("%q ok", e.Name())
  3406  		} else {
  3407  			t.Errorf("%q INVALID", e.Name())
  3408  		}
  3409  		return nil
  3410  	})
  3411  	if err != nil {
  3412  		t.Fatal(err)
  3413  	}
  3414  }
  3415  
  3416  func TestReadFileProc(t *testing.T) {
  3417  	t.Parallel()
  3418  
  3419  	// Linux files in /proc report 0 size,
  3420  	// but then if ReadFile reads just a single byte at offset 0,
  3421  	// the read at offset 1 returns EOF instead of more data.
  3422  	// ReadFile has a minimum read size of 512 to work around this,
  3423  	// but test explicitly that it's working.
  3424  	name := "/proc/sys/fs/pipe-max-size"
  3425  	if _, err := Stat(name); err != nil {
  3426  		t.Skip(err)
  3427  	}
  3428  	data, err := ReadFile(name)
  3429  	if err != nil {
  3430  		t.Fatal(err)
  3431  	}
  3432  	if len(data) == 0 || data[len(data)-1] != '\n' {
  3433  		t.Fatalf("read %s: not newline-terminated: %q", name, data)
  3434  	}
  3435  }
  3436  
  3437  func TestDirFSReadFileProc(t *testing.T) {
  3438  	t.Parallel()
  3439  
  3440  	fsys := DirFS("/")
  3441  	name := "proc/sys/fs/pipe-max-size"
  3442  	if _, err := fs.Stat(fsys, name); err != nil {
  3443  		t.Skip()
  3444  	}
  3445  	data, err := fs.ReadFile(fsys, name)
  3446  	if err != nil {
  3447  		t.Fatal(err)
  3448  	}
  3449  	if len(data) == 0 || data[len(data)-1] != '\n' {
  3450  		t.Fatalf("read %s: not newline-terminated: %q", name, data)
  3451  	}
  3452  }
  3453  
  3454  func TestWriteStringAlloc(t *testing.T) {
  3455  	if runtime.GOOS == "js" {
  3456  		t.Skip("js allocates a lot during File.WriteString")
  3457  	}
  3458  	d := t.TempDir()
  3459  	f, err := Create(filepath.Join(d, "whiteboard.txt"))
  3460  	if err != nil {
  3461  		t.Fatal(err)
  3462  	}
  3463  	defer f.Close()
  3464  	allocs := testing.AllocsPerRun(100, func() {
  3465  		f.WriteString("I will not allocate when passed a string longer than 32 bytes.\n")
  3466  	})
  3467  	if allocs != 0 {
  3468  		t.Errorf("expected 0 allocs for File.WriteString, got %v", allocs)
  3469  	}
  3470  }
  3471  
  3472  // Test that it's OK to have parallel I/O and Close on a pipe.
  3473  func TestPipeIOCloseRace(t *testing.T) {
  3474  	// Skip on wasm, which doesn't have pipes.
  3475  	if runtime.GOOS == "js" || runtime.GOOS == "wasip1" {
  3476  		t.Skipf("skipping on %s: no pipes", runtime.GOOS)
  3477  	}
  3478  	t.Parallel()
  3479  
  3480  	r, w, err := Pipe()
  3481  	if err != nil {
  3482  		t.Fatal(err)
  3483  	}
  3484  
  3485  	var wg sync.WaitGroup
  3486  	wg.Add(3)
  3487  
  3488  	go func() {
  3489  		defer wg.Done()
  3490  		for {
  3491  			n, err := w.Write([]byte("hi"))
  3492  			if err != nil {
  3493  				// We look at error strings as the
  3494  				// expected errors are OS-specific.
  3495  				switch {
  3496  				case errors.Is(err, ErrClosed),
  3497  					strings.Contains(err.Error(), "broken pipe"),
  3498  					strings.Contains(err.Error(), "pipe is being closed"),
  3499  					strings.Contains(err.Error(), "hungup channel"):
  3500  					// Ignore an expected error.
  3501  				default:
  3502  					// Unexpected error.
  3503  					t.Error(err)
  3504  				}
  3505  				return
  3506  			}
  3507  			if n != 2 {
  3508  				t.Errorf("wrote %d bytes, expected 2", n)
  3509  				return
  3510  			}
  3511  		}
  3512  	}()
  3513  
  3514  	go func() {
  3515  		defer wg.Done()
  3516  		for {
  3517  			var buf [2]byte
  3518  			n, err := r.Read(buf[:])
  3519  			if err != nil {
  3520  				if err != io.EOF && !errors.Is(err, ErrClosed) {
  3521  					t.Error(err)
  3522  				}
  3523  				return
  3524  			}
  3525  			if n != 2 {
  3526  				t.Errorf("read %d bytes, want 2", n)
  3527  			}
  3528  		}
  3529  	}()
  3530  
  3531  	go func() {
  3532  		defer wg.Done()
  3533  
  3534  		// Let the other goroutines start. This is just to get
  3535  		// a better test, the test will still pass if they
  3536  		// don't start.
  3537  		time.Sleep(time.Millisecond)
  3538  
  3539  		if err := r.Close(); err != nil {
  3540  			t.Error(err)
  3541  		}
  3542  		if err := w.Close(); err != nil {
  3543  			t.Error(err)
  3544  		}
  3545  	}()
  3546  
  3547  	wg.Wait()
  3548  }
  3549  
  3550  // Test that it's OK to call Close concurrently on a pipe.
  3551  func TestPipeCloseRace(t *testing.T) {
  3552  	// Skip on wasm, which doesn't have pipes.
  3553  	if runtime.GOOS == "js" || runtime.GOOS == "wasip1" {
  3554  		t.Skipf("skipping on %s: no pipes", runtime.GOOS)
  3555  	}
  3556  	t.Parallel()
  3557  
  3558  	r, w, err := Pipe()
  3559  	if err != nil {
  3560  		t.Fatal(err)
  3561  	}
  3562  	var wg sync.WaitGroup
  3563  	c := make(chan error, 4)
  3564  	f := func() {
  3565  		defer wg.Done()
  3566  		c <- r.Close()
  3567  		c <- w.Close()
  3568  	}
  3569  	wg.Add(2)
  3570  	go f()
  3571  	go f()
  3572  	nils, errs := 0, 0
  3573  	for i := 0; i < 4; i++ {
  3574  		err := <-c
  3575  		if err == nil {
  3576  			nils++
  3577  		} else {
  3578  			errs++
  3579  		}
  3580  	}
  3581  	if nils != 2 || errs != 2 {
  3582  		t.Errorf("got nils %d errs %d, want 2 2", nils, errs)
  3583  	}
  3584  }
  3585  
  3586  func TestRandomLen(t *testing.T) {
  3587  	for range 5 {
  3588  		dir, err := MkdirTemp(t.TempDir(), "*")
  3589  		if err != nil {
  3590  			t.Fatal(err)
  3591  		}
  3592  		base := filepath.Base(dir)
  3593  		if len(base) > 10 {
  3594  			t.Errorf("MkdirTemp returned len %d: %s", len(base), base)
  3595  		}
  3596  	}
  3597  	for range 5 {
  3598  		f, err := CreateTemp(t.TempDir(), "*")
  3599  		if err != nil {
  3600  			t.Fatal(err)
  3601  		}
  3602  		base := filepath.Base(f.Name())
  3603  		f.Close()
  3604  		if len(base) > 10 {
  3605  			t.Errorf("CreateTemp returned len %d: %s", len(base), base)
  3606  		}
  3607  	}
  3608  }
  3609  
  3610  func TestCopyFS(t *testing.T) {
  3611  	t.Parallel()
  3612  
  3613  	// Test with disk filesystem.
  3614  	forceMFTUpdateOnWindows(t, "./testdata/dirfs")
  3615  	fsys := DirFS("./testdata/dirfs")
  3616  	tmpDir := t.TempDir()
  3617  	if err := CopyFS(tmpDir, fsys); err != nil {
  3618  		t.Fatal("CopyFS:", err)
  3619  	}
  3620  	forceMFTUpdateOnWindows(t, tmpDir)
  3621  	tmpFsys := DirFS(tmpDir)
  3622  	if err := fstest.TestFS(tmpFsys, "a", "b", "dir/x"); err != nil {
  3623  		t.Fatal("TestFS:", err)
  3624  	}
  3625  	if err := verifyCopyFS(t, fsys, tmpFsys); err != nil {
  3626  		t.Fatal("comparing two directories:", err)
  3627  	}
  3628  
  3629  	// Test whether CopyFS disallows copying for disk filesystem when there is any
  3630  	// existing file in the destination directory.
  3631  	if err := CopyFS(tmpDir, fsys); !errors.Is(err, fs.ErrExist) {
  3632  		t.Errorf("CopyFS should have failed and returned error when there is"+
  3633  			"any existing file in the destination directory (in disk filesystem), "+
  3634  			"got: %v, expected any error that indicates <file exists>", err)
  3635  	}
  3636  
  3637  	// Test with memory filesystem.
  3638  	fsys = fstest.MapFS{
  3639  		"william":    {Data: []byte("Shakespeare\n")},
  3640  		"carl":       {Data: []byte("Gauss\n")},
  3641  		"daVinci":    {Data: []byte("Leonardo\n")},
  3642  		"einstein":   {Data: []byte("Albert\n")},
  3643  		"dir/newton": {Data: []byte("Sir Isaac\n")},
  3644  	}
  3645  	tmpDir = t.TempDir()
  3646  	if err := CopyFS(tmpDir, fsys); err != nil {
  3647  		t.Fatal("CopyFS:", err)
  3648  	}
  3649  	forceMFTUpdateOnWindows(t, tmpDir)
  3650  	tmpFsys = DirFS(tmpDir)
  3651  	if err := fstest.TestFS(tmpFsys, "william", "carl", "daVinci", "einstein", "dir/newton"); err != nil {
  3652  		t.Fatal("TestFS:", err)
  3653  	}
  3654  	if err := verifyCopyFS(t, fsys, tmpFsys); err != nil {
  3655  		t.Fatal("comparing two directories:", err)
  3656  	}
  3657  
  3658  	// Test whether CopyFS disallows copying for memory filesystem when there is any
  3659  	// existing file in the destination directory.
  3660  	if err := CopyFS(tmpDir, fsys); !errors.Is(err, fs.ErrExist) {
  3661  		t.Errorf("CopyFS should have failed and returned error when there is"+
  3662  			"any existing file in the destination directory (in memory filesystem), "+
  3663  			"got: %v, expected any error that indicates <file exists>", err)
  3664  	}
  3665  }
  3666  
  3667  // verifyCopyFS checks the content and permission of each file inside copied FS to ensure
  3668  // the copied files satisfy the convention stipulated in CopyFS.
  3669  func verifyCopyFS(t *testing.T, originFS, copiedFS fs.FS) error {
  3670  	testDir := filepath.Join(t.TempDir(), "test")
  3671  	// umask doesn't apply to the wasip and windows and there is no general way to get masked perm,
  3672  	// so create a dir and a file to compare the permission after umask if any
  3673  	if err := Mkdir(testDir, ModePerm); err != nil {
  3674  		return fmt.Errorf("mkdir %q failed: %v", testDir, err)
  3675  	}
  3676  	dirStat, err := Stat(testDir)
  3677  	if err != nil {
  3678  		return fmt.Errorf("stat dir %q failed: %v", testDir, err)
  3679  	}
  3680  	wantDirMode := dirStat.Mode()
  3681  
  3682  	f, err := Create(filepath.Join(testDir, "tmp"))
  3683  	if err != nil {
  3684  		return fmt.Errorf("open %q failed: %v", filepath.Join(testDir, "tmp"), err)
  3685  	}
  3686  	defer f.Close()
  3687  	wantFileRWStat, err := f.Stat()
  3688  	if err != nil {
  3689  		return fmt.Errorf("stat file %q failed: %v", f.Name(), err)
  3690  	}
  3691  	wantFileRWMode := wantFileRWStat.Mode()
  3692  
  3693  	return fs.WalkDir(originFS, ".", func(path string, d fs.DirEntry, err error) error {
  3694  		if d.IsDir() {
  3695  			// the dir . is not the dir created by CopyFS so skip checking its permission
  3696  			if d.Name() == "." {
  3697  				return nil
  3698  			}
  3699  
  3700  			dinfo, err := fs.Stat(copiedFS, path)
  3701  			if err != nil {
  3702  				return err
  3703  			}
  3704  
  3705  			if dinfo.Mode() != wantDirMode {
  3706  				return fmt.Errorf("dir %q mode is %v, want %v",
  3707  					d.Name(), dinfo.Mode(), wantDirMode)
  3708  			}
  3709  			return nil
  3710  		}
  3711  
  3712  		fInfo, err := originFS.Open(path)
  3713  		if err != nil {
  3714  			return err
  3715  		}
  3716  		defer fInfo.Close()
  3717  		copiedInfo, err := copiedFS.Open(path)
  3718  		if err != nil {
  3719  			return err
  3720  		}
  3721  		defer copiedInfo.Close()
  3722  
  3723  		// verify the file contents are the same
  3724  		data, err := io.ReadAll(fInfo)
  3725  		if err != nil {
  3726  			return err
  3727  		}
  3728  		newData, err := io.ReadAll(copiedInfo)
  3729  		if err != nil {
  3730  			return err
  3731  		}
  3732  		if !bytes.Equal(data, newData) {
  3733  			return fmt.Errorf("file %q content is %s, want %s", path, newData, data)
  3734  		}
  3735  
  3736  		fStat, err := fInfo.Stat()
  3737  		if err != nil {
  3738  			return err
  3739  		}
  3740  		copiedStat, err := copiedInfo.Stat()
  3741  		if err != nil {
  3742  			return err
  3743  		}
  3744  
  3745  		// check whether the execute permission is inherited from original FS
  3746  
  3747  		if copiedStat.Mode()&0111&wantFileRWMode != fStat.Mode()&0111&wantFileRWMode {
  3748  			return fmt.Errorf("file %q execute mode is %v, want %v",
  3749  				path, copiedStat.Mode()&0111, fStat.Mode()&0111)
  3750  		}
  3751  
  3752  		rwMode := copiedStat.Mode() &^ 0111 // unset the executable permission from file mode
  3753  		if rwMode != wantFileRWMode {
  3754  			return fmt.Errorf("file %q rw mode is %v, want %v",
  3755  				path, rwMode, wantFileRWStat.Mode())
  3756  		}
  3757  		return nil
  3758  	})
  3759  }
  3760  
  3761  func TestCopyFSWithSymlinks(t *testing.T) {
  3762  	// Test it with absolute and relative symlinks that point inside and outside the tree.
  3763  	testenv.MustHaveSymlink(t)
  3764  
  3765  	// Create a directory and file outside.
  3766  	tmpDir := t.TempDir()
  3767  	outsideDir := filepath.Join(tmpDir, "copyfs_out")
  3768  	if err := Mkdir(outsideDir, 0755); err != nil {
  3769  		t.Fatalf("Mkdir: %v", err)
  3770  	}
  3771  	outsideFile := filepath.Join(outsideDir, "file.out.txt")
  3772  
  3773  	if err := WriteFile(outsideFile, []byte("Testing CopyFS outside"), 0644); err != nil {
  3774  		t.Fatalf("WriteFile: %v", err)
  3775  	}
  3776  
  3777  	// Create a directory and file inside.
  3778  	insideDir := filepath.Join(tmpDir, "copyfs_in")
  3779  	if err := Mkdir(insideDir, 0755); err != nil {
  3780  		t.Fatalf("Mkdir: %v", err)
  3781  	}
  3782  	insideFile := filepath.Join(insideDir, "file.in.txt")
  3783  	if err := WriteFile(insideFile, []byte("Testing CopyFS inside"), 0644); err != nil {
  3784  		t.Fatalf("WriteFile: %v", err)
  3785  	}
  3786  
  3787  	// Create directories for symlinks.
  3788  	linkInDir := filepath.Join(insideDir, "in_symlinks")
  3789  	if err := Mkdir(linkInDir, 0755); err != nil {
  3790  		t.Fatalf("Mkdir: %v", err)
  3791  	}
  3792  	linkOutDir := filepath.Join(insideDir, "out_symlinks")
  3793  	if err := Mkdir(linkOutDir, 0755); err != nil {
  3794  		t.Fatalf("Mkdir: %v", err)
  3795  	}
  3796  
  3797  	// First, we create the absolute symlink pointing outside.
  3798  	outLinkFile := filepath.Join(linkOutDir, "file.abs.out.link")
  3799  	if err := Symlink(outsideFile, outLinkFile); err != nil {
  3800  		t.Fatalf("Symlink: %v", err)
  3801  	}
  3802  
  3803  	// Then, we create the relative symlink pointing outside.
  3804  	relOutsideFile, err := filepath.Rel(filepath.Join(linkOutDir, "."), outsideFile)
  3805  	if err != nil {
  3806  		t.Fatalf("filepath.Rel: %v", err)
  3807  	}
  3808  	relOutLinkFile := filepath.Join(linkOutDir, "file.rel.out.link")
  3809  	if err := Symlink(relOutsideFile, relOutLinkFile); err != nil {
  3810  		t.Fatalf("Symlink: %v", err)
  3811  	}
  3812  
  3813  	// Last, we create the relative symlink pointing inside.
  3814  	relInsideFile, err := filepath.Rel(filepath.Join(linkInDir, "."), insideFile)
  3815  	if err != nil {
  3816  		t.Fatalf("filepath.Rel: %v", err)
  3817  	}
  3818  	relInLinkFile := filepath.Join(linkInDir, "file.rel.in.link")
  3819  	if err := Symlink(relInsideFile, relInLinkFile); err != nil {
  3820  		t.Fatalf("Symlink: %v", err)
  3821  	}
  3822  
  3823  	// Copy the directory tree and verify.
  3824  	forceMFTUpdateOnWindows(t, insideDir)
  3825  	fsys := DirFS(insideDir)
  3826  	tmpDupDir := filepath.Join(tmpDir, "copyfs_dup")
  3827  	if err := Mkdir(tmpDupDir, 0755); err != nil {
  3828  		t.Fatalf("Mkdir: %v", err)
  3829  	}
  3830  
  3831  	if err := CopyFS(tmpDupDir, fsys); err != nil {
  3832  		t.Fatalf("CopyFS: %v", err)
  3833  	}
  3834  
  3835  	forceMFTUpdateOnWindows(t, tmpDupDir)
  3836  	tmpFsys := DirFS(tmpDupDir)
  3837  	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 {
  3838  		t.Fatal("TestFS:", err)
  3839  	}
  3840  	if err := fs.WalkDir(fsys, ".", func(path string, d fs.DirEntry, err error) error {
  3841  		if d.IsDir() {
  3842  			return nil
  3843  		}
  3844  
  3845  		fi, err := d.Info()
  3846  		if err != nil {
  3847  			return err
  3848  		}
  3849  		if filepath.Ext(path) == ".link" {
  3850  			if fi.Mode()&ModeSymlink == 0 {
  3851  				return errors.New("original file " + path + " should be a symlink")
  3852  			}
  3853  			tmpfi, err := fs.Stat(tmpFsys, path)
  3854  			if err != nil {
  3855  				return err
  3856  			}
  3857  			if tmpfi.Mode()&ModeSymlink != 0 {
  3858  				return errors.New("copied file " + path + " should not be a symlink")
  3859  			}
  3860  		}
  3861  
  3862  		data, err := fs.ReadFile(fsys, path)
  3863  		if err != nil {
  3864  			return err
  3865  		}
  3866  		newData, err := fs.ReadFile(tmpFsys, path)
  3867  		if err != nil {
  3868  			return err
  3869  		}
  3870  		if !bytes.Equal(data, newData) {
  3871  			return errors.New("file " + path + " contents differ")
  3872  		}
  3873  
  3874  		var target string
  3875  		switch fileName := filepath.Base(path); fileName {
  3876  		case "file.abs.out.link", "file.rel.out.link":
  3877  			target = outsideFile
  3878  		case "file.rel.in.link":
  3879  			target = insideFile
  3880  		}
  3881  		if len(target) > 0 {
  3882  			targetData, err := ReadFile(target)
  3883  			if err != nil {
  3884  				return err
  3885  			}
  3886  			if !bytes.Equal(targetData, newData) {
  3887  				return errors.New("file " + path + " contents differ from target")
  3888  			}
  3889  		}
  3890  
  3891  		return nil
  3892  	}); err != nil {
  3893  		t.Fatal("comparing two directories:", err)
  3894  	}
  3895  }
  3896  
  3897  func TestAppendDoesntOverwrite(t *testing.T) {
  3898  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  3899  		name := "file"
  3900  		if err := WriteFile(name, []byte("hello"), 0666); err != nil {
  3901  			t.Fatal(err)
  3902  		}
  3903  		var f *File
  3904  		var err error
  3905  		if r == nil {
  3906  			f, err = OpenFile(name, O_APPEND|O_WRONLY, 0)
  3907  		} else {
  3908  			f, err = r.OpenFile(name, O_APPEND|O_WRONLY, 0)
  3909  		}
  3910  		if err != nil {
  3911  			t.Fatal(err)
  3912  		}
  3913  		if _, err := f.Write([]byte(" world")); err != nil {
  3914  			f.Close()
  3915  			t.Fatal(err)
  3916  		}
  3917  		if err := f.Close(); err != nil {
  3918  			t.Fatal(err)
  3919  		}
  3920  		got, err := ReadFile(name)
  3921  		if err != nil {
  3922  			t.Fatal(err)
  3923  		}
  3924  		want := "hello world"
  3925  		if string(got) != want {
  3926  			t.Fatalf("got %q, want %q", got, want)
  3927  		}
  3928  	})
  3929  }
  3930  
  3931  func TestRemoveReadOnlyFile(t *testing.T) {
  3932  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  3933  		if err := WriteFile("file", []byte("1"), 0); err != nil {
  3934  			t.Fatal(err)
  3935  		}
  3936  		var err error
  3937  		if r == nil {
  3938  			err = Remove("file")
  3939  		} else {
  3940  			err = r.Remove("file")
  3941  		}
  3942  		if err != nil {
  3943  			t.Fatalf("Remove read-only file: %v", err)
  3944  		}
  3945  		if _, err := Stat("file"); !IsNotExist(err) {
  3946  			t.Fatalf("Stat read-only file after removal: %v (want IsNotExist)", err)
  3947  		}
  3948  	})
  3949  }
  3950  
  3951  func TestOpenFileDevNull(t *testing.T) {
  3952  	// See https://go.dev/issue/71752.
  3953  	t.Parallel()
  3954  
  3955  	f, err := OpenFile(DevNull, O_WRONLY|O_CREATE|O_TRUNC, 0o644)
  3956  	if err != nil {
  3957  		t.Fatalf("OpenFile(DevNull): %v", err)
  3958  	}
  3959  	f.Close()
  3960  }
  3961  
  3962  func TestReadFileContents(t *testing.T) {
  3963  	type readStep struct {
  3964  		bufSize int   // non-zero to check length of buf to Read
  3965  		retN    int   // result of Read call
  3966  		retErr  error // error result of Read call
  3967  	}
  3968  	errFoo := errors.New("foo")
  3969  	tests := []struct {
  3970  		name     string
  3971  		statSize int64 // size of file to read, per stat (may be 0 for /proc files)
  3972  		wantSize int   // wanted length of []byte from readFileContents
  3973  		wantErr  error // wanted error from readFileContents
  3974  		reads    []readStep
  3975  	}{
  3976  		{
  3977  			name:     "big-file",
  3978  			statSize: 2000,
  3979  			wantSize: 2000,
  3980  			reads: []readStep{
  3981  				{bufSize: 2001, retN: 21, retErr: nil},
  3982  				{bufSize: 1980, retN: 1979, retErr: io.EOF},
  3983  			},
  3984  		},
  3985  		{
  3986  			name:     "small-file",
  3987  			statSize: 100,
  3988  			wantSize: 100,
  3989  			reads: []readStep{
  3990  				{bufSize: 512, retN: 100, retErr: io.EOF},
  3991  			},
  3992  		},
  3993  		{
  3994  			name:     "returning-error",
  3995  			statSize: 1000,
  3996  			wantSize: 50,
  3997  			wantErr:  errFoo,
  3998  			reads: []readStep{
  3999  				{bufSize: 1001, retN: 25, retErr: nil},
  4000  				{retN: 25, retErr: errFoo},
  4001  			},
  4002  		},
  4003  		{
  4004  			name:     "proc-file",
  4005  			statSize: 0,
  4006  			wantSize: 1023,
  4007  			reads: []readStep{
  4008  				{bufSize: 512, retN: 512, retErr: nil},
  4009  				{retN: 511, retErr: io.EOF},
  4010  			},
  4011  		},
  4012  		{
  4013  			name:     "plan9-iproute-file", // Issue 72080
  4014  			statSize: 0,
  4015  			wantSize: 1032,
  4016  			reads: []readStep{
  4017  				{bufSize: 512, retN: 511, retErr: nil},
  4018  				{retN: 511, retErr: nil},
  4019  				{retN: 10, retErr: io.EOF},
  4020  			},
  4021  		},
  4022  	}
  4023  	for _, tt := range tests {
  4024  		t.Run(tt.name, func(t *testing.T) {
  4025  			remain := tt.reads
  4026  			i := -1
  4027  			got, err := ExportReadFileContents(tt.statSize, func(buf []byte) (int, error) {
  4028  				i++
  4029  				t.Logf("read[%d] with buf size %d", i, len(buf))
  4030  				if len(remain) == 0 {
  4031  					t.Fatalf("unexpected read of length %d after %d expected reads", len(buf), len(tt.reads))
  4032  				}
  4033  				if tt.statSize == 0 && len(buf) < 512 {
  4034  					// Issue 72080: readFileContents should not do /proc reads with buffers
  4035  					// smaller than 512.
  4036  					t.Fatalf("read[%d] with buf size %d; want at least 512 for 0-sized file", i, len(buf))
  4037  				}
  4038  				step := remain[0]
  4039  				remain = remain[1:]
  4040  				if step.bufSize != 0 && len(buf) != step.bufSize {
  4041  					t.Fatalf("read[%d] has buffer size %d; want %d", i, len(buf), step.bufSize)
  4042  				}
  4043  				return step.retN, step.retErr
  4044  			})
  4045  			if len(remain) > 0 {
  4046  				t.Fatalf("expected %d reads, got %d", len(tt.reads), i+1)
  4047  			}
  4048  			if fmt.Sprint(err) != fmt.Sprint(tt.wantErr) {
  4049  				t.Errorf("got error %v; want %v", err, tt.wantErr)
  4050  			}
  4051  			if len(got) != tt.wantSize {
  4052  				t.Errorf("got size %d; want %d", len(got), tt.wantSize)
  4053  			}
  4054  		})
  4055  	}
  4056  }
  4057  

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