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  	SetStatHook(t, func(f *File, path string) (FileInfo, error) {
   771  		if xerr != nil && strings.HasSuffix(path, "x") {
   772  			return nil, xerr
   773  		}
   774  		return nil, nil
   775  	})
   776  
   777  	dir := t.TempDir()
   778  	touch(t, filepath.Join(dir, "good1"))
   779  	touch(t, filepath.Join(dir, "x")) // will disappear or have an error
   780  	touch(t, filepath.Join(dir, "good2"))
   781  	readDir := func() ([]FileInfo, error) {
   782  		d, err := Open(dir)
   783  		if err != nil {
   784  			t.Fatal(err)
   785  		}
   786  		defer d.Close()
   787  		return d.Readdir(-1)
   788  	}
   789  	mustReadDir := func(testName string) []FileInfo {
   790  		fis, err := readDir()
   791  		if err != nil {
   792  			t.Fatalf("%s: Readdir: %v", testName, err)
   793  		}
   794  		return fis
   795  	}
   796  	names := func(fis []FileInfo) []string {
   797  		s := make([]string, len(fis))
   798  		for i, fi := range fis {
   799  			s[i] = fi.Name()
   800  		}
   801  		slices.Sort(s)
   802  		return s
   803  	}
   804  
   805  	if got, want := names(mustReadDir("initial readdir")),
   806  		[]string{"good1", "good2", "x"}; !slices.Equal(got, want) {
   807  		t.Errorf("initial readdir got %q; want %q", got, want)
   808  	}
   809  
   810  	xerr = ErrNotExist
   811  	if got, want := names(mustReadDir("with x disappearing")),
   812  		[]string{"good1", "good2"}; !slices.Equal(got, want) {
   813  		t.Errorf("with x disappearing, got %q; want %q", got, want)
   814  	}
   815  
   816  	xerr = errors.New("some real error")
   817  	if _, err := readDir(); err != xerr {
   818  		t.Errorf("with a non-ErrNotExist error, got error %v; want %v", err, xerr)
   819  	}
   820  }
   821  
   822  // Readdir on a regular file should fail.
   823  func TestReaddirOfFile(t *testing.T) {
   824  	t.Parallel()
   825  
   826  	f, err := CreateTemp(t.TempDir(), "_Go_ReaddirOfFile")
   827  	if err != nil {
   828  		t.Fatal(err)
   829  	}
   830  	f.Write([]byte("foo"))
   831  	f.Close()
   832  	reg, err := Open(f.Name())
   833  	if err != nil {
   834  		t.Fatal(err)
   835  	}
   836  	defer reg.Close()
   837  
   838  	names, err := reg.Readdirnames(-1)
   839  	if err == nil {
   840  		t.Error("Readdirnames succeeded; want non-nil error")
   841  	}
   842  	if pe, ok := errors.AsType[*PathError](err); !ok || pe.Path != f.Name() {
   843  		t.Errorf("Readdirnames returned %q; want a PathError with path %q", err, f.Name())
   844  	}
   845  	if len(names) > 0 {
   846  		t.Errorf("unexpected dir names in regular file: %q", names)
   847  	}
   848  }
   849  
   850  func TestHardLink(t *testing.T) {
   851  	testMaybeRooted(t, testHardLink)
   852  }
   853  func testHardLink(t *testing.T, root *Root) {
   854  	testenv.MustHaveLink(t)
   855  
   856  	var (
   857  		create = Create
   858  		link   = Link
   859  		stat   = Stat
   860  		op     = "link"
   861  	)
   862  	if root != nil {
   863  		create = root.Create
   864  		link = root.Link
   865  		stat = root.Stat
   866  		op = "linkat"
   867  	}
   868  
   869  	from, to := "hardlinktestfrom", "hardlinktestto"
   870  	file, err := create(to)
   871  	if err != nil {
   872  		t.Fatalf("open %q failed: %v", to, err)
   873  	}
   874  	if err = file.Close(); err != nil {
   875  		t.Errorf("close %q failed: %v", to, err)
   876  	}
   877  	err = link(to, from)
   878  	if err != nil {
   879  		t.Fatalf("link %q, %q failed: %v", to, from, err)
   880  	}
   881  
   882  	none := "hardlinktestnone"
   883  	err = link(none, none)
   884  	// Check the returned error is well-formed.
   885  	if lerr, ok := err.(*LinkError); !ok || lerr.Error() == "" {
   886  		t.Errorf("link %q, %q failed to return a valid error", none, none)
   887  	}
   888  
   889  	tostat, err := stat(to)
   890  	if err != nil {
   891  		t.Fatalf("stat %q failed: %v", to, err)
   892  	}
   893  	fromstat, err := stat(from)
   894  	if err != nil {
   895  		t.Fatalf("stat %q failed: %v", from, err)
   896  	}
   897  	if !SameFile(tostat, fromstat) {
   898  		t.Errorf("link %q, %q did not create hard link", to, from)
   899  	}
   900  	// We should not be able to perform the same Link() a second time
   901  	err = link(to, from)
   902  	switch err := err.(type) {
   903  	case *LinkError:
   904  		if err.Op != op {
   905  			t.Errorf("Link(%q, %q) err.Op = %q; want %q", to, from, err.Op, op)
   906  		}
   907  		if err.Old != to {
   908  			t.Errorf("Link(%q, %q) err.Old = %q; want %q", to, from, err.Old, to)
   909  		}
   910  		if err.New != from {
   911  			t.Errorf("Link(%q, %q) err.New = %q; want %q", to, from, err.New, from)
   912  		}
   913  		if !IsExist(err.Err) {
   914  			t.Errorf("Link(%q, %q) err.Err = %q; want %q", to, from, err.Err, "file exists error")
   915  		}
   916  	case nil:
   917  		t.Errorf("link %q, %q: expected error, got nil", from, to)
   918  	default:
   919  		t.Errorf("link %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
   920  	}
   921  }
   922  
   923  func TestSymlink(t *testing.T) {
   924  	testMaybeRooted(t, testSymlink)
   925  }
   926  func testSymlink(t *testing.T, root *Root) {
   927  	testenv.MustHaveSymlink(t)
   928  
   929  	var (
   930  		create   = Create
   931  		open     = Open
   932  		symlink  = Symlink
   933  		stat     = Stat
   934  		lstat    = Lstat
   935  		readlink = Readlink
   936  	)
   937  	if root != nil {
   938  		create = root.Create
   939  		open = root.Open
   940  		symlink = root.Symlink
   941  		stat = root.Stat
   942  		lstat = root.Lstat
   943  		readlink = root.Readlink
   944  	}
   945  
   946  	from, to := "symlinktestfrom", "symlinktestto"
   947  	file, err := create(to)
   948  	if err != nil {
   949  		t.Fatalf("Create(%q) failed: %v", to, err)
   950  	}
   951  	if err = file.Close(); err != nil {
   952  		t.Errorf("Close(%q) failed: %v", to, err)
   953  	}
   954  	err = symlink(to, from)
   955  	if err != nil {
   956  		t.Fatalf("Symlink(%q, %q) failed: %v", to, from, err)
   957  	}
   958  	tostat, err := lstat(to)
   959  	if err != nil {
   960  		t.Fatalf("Lstat(%q) failed: %v", to, err)
   961  	}
   962  	if tostat.Mode()&ModeSymlink != 0 {
   963  		t.Fatalf("Lstat(%q).Mode()&ModeSymlink = %v, want 0", to, tostat.Mode()&ModeSymlink)
   964  	}
   965  	fromstat, err := stat(from)
   966  	if err != nil {
   967  		t.Fatalf("Stat(%q) failed: %v", from, err)
   968  	}
   969  	if !SameFile(tostat, fromstat) {
   970  		t.Errorf("Symlink(%q, %q) did not create symlink", to, from)
   971  	}
   972  	fromstat, err = lstat(from)
   973  	if err != nil {
   974  		t.Fatalf("Lstat(%q) failed: %v", from, err)
   975  	}
   976  	if fromstat.Mode()&ModeSymlink == 0 {
   977  		t.Fatalf("Lstat(%q).Mode()&ModeSymlink = 0, want %v", from, ModeSymlink)
   978  	}
   979  	fromstat, err = stat(from)
   980  	if err != nil {
   981  		t.Fatalf("Stat(%q) failed: %v", from, err)
   982  	}
   983  	if fromstat.Name() != from {
   984  		t.Errorf("Stat(%q).Name() = %q, want %q", from, fromstat.Name(), from)
   985  	}
   986  	if fromstat.Mode()&ModeSymlink != 0 {
   987  		t.Fatalf("Stat(%q).Mode()&ModeSymlink = %v, want 0", from, fromstat.Mode()&ModeSymlink)
   988  	}
   989  	s, err := readlink(from)
   990  	if err != nil {
   991  		t.Fatalf("Readlink(%q) failed: %v", from, err)
   992  	}
   993  	if s != to {
   994  		t.Fatalf("Readlink(%q) = %q, want %q", from, s, to)
   995  	}
   996  	file, err = open(from)
   997  	if err != nil {
   998  		t.Fatalf("Open(%q) failed: %v", from, err)
   999  	}
  1000  	file.Close()
  1001  }
  1002  
  1003  func TestLongSymlink(t *testing.T) {
  1004  	testenv.MustHaveSymlink(t)
  1005  	t.Chdir(t.TempDir())
  1006  
  1007  	s := "0123456789abcdef"
  1008  	// Long, but not too long: a common limit is 255.
  1009  	s = s + s + s + s + s + s + s + s + s + s + s + s + s + s + s
  1010  	from := "longsymlinktestfrom"
  1011  	err := Symlink(s, from)
  1012  	if err != nil {
  1013  		t.Fatalf("symlink %q, %q failed: %v", s, from, err)
  1014  	}
  1015  	r, err := Readlink(from)
  1016  	if err != nil {
  1017  		t.Fatalf("readlink %q failed: %v", from, err)
  1018  	}
  1019  	if r != s {
  1020  		t.Fatalf("after symlink %q != %q", r, s)
  1021  	}
  1022  }
  1023  
  1024  func TestRename(t *testing.T) {
  1025  	t.Chdir(t.TempDir())
  1026  	from, to := "renamefrom", "renameto"
  1027  
  1028  	file, err := Create(from)
  1029  	if err != nil {
  1030  		t.Fatalf("open %q failed: %v", from, err)
  1031  	}
  1032  	if err = file.Close(); err != nil {
  1033  		t.Errorf("close %q failed: %v", from, err)
  1034  	}
  1035  	err = Rename(from, to)
  1036  	if err != nil {
  1037  		t.Fatalf("rename %q, %q failed: %v", to, from, err)
  1038  	}
  1039  	_, err = Stat(to)
  1040  	if err != nil {
  1041  		t.Errorf("stat %q failed: %v", to, err)
  1042  	}
  1043  }
  1044  
  1045  func TestRenameOverwriteDest(t *testing.T) {
  1046  	t.Chdir(t.TempDir())
  1047  	from, to := "renamefrom", "renameto"
  1048  
  1049  	toData := []byte("to")
  1050  	fromData := []byte("from")
  1051  
  1052  	err := WriteFile(to, toData, 0777)
  1053  	if err != nil {
  1054  		t.Fatalf("write file %q failed: %v", to, err)
  1055  	}
  1056  
  1057  	err = WriteFile(from, fromData, 0777)
  1058  	if err != nil {
  1059  		t.Fatalf("write file %q failed: %v", from, err)
  1060  	}
  1061  	err = Rename(from, to)
  1062  	if err != nil {
  1063  		t.Fatalf("rename %q, %q failed: %v", to, from, err)
  1064  	}
  1065  
  1066  	_, err = Stat(from)
  1067  	if err == nil {
  1068  		t.Errorf("from file %q still exists", from)
  1069  	}
  1070  	if err != nil && !IsNotExist(err) {
  1071  		t.Fatalf("stat from: %v", err)
  1072  	}
  1073  	toFi, err := Stat(to)
  1074  	if err != nil {
  1075  		t.Fatalf("stat %q failed: %v", to, err)
  1076  	}
  1077  	if toFi.Size() != int64(len(fromData)) {
  1078  		t.Errorf(`"to" size = %d; want %d (old "from" size)`, toFi.Size(), len(fromData))
  1079  	}
  1080  }
  1081  
  1082  func TestRenameFailed(t *testing.T) {
  1083  	t.Chdir(t.TempDir())
  1084  	from, to := "renamefrom", "renameto"
  1085  
  1086  	err := Rename(from, to)
  1087  	switch err := err.(type) {
  1088  	case *LinkError:
  1089  		if err.Op != "rename" {
  1090  			t.Errorf("rename %q, %q: err.Op: want %q, got %q", from, to, "rename", err.Op)
  1091  		}
  1092  		if err.Old != from {
  1093  			t.Errorf("rename %q, %q: err.Old: want %q, got %q", from, to, from, err.Old)
  1094  		}
  1095  		if err.New != to {
  1096  			t.Errorf("rename %q, %q: err.New: want %q, got %q", from, to, to, err.New)
  1097  		}
  1098  	case nil:
  1099  		t.Errorf("rename %q, %q: expected error, got nil", from, to)
  1100  	default:
  1101  		t.Errorf("rename %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
  1102  	}
  1103  }
  1104  
  1105  func TestRenameNotExisting(t *testing.T) {
  1106  	t.Chdir(t.TempDir())
  1107  	from, to := "doesnt-exist", "dest"
  1108  
  1109  	Mkdir(to, 0777)
  1110  
  1111  	if err := Rename(from, to); !IsNotExist(err) {
  1112  		t.Errorf("Rename(%q, %q) = %v; want an IsNotExist error", from, to, err)
  1113  	}
  1114  }
  1115  
  1116  func TestRenameToDirFailed(t *testing.T) {
  1117  	t.Chdir(t.TempDir())
  1118  	from, to := "renamefrom", "renameto"
  1119  
  1120  	Mkdir(from, 0777)
  1121  	Mkdir(to, 0777)
  1122  
  1123  	err := Rename(from, to)
  1124  	switch err := err.(type) {
  1125  	case *LinkError:
  1126  		if err.Op != "rename" {
  1127  			t.Errorf("rename %q, %q: err.Op: want %q, got %q", from, to, "rename", err.Op)
  1128  		}
  1129  		if err.Old != from {
  1130  			t.Errorf("rename %q, %q: err.Old: want %q, got %q", from, to, from, err.Old)
  1131  		}
  1132  		if err.New != to {
  1133  			t.Errorf("rename %q, %q: err.New: want %q, got %q", from, to, to, err.New)
  1134  		}
  1135  	case nil:
  1136  		t.Errorf("rename %q, %q: expected error, got nil", from, to)
  1137  	default:
  1138  		t.Errorf("rename %q, %q: expected %T, got %T %v", from, to, new(LinkError), err, err)
  1139  	}
  1140  }
  1141  
  1142  func TestRenameCaseDifference(pt *testing.T) {
  1143  	from, to := "renameFROM", "RENAMEfrom"
  1144  	tests := []struct {
  1145  		name   string
  1146  		create func() error
  1147  	}{
  1148  		{"dir", func() error {
  1149  			return Mkdir(from, 0777)
  1150  		}},
  1151  		{"file", func() error {
  1152  			fd, err := Create(from)
  1153  			if err != nil {
  1154  				return err
  1155  			}
  1156  			return fd.Close()
  1157  		}},
  1158  	}
  1159  
  1160  	for _, test := range tests {
  1161  		pt.Run(test.name, func(t *testing.T) {
  1162  			t.Chdir(t.TempDir())
  1163  
  1164  			if err := test.create(); err != nil {
  1165  				t.Fatalf("failed to create test file: %s", err)
  1166  			}
  1167  
  1168  			if _, err := Stat(to); err != nil {
  1169  				// Sanity check that the underlying filesystem is not case sensitive.
  1170  				if IsNotExist(err) {
  1171  					t.Skipf("case sensitive filesystem")
  1172  				}
  1173  				t.Fatalf("stat %q, got: %q", to, err)
  1174  			}
  1175  
  1176  			if err := Rename(from, to); err != nil {
  1177  				t.Fatalf("unexpected error when renaming from %q to %q: %s", from, to, err)
  1178  			}
  1179  
  1180  			fd, err := Open(".")
  1181  			if err != nil {
  1182  				t.Fatalf("Open .: %s", err)
  1183  			}
  1184  
  1185  			// Stat does not return the real case of the file (it returns what the called asked for)
  1186  			// So we have to use readdir to get the real name of the file.
  1187  			dirNames, err := fd.Readdirnames(-1)
  1188  			fd.Close()
  1189  			if err != nil {
  1190  				t.Fatalf("readdirnames: %s", err)
  1191  			}
  1192  
  1193  			if dirNamesLen := len(dirNames); dirNamesLen != 1 {
  1194  				t.Fatalf("unexpected dirNames len, got %d, want %d", dirNamesLen, 1)
  1195  			}
  1196  
  1197  			if dirNames[0] != to {
  1198  				t.Errorf("unexpected name, got %q, want %q", dirNames[0], to)
  1199  			}
  1200  		})
  1201  	}
  1202  }
  1203  
  1204  func testStartProcess(dir, cmd string, args []string, expect string) func(t *testing.T) {
  1205  	return func(t *testing.T) {
  1206  		t.Parallel()
  1207  
  1208  		r, w, err := Pipe()
  1209  		if err != nil {
  1210  			t.Fatalf("Pipe: %v", err)
  1211  		}
  1212  		defer r.Close()
  1213  		attr := &ProcAttr{Dir: dir, Files: []*File{nil, w, Stderr}}
  1214  		p, err := StartProcess(cmd, args, attr)
  1215  		if err != nil {
  1216  			t.Fatalf("StartProcess: %v", err)
  1217  		}
  1218  		w.Close()
  1219  
  1220  		var b strings.Builder
  1221  		io.Copy(&b, r)
  1222  		output := b.String()
  1223  
  1224  		fi1, _ := Stat(strings.TrimSpace(output))
  1225  		fi2, _ := Stat(expect)
  1226  		if !SameFile(fi1, fi2) {
  1227  			t.Errorf("exec %q returned %q wanted %q",
  1228  				strings.Join(append([]string{cmd}, args...), " "), output, expect)
  1229  		}
  1230  		p.Wait()
  1231  	}
  1232  }
  1233  
  1234  func TestStartProcess(t *testing.T) {
  1235  	testenv.MustHaveExec(t)
  1236  	t.Parallel()
  1237  
  1238  	var dir, cmd string
  1239  	var args []string
  1240  	switch runtime.GOOS {
  1241  	case "android":
  1242  		t.Skip("android doesn't have /bin/pwd")
  1243  	case "windows":
  1244  		cmd = Getenv("COMSPEC")
  1245  		dir = Getenv("SystemRoot")
  1246  		args = []string{"/c", "cd"}
  1247  	default:
  1248  		var err error
  1249  		cmd, err = exec.LookPath("pwd")
  1250  		if err != nil {
  1251  			t.Fatalf("Can't find pwd: %v", err)
  1252  		}
  1253  		dir = "/"
  1254  		args = []string{}
  1255  		t.Logf("Testing with %v", cmd)
  1256  	}
  1257  	cmddir, cmdbase := filepath.Split(cmd)
  1258  	args = append([]string{cmdbase}, args...)
  1259  	t.Run("absolute", testStartProcess(dir, cmd, args, dir))
  1260  	t.Run("relative", testStartProcess(cmddir, cmdbase, args, cmddir))
  1261  }
  1262  
  1263  func checkMode(t *testing.T, path string, mode FileMode) {
  1264  	dir, err := Stat(path)
  1265  	if err != nil {
  1266  		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
  1267  	}
  1268  	if dir.Mode()&ModePerm != mode {
  1269  		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode(), mode)
  1270  	}
  1271  }
  1272  
  1273  func TestChmod(t *testing.T) {
  1274  	// Chmod is not supported on wasip1.
  1275  	if runtime.GOOS == "wasip1" {
  1276  		t.Skip("Chmod is not supported on " + runtime.GOOS)
  1277  	}
  1278  	t.Parallel()
  1279  
  1280  	f := newFile(t)
  1281  	// Creation mode is read write
  1282  
  1283  	fm := FileMode(0456)
  1284  	if runtime.GOOS == "windows" {
  1285  		fm = FileMode(0444) // read-only file
  1286  	}
  1287  	if err := Chmod(f.Name(), fm); err != nil {
  1288  		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
  1289  	}
  1290  	checkMode(t, f.Name(), fm)
  1291  
  1292  	fm = FileMode(0123)
  1293  	if runtime.GOOS == "windows" {
  1294  		fm = FileMode(0666) // read-write file
  1295  	}
  1296  	if err := f.Chmod(fm); err != nil {
  1297  		t.Fatalf("chmod %s %#o: %s", f.Name(), fm, err)
  1298  	}
  1299  	checkMode(t, f.Name(), fm)
  1300  }
  1301  
  1302  func checkSize(t *testing.T, f *File, size int64) {
  1303  	t.Helper()
  1304  	dir, err := f.Stat()
  1305  	if err != nil {
  1306  		t.Fatalf("Stat %q (looking for size %d): %s", f.Name(), size, err)
  1307  	}
  1308  	if dir.Size() != size {
  1309  		t.Errorf("Stat %q: size %d want %d", f.Name(), dir.Size(), size)
  1310  	}
  1311  }
  1312  
  1313  func TestFTruncate(t *testing.T) {
  1314  	t.Parallel()
  1315  
  1316  	f := newFile(t)
  1317  
  1318  	checkSize(t, f, 0)
  1319  	f.Write([]byte("hello, world\n"))
  1320  	checkSize(t, f, 13)
  1321  	f.Truncate(10)
  1322  	checkSize(t, f, 10)
  1323  	f.Truncate(1024)
  1324  	checkSize(t, f, 1024)
  1325  	f.Truncate(0)
  1326  	checkSize(t, f, 0)
  1327  	_, err := f.Write([]byte("surprise!"))
  1328  	if err == nil {
  1329  		checkSize(t, f, 13+9) // wrote at offset past where hello, world was.
  1330  	}
  1331  }
  1332  
  1333  func TestTruncate(t *testing.T) {
  1334  	t.Parallel()
  1335  
  1336  	f := newFile(t)
  1337  
  1338  	checkSize(t, f, 0)
  1339  	f.Write([]byte("hello, world\n"))
  1340  	checkSize(t, f, 13)
  1341  	Truncate(f.Name(), 10)
  1342  	checkSize(t, f, 10)
  1343  	Truncate(f.Name(), 1024)
  1344  	checkSize(t, f, 1024)
  1345  	Truncate(f.Name(), 0)
  1346  	checkSize(t, f, 0)
  1347  	_, err := f.Write([]byte("surprise!"))
  1348  	if err == nil {
  1349  		checkSize(t, f, 13+9) // wrote at offset past where hello, world was.
  1350  	}
  1351  }
  1352  
  1353  func TestTruncateNonexistentFile(t *testing.T) {
  1354  	t.Parallel()
  1355  
  1356  	assertPathError := func(t testing.TB, path string, err error) {
  1357  		t.Helper()
  1358  		if pe, ok := err.(*PathError); !ok || !IsNotExist(err) || pe.Path != path {
  1359  			t.Errorf("got error: %v\nwant an ErrNotExist PathError with path %q", err, path)
  1360  		}
  1361  	}
  1362  
  1363  	path := filepath.Join(t.TempDir(), "nonexistent")
  1364  
  1365  	err := Truncate(path, 1)
  1366  	assertPathError(t, path, err)
  1367  
  1368  	// Truncate shouldn't create any new file.
  1369  	_, err = Stat(path)
  1370  	assertPathError(t, path, err)
  1371  }
  1372  
  1373  var hasNoatime = sync.OnceValue(func() bool {
  1374  	// A sloppy way to check if noatime flag is set (as all filesystems are
  1375  	// checked, not just the one we're interested in). A correct way
  1376  	// would be to use statvfs syscall and check if flags has ST_NOATIME,
  1377  	// but the syscall is OS-specific and is not even wired into Go stdlib.
  1378  	//
  1379  	// Only used on NetBSD (which ignores explicit atime updates with noatime).
  1380  	if runtime.GOOS != "netbsd" {
  1381  		return false
  1382  	}
  1383  	mounts, _ := ReadFile("/proc/mounts")
  1384  	return bytes.Contains(mounts, []byte("noatime"))
  1385  })
  1386  
  1387  func TestChtimes(t *testing.T) {
  1388  	t.Parallel()
  1389  
  1390  	f := newFile(t)
  1391  	// This should be an empty file (see #68687, #68663).
  1392  	f.Close()
  1393  
  1394  	testChtimes(t, f.Name())
  1395  }
  1396  
  1397  func TestChtimesOmit(t *testing.T) {
  1398  	t.Parallel()
  1399  
  1400  	testChtimesOmit(t, true, false)
  1401  	testChtimesOmit(t, false, true)
  1402  	testChtimesOmit(t, true, true)
  1403  	testChtimesOmit(t, false, false) // Same as TestChtimes.
  1404  }
  1405  
  1406  func testChtimesOmit(t *testing.T, omitAt, omitMt bool) {
  1407  	t.Logf("omit atime: %v, mtime: %v", omitAt, omitMt)
  1408  	file := newFile(t)
  1409  	// This should be an empty file (see #68687, #68663).
  1410  	name := file.Name()
  1411  	err := file.Close()
  1412  	if err != nil {
  1413  		t.Error(err)
  1414  	}
  1415  	fs, err := Stat(name)
  1416  	if err != nil {
  1417  		t.Fatal(err)
  1418  	}
  1419  
  1420  	wantAtime := Atime(fs)
  1421  	wantMtime := fs.ModTime()
  1422  	switch runtime.GOOS {
  1423  	case "js":
  1424  		wantAtime = wantAtime.Truncate(time.Second)
  1425  		wantMtime = wantMtime.Truncate(time.Second)
  1426  	}
  1427  
  1428  	var setAtime, setMtime time.Time // Zero value means omit.
  1429  	if !omitAt {
  1430  		wantAtime = wantAtime.Add(-1 * time.Second)
  1431  		setAtime = wantAtime
  1432  	}
  1433  	if !omitMt {
  1434  		wantMtime = wantMtime.Add(-1 * time.Second)
  1435  		setMtime = wantMtime
  1436  	}
  1437  
  1438  	// Change the times accordingly.
  1439  	if err := Chtimes(name, setAtime, setMtime); err != nil {
  1440  		t.Error(err)
  1441  	}
  1442  
  1443  	// Verify the expectations.
  1444  	fs, err = Stat(name)
  1445  	if err != nil {
  1446  		t.Error(err)
  1447  	}
  1448  	gotAtime := Atime(fs)
  1449  	gotMtime := fs.ModTime()
  1450  
  1451  	// TODO: remove the dragonfly omitAt && omitMt exceptions below once the
  1452  	// fix (https://github.com/DragonFlyBSD/DragonFlyBSD/commit/c7c71870ed0)
  1453  	// is available generally and on CI runners.
  1454  	if !gotAtime.Equal(wantAtime) {
  1455  		errormsg := fmt.Sprintf("atime mismatch, got: %q, want: %q", gotAtime, wantAtime)
  1456  		switch runtime.GOOS {
  1457  		case "plan9":
  1458  			// Mtime is the time of the last change of content.
  1459  			// Similarly, atime is set whenever the contents are
  1460  			// accessed; also, it is set whenever mtime is set.
  1461  		case "dragonfly":
  1462  			if omitAt && omitMt {
  1463  				t.Log(errormsg)
  1464  				t.Log("Known DragonFly BSD issue (won't work when both times are omitted); ignoring.")
  1465  			} else {
  1466  				// Assume hammer2 fs; https://www.dragonflybsd.org/hammer/ says:
  1467  				// > Because HAMMER2 is a block copy-on-write filesystem,
  1468  				// > the "atime" field is not supported and will typically
  1469  				// > just reflect local system in-memory caches or mtime.
  1470  				//
  1471  				// TODO: if only can CI define TMPDIR to point to a tmpfs
  1472  				// (e.g. /var/run/shm), this exception can be removed.
  1473  				t.Log(errormsg)
  1474  				t.Log("Known DragonFly BSD issue (atime not supported on hammer2); ignoring.")
  1475  			}
  1476  		case "netbsd":
  1477  			if !omitAt && hasNoatime() {
  1478  				t.Log(errormsg)
  1479  				t.Log("Known NetBSD issue (atime not changed on fs mounted with noatime); ignoring.")
  1480  			} else {
  1481  				t.Error(errormsg)
  1482  			}
  1483  		default:
  1484  			t.Error(errormsg)
  1485  		}
  1486  	}
  1487  	if !gotMtime.Equal(wantMtime) {
  1488  		errormsg := fmt.Sprintf("mtime mismatch, got: %q, want: %q", gotMtime, wantMtime)
  1489  		switch runtime.GOOS {
  1490  		case "dragonfly":
  1491  			if omitAt && omitMt {
  1492  				t.Log(errormsg)
  1493  				t.Log("Known DragonFly BSD issue (won't work when both times are omitted); ignoring.")
  1494  			} else {
  1495  				t.Error(errormsg)
  1496  			}
  1497  		default:
  1498  			t.Error(errormsg)
  1499  		}
  1500  	}
  1501  }
  1502  
  1503  func TestChtimesDir(t *testing.T) {
  1504  	t.Parallel()
  1505  
  1506  	testChtimes(t, t.TempDir())
  1507  }
  1508  
  1509  func testChtimes(t *testing.T, name string) {
  1510  	st, err := Stat(name)
  1511  	if err != nil {
  1512  		t.Fatalf("Stat %s: %s", name, err)
  1513  	}
  1514  	preStat := st
  1515  
  1516  	// Move access and modification time back a second
  1517  	at := Atime(preStat)
  1518  	mt := preStat.ModTime()
  1519  	err = Chtimes(name, at.Add(-time.Second), mt.Add(-time.Second))
  1520  	if err != nil {
  1521  		t.Fatalf("Chtimes %s: %s", name, err)
  1522  	}
  1523  
  1524  	st, err = Stat(name)
  1525  	if err != nil {
  1526  		t.Fatalf("second Stat %s: %s", name, err)
  1527  	}
  1528  	postStat := st
  1529  
  1530  	pat := Atime(postStat)
  1531  	pmt := postStat.ModTime()
  1532  	if !pat.Before(at) {
  1533  		errormsg := fmt.Sprintf("AccessTime didn't go backwards; was=%v, after=%v", at, pat)
  1534  		switch runtime.GOOS {
  1535  		case "plan9":
  1536  			// Mtime is the time of the last change of
  1537  			// content.  Similarly, atime is set whenever
  1538  			// the contents are accessed; also, it is set
  1539  			// whenever mtime is set.
  1540  		case "netbsd":
  1541  			if hasNoatime() {
  1542  				t.Log(errormsg)
  1543  				t.Log("Known NetBSD issue (atime not changed on fs mounted with noatime); ignoring.")
  1544  			} else {
  1545  				t.Error(errormsg)
  1546  			}
  1547  		default:
  1548  			t.Error(errormsg)
  1549  		}
  1550  	}
  1551  
  1552  	if !pmt.Before(mt) {
  1553  		t.Errorf("ModTime didn't go backwards; was=%v, after=%v", mt, pmt)
  1554  	}
  1555  }
  1556  
  1557  func TestChtimesToUnixZero(t *testing.T) {
  1558  	file := newFile(t)
  1559  	fn := file.Name()
  1560  	if _, err := file.Write([]byte("hi")); err != nil {
  1561  		t.Fatal(err)
  1562  	}
  1563  	if err := file.Close(); err != nil {
  1564  		t.Fatal(err)
  1565  	}
  1566  
  1567  	unixZero := time.Unix(0, 0)
  1568  	if err := Chtimes(fn, unixZero, unixZero); err != nil {
  1569  		t.Fatalf("Chtimes failed: %v", err)
  1570  	}
  1571  
  1572  	st, err := Stat(fn)
  1573  	if err != nil {
  1574  		t.Fatal(err)
  1575  	}
  1576  
  1577  	if mt := st.ModTime(); mt != unixZero {
  1578  		t.Errorf("mtime is %v, want %v", mt, unixZero)
  1579  	}
  1580  }
  1581  
  1582  func TestFileChdir(t *testing.T) {
  1583  	wd, err := Getwd()
  1584  	if err != nil {
  1585  		t.Fatalf("Getwd: %s", err)
  1586  	}
  1587  	t.Chdir(".") // Ensure wd is restored after the test.
  1588  
  1589  	fd, err := Open(".")
  1590  	if err != nil {
  1591  		t.Fatalf("Open .: %s", err)
  1592  	}
  1593  	defer fd.Close()
  1594  
  1595  	if err := Chdir("/"); err != nil {
  1596  		t.Fatalf("Chdir /: %s", err)
  1597  	}
  1598  
  1599  	if err := fd.Chdir(); err != nil {
  1600  		t.Fatalf("fd.Chdir: %s", err)
  1601  	}
  1602  
  1603  	wdNew, err := Getwd()
  1604  	if err != nil {
  1605  		t.Fatalf("Getwd: %s", err)
  1606  	}
  1607  
  1608  	wdInfo, err := fd.Stat()
  1609  	if err != nil {
  1610  		t.Fatal(err)
  1611  	}
  1612  	newInfo, err := Stat(wdNew)
  1613  	if err != nil {
  1614  		t.Fatal(err)
  1615  	}
  1616  	if !SameFile(wdInfo, newInfo) {
  1617  		t.Fatalf("fd.Chdir failed: got %s, want %s", wdNew, wd)
  1618  	}
  1619  }
  1620  
  1621  // TestFileChdirTestlog verifies that (*File).Chdir notifies the testlog,
  1622  // just like os.Chdir does. cmd/go's test cache relies on every working
  1623  // directory change being recorded so that relative paths logged by later
  1624  // Open/Stat calls can be resolved against the correct directory.
  1625  func TestFileChdirTestlog(t *testing.T) {
  1626  	if Getenv("GO_TEST_FILE_CHDIR_TESTLOG") == "1" {
  1627  		fd, err := Open(".")
  1628  		if err != nil {
  1629  			t.Fatalf("Open .: %s", err)
  1630  		}
  1631  		defer fd.Close()
  1632  		if err := Chdir(TempDir()); err != nil {
  1633  			t.Fatalf("Chdir: %s", err)
  1634  		}
  1635  		if err := fd.Chdir(); err != nil {
  1636  			t.Fatalf("fd.Chdir: %s", err)
  1637  		}
  1638  		return
  1639  	}
  1640  
  1641  	testenv.MustHaveExec(t)
  1642  	exe := testenv.Executable(t)
  1643  	logfile := filepath.Join(t.TempDir(), "testlog.txt")
  1644  	cmd := testenv.Command(t, exe,
  1645  		"-test.run=^TestFileChdirTestlog$",
  1646  		"-test.testlogfile="+logfile)
  1647  	cmd = testenv.CleanCmdEnv(cmd)
  1648  	cmd.Env = append(cmd.Env, "GO_TEST_FILE_CHDIR_TESTLOG=1")
  1649  	if out, err := cmd.CombinedOutput(); err != nil {
  1650  		t.Fatalf("helper failed: %v\n%s", err, out)
  1651  	}
  1652  
  1653  	data, err := ReadFile(logfile)
  1654  	if err != nil {
  1655  		t.Fatal(err)
  1656  	}
  1657  	chdirs := 0
  1658  	for _, line := range strings.Split(string(data), "\n") {
  1659  		if strings.HasPrefix(line, "chdir ") {
  1660  			chdirs++
  1661  		}
  1662  	}
  1663  	if chdirs < 2 {
  1664  		t.Fatalf("got %d chdir testlog entries, want at least 2; testlog:\n%s", chdirs, data)
  1665  	}
  1666  }
  1667  
  1668  func TestChdirAndGetwd(t *testing.T) {
  1669  	t.Chdir(t.TempDir()) // Ensure wd is restored after the test.
  1670  
  1671  	// These are chosen carefully not to be symlinks on a Mac
  1672  	// (unlike, say, /var, /etc), except /tmp, which we handle below.
  1673  	dirs := []string{"/", "/usr/bin", "/tmp"}
  1674  	// /usr/bin does not usually exist on Plan 9 or Android.
  1675  	switch runtime.GOOS {
  1676  	case "android":
  1677  		dirs = []string{"/system/bin"}
  1678  	case "plan9":
  1679  		dirs = []string{"/", "/usr"}
  1680  	case "ios", "windows", "wasip1":
  1681  		dirs = nil
  1682  		for _, dir := range []string{t.TempDir(), t.TempDir()} {
  1683  			// Expand symlinks so path equality tests work.
  1684  			dir, err := filepath.EvalSymlinks(dir)
  1685  			if err != nil {
  1686  				t.Fatalf("EvalSymlinks: %v", err)
  1687  			}
  1688  			dirs = append(dirs, dir)
  1689  		}
  1690  	}
  1691  	for mode := 0; mode < 2; mode++ {
  1692  		for _, d := range dirs {
  1693  			var err error
  1694  			if mode == 0 {
  1695  				err = Chdir(d)
  1696  			} else {
  1697  				fd1, err1 := Open(d)
  1698  				if err1 != nil {
  1699  					t.Errorf("Open %s: %s", d, err1)
  1700  					continue
  1701  				}
  1702  				err = fd1.Chdir()
  1703  				fd1.Close()
  1704  			}
  1705  			if d == "/tmp" {
  1706  				Setenv("PWD", "/tmp")
  1707  			}
  1708  			pwd, err1 := Getwd()
  1709  			if err != nil {
  1710  				t.Fatalf("Chdir %s: %s", d, err)
  1711  			}
  1712  			if err1 != nil {
  1713  				t.Fatalf("Getwd in %s: %s", d, err1)
  1714  			}
  1715  			if !equal(pwd, d) {
  1716  				t.Fatalf("Getwd returned %q want %q", pwd, d)
  1717  			}
  1718  		}
  1719  	}
  1720  }
  1721  
  1722  // Test that Chdir+Getwd is program-wide.
  1723  func TestProgWideChdir(t *testing.T) {
  1724  	const N = 10
  1725  	var wg sync.WaitGroup
  1726  	hold := make(chan struct{})
  1727  	done := make(chan struct{})
  1728  
  1729  	d := t.TempDir()
  1730  	t.Chdir(d)
  1731  
  1732  	// Note the deferred Wait must be called after the deferred close(done),
  1733  	// to ensure the N goroutines have been released even if the main goroutine
  1734  	// calls Fatalf. It must be called before the Chdir back to the original
  1735  	// directory, and before the deferred deletion implied by TempDir,
  1736  	// so as not to interfere while the N goroutines are still running.
  1737  	defer wg.Wait()
  1738  	defer close(done)
  1739  
  1740  	for i := 0; i < N; i++ {
  1741  		wg.Add(1)
  1742  		go func(i int) {
  1743  			defer wg.Done()
  1744  			// Lock half the goroutines in their own operating system
  1745  			// thread to exercise more scheduler possibilities.
  1746  			if i%2 == 1 {
  1747  				// On Plan 9, after calling LockOSThread, the goroutines
  1748  				// run on different processes which don't share the working
  1749  				// directory. This used to be an issue because Go expects
  1750  				// the working directory to be program-wide.
  1751  				// See issue 9428.
  1752  				runtime.LockOSThread()
  1753  			}
  1754  			select {
  1755  			case <-done:
  1756  				return
  1757  			case <-hold:
  1758  			}
  1759  			// Getwd might be wrong
  1760  			f0, err := Stat(".")
  1761  			if err != nil {
  1762  				t.Error(err)
  1763  				return
  1764  			}
  1765  			pwd, err := Getwd()
  1766  			if err != nil {
  1767  				t.Errorf("Getwd: %v", err)
  1768  				return
  1769  			}
  1770  			if pwd != d {
  1771  				t.Errorf("Getwd() = %q, want %q", pwd, d)
  1772  				return
  1773  			}
  1774  			f1, err := Stat(pwd)
  1775  			if err != nil {
  1776  				t.Error(err)
  1777  				return
  1778  			}
  1779  			if !SameFile(f0, f1) {
  1780  				t.Errorf(`Samefile(Stat("."), Getwd()) reports false (%s != %s)`, f0.Name(), f1.Name())
  1781  				return
  1782  			}
  1783  		}(i)
  1784  	}
  1785  	var err error
  1786  	if err = Chdir(d); err != nil {
  1787  		t.Fatalf("Chdir: %v", err)
  1788  	}
  1789  	// OS X sets TMPDIR to a symbolic link.
  1790  	// So we resolve our working directory again before the test.
  1791  	d, err = Getwd()
  1792  	if err != nil {
  1793  		t.Fatalf("Getwd: %v", err)
  1794  	}
  1795  	close(hold)
  1796  	wg.Wait()
  1797  }
  1798  
  1799  func TestSeek(t *testing.T) {
  1800  	t.Parallel()
  1801  
  1802  	f := newFile(t)
  1803  
  1804  	const data = "hello, world\n"
  1805  	io.WriteString(f, data)
  1806  
  1807  	type test struct {
  1808  		in     int64
  1809  		whence int
  1810  		out    int64
  1811  	}
  1812  	var tests = []test{
  1813  		{0, io.SeekCurrent, int64(len(data))},
  1814  		{0, io.SeekStart, 0},
  1815  		{5, io.SeekStart, 5},
  1816  		{0, io.SeekEnd, int64(len(data))},
  1817  		{0, io.SeekStart, 0},
  1818  		{-1, io.SeekEnd, int64(len(data)) - 1},
  1819  		{1 << 33, io.SeekStart, 1 << 33},
  1820  		{1 << 33, io.SeekEnd, 1<<33 + int64(len(data))},
  1821  
  1822  		// Issue 21681, Windows 4G-1, etc:
  1823  		{1<<32 - 1, io.SeekStart, 1<<32 - 1},
  1824  		{0, io.SeekCurrent, 1<<32 - 1},
  1825  		{2<<32 - 1, io.SeekStart, 2<<32 - 1},
  1826  		{0, io.SeekCurrent, 2<<32 - 1},
  1827  	}
  1828  	for i, tt := range tests {
  1829  		off, err := f.Seek(tt.in, tt.whence)
  1830  		if off != tt.out || err != nil {
  1831  			t.Errorf("#%d: Seek(%v, %v) = %v, %v want %v, nil", i, tt.in, tt.whence, off, err, tt.out)
  1832  		}
  1833  	}
  1834  }
  1835  
  1836  func TestSeekError(t *testing.T) {
  1837  	switch runtime.GOOS {
  1838  	case "js", "plan9", "wasip1":
  1839  		t.Skipf("skipping test on %v", runtime.GOOS)
  1840  	}
  1841  	t.Parallel()
  1842  
  1843  	r, w, err := Pipe()
  1844  	if err != nil {
  1845  		t.Fatal(err)
  1846  	}
  1847  	_, err = r.Seek(0, 0)
  1848  	if err == nil {
  1849  		t.Fatal("Seek on pipe should fail")
  1850  	}
  1851  	if perr, ok := err.(*PathError); !ok || perr.Err != syscall.ESPIPE {
  1852  		t.Errorf("Seek returned error %v, want &PathError{Err: syscall.ESPIPE}", err)
  1853  	}
  1854  	_, err = w.Seek(0, 0)
  1855  	if err == nil {
  1856  		t.Fatal("Seek on pipe should fail")
  1857  	}
  1858  	if perr, ok := err.(*PathError); !ok || perr.Err != syscall.ESPIPE {
  1859  		t.Errorf("Seek returned error %v, want &PathError{Err: syscall.ESPIPE}", err)
  1860  	}
  1861  }
  1862  
  1863  func TestOpenError(t *testing.T) {
  1864  	t.Parallel()
  1865  	dir := makefs(t, []string{
  1866  		"is-a-file",
  1867  		"is-a-dir/",
  1868  	})
  1869  	t.Run("NoRoot", func(t *testing.T) { testOpenError(t, dir, false) })
  1870  	t.Run("InRoot", func(t *testing.T) { testOpenError(t, dir, true) })
  1871  }
  1872  func testOpenError(t *testing.T, dir string, rooted bool) {
  1873  	t.Parallel()
  1874  	var r *Root
  1875  	if rooted {
  1876  		var err error
  1877  		r, err = OpenRoot(dir)
  1878  		if err != nil {
  1879  			t.Fatal(err)
  1880  		}
  1881  		defer r.Close()
  1882  	}
  1883  	for _, tt := range []struct {
  1884  		path  string
  1885  		mode  int
  1886  		error error
  1887  	}{{
  1888  		"no-such-file",
  1889  		O_RDONLY,
  1890  		syscall.ENOENT,
  1891  	}, {
  1892  		"is-a-dir",
  1893  		O_WRONLY,
  1894  		syscall.EISDIR,
  1895  	}, {
  1896  		"is-a-file/no-such-file",
  1897  		O_WRONLY,
  1898  		syscall.ENOTDIR,
  1899  	}} {
  1900  		var f *File
  1901  		var err error
  1902  		var name string
  1903  		if rooted {
  1904  			name = fmt.Sprintf("Root(%q).OpenFile(%q, %d)", dir, tt.path, tt.mode)
  1905  			f, err = r.OpenFile(tt.path, tt.mode, 0)
  1906  		} else {
  1907  			path := filepath.Join(dir, tt.path)
  1908  			name = fmt.Sprintf("OpenFile(%q, %d)", path, tt.mode)
  1909  			f, err = OpenFile(path, tt.mode, 0)
  1910  		}
  1911  		if err == nil {
  1912  			t.Errorf("%v succeeded", name)
  1913  			f.Close()
  1914  			continue
  1915  		}
  1916  		perr, ok := err.(*PathError)
  1917  		if !ok {
  1918  			t.Errorf("%v returns error of %T type; want *PathError", name, err)
  1919  		}
  1920  		if perr.Err != tt.error {
  1921  			if runtime.GOOS == "plan9" {
  1922  				syscallErrStr := perr.Err.Error()
  1923  				expectedErrStr := strings.Replace(tt.error.Error(), "file ", "", 1)
  1924  				if !strings.HasSuffix(syscallErrStr, expectedErrStr) {
  1925  					// Some Plan 9 file servers incorrectly return
  1926  					// EPERM or EACCES rather than EISDIR when a directory is
  1927  					// opened for write.
  1928  					if tt.error == syscall.EISDIR &&
  1929  						(strings.HasSuffix(syscallErrStr, syscall.EPERM.Error()) ||
  1930  							strings.HasSuffix(syscallErrStr, syscall.EACCES.Error())) {
  1931  						continue
  1932  					}
  1933  					t.Errorf("%v = _, %q; want suffix %q", name, syscallErrStr, expectedErrStr)
  1934  				}
  1935  				continue
  1936  			}
  1937  			if runtime.GOOS == "dragonfly" {
  1938  				// DragonFly incorrectly returns EACCES rather
  1939  				// EISDIR when a directory is opened for write.
  1940  				if tt.error == syscall.EISDIR && perr.Err == syscall.EACCES {
  1941  					continue
  1942  				}
  1943  			}
  1944  			t.Errorf("%v = _, %q; want %q", name, perr.Err.Error(), tt.error.Error())
  1945  		}
  1946  	}
  1947  }
  1948  
  1949  func TestOpenNoName(t *testing.T) {
  1950  	f, err := Open("")
  1951  	if err == nil {
  1952  		f.Close()
  1953  		t.Fatal(`Open("") succeeded`)
  1954  	}
  1955  }
  1956  
  1957  func runBinHostname(t *testing.T) string {
  1958  	// Run /bin/hostname and collect output.
  1959  	r, w, err := Pipe()
  1960  	if err != nil {
  1961  		t.Fatal(err)
  1962  	}
  1963  	defer r.Close()
  1964  
  1965  	path, err := exec.LookPath("hostname")
  1966  	if err != nil {
  1967  		if errors.Is(err, exec.ErrNotFound) {
  1968  			t.Skip("skipping test; test requires hostname but it does not exist")
  1969  		}
  1970  		t.Fatal(err)
  1971  	}
  1972  
  1973  	argv := []string{"hostname"}
  1974  	if runtime.GOOS == "aix" {
  1975  		argv = []string{"hostname", "-s"}
  1976  	}
  1977  	p, err := StartProcess(path, argv, &ProcAttr{Files: []*File{nil, w, Stderr}})
  1978  	if err != nil {
  1979  		t.Fatal(err)
  1980  	}
  1981  	w.Close()
  1982  
  1983  	var b strings.Builder
  1984  	io.Copy(&b, r)
  1985  	_, err = p.Wait()
  1986  	if err != nil {
  1987  		t.Fatalf("run hostname Wait: %v", err)
  1988  	}
  1989  	err = p.Kill()
  1990  	if err == nil {
  1991  		t.Errorf("expected an error from Kill running 'hostname'")
  1992  	}
  1993  	output := b.String()
  1994  	if n := len(output); n > 0 && output[n-1] == '\n' {
  1995  		output = output[0 : n-1]
  1996  	}
  1997  	if output == "" {
  1998  		t.Fatalf("/bin/hostname produced no output")
  1999  	}
  2000  
  2001  	return output
  2002  }
  2003  
  2004  func testWindowsHostname(t *testing.T, hostname string) {
  2005  	cmd := testenv.Command(t, "hostname")
  2006  	out, err := cmd.Output()
  2007  	if err != nil {
  2008  		t.Fatalf("Failed to execute hostname command: %v %s", err, out)
  2009  	}
  2010  	want := strings.Trim(string(out), "\r\n")
  2011  	if hostname != want {
  2012  		t.Fatalf("Hostname() = %q != system hostname of %q", hostname, want)
  2013  	}
  2014  }
  2015  
  2016  func TestHostname(t *testing.T) {
  2017  	t.Parallel()
  2018  
  2019  	hostname, err := Hostname()
  2020  	if err != nil {
  2021  		t.Fatal(err)
  2022  	}
  2023  	if hostname == "" {
  2024  		t.Fatal("Hostname returned empty string and no error")
  2025  	}
  2026  	if strings.Contains(hostname, "\x00") {
  2027  		t.Fatalf("unexpected zero byte in hostname: %q", hostname)
  2028  	}
  2029  
  2030  	// There is no other way to fetch hostname on windows, but via winapi.
  2031  	// On Plan 9 it can be taken from #c/sysname as Hostname() does.
  2032  	switch runtime.GOOS {
  2033  	case "android", "plan9":
  2034  		// No /bin/hostname to verify against.
  2035  		return
  2036  	case "windows":
  2037  		testWindowsHostname(t, hostname)
  2038  		return
  2039  	}
  2040  
  2041  	testenv.MustHaveExec(t)
  2042  
  2043  	// Check internal Hostname() against the output of /bin/hostname.
  2044  	// Allow that the internal Hostname returns a Fully Qualified Domain Name
  2045  	// and the /bin/hostname only returns the first component
  2046  	want := runBinHostname(t)
  2047  	if hostname != want {
  2048  		host, _, ok := strings.Cut(hostname, ".")
  2049  		if !ok || host != want {
  2050  			t.Errorf("Hostname() = %q, want %q", hostname, want)
  2051  		}
  2052  	}
  2053  }
  2054  
  2055  func TestReadAt(t *testing.T) {
  2056  	t.Parallel()
  2057  
  2058  	f := newFile(t)
  2059  
  2060  	const data = "hello, world\n"
  2061  	io.WriteString(f, data)
  2062  
  2063  	b := make([]byte, 5)
  2064  	n, err := f.ReadAt(b, 7)
  2065  	if err != nil || n != len(b) {
  2066  		t.Fatalf("ReadAt 7: %d, %v", n, err)
  2067  	}
  2068  	if string(b) != "world" {
  2069  		t.Fatalf("ReadAt 7: have %q want %q", string(b), "world")
  2070  	}
  2071  }
  2072  
  2073  // Verify that ReadAt doesn't affect seek offset.
  2074  // In the Plan 9 kernel, there used to be a bug in the implementation of
  2075  // the pread syscall, where the channel offset was erroneously updated after
  2076  // calling pread on a file.
  2077  func TestReadAtOffset(t *testing.T) {
  2078  	t.Parallel()
  2079  
  2080  	f := newFile(t)
  2081  
  2082  	const data = "hello, world\n"
  2083  	io.WriteString(f, data)
  2084  
  2085  	f.Seek(0, 0)
  2086  	b := make([]byte, 5)
  2087  
  2088  	n, err := f.ReadAt(b, 7)
  2089  	if err != nil || n != len(b) {
  2090  		t.Fatalf("ReadAt 7: %d, %v", n, err)
  2091  	}
  2092  	if string(b) != "world" {
  2093  		t.Fatalf("ReadAt 7: have %q want %q", string(b), "world")
  2094  	}
  2095  
  2096  	n, err = f.Read(b)
  2097  	if err != nil || n != len(b) {
  2098  		t.Fatalf("Read: %d, %v", n, err)
  2099  	}
  2100  	if string(b) != "hello" {
  2101  		t.Fatalf("Read: have %q want %q", string(b), "hello")
  2102  	}
  2103  }
  2104  
  2105  // Verify that ReadAt doesn't allow negative offset.
  2106  func TestReadAtNegativeOffset(t *testing.T) {
  2107  	t.Parallel()
  2108  
  2109  	f := newFile(t)
  2110  
  2111  	const data = "hello, world\n"
  2112  	io.WriteString(f, data)
  2113  
  2114  	f.Seek(0, 0)
  2115  	b := make([]byte, 5)
  2116  
  2117  	n, err := f.ReadAt(b, -10)
  2118  
  2119  	const wantsub = "negative offset"
  2120  	if !strings.Contains(fmt.Sprint(err), wantsub) || n != 0 {
  2121  		t.Errorf("ReadAt(-10) = %v, %v; want 0, ...%q...", n, err, wantsub)
  2122  	}
  2123  }
  2124  
  2125  func TestWriteAt(t *testing.T) {
  2126  	t.Parallel()
  2127  
  2128  	f := newFile(t)
  2129  
  2130  	const data = "hello, world"
  2131  	io.WriteString(f, data)
  2132  
  2133  	n, err := f.WriteAt([]byte("WOR"), 7)
  2134  	if err != nil || n != 3 {
  2135  		t.Fatalf("WriteAt 7: %d, %v", n, err)
  2136  	}
  2137  	n, err = io.WriteString(f, "!") // test that WriteAt doesn't change the file offset
  2138  	if err != nil || n != 1 {
  2139  		t.Fatal(err)
  2140  	}
  2141  
  2142  	got, err := ReadFile(f.Name())
  2143  	if err != nil {
  2144  		t.Fatalf("ReadFile %s: %v", f.Name(), err)
  2145  	}
  2146  	want := "hello, WORld!"
  2147  	if string(got) != want {
  2148  		t.Fatalf("after write: have %q want %q", string(got), want)
  2149  	}
  2150  }
  2151  
  2152  func TestWriteAtConcurrent(t *testing.T) {
  2153  	t.Parallel()
  2154  
  2155  	f := newFile(t)
  2156  	io.WriteString(f, "0000000000")
  2157  
  2158  	var wg sync.WaitGroup
  2159  	for i := range 10 {
  2160  		wg.Add(1)
  2161  		go func() {
  2162  			defer wg.Done()
  2163  			n, err := f.WriteAt([]byte(strconv.Itoa(i)), int64(i))
  2164  			if err != nil || n != 1 {
  2165  				t.Errorf("WriteAt %d: %d, %v", i, n, err)
  2166  			}
  2167  			n, err = io.WriteString(f, "!") // test that WriteAt doesn't change the file offset
  2168  			if err != nil || n != 1 {
  2169  				t.Error(err)
  2170  			}
  2171  		}()
  2172  	}
  2173  	wg.Wait()
  2174  
  2175  	got, err := ReadFile(f.Name())
  2176  	if err != nil {
  2177  		t.Fatalf("ReadFile %s: %v", f.Name(), err)
  2178  	}
  2179  	want := "0123456789!!!!!!!!!!"
  2180  	if string(got) != want {
  2181  		t.Fatalf("after write: have %q want %q", string(got), want)
  2182  	}
  2183  }
  2184  
  2185  // Verify that WriteAt doesn't allow negative offset.
  2186  func TestWriteAtNegativeOffset(t *testing.T) {
  2187  	t.Parallel()
  2188  
  2189  	f := newFile(t)
  2190  
  2191  	n, err := f.WriteAt([]byte("WORLD"), -10)
  2192  
  2193  	const wantsub = "negative offset"
  2194  	if !strings.Contains(fmt.Sprint(err), wantsub) || n != 0 {
  2195  		t.Errorf("WriteAt(-10) = %v, %v; want 0, ...%q...", n, err, wantsub)
  2196  	}
  2197  }
  2198  
  2199  // Verify that WriteAt doesn't work in append mode.
  2200  func TestWriteAtInAppendMode(t *testing.T) {
  2201  	t.Chdir(t.TempDir())
  2202  	f, err := OpenFile("write_at_in_append_mode.txt", O_APPEND|O_CREATE, 0666)
  2203  	if err != nil {
  2204  		t.Fatalf("OpenFile: %v", err)
  2205  	}
  2206  	defer f.Close()
  2207  
  2208  	_, err = f.WriteAt([]byte(""), 1)
  2209  	if err != ErrWriteAtInAppendMode {
  2210  		t.Fatalf("f.WriteAt returned %v, expected %v", err, ErrWriteAtInAppendMode)
  2211  	}
  2212  }
  2213  
  2214  func writeFile(t *testing.T, r *Root, fname string, flag int, text string) string {
  2215  	t.Helper()
  2216  	var f *File
  2217  	var err error
  2218  	if r == nil {
  2219  		f, err = OpenFile(fname, flag, 0666)
  2220  	} else {
  2221  		f, err = r.OpenFile(fname, flag, 0666)
  2222  	}
  2223  	if err != nil {
  2224  		t.Fatalf("Open: %v", err)
  2225  	}
  2226  	n, err := io.WriteString(f, text)
  2227  	if err != nil {
  2228  		t.Fatalf("WriteString: %d, %v", n, err)
  2229  	}
  2230  	f.Close()
  2231  	data, err := ReadFile(fname)
  2232  	if err != nil {
  2233  		t.Fatalf("ReadFile: %v", err)
  2234  	}
  2235  	return string(data)
  2236  }
  2237  
  2238  func TestAppend(t *testing.T) {
  2239  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  2240  		const f = "append.txt"
  2241  		s := writeFile(t, r, f, O_CREATE|O_TRUNC|O_RDWR, "new")
  2242  		if s != "new" {
  2243  			t.Fatalf("writeFile: have %q want %q", s, "new")
  2244  		}
  2245  		s = writeFile(t, r, f, O_APPEND|O_RDWR, "|append")
  2246  		if s != "new|append" {
  2247  			t.Fatalf("writeFile: have %q want %q", s, "new|append")
  2248  		}
  2249  		s = writeFile(t, r, f, O_CREATE|O_APPEND|O_RDWR, "|append")
  2250  		if s != "new|append|append" {
  2251  			t.Fatalf("writeFile: have %q want %q", s, "new|append|append")
  2252  		}
  2253  		err := Remove(f)
  2254  		if err != nil {
  2255  			t.Fatalf("Remove: %v", err)
  2256  		}
  2257  		s = writeFile(t, r, f, O_CREATE|O_APPEND|O_RDWR, "new&append")
  2258  		if s != "new&append" {
  2259  			t.Fatalf("writeFile: after append have %q want %q", s, "new&append")
  2260  		}
  2261  		s = writeFile(t, r, f, O_CREATE|O_RDWR, "old")
  2262  		if s != "old&append" {
  2263  			t.Fatalf("writeFile: after create have %q want %q", s, "old&append")
  2264  		}
  2265  		s = writeFile(t, r, f, O_CREATE|O_TRUNC|O_RDWR, "new")
  2266  		if s != "new" {
  2267  			t.Fatalf("writeFile: after truncate have %q want %q", s, "new")
  2268  		}
  2269  	})
  2270  }
  2271  
  2272  // TestFilePermissions tests setting Unix permission bits on file creation.
  2273  func TestFilePermissions(t *testing.T) {
  2274  	if Getuid() == 0 {
  2275  		t.Skip("skipping test when running as root")
  2276  	}
  2277  	for _, test := range []struct {
  2278  		name string
  2279  		mode FileMode
  2280  	}{
  2281  		{"r", 0o444},
  2282  		{"w", 0o222},
  2283  		{"rw", 0o666},
  2284  	} {
  2285  		t.Run(test.name, func(t *testing.T) {
  2286  			switch runtime.GOOS {
  2287  			case "windows":
  2288  				if test.mode&0444 == 0 {
  2289  					t.Skip("write-only files not supported on " + runtime.GOOS)
  2290  				}
  2291  			case "wasip1":
  2292  				t.Skip("file permissions not supported on " + runtime.GOOS)
  2293  			}
  2294  			testMaybeRooted(t, func(t *testing.T, r *Root) {
  2295  				const filename = "f"
  2296  				var f *File
  2297  				var err error
  2298  				if r == nil {
  2299  					f, err = OpenFile(filename, O_RDWR|O_CREATE|O_EXCL, test.mode)
  2300  				} else {
  2301  					f, err = r.OpenFile(filename, O_RDWR|O_CREATE|O_EXCL, test.mode)
  2302  				}
  2303  				if err != nil {
  2304  					t.Fatal(err)
  2305  				}
  2306  				f.Close()
  2307  				b, err := ReadFile(filename)
  2308  				if test.mode&0o444 != 0 {
  2309  					if err != nil {
  2310  						t.Errorf("ReadFile = %v; want success", err)
  2311  					}
  2312  				} else {
  2313  					if err == nil {
  2314  						t.Errorf("ReadFile = %q, <nil>; want failure", string(b))
  2315  					}
  2316  				}
  2317  				_, err = Stat(filename)
  2318  				if err != nil {
  2319  					t.Errorf("Stat = %v; want success", err)
  2320  				}
  2321  				err = WriteFile(filename, nil, 0666)
  2322  				if test.mode&0o222 != 0 {
  2323  					if err != nil {
  2324  						t.Errorf("WriteFile = %v; want success", err)
  2325  						b, err := ReadFile(filename)
  2326  						t.Errorf("ReadFile: %v", err)
  2327  						t.Errorf("file contents: %q", b)
  2328  					}
  2329  				} else {
  2330  					if err == nil {
  2331  						t.Errorf("WriteFile(%q) = <nil>; want failure", filename)
  2332  						st, err := Stat(filename)
  2333  						if err == nil {
  2334  							t.Errorf("mode: %s", st.Mode())
  2335  						}
  2336  						b, err := ReadFile(filename)
  2337  						t.Errorf("ReadFile: %v", err)
  2338  						t.Errorf("file contents: %q", b)
  2339  					}
  2340  				}
  2341  			})
  2342  		})
  2343  	}
  2344  
  2345  }
  2346  
  2347  func TestOpenFileCreateExclDanglingSymlink(t *testing.T) {
  2348  	testenv.MustHaveSymlink(t)
  2349  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  2350  		const link = "link"
  2351  		if err := Symlink("does_not_exist", link); err != nil {
  2352  			t.Fatal(err)
  2353  		}
  2354  		var f *File
  2355  		var err error
  2356  		if r == nil {
  2357  			f, err = OpenFile(link, O_WRONLY|O_CREATE|O_EXCL, 0o444)
  2358  		} else {
  2359  			f, err = r.OpenFile(link, O_WRONLY|O_CREATE|O_EXCL, 0o444)
  2360  		}
  2361  		if err == nil {
  2362  			f.Close()
  2363  		}
  2364  		if !errors.Is(err, ErrExist) {
  2365  			t.Errorf("OpenFile of a dangling symlink with O_CREATE|O_EXCL = %v, want ErrExist", err)
  2366  		}
  2367  		if _, err := Stat(link); err == nil {
  2368  			t.Errorf("OpenFile of a dangling symlink with O_CREATE|O_EXCL created a file")
  2369  		}
  2370  	})
  2371  }
  2372  
  2373  // TestFileRDWRFlags tests the O_RDONLY, O_WRONLY, and O_RDWR flags.
  2374  func TestFileRDWRFlags(t *testing.T) {
  2375  	for _, test := range []struct {
  2376  		name string
  2377  		flag int
  2378  	}{
  2379  		{"O_RDONLY", O_RDONLY},
  2380  		{"O_WRONLY", O_WRONLY},
  2381  		{"O_RDWR", O_RDWR},
  2382  	} {
  2383  		t.Run(test.name, func(t *testing.T) {
  2384  			testMaybeRooted(t, func(t *testing.T, r *Root) {
  2385  				const filename = "f"
  2386  				content := []byte("content")
  2387  				if err := WriteFile(filename, content, 0666); err != nil {
  2388  					t.Fatal(err)
  2389  				}
  2390  				var f *File
  2391  				var err error
  2392  				if r == nil {
  2393  					f, err = OpenFile(filename, test.flag, 0)
  2394  				} else {
  2395  					f, err = r.OpenFile(filename, test.flag, 0)
  2396  				}
  2397  				if err != nil {
  2398  					t.Fatal(err)
  2399  				}
  2400  				defer f.Close()
  2401  				got, err := io.ReadAll(f)
  2402  				if test.flag == O_WRONLY {
  2403  					if err == nil {
  2404  						t.Errorf("read file: %q, %v; want error", got, err)
  2405  					}
  2406  				} else {
  2407  					if err != nil || !bytes.Equal(got, content) {
  2408  						t.Errorf("read file: %q, %v; want %q, <nil>", got, err, content)
  2409  					}
  2410  				}
  2411  				if _, err := f.Seek(0, 0); err != nil {
  2412  					t.Fatalf("f.Seek: %v", err)
  2413  				}
  2414  				newcontent := []byte("CONTENT")
  2415  				_, err = f.Write(newcontent)
  2416  				if test.flag == O_RDONLY {
  2417  					if err == nil {
  2418  						t.Errorf("write file: succeeded, want error")
  2419  					}
  2420  				} else {
  2421  					if err != nil {
  2422  						t.Errorf("write file: %v, want success", err)
  2423  					}
  2424  				}
  2425  				f.Close()
  2426  				got, err = ReadFile(filename)
  2427  				if err != nil {
  2428  					t.Fatal(err)
  2429  				}
  2430  				want := content
  2431  				if test.flag != O_RDONLY {
  2432  					want = newcontent
  2433  				}
  2434  				if !bytes.Equal(got, want) {
  2435  					t.Fatalf("after write, file contains %q, want %q", got, want)
  2436  				}
  2437  			})
  2438  		})
  2439  	}
  2440  }
  2441  
  2442  func TestStatDirWithTrailingSlash(t *testing.T) {
  2443  	t.Parallel()
  2444  
  2445  	// Create new temporary directory and arrange to clean it up.
  2446  	path := t.TempDir()
  2447  
  2448  	// Stat of path should succeed.
  2449  	if _, err := Stat(path); err != nil {
  2450  		t.Fatalf("stat %s failed: %s", path, err)
  2451  	}
  2452  
  2453  	// Stat of path+"/" should succeed too.
  2454  	path += "/"
  2455  	if _, err := Stat(path); err != nil {
  2456  		t.Fatalf("stat %s failed: %s", path, err)
  2457  	}
  2458  }
  2459  
  2460  func TestNilProcessStateString(t *testing.T) {
  2461  	var ps *ProcessState
  2462  	s := ps.String()
  2463  	if s != "<nil>" {
  2464  		t.Errorf("(*ProcessState)(nil).String() = %q, want %q", s, "<nil>")
  2465  	}
  2466  }
  2467  
  2468  func TestSameFile(t *testing.T) {
  2469  	t.Chdir(t.TempDir())
  2470  	fa, err := Create("a")
  2471  	if err != nil {
  2472  		t.Fatalf("Create(a): %v", err)
  2473  	}
  2474  	fa.Close()
  2475  	fb, err := Create("b")
  2476  	if err != nil {
  2477  		t.Fatalf("Create(b): %v", err)
  2478  	}
  2479  	fb.Close()
  2480  
  2481  	ia1, err := Stat("a")
  2482  	if err != nil {
  2483  		t.Fatalf("Stat(a): %v", err)
  2484  	}
  2485  	ia2, err := Stat("a")
  2486  	if err != nil {
  2487  		t.Fatalf("Stat(a): %v", err)
  2488  	}
  2489  	if !SameFile(ia1, ia2) {
  2490  		t.Errorf("files should be same")
  2491  	}
  2492  
  2493  	ib, err := Stat("b")
  2494  	if err != nil {
  2495  		t.Fatalf("Stat(b): %v", err)
  2496  	}
  2497  	if SameFile(ia1, ib) {
  2498  		t.Errorf("files should be different")
  2499  	}
  2500  }
  2501  
  2502  func testDevNullFileInfo(t *testing.T, statname, devNullName string, fi FileInfo) {
  2503  	pre := fmt.Sprintf("%s(%q): ", statname, devNullName)
  2504  	if fi.Size() != 0 {
  2505  		t.Errorf(pre+"wrong file size have %d want 0", fi.Size())
  2506  	}
  2507  	if fi.Mode()&ModeDevice == 0 {
  2508  		t.Errorf(pre+"wrong file mode %q: ModeDevice is not set", fi.Mode())
  2509  	}
  2510  	if fi.Mode()&ModeCharDevice == 0 {
  2511  		t.Errorf(pre+"wrong file mode %q: ModeCharDevice is not set", fi.Mode())
  2512  	}
  2513  	if fi.Mode().IsRegular() {
  2514  		t.Errorf(pre+"wrong file mode %q: IsRegular returns true", fi.Mode())
  2515  	}
  2516  }
  2517  
  2518  func testDevNullFile(t *testing.T, devNullName string) {
  2519  	f, err := Open(devNullName)
  2520  	if err != nil {
  2521  		t.Fatalf("Open(%s): %v", devNullName, err)
  2522  	}
  2523  	defer f.Close()
  2524  
  2525  	fi, err := f.Stat()
  2526  	if err != nil {
  2527  		t.Fatalf("Stat(%s): %v", devNullName, err)
  2528  	}
  2529  	testDevNullFileInfo(t, "f.Stat", devNullName, fi)
  2530  
  2531  	fi, err = Stat(devNullName)
  2532  	if err != nil {
  2533  		t.Fatalf("Stat(%s): %v", devNullName, err)
  2534  	}
  2535  	testDevNullFileInfo(t, "Stat", devNullName, fi)
  2536  }
  2537  
  2538  func TestDevNullFile(t *testing.T) {
  2539  	t.Parallel()
  2540  
  2541  	testDevNullFile(t, DevNull)
  2542  	if runtime.GOOS == "windows" {
  2543  		testDevNullFile(t, "./nul")
  2544  		testDevNullFile(t, "//./nul")
  2545  	}
  2546  }
  2547  
  2548  var testLargeWrite = flag.Bool("large_write", false, "run TestLargeWriteToConsole test that floods console with output")
  2549  
  2550  func TestLargeWriteToConsole(t *testing.T) {
  2551  	if !*testLargeWrite {
  2552  		t.Skip("skipping console-flooding test; enable with -large_write")
  2553  	}
  2554  	b := make([]byte, 32000)
  2555  	for i := range b {
  2556  		b[i] = '.'
  2557  	}
  2558  	b[len(b)-1] = '\n'
  2559  	n, err := Stdout.Write(b)
  2560  	if err != nil {
  2561  		t.Fatalf("Write to os.Stdout failed: %v", err)
  2562  	}
  2563  	if n != len(b) {
  2564  		t.Errorf("Write to os.Stdout should return %d; got %d", len(b), n)
  2565  	}
  2566  	n, err = Stderr.Write(b)
  2567  	if err != nil {
  2568  		t.Fatalf("Write to os.Stderr failed: %v", err)
  2569  	}
  2570  	if n != len(b) {
  2571  		t.Errorf("Write to os.Stderr should return %d; got %d", len(b), n)
  2572  	}
  2573  }
  2574  
  2575  func TestStatDirModeExec(t *testing.T) {
  2576  	if runtime.GOOS == "wasip1" {
  2577  		t.Skip("Chmod is not supported on " + runtime.GOOS)
  2578  	}
  2579  	t.Parallel()
  2580  
  2581  	const mode = 0111
  2582  
  2583  	path := t.TempDir()
  2584  	if err := Chmod(path, 0777); err != nil {
  2585  		t.Fatalf("Chmod %q 0777: %v", path, err)
  2586  	}
  2587  
  2588  	dir, err := Stat(path)
  2589  	if err != nil {
  2590  		t.Fatalf("Stat %q (looking for mode %#o): %s", path, mode, err)
  2591  	}
  2592  	if dir.Mode()&mode != mode {
  2593  		t.Errorf("Stat %q: mode %#o want %#o", path, dir.Mode()&mode, mode)
  2594  	}
  2595  }
  2596  
  2597  func TestStatStdin(t *testing.T) {
  2598  	switch runtime.GOOS {
  2599  	case "android", "plan9":
  2600  		t.Skipf("%s doesn't have /bin/sh", runtime.GOOS)
  2601  	}
  2602  
  2603  	if Getenv("GO_WANT_HELPER_PROCESS") == "1" {
  2604  		st, err := Stdin.Stat()
  2605  		if err != nil {
  2606  			t.Fatalf("Stat failed: %v", err)
  2607  		}
  2608  		fmt.Println(st.Mode() & ModeNamedPipe)
  2609  		Exit(0)
  2610  	}
  2611  
  2612  	t.Parallel()
  2613  	exe := testenv.Executable(t)
  2614  
  2615  	fi, err := Stdin.Stat()
  2616  	if err != nil {
  2617  		t.Fatal(err)
  2618  	}
  2619  	switch mode := fi.Mode(); {
  2620  	case mode&ModeCharDevice != 0 && mode&ModeDevice != 0:
  2621  	case mode&ModeNamedPipe != 0:
  2622  	default:
  2623  		t.Fatalf("unexpected Stdin mode (%v), want ModeCharDevice or ModeNamedPipe", mode)
  2624  	}
  2625  
  2626  	cmd := testenv.Command(t, exe, "-test.run=^TestStatStdin$")
  2627  	cmd = testenv.CleanCmdEnv(cmd)
  2628  	cmd.Env = append(cmd.Env, "GO_WANT_HELPER_PROCESS=1")
  2629  	// This will make standard input a pipe.
  2630  	cmd.Stdin = strings.NewReader("output")
  2631  
  2632  	output, err := cmd.CombinedOutput()
  2633  	if err != nil {
  2634  		t.Fatalf("Failed to spawn child process: %v %q", err, string(output))
  2635  	}
  2636  
  2637  	// result will be like "prw-rw-rw"
  2638  	if len(output) < 1 || output[0] != 'p' {
  2639  		t.Fatalf("Child process reports stdin is not pipe '%v'", string(output))
  2640  	}
  2641  }
  2642  
  2643  func TestStatRelativeSymlink(t *testing.T) {
  2644  	testenv.MustHaveSymlink(t)
  2645  	t.Parallel()
  2646  
  2647  	tmpdir := t.TempDir()
  2648  	target := filepath.Join(tmpdir, "target")
  2649  	f, err := Create(target)
  2650  	if err != nil {
  2651  		t.Fatal(err)
  2652  	}
  2653  	defer f.Close()
  2654  
  2655  	st, err := f.Stat()
  2656  	if err != nil {
  2657  		t.Fatal(err)
  2658  	}
  2659  
  2660  	link := filepath.Join(tmpdir, "link")
  2661  	err = Symlink(filepath.Base(target), link)
  2662  	if err != nil {
  2663  		t.Fatal(err)
  2664  	}
  2665  
  2666  	st1, err := Stat(link)
  2667  	if err != nil {
  2668  		t.Fatal(err)
  2669  	}
  2670  
  2671  	if !SameFile(st, st1) {
  2672  		t.Error("Stat doesn't follow relative symlink")
  2673  	}
  2674  
  2675  	if runtime.GOOS == "windows" {
  2676  		Remove(link)
  2677  		err = Symlink(target[len(filepath.VolumeName(target)):], link)
  2678  		if err != nil {
  2679  			t.Fatal(err)
  2680  		}
  2681  
  2682  		st1, err := Stat(link)
  2683  		if err != nil {
  2684  			t.Fatal(err)
  2685  		}
  2686  
  2687  		if !SameFile(st, st1) {
  2688  			t.Error("Stat doesn't follow relative symlink")
  2689  		}
  2690  	}
  2691  }
  2692  
  2693  func TestReadAtEOF(t *testing.T) {
  2694  	t.Parallel()
  2695  
  2696  	f := newFile(t)
  2697  
  2698  	_, err := f.ReadAt(make([]byte, 10), 0)
  2699  	switch err {
  2700  	case io.EOF:
  2701  		// all good
  2702  	case nil:
  2703  		t.Fatalf("ReadAt succeeded")
  2704  	default:
  2705  		t.Fatalf("ReadAt failed: %s", err)
  2706  	}
  2707  }
  2708  
  2709  func TestLongPath(t *testing.T) {
  2710  	t.Parallel()
  2711  
  2712  	tmpdir := t.TempDir()
  2713  
  2714  	// Test the boundary of 247 and fewer bytes (normal) and 248 and more bytes (adjusted).
  2715  	sizes := []int{247, 248, 249, 400}
  2716  	for len(tmpdir) < 400 {
  2717  		tmpdir += "/dir3456789"
  2718  	}
  2719  	for _, sz := range sizes {
  2720  		t.Run(fmt.Sprintf("length=%d", sz), func(t *testing.T) {
  2721  			sizedTempDir := tmpdir[:sz-1] + "x" // Ensure it does not end with a slash.
  2722  
  2723  			// The various sized runs are for this call to trigger the boundary
  2724  			// condition.
  2725  			if err := MkdirAll(sizedTempDir, 0755); err != nil {
  2726  				t.Fatalf("MkdirAll failed: %v", err)
  2727  			}
  2728  			data := []byte("hello world\n")
  2729  			if err := WriteFile(sizedTempDir+"/foo.txt", data, 0644); err != nil {
  2730  				t.Fatalf("os.WriteFile() failed: %v", err)
  2731  			}
  2732  			if err := Rename(sizedTempDir+"/foo.txt", sizedTempDir+"/bar.txt"); err != nil {
  2733  				t.Fatalf("Rename failed: %v", err)
  2734  			}
  2735  			mtime := time.Now().Truncate(time.Minute)
  2736  			if err := Chtimes(sizedTempDir+"/bar.txt", mtime, mtime); err != nil {
  2737  				t.Fatalf("Chtimes failed: %v", err)
  2738  			}
  2739  			names := []string{"bar.txt"}
  2740  			if testenv.HasSymlink() {
  2741  				if err := Symlink(sizedTempDir+"/bar.txt", sizedTempDir+"/symlink.txt"); err != nil {
  2742  					t.Fatalf("Symlink failed: %v", err)
  2743  				}
  2744  				names = append(names, "symlink.txt")
  2745  			}
  2746  			if testenv.HasLink() {
  2747  				if err := Link(sizedTempDir+"/bar.txt", sizedTempDir+"/link.txt"); err != nil {
  2748  					t.Fatalf("Link failed: %v", err)
  2749  				}
  2750  				names = append(names, "link.txt")
  2751  			}
  2752  			for _, wantSize := range []int64{int64(len(data)), 0} {
  2753  				for _, name := range names {
  2754  					path := sizedTempDir + "/" + name
  2755  					dir, err := Stat(path)
  2756  					if err != nil {
  2757  						t.Fatalf("Stat(%q) failed: %v", path, err)
  2758  					}
  2759  					filesize := size(path, t)
  2760  					if dir.Size() != filesize || filesize != wantSize {
  2761  						t.Errorf("Size(%q) is %d, len(ReadFile()) is %d, want %d", path, dir.Size(), filesize, wantSize)
  2762  					}
  2763  					if runtime.GOOS != "wasip1" { // Chmod is not supported on wasip1
  2764  						err = Chmod(path, dir.Mode())
  2765  						if err != nil {
  2766  							t.Fatalf("Chmod(%q) failed: %v", path, err)
  2767  						}
  2768  					}
  2769  				}
  2770  				if err := Truncate(sizedTempDir+"/bar.txt", 0); err != nil {
  2771  					t.Fatalf("Truncate failed: %v", err)
  2772  				}
  2773  			}
  2774  		})
  2775  	}
  2776  }
  2777  
  2778  func testKillProcess(t *testing.T, processKiller func(p *Process)) {
  2779  	t.Parallel()
  2780  
  2781  	// Re-exec the test binary to start a process that hangs until stdin is closed.
  2782  	cmd := testenv.Command(t, testenv.Executable(t))
  2783  	cmd.Env = append(cmd.Environ(), "GO_OS_TEST_DRAIN_STDIN=1")
  2784  	stdout, err := cmd.StdoutPipe()
  2785  	if err != nil {
  2786  		t.Fatal(err)
  2787  	}
  2788  	stdin, err := cmd.StdinPipe()
  2789  	if err != nil {
  2790  		t.Fatal(err)
  2791  	}
  2792  	err = cmd.Start()
  2793  	if err != nil {
  2794  		t.Fatalf("Failed to start test process: %v", err)
  2795  	}
  2796  
  2797  	defer func() {
  2798  		if err := cmd.Wait(); err == nil {
  2799  			t.Errorf("Test process succeeded, but expected to fail")
  2800  		}
  2801  		stdin.Close() // Keep stdin alive until the process has finished dying.
  2802  	}()
  2803  
  2804  	// Wait for the process to be started.
  2805  	// (It will close its stdout when it reaches TestMain.)
  2806  	io.Copy(io.Discard, stdout)
  2807  
  2808  	processKiller(cmd.Process)
  2809  }
  2810  
  2811  func TestKillStartProcess(t *testing.T) {
  2812  	testKillProcess(t, func(p *Process) {
  2813  		err := p.Kill()
  2814  		if err != nil {
  2815  			t.Fatalf("Failed to kill test process: %v", err)
  2816  		}
  2817  	})
  2818  }
  2819  
  2820  func TestGetppid(t *testing.T) {
  2821  	if runtime.GOOS == "plan9" {
  2822  		// TODO: golang.org/issue/8206
  2823  		t.Skipf("skipping test on plan9; see issue 8206")
  2824  	}
  2825  
  2826  	if Getenv("GO_WANT_HELPER_PROCESS") == "1" {
  2827  		fmt.Print(Getppid())
  2828  		Exit(0)
  2829  	}
  2830  
  2831  	t.Parallel()
  2832  
  2833  	cmd := testenv.Command(t, testenv.Executable(t), "-test.run=^TestGetppid$")
  2834  	cmd.Env = append(Environ(), "GO_WANT_HELPER_PROCESS=1")
  2835  
  2836  	// verify that Getppid() from the forked process reports our process id
  2837  	output, err := cmd.CombinedOutput()
  2838  	if err != nil {
  2839  		t.Fatalf("Failed to spawn child process: %v %q", err, string(output))
  2840  	}
  2841  
  2842  	childPpid := string(output)
  2843  	ourPid := fmt.Sprintf("%d", Getpid())
  2844  	if childPpid != ourPid {
  2845  		t.Fatalf("Child process reports parent process id '%v', expected '%v'", childPpid, ourPid)
  2846  	}
  2847  }
  2848  
  2849  func TestKillFindProcess(t *testing.T) {
  2850  	testKillProcess(t, func(p *Process) {
  2851  		p2, err := FindProcess(p.Pid)
  2852  		if err != nil {
  2853  			t.Fatalf("Failed to find test process: %v", err)
  2854  		}
  2855  		err = p2.Kill()
  2856  		if err != nil {
  2857  			t.Fatalf("Failed to kill test process: %v", err)
  2858  		}
  2859  	})
  2860  }
  2861  
  2862  var nilFileMethodTests = []struct {
  2863  	name string
  2864  	f    func(*File) error
  2865  }{
  2866  	{"Chdir", func(f *File) error { return f.Chdir() }},
  2867  	{"Close", func(f *File) error { return f.Close() }},
  2868  	{"Chmod", func(f *File) error { return f.Chmod(0) }},
  2869  	{"Chown", func(f *File) error { return f.Chown(0, 0) }},
  2870  	{"Read", func(f *File) error { _, err := f.Read(make([]byte, 0)); return err }},
  2871  	{"ReadAt", func(f *File) error { _, err := f.ReadAt(make([]byte, 0), 0); return err }},
  2872  	{"Readdir", func(f *File) error { _, err := f.Readdir(1); return err }},
  2873  	{"Readdirnames", func(f *File) error { _, err := f.Readdirnames(1); return err }},
  2874  	{"Seek", func(f *File) error { _, err := f.Seek(0, io.SeekStart); return err }},
  2875  	{"Stat", func(f *File) error { _, err := f.Stat(); return err }},
  2876  	{"Sync", func(f *File) error { return f.Sync() }},
  2877  	{"Truncate", func(f *File) error { return f.Truncate(0) }},
  2878  	{"Write", func(f *File) error { _, err := f.Write(make([]byte, 0)); return err }},
  2879  	{"WriteAt", func(f *File) error { _, err := f.WriteAt(make([]byte, 0), 0); return err }},
  2880  	{"WriteString", func(f *File) error { _, err := f.WriteString(""); return err }},
  2881  }
  2882  
  2883  // Test that all File methods give ErrInvalid if the receiver is nil.
  2884  func TestNilFileMethods(t *testing.T) {
  2885  	t.Parallel()
  2886  
  2887  	for _, tt := range nilFileMethodTests {
  2888  		var file *File
  2889  		got := tt.f(file)
  2890  		if got != ErrInvalid {
  2891  			t.Errorf("%v should fail when f is nil; got %v", tt.name, got)
  2892  		}
  2893  	}
  2894  }
  2895  
  2896  func mkdirTree(t *testing.T, root string, level, max int) {
  2897  	if level >= max {
  2898  		return
  2899  	}
  2900  	level++
  2901  	for i := 'a'; i < 'c'; i++ {
  2902  		dir := filepath.Join(root, string(i))
  2903  		if err := Mkdir(dir, 0700); err != nil {
  2904  			t.Fatal(err)
  2905  		}
  2906  		mkdirTree(t, dir, level, max)
  2907  	}
  2908  }
  2909  
  2910  // Test that simultaneous RemoveAll do not report an error.
  2911  // As long as it gets removed, we should be happy.
  2912  func TestRemoveAllRace(t *testing.T) {
  2913  	if runtime.GOOS == "windows" {
  2914  		// Windows has very strict rules about things like
  2915  		// removing directories while someone else has
  2916  		// them open. The racing doesn't work out nicely
  2917  		// like it does on Unix.
  2918  		t.Skip("skipping on windows")
  2919  	}
  2920  	if runtime.GOOS == "dragonfly" {
  2921  		testenv.SkipFlaky(t, 52301)
  2922  	}
  2923  
  2924  	n := runtime.GOMAXPROCS(16)
  2925  	defer runtime.GOMAXPROCS(n)
  2926  	root := t.TempDir()
  2927  	mkdirTree(t, root, 1, 6)
  2928  	hold := make(chan struct{})
  2929  	var wg sync.WaitGroup
  2930  	for i := 0; i < 4; i++ {
  2931  		wg.Add(1)
  2932  		go func() {
  2933  			defer wg.Done()
  2934  			<-hold
  2935  			err := RemoveAll(root)
  2936  			if err != nil {
  2937  				t.Errorf("unexpected error: %T, %q", err, err)
  2938  			}
  2939  		}()
  2940  	}
  2941  	close(hold) // let workers race to remove root
  2942  	wg.Wait()
  2943  }
  2944  
  2945  // Test that reading from a pipe doesn't use up a thread.
  2946  func TestPipeThreads(t *testing.T) {
  2947  	switch runtime.GOOS {
  2948  	case "aix":
  2949  		t.Skip("skipping on aix; issue 70131")
  2950  	case "illumos", "solaris":
  2951  		t.Skip("skipping on Solaris and illumos; issue 19111")
  2952  	case "windows":
  2953  		t.Skip("skipping on Windows; issue 19098")
  2954  	case "plan9":
  2955  		t.Skip("skipping on Plan 9; does not support runtime poller")
  2956  	case "js":
  2957  		t.Skip("skipping on js; no support for os.Pipe")
  2958  	case "wasip1":
  2959  		t.Skip("skipping on wasip1; no support for os.Pipe")
  2960  	}
  2961  
  2962  	threads := 100
  2963  
  2964  	r := make([]*File, threads)
  2965  	w := make([]*File, threads)
  2966  	for i := 0; i < threads; i++ {
  2967  		rp, wp, err := Pipe()
  2968  		if err != nil {
  2969  			for j := 0; j < i; j++ {
  2970  				r[j].Close()
  2971  				w[j].Close()
  2972  			}
  2973  			t.Fatal(err)
  2974  		}
  2975  		r[i] = rp
  2976  		w[i] = wp
  2977  	}
  2978  
  2979  	defer debug.SetMaxThreads(debug.SetMaxThreads(threads / 2))
  2980  
  2981  	creading := make(chan bool, threads)
  2982  	cdone := make(chan bool, threads)
  2983  	for i := 0; i < threads; i++ {
  2984  		go func(i int) {
  2985  			var b [1]byte
  2986  			creading <- true
  2987  			if _, err := r[i].Read(b[:]); err != nil {
  2988  				t.Error(err)
  2989  			}
  2990  			if err := r[i].Close(); err != nil {
  2991  				t.Error(err)
  2992  			}
  2993  			cdone <- true
  2994  		}(i)
  2995  	}
  2996  
  2997  	for i := 0; i < threads; i++ {
  2998  		<-creading
  2999  	}
  3000  
  3001  	// If we are still alive, it means that the 100 goroutines did
  3002  	// not require 100 threads.
  3003  
  3004  	for i := 0; i < threads; i++ {
  3005  		if _, err := w[i].Write([]byte{0}); err != nil {
  3006  			t.Error(err)
  3007  		}
  3008  		if err := w[i].Close(); err != nil {
  3009  			t.Error(err)
  3010  		}
  3011  		<-cdone
  3012  	}
  3013  }
  3014  
  3015  func testDoubleCloseError(path string) func(*testing.T) {
  3016  	return func(t *testing.T) {
  3017  		t.Parallel()
  3018  
  3019  		file, err := Open(path)
  3020  		if err != nil {
  3021  			t.Fatal(err)
  3022  		}
  3023  		if err := file.Close(); err != nil {
  3024  			t.Fatalf("unexpected error from Close: %v", err)
  3025  		}
  3026  		if err := file.Close(); err == nil {
  3027  			t.Error("second Close did not fail")
  3028  		} else if pe, ok := err.(*PathError); !ok {
  3029  			t.Errorf("second Close: got %T, want %T", err, pe)
  3030  		} else if pe.Err != ErrClosed {
  3031  			t.Errorf("second Close: got %q, want %q", pe.Err, ErrClosed)
  3032  		} else {
  3033  			t.Logf("second close returned expected error %q", err)
  3034  		}
  3035  	}
  3036  }
  3037  
  3038  func TestDoubleCloseError(t *testing.T) {
  3039  	t.Parallel()
  3040  	t.Run("file", testDoubleCloseError(filepath.Join(sfdir, sfname)))
  3041  	t.Run("dir", testDoubleCloseError(sfdir))
  3042  }
  3043  
  3044  func TestUserCacheDir(t *testing.T) {
  3045  	t.Parallel()
  3046  
  3047  	dir, err := UserCacheDir()
  3048  	if err != nil {
  3049  		t.Skipf("skipping: %v", err)
  3050  	}
  3051  	if dir == "" {
  3052  		t.Fatalf("UserCacheDir returned %q; want non-empty path or error", dir)
  3053  	}
  3054  
  3055  	fi, err := Stat(dir)
  3056  	if err != nil {
  3057  		if IsNotExist(err) {
  3058  			t.Log(err)
  3059  			return
  3060  		}
  3061  		t.Fatal(err)
  3062  	}
  3063  	if !fi.IsDir() {
  3064  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3065  	}
  3066  }
  3067  
  3068  func TestUserCacheDirXDGConfigDirEnvVar(t *testing.T) {
  3069  	switch runtime.GOOS {
  3070  	case "windows", "darwin", "plan9":
  3071  		t.Skip("$XDG_CACHE_HOME is effective only on Unix systems")
  3072  	}
  3073  
  3074  	wd, err := Getwd()
  3075  	if err != nil {
  3076  		t.Fatal(err)
  3077  	}
  3078  	t.Setenv("XDG_CACHE_HOME", wd)
  3079  
  3080  	dir, err := UserCacheDir()
  3081  	if err != nil {
  3082  		t.Fatal(err)
  3083  	}
  3084  	if dir != wd {
  3085  		t.Fatalf("UserCacheDir returned %q; want the value of $XDG_CACHE_HOME %q", dir, wd)
  3086  	}
  3087  
  3088  	t.Setenv("XDG_CACHE_HOME", "some-dir")
  3089  	_, err = UserCacheDir()
  3090  	if err == nil {
  3091  		t.Fatal("UserCacheDir succeeded though $XDG_CACHE_HOME contains a relative path")
  3092  	}
  3093  }
  3094  
  3095  func TestUserConfigDir(t *testing.T) {
  3096  	t.Parallel()
  3097  
  3098  	dir, err := UserConfigDir()
  3099  	if err != nil {
  3100  		t.Skipf("skipping: %v", err)
  3101  	}
  3102  	if dir == "" {
  3103  		t.Fatalf("UserConfigDir returned %q; want non-empty path or error", dir)
  3104  	}
  3105  
  3106  	fi, err := Stat(dir)
  3107  	if err != nil {
  3108  		if IsNotExist(err) {
  3109  			t.Log(err)
  3110  			return
  3111  		}
  3112  		t.Fatal(err)
  3113  	}
  3114  	if !fi.IsDir() {
  3115  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3116  	}
  3117  }
  3118  
  3119  func TestUserConfigDirXDGConfigDirEnvVar(t *testing.T) {
  3120  	switch runtime.GOOS {
  3121  	case "windows", "darwin", "plan9":
  3122  		t.Skip("$XDG_CONFIG_HOME is effective only on Unix systems")
  3123  	}
  3124  
  3125  	wd, err := Getwd()
  3126  	if err != nil {
  3127  		t.Fatal(err)
  3128  	}
  3129  	t.Setenv("XDG_CONFIG_HOME", wd)
  3130  
  3131  	dir, err := UserConfigDir()
  3132  	if err != nil {
  3133  		t.Fatal(err)
  3134  	}
  3135  	if dir != wd {
  3136  		t.Fatalf("UserConfigDir returned %q; want the value of $XDG_CONFIG_HOME %q", dir, wd)
  3137  	}
  3138  
  3139  	t.Setenv("XDG_CONFIG_HOME", "some-dir")
  3140  	_, err = UserConfigDir()
  3141  	if err == nil {
  3142  		t.Fatal("UserConfigDir succeeded though $XDG_CONFIG_HOME contains a relative path")
  3143  	}
  3144  }
  3145  
  3146  func TestUserHomeDir(t *testing.T) {
  3147  	t.Parallel()
  3148  
  3149  	dir, err := UserHomeDir()
  3150  	if dir == "" && err == nil {
  3151  		t.Fatal("UserHomeDir returned an empty string but no error")
  3152  	}
  3153  	if err != nil {
  3154  		// UserHomeDir may return a non-nil error if the environment variable
  3155  		// for the home directory is empty or unset in the environment.
  3156  		t.Skipf("skipping: %v", err)
  3157  	}
  3158  
  3159  	fi, err := Stat(dir)
  3160  	if err != nil {
  3161  		if IsNotExist(err) {
  3162  			// The user's home directory has a well-defined location, but does not
  3163  			// exist. (Maybe nothing has written to it yet? That could happen, for
  3164  			// example, on minimal VM images used for CI testing.)
  3165  			t.Log(err)
  3166  			return
  3167  		}
  3168  		t.Fatal(err)
  3169  	}
  3170  	if !fi.IsDir() {
  3171  		t.Fatalf("dir %s is not directory; type = %v", dir, fi.Mode())
  3172  	}
  3173  }
  3174  
  3175  func TestDirSeek(t *testing.T) {
  3176  	t.Parallel()
  3177  
  3178  	wd, err := Getwd()
  3179  	if err != nil {
  3180  		t.Fatal(err)
  3181  	}
  3182  	f, err := Open(wd)
  3183  	if err != nil {
  3184  		t.Fatal(err)
  3185  	}
  3186  	dirnames1, err := f.Readdirnames(0)
  3187  	if err != nil {
  3188  		t.Fatal(err)
  3189  	}
  3190  
  3191  	ret, err := f.Seek(0, 0)
  3192  	if err != nil {
  3193  		t.Fatal(err)
  3194  	}
  3195  	if ret != 0 {
  3196  		t.Fatalf("seek result not zero: %d", ret)
  3197  	}
  3198  
  3199  	dirnames2, err := f.Readdirnames(0)
  3200  	if err != nil {
  3201  		t.Fatal(err)
  3202  	}
  3203  
  3204  	if len(dirnames1) != len(dirnames2) {
  3205  		t.Fatalf("listings have different lengths: %d and %d\n", len(dirnames1), len(dirnames2))
  3206  	}
  3207  	for i, n1 := range dirnames1 {
  3208  		n2 := dirnames2[i]
  3209  		if n1 != n2 {
  3210  			t.Fatalf("different name i=%d n1=%s n2=%s\n", i, n1, n2)
  3211  		}
  3212  	}
  3213  }
  3214  
  3215  func TestReaddirSmallSeek(t *testing.T) {
  3216  	// See issue 37161. Read only one entry from a directory,
  3217  	// seek to the beginning, and read again. We should not see
  3218  	// duplicate entries.
  3219  	t.Parallel()
  3220  
  3221  	wd, err := Getwd()
  3222  	if err != nil {
  3223  		t.Fatal(err)
  3224  	}
  3225  	df, err := Open(filepath.Join(wd, "testdata", "issue37161"))
  3226  	if err != nil {
  3227  		t.Fatal(err)
  3228  	}
  3229  	names1, err := df.Readdirnames(1)
  3230  	if err != nil {
  3231  		t.Fatal(err)
  3232  	}
  3233  	if _, err = df.Seek(0, 0); err != nil {
  3234  		t.Fatal(err)
  3235  	}
  3236  	names2, err := df.Readdirnames(0)
  3237  	if err != nil {
  3238  		t.Fatal(err)
  3239  	}
  3240  	if len(names2) != 3 {
  3241  		t.Fatalf("first names: %v, second names: %v", names1, names2)
  3242  	}
  3243  }
  3244  
  3245  // isDeadlineExceeded reports whether err is or wraps ErrDeadlineExceeded.
  3246  // We also check that the error has a Timeout method that returns true.
  3247  func isDeadlineExceeded(err error) bool {
  3248  	if !IsTimeout(err) {
  3249  		return false
  3250  	}
  3251  	if !errors.Is(err, ErrDeadlineExceeded) {
  3252  		return false
  3253  	}
  3254  	return true
  3255  }
  3256  
  3257  // Test that opening a file does not change its permissions.  Issue 38225.
  3258  func TestOpenFileKeepsPermissions(t *testing.T) {
  3259  	t.Run("OpenFile", func(t *testing.T) {
  3260  		testOpenFileKeepsPermissions(t, OpenFile)
  3261  	})
  3262  	t.Run("RootOpenFile", func(t *testing.T) {
  3263  		testOpenFileKeepsPermissions(t, func(name string, flag int, perm FileMode) (*File, error) {
  3264  			dir, file := filepath.Split(name)
  3265  			r, err := OpenRoot(dir)
  3266  			if err != nil {
  3267  				return nil, err
  3268  			}
  3269  			defer r.Close()
  3270  			return r.OpenFile(file, flag, perm)
  3271  		})
  3272  	})
  3273  }
  3274  func testOpenFileKeepsPermissions(t *testing.T, openf func(name string, flag int, perm FileMode) (*File, error)) {
  3275  	t.Parallel()
  3276  
  3277  	dir := t.TempDir()
  3278  	name := filepath.Join(dir, "x")
  3279  	f, err := Create(name)
  3280  	if err != nil {
  3281  		t.Fatal(err)
  3282  	}
  3283  	if err := f.Close(); err != nil {
  3284  		t.Error(err)
  3285  	}
  3286  	f, err = openf(name, O_WRONLY|O_CREATE|O_TRUNC, 0)
  3287  	if err != nil {
  3288  		t.Fatal(err)
  3289  	}
  3290  	if fi, err := f.Stat(); err != nil {
  3291  		t.Error(err)
  3292  	} else if fi.Mode()&0222 == 0 {
  3293  		t.Errorf("f.Stat.Mode after OpenFile is %v, should be writable", fi.Mode())
  3294  	}
  3295  	if err := f.Close(); err != nil {
  3296  		t.Error(err)
  3297  	}
  3298  	if fi, err := Stat(name); err != nil {
  3299  		t.Error(err)
  3300  	} else if fi.Mode()&0222 == 0 {
  3301  		t.Errorf("Stat after OpenFile is %v, should be writable", fi.Mode())
  3302  	}
  3303  }
  3304  
  3305  func forceMFTUpdateOnWindows(t *testing.T, path string) {
  3306  	t.Helper()
  3307  
  3308  	if runtime.GOOS != "windows" {
  3309  		return
  3310  	}
  3311  
  3312  	// On Windows, we force the MFT to update by reading the actual metadata from GetFileInformationByHandle and then
  3313  	// explicitly setting that. Otherwise it might get out of sync with FindFirstFile. See golang.org/issues/42637.
  3314  	if err := filepath.WalkDir(path, func(path string, d fs.DirEntry, err error) error {
  3315  		if err != nil {
  3316  			t.Fatal(err)
  3317  		}
  3318  		info, err := d.Info()
  3319  		if err != nil {
  3320  			t.Fatal(err)
  3321  		}
  3322  		stat, err := Stat(path) // This uses GetFileInformationByHandle internally.
  3323  		if err != nil {
  3324  			t.Fatal(err)
  3325  		}
  3326  		if stat.ModTime() == info.ModTime() {
  3327  			return nil
  3328  		}
  3329  		if err := Chtimes(path, stat.ModTime(), stat.ModTime()); err != nil {
  3330  			t.Log(err) // We only log, not die, in case the test directory is not writable.
  3331  		}
  3332  		return nil
  3333  	}); err != nil {
  3334  		t.Fatal(err)
  3335  	}
  3336  }
  3337  
  3338  func TestDirFS(t *testing.T) {
  3339  	t.Parallel()
  3340  	testDirFS(t, DirFS("./testdata/dirfs"))
  3341  }
  3342  
  3343  func TestRootDirFS(t *testing.T) {
  3344  	t.Parallel()
  3345  	r, err := OpenRoot("./testdata/dirfs")
  3346  	if err != nil {
  3347  		t.Fatal(err)
  3348  	}
  3349  	defer r.Close()
  3350  	testDirFS(t, r.FS())
  3351  }
  3352  
  3353  func testDirFS(t *testing.T, fsys fs.FS) {
  3354  	forceMFTUpdateOnWindows(t, "./testdata/dirfs")
  3355  
  3356  	if err := fstest.TestFS(fsys, "a", "b", "dir/x"); err != nil {
  3357  		t.Fatal(err)
  3358  	}
  3359  
  3360  	rdfs, ok := fsys.(fs.ReadDirFS)
  3361  	if !ok {
  3362  		t.Error("expected DirFS result to implement fs.ReadDirFS")
  3363  	}
  3364  	if _, err := rdfs.ReadDir("nonexistent"); err == nil {
  3365  		t.Error("fs.ReadDir of nonexistent directory succeeded")
  3366  	}
  3367  
  3368  	// Test that the error message does not contain a backslash,
  3369  	// and does not contain the DirFS argument.
  3370  	const nonesuch = "dir/nonesuch"
  3371  	_, err := fsys.Open(nonesuch)
  3372  	if err == nil {
  3373  		t.Error("fs.Open of nonexistent file succeeded")
  3374  	} else {
  3375  		if !strings.Contains(err.Error(), nonesuch) {
  3376  			t.Errorf("error %q does not contain %q", err, nonesuch)
  3377  		}
  3378  		if strings.Contains(err.(*PathError).Path, "testdata") {
  3379  			t.Errorf("error %q contains %q", err, "testdata")
  3380  		}
  3381  	}
  3382  
  3383  	// Test that Open does not accept backslash as separator.
  3384  	d := DirFS(".")
  3385  	_, err = d.Open(`testdata\dirfs`)
  3386  	if err == nil {
  3387  		t.Fatalf(`Open testdata\dirfs succeeded`)
  3388  	}
  3389  
  3390  	// Test that Open does not open Windows device files.
  3391  	_, err = d.Open(`NUL`)
  3392  	if err == nil {
  3393  		t.Errorf(`Open NUL succeeded`)
  3394  	}
  3395  }
  3396  
  3397  func TestDirFSRootDir(t *testing.T) {
  3398  	t.Parallel()
  3399  
  3400  	cwd, err := Getwd()
  3401  	if err != nil {
  3402  		t.Fatal(err)
  3403  	}
  3404  	cwd = cwd[len(filepath.VolumeName(cwd)):] // trim volume prefix (C:) on Windows
  3405  	cwd = filepath.ToSlash(cwd)               // convert \ to /
  3406  	cwd = strings.TrimPrefix(cwd, "/")        // trim leading /
  3407  
  3408  	// Test that Open can open a path starting at /.
  3409  	d := DirFS("/")
  3410  	f, err := d.Open(cwd + "/testdata/dirfs/a")
  3411  	if err != nil {
  3412  		t.Fatal(err)
  3413  	}
  3414  	f.Close()
  3415  }
  3416  
  3417  func TestDirFSEmptyDir(t *testing.T) {
  3418  	t.Parallel()
  3419  
  3420  	d := DirFS("")
  3421  	cwd, _ := Getwd()
  3422  	for _, path := range []string{
  3423  		"testdata/dirfs/a",                          // not DirFS(".")
  3424  		filepath.ToSlash(cwd) + "/testdata/dirfs/a", // not DirFS("/")
  3425  	} {
  3426  		_, err := d.Open(path)
  3427  		if err == nil {
  3428  			t.Fatalf(`DirFS("").Open(%q) succeeded`, path)
  3429  		}
  3430  	}
  3431  }
  3432  
  3433  func TestDirFSPathsValid(t *testing.T) {
  3434  	if runtime.GOOS == "windows" {
  3435  		t.Skipf("skipping on Windows")
  3436  	}
  3437  	t.Parallel()
  3438  
  3439  	d := t.TempDir()
  3440  	if err := WriteFile(filepath.Join(d, "control.txt"), []byte(string("Hello, world!")), 0644); err != nil {
  3441  		t.Fatal(err)
  3442  	}
  3443  	if err := WriteFile(filepath.Join(d, `e:xperi\ment.txt`), []byte(string("Hello, colon and backslash!")), 0644); err != nil {
  3444  		t.Fatal(err)
  3445  	}
  3446  
  3447  	fsys := DirFS(d)
  3448  	err := fs.WalkDir(fsys, ".", func(path string, e fs.DirEntry, err error) error {
  3449  		if fs.ValidPath(e.Name()) {
  3450  			t.Logf("%q ok", e.Name())
  3451  		} else {
  3452  			t.Errorf("%q INVALID", e.Name())
  3453  		}
  3454  		return nil
  3455  	})
  3456  	if err != nil {
  3457  		t.Fatal(err)
  3458  	}
  3459  }
  3460  
  3461  func TestReadFileProc(t *testing.T) {
  3462  	t.Parallel()
  3463  
  3464  	// Linux files in /proc report 0 size,
  3465  	// but then if ReadFile reads just a single byte at offset 0,
  3466  	// the read at offset 1 returns EOF instead of more data.
  3467  	// ReadFile has a minimum read size of 512 to work around this,
  3468  	// but test explicitly that it's working.
  3469  	name := "/proc/sys/fs/pipe-max-size"
  3470  	if _, err := Stat(name); err != nil {
  3471  		t.Skip(err)
  3472  	}
  3473  	data, err := ReadFile(name)
  3474  	if err != nil {
  3475  		t.Fatal(err)
  3476  	}
  3477  	if len(data) == 0 || data[len(data)-1] != '\n' {
  3478  		t.Fatalf("read %s: not newline-terminated: %q", name, data)
  3479  	}
  3480  }
  3481  
  3482  func TestDirFSReadFileProc(t *testing.T) {
  3483  	t.Parallel()
  3484  
  3485  	fsys := DirFS("/")
  3486  	name := "proc/sys/fs/pipe-max-size"
  3487  	if _, err := fs.Stat(fsys, name); err != nil {
  3488  		t.Skip()
  3489  	}
  3490  	data, err := fs.ReadFile(fsys, name)
  3491  	if err != nil {
  3492  		t.Fatal(err)
  3493  	}
  3494  	if len(data) == 0 || data[len(data)-1] != '\n' {
  3495  		t.Fatalf("read %s: not newline-terminated: %q", name, data)
  3496  	}
  3497  }
  3498  
  3499  func TestWriteStringAlloc(t *testing.T) {
  3500  	if runtime.GOOS == "js" {
  3501  		t.Skip("js allocates a lot during File.WriteString")
  3502  	}
  3503  	d := t.TempDir()
  3504  	f, err := Create(filepath.Join(d, "whiteboard.txt"))
  3505  	if err != nil {
  3506  		t.Fatal(err)
  3507  	}
  3508  	defer f.Close()
  3509  	allocs := testing.AllocsPerRun(100, func() {
  3510  		f.WriteString("I will not allocate when passed a string longer than 32 bytes.\n")
  3511  	})
  3512  	if allocs != 0 {
  3513  		t.Errorf("expected 0 allocs for File.WriteString, got %v", allocs)
  3514  	}
  3515  }
  3516  
  3517  // Test that it's OK to have parallel I/O and Close on a file.
  3518  func TestFileIOCloseRace(t *testing.T) {
  3519  	t.Parallel()
  3520  	file, err := Create(filepath.Join(t.TempDir(), "test.txt"))
  3521  	if err != nil {
  3522  		t.Fatal(err)
  3523  	}
  3524  	var wg sync.WaitGroup
  3525  	wg.Go(func() {
  3526  		var tmp [100]byte
  3527  		if _, err := file.Write(tmp[:]); err != nil && !errors.Is(err, ErrClosed) {
  3528  			t.Error(err)
  3529  		}
  3530  	})
  3531  	wg.Go(func() {
  3532  		var tmp [100]byte
  3533  		if _, err := file.Read(tmp[:]); err != nil && err != io.EOF && !errors.Is(err, ErrClosed) {
  3534  			t.Error(err)
  3535  		}
  3536  	})
  3537  	wg.Go(func() {
  3538  		if err := file.Close(); err != nil {
  3539  			t.Error(err)
  3540  		}
  3541  	})
  3542  	wg.Wait()
  3543  }
  3544  
  3545  // Test that it's OK to have parallel I/O and Close on a pipe.
  3546  func TestPipeIOCloseRace(t *testing.T) {
  3547  	// Skip on wasm, which doesn't have pipes.
  3548  	if runtime.GOOS == "js" || runtime.GOOS == "wasip1" {
  3549  		t.Skipf("skipping on %s: no pipes", runtime.GOOS)
  3550  	}
  3551  	t.Parallel()
  3552  
  3553  	r, w, err := Pipe()
  3554  	if err != nil {
  3555  		t.Fatal(err)
  3556  	}
  3557  
  3558  	var wg sync.WaitGroup
  3559  	wg.Add(3)
  3560  
  3561  	go func() {
  3562  		defer wg.Done()
  3563  		for {
  3564  			n, err := w.Write([]byte("hi"))
  3565  			if err != nil {
  3566  				// We look at error strings as the
  3567  				// expected errors are OS-specific.
  3568  				switch {
  3569  				case errors.Is(err, ErrClosed),
  3570  					strings.Contains(err.Error(), "broken pipe"),
  3571  					strings.Contains(err.Error(), "pipe is being closed"),
  3572  					strings.Contains(err.Error(), "hungup channel"):
  3573  					// Ignore an expected error.
  3574  				default:
  3575  					// Unexpected error.
  3576  					t.Error(err)
  3577  				}
  3578  				return
  3579  			}
  3580  			if n != 2 {
  3581  				t.Errorf("wrote %d bytes, expected 2", n)
  3582  				return
  3583  			}
  3584  		}
  3585  	}()
  3586  
  3587  	go func() {
  3588  		defer wg.Done()
  3589  		for {
  3590  			var buf [2]byte
  3591  			n, err := r.Read(buf[:])
  3592  			if err != nil {
  3593  				if err != io.EOF && !errors.Is(err, ErrClosed) {
  3594  					t.Error(err)
  3595  				}
  3596  				return
  3597  			}
  3598  			if n != 2 {
  3599  				t.Errorf("read %d bytes, want 2", n)
  3600  			}
  3601  		}
  3602  	}()
  3603  
  3604  	go func() {
  3605  		defer wg.Done()
  3606  
  3607  		// Let the other goroutines start. This is just to get
  3608  		// a better test, the test will still pass if they
  3609  		// don't start.
  3610  		time.Sleep(time.Millisecond)
  3611  
  3612  		if err := r.Close(); err != nil {
  3613  			t.Error(err)
  3614  		}
  3615  		if err := w.Close(); err != nil {
  3616  			t.Error(err)
  3617  		}
  3618  	}()
  3619  
  3620  	wg.Wait()
  3621  }
  3622  
  3623  // Test that it's OK to call Close concurrently on a pipe.
  3624  func TestPipeCloseRace(t *testing.T) {
  3625  	// Skip on wasm, which doesn't have pipes.
  3626  	if runtime.GOOS == "js" || runtime.GOOS == "wasip1" {
  3627  		t.Skipf("skipping on %s: no pipes", runtime.GOOS)
  3628  	}
  3629  	t.Parallel()
  3630  
  3631  	r, w, err := Pipe()
  3632  	if err != nil {
  3633  		t.Fatal(err)
  3634  	}
  3635  	var wg sync.WaitGroup
  3636  	c := make(chan error, 4)
  3637  	f := func() {
  3638  		defer wg.Done()
  3639  		c <- r.Close()
  3640  		c <- w.Close()
  3641  	}
  3642  	wg.Add(2)
  3643  	go f()
  3644  	go f()
  3645  	nils, errs := 0, 0
  3646  	for i := 0; i < 4; i++ {
  3647  		err := <-c
  3648  		if err == nil {
  3649  			nils++
  3650  		} else {
  3651  			errs++
  3652  		}
  3653  	}
  3654  	if nils != 2 || errs != 2 {
  3655  		t.Errorf("got nils %d errs %d, want 2 2", nils, errs)
  3656  	}
  3657  }
  3658  
  3659  func TestRandomLen(t *testing.T) {
  3660  	for range 5 {
  3661  		dir, err := MkdirTemp(t.TempDir(), "*")
  3662  		if err != nil {
  3663  			t.Fatal(err)
  3664  		}
  3665  		base := filepath.Base(dir)
  3666  		if len(base) > 10 {
  3667  			t.Errorf("MkdirTemp returned len %d: %s", len(base), base)
  3668  		}
  3669  	}
  3670  	for range 5 {
  3671  		f, err := CreateTemp(t.TempDir(), "*")
  3672  		if err != nil {
  3673  			t.Fatal(err)
  3674  		}
  3675  		base := filepath.Base(f.Name())
  3676  		f.Close()
  3677  		if len(base) > 10 {
  3678  			t.Errorf("CreateTemp returned len %d: %s", len(base), base)
  3679  		}
  3680  	}
  3681  }
  3682  
  3683  func TestCopyFS(t *testing.T) {
  3684  	t.Parallel()
  3685  
  3686  	// Test with disk filesystem.
  3687  	forceMFTUpdateOnWindows(t, "./testdata/dirfs")
  3688  	fsys := DirFS("./testdata/dirfs")
  3689  	tmpDir := t.TempDir()
  3690  	if err := CopyFS(tmpDir, fsys); err != nil {
  3691  		t.Fatal("CopyFS:", err)
  3692  	}
  3693  	forceMFTUpdateOnWindows(t, tmpDir)
  3694  	tmpFsys := DirFS(tmpDir)
  3695  	if err := fstest.TestFS(tmpFsys, "a", "b", "dir/x"); err != nil {
  3696  		t.Fatal("TestFS:", err)
  3697  	}
  3698  	if err := verifyCopyFS(t, fsys, tmpFsys); err != nil {
  3699  		t.Fatal("comparing two directories:", err)
  3700  	}
  3701  
  3702  	// Test whether CopyFS disallows copying for disk filesystem when there is any
  3703  	// existing file in the destination directory.
  3704  	if err := CopyFS(tmpDir, fsys); !errors.Is(err, fs.ErrExist) {
  3705  		t.Errorf("CopyFS should have failed and returned error when there is"+
  3706  			"any existing file in the destination directory (in disk filesystem), "+
  3707  			"got: %v, expected any error that indicates <file exists>", err)
  3708  	}
  3709  
  3710  	// Test with memory filesystem.
  3711  	fsys = fstest.MapFS{
  3712  		"william":    {Data: []byte("Shakespeare\n")},
  3713  		"carl":       {Data: []byte("Gauss\n")},
  3714  		"daVinci":    {Data: []byte("Leonardo\n")},
  3715  		"einstein":   {Data: []byte("Albert\n")},
  3716  		"dir/newton": {Data: []byte("Sir Isaac\n")},
  3717  	}
  3718  	tmpDir = t.TempDir()
  3719  	if err := CopyFS(tmpDir, fsys); err != nil {
  3720  		t.Fatal("CopyFS:", err)
  3721  	}
  3722  	forceMFTUpdateOnWindows(t, tmpDir)
  3723  	tmpFsys = DirFS(tmpDir)
  3724  	if err := fstest.TestFS(tmpFsys, "william", "carl", "daVinci", "einstein", "dir/newton"); err != nil {
  3725  		t.Fatal("TestFS:", err)
  3726  	}
  3727  	if err := verifyCopyFS(t, fsys, tmpFsys); err != nil {
  3728  		t.Fatal("comparing two directories:", err)
  3729  	}
  3730  
  3731  	// Test whether CopyFS disallows copying for memory filesystem when there is any
  3732  	// existing file in the destination directory.
  3733  	if err := CopyFS(tmpDir, fsys); !errors.Is(err, fs.ErrExist) {
  3734  		t.Errorf("CopyFS should have failed and returned error when there is"+
  3735  			"any existing file in the destination directory (in memory filesystem), "+
  3736  			"got: %v, expected any error that indicates <file exists>", err)
  3737  	}
  3738  }
  3739  
  3740  // verifyCopyFS checks the content and permission of each file inside copied FS to ensure
  3741  // the copied files satisfy the convention stipulated in CopyFS.
  3742  func verifyCopyFS(t *testing.T, originFS, copiedFS fs.FS) error {
  3743  	testDir := filepath.Join(t.TempDir(), "test")
  3744  	// umask doesn't apply to the wasip and windows and there is no general way to get masked perm,
  3745  	// so create a dir and a file to compare the permission after umask if any
  3746  	if err := Mkdir(testDir, ModePerm); err != nil {
  3747  		return fmt.Errorf("mkdir %q failed: %v", testDir, err)
  3748  	}
  3749  	dirStat, err := Stat(testDir)
  3750  	if err != nil {
  3751  		return fmt.Errorf("stat dir %q failed: %v", testDir, err)
  3752  	}
  3753  	wantDirMode := dirStat.Mode()
  3754  
  3755  	f, err := Create(filepath.Join(testDir, "tmp"))
  3756  	if err != nil {
  3757  		return fmt.Errorf("open %q failed: %v", filepath.Join(testDir, "tmp"), err)
  3758  	}
  3759  	defer f.Close()
  3760  	wantFileRWStat, err := f.Stat()
  3761  	if err != nil {
  3762  		return fmt.Errorf("stat file %q failed: %v", f.Name(), err)
  3763  	}
  3764  	wantFileRWMode := wantFileRWStat.Mode()
  3765  
  3766  	return fs.WalkDir(originFS, ".", func(path string, d fs.DirEntry, err error) error {
  3767  		if d.IsDir() {
  3768  			// the dir . is not the dir created by CopyFS so skip checking its permission
  3769  			if d.Name() == "." {
  3770  				return nil
  3771  			}
  3772  
  3773  			dinfo, err := fs.Stat(copiedFS, path)
  3774  			if err != nil {
  3775  				return err
  3776  			}
  3777  
  3778  			if dinfo.Mode() != wantDirMode {
  3779  				return fmt.Errorf("dir %q mode is %v, want %v",
  3780  					d.Name(), dinfo.Mode(), wantDirMode)
  3781  			}
  3782  			return nil
  3783  		}
  3784  
  3785  		fInfo, err := originFS.Open(path)
  3786  		if err != nil {
  3787  			return err
  3788  		}
  3789  		defer fInfo.Close()
  3790  		copiedInfo, err := copiedFS.Open(path)
  3791  		if err != nil {
  3792  			return err
  3793  		}
  3794  		defer copiedInfo.Close()
  3795  
  3796  		// verify the file contents are the same
  3797  		data, err := io.ReadAll(fInfo)
  3798  		if err != nil {
  3799  			return err
  3800  		}
  3801  		newData, err := io.ReadAll(copiedInfo)
  3802  		if err != nil {
  3803  			return err
  3804  		}
  3805  		if !bytes.Equal(data, newData) {
  3806  			return fmt.Errorf("file %q content is %s, want %s", path, newData, data)
  3807  		}
  3808  
  3809  		fStat, err := fInfo.Stat()
  3810  		if err != nil {
  3811  			return err
  3812  		}
  3813  		copiedStat, err := copiedInfo.Stat()
  3814  		if err != nil {
  3815  			return err
  3816  		}
  3817  
  3818  		// check whether the execute permission is inherited from original FS
  3819  
  3820  		if copiedStat.Mode()&0111&wantFileRWMode != fStat.Mode()&0111&wantFileRWMode {
  3821  			return fmt.Errorf("file %q execute mode is %v, want %v",
  3822  				path, copiedStat.Mode()&0111, fStat.Mode()&0111)
  3823  		}
  3824  
  3825  		rwMode := copiedStat.Mode() &^ 0111 // unset the executable permission from file mode
  3826  		if rwMode != wantFileRWMode {
  3827  			return fmt.Errorf("file %q rw mode is %v, want %v",
  3828  				path, rwMode, wantFileRWStat.Mode())
  3829  		}
  3830  		return nil
  3831  	})
  3832  }
  3833  
  3834  func TestCopyFSWithSymlinks(t *testing.T) {
  3835  	// Test it with absolute and relative symlinks that point inside and outside the tree.
  3836  	testenv.MustHaveSymlink(t)
  3837  
  3838  	// Create a directory and file outside.
  3839  	tmpDir := t.TempDir()
  3840  	outsideDir := filepath.Join(tmpDir, "copyfs_out")
  3841  	if err := Mkdir(outsideDir, 0755); err != nil {
  3842  		t.Fatalf("Mkdir: %v", err)
  3843  	}
  3844  	outsideFile := filepath.Join(outsideDir, "file.out.txt")
  3845  
  3846  	if err := WriteFile(outsideFile, []byte("Testing CopyFS outside"), 0644); err != nil {
  3847  		t.Fatalf("WriteFile: %v", err)
  3848  	}
  3849  
  3850  	// Create a directory and file inside.
  3851  	insideDir := filepath.Join(tmpDir, "copyfs_in")
  3852  	if err := Mkdir(insideDir, 0755); err != nil {
  3853  		t.Fatalf("Mkdir: %v", err)
  3854  	}
  3855  	insideFile := filepath.Join(insideDir, "file.in.txt")
  3856  	if err := WriteFile(insideFile, []byte("Testing CopyFS inside"), 0644); err != nil {
  3857  		t.Fatalf("WriteFile: %v", err)
  3858  	}
  3859  
  3860  	// Create directories for symlinks.
  3861  	linkInDir := filepath.Join(insideDir, "in_symlinks")
  3862  	if err := Mkdir(linkInDir, 0755); err != nil {
  3863  		t.Fatalf("Mkdir: %v", err)
  3864  	}
  3865  	linkOutDir := filepath.Join(insideDir, "out_symlinks")
  3866  	if err := Mkdir(linkOutDir, 0755); err != nil {
  3867  		t.Fatalf("Mkdir: %v", err)
  3868  	}
  3869  
  3870  	// First, we create the absolute symlink pointing outside.
  3871  	outLinkFile := filepath.Join(linkOutDir, "file.abs.out.link")
  3872  	if err := Symlink(outsideFile, outLinkFile); err != nil {
  3873  		t.Fatalf("Symlink: %v", err)
  3874  	}
  3875  
  3876  	// Then, we create the relative symlink pointing outside.
  3877  	relOutsideFile, err := filepath.Rel(filepath.Join(linkOutDir, "."), outsideFile)
  3878  	if err != nil {
  3879  		t.Fatalf("filepath.Rel: %v", err)
  3880  	}
  3881  	relOutLinkFile := filepath.Join(linkOutDir, "file.rel.out.link")
  3882  	if err := Symlink(relOutsideFile, relOutLinkFile); err != nil {
  3883  		t.Fatalf("Symlink: %v", err)
  3884  	}
  3885  
  3886  	// Last, we create the relative symlink pointing inside.
  3887  	relInsideFile, err := filepath.Rel(filepath.Join(linkInDir, "."), insideFile)
  3888  	if err != nil {
  3889  		t.Fatalf("filepath.Rel: %v", err)
  3890  	}
  3891  	relInLinkFile := filepath.Join(linkInDir, "file.rel.in.link")
  3892  	if err := Symlink(relInsideFile, relInLinkFile); err != nil {
  3893  		t.Fatalf("Symlink: %v", err)
  3894  	}
  3895  
  3896  	// Copy the directory tree and verify.
  3897  	forceMFTUpdateOnWindows(t, insideDir)
  3898  	fsys := DirFS(insideDir)
  3899  	tmpDupDir := filepath.Join(tmpDir, "copyfs_dup")
  3900  	if err := Mkdir(tmpDupDir, 0755); err != nil {
  3901  		t.Fatalf("Mkdir: %v", err)
  3902  	}
  3903  
  3904  	if err := CopyFS(tmpDupDir, fsys); err != nil {
  3905  		t.Fatalf("CopyFS: %v", err)
  3906  	}
  3907  
  3908  	forceMFTUpdateOnWindows(t, tmpDupDir)
  3909  	tmpFsys := DirFS(tmpDupDir)
  3910  	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 {
  3911  		t.Fatal("TestFS:", err)
  3912  	}
  3913  	if err := fs.WalkDir(fsys, ".", func(path string, d fs.DirEntry, err error) error {
  3914  		if d.IsDir() {
  3915  			return nil
  3916  		}
  3917  
  3918  		fi, err := d.Info()
  3919  		if err != nil {
  3920  			return err
  3921  		}
  3922  		if filepath.Ext(path) == ".link" {
  3923  			if fi.Mode()&ModeSymlink == 0 {
  3924  				return errors.New("original file " + path + " should be a symlink")
  3925  			}
  3926  			tmpfi, err := fs.Stat(tmpFsys, path)
  3927  			if err != nil {
  3928  				return err
  3929  			}
  3930  			if tmpfi.Mode()&ModeSymlink != 0 {
  3931  				return errors.New("copied file " + path + " should not be a symlink")
  3932  			}
  3933  		}
  3934  
  3935  		data, err := fs.ReadFile(fsys, path)
  3936  		if err != nil {
  3937  			return err
  3938  		}
  3939  		newData, err := fs.ReadFile(tmpFsys, path)
  3940  		if err != nil {
  3941  			return err
  3942  		}
  3943  		if !bytes.Equal(data, newData) {
  3944  			return errors.New("file " + path + " contents differ")
  3945  		}
  3946  
  3947  		var target string
  3948  		switch fileName := filepath.Base(path); fileName {
  3949  		case "file.abs.out.link", "file.rel.out.link":
  3950  			target = outsideFile
  3951  		case "file.rel.in.link":
  3952  			target = insideFile
  3953  		}
  3954  		if len(target) > 0 {
  3955  			targetData, err := ReadFile(target)
  3956  			if err != nil {
  3957  				return err
  3958  			}
  3959  			if !bytes.Equal(targetData, newData) {
  3960  				return errors.New("file " + path + " contents differ from target")
  3961  			}
  3962  		}
  3963  
  3964  		return nil
  3965  	}); err != nil {
  3966  		t.Fatal("comparing two directories:", err)
  3967  	}
  3968  }
  3969  
  3970  func TestAppendDoesntOverwrite(t *testing.T) {
  3971  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  3972  		name := "file"
  3973  		if err := WriteFile(name, []byte("hello"), 0666); err != nil {
  3974  			t.Fatal(err)
  3975  		}
  3976  		var f *File
  3977  		var err error
  3978  		if r == nil {
  3979  			f, err = OpenFile(name, O_APPEND|O_WRONLY, 0)
  3980  		} else {
  3981  			f, err = r.OpenFile(name, O_APPEND|O_WRONLY, 0)
  3982  		}
  3983  		if err != nil {
  3984  			t.Fatal(err)
  3985  		}
  3986  		if _, err := f.Write([]byte(" world")); err != nil {
  3987  			f.Close()
  3988  			t.Fatal(err)
  3989  		}
  3990  		if err := f.Close(); err != nil {
  3991  			t.Fatal(err)
  3992  		}
  3993  		got, err := ReadFile(name)
  3994  		if err != nil {
  3995  			t.Fatal(err)
  3996  		}
  3997  		want := "hello world"
  3998  		if string(got) != want {
  3999  			t.Fatalf("got %q, want %q", got, want)
  4000  		}
  4001  	})
  4002  }
  4003  
  4004  func TestRemoveReadOnlyFile(t *testing.T) {
  4005  	testMaybeRooted(t, func(t *testing.T, r *Root) {
  4006  		if err := WriteFile("file", []byte("1"), 0); err != nil {
  4007  			t.Fatal(err)
  4008  		}
  4009  		var err error
  4010  		if r == nil {
  4011  			err = Remove("file")
  4012  		} else {
  4013  			err = r.Remove("file")
  4014  		}
  4015  		if err != nil {
  4016  			t.Fatalf("Remove read-only file: %v", err)
  4017  		}
  4018  		if _, err := Stat("file"); !IsNotExist(err) {
  4019  			t.Fatalf("Stat read-only file after removal: %v (want IsNotExist)", err)
  4020  		}
  4021  	})
  4022  }
  4023  
  4024  func TestOpenFileDevNull(t *testing.T) {
  4025  	// See https://go.dev/issue/71752.
  4026  	t.Parallel()
  4027  
  4028  	f, err := OpenFile(DevNull, O_WRONLY|O_CREATE|O_TRUNC, 0o644)
  4029  	if err != nil {
  4030  		t.Fatalf("OpenFile(DevNull): %v", err)
  4031  	}
  4032  	f.Close()
  4033  }
  4034  
  4035  func TestReadFileContents(t *testing.T) {
  4036  	type readStep struct {
  4037  		bufSize int   // non-zero to check length of buf to Read
  4038  		retN    int   // result of Read call
  4039  		retErr  error // error result of Read call
  4040  	}
  4041  	errFoo := errors.New("foo")
  4042  	tests := []struct {
  4043  		name     string
  4044  		statSize int64 // size of file to read, per stat (may be 0 for /proc files)
  4045  		wantSize int   // wanted length of []byte from readFileContents
  4046  		wantErr  error // wanted error from readFileContents
  4047  		reads    []readStep
  4048  	}{
  4049  		{
  4050  			name:     "big-file",
  4051  			statSize: 2000,
  4052  			wantSize: 2000,
  4053  			reads: []readStep{
  4054  				{bufSize: 2001, retN: 21, retErr: nil},
  4055  				{bufSize: 1980, retN: 1979, retErr: io.EOF},
  4056  			},
  4057  		},
  4058  		{
  4059  			name:     "small-file",
  4060  			statSize: 100,
  4061  			wantSize: 100,
  4062  			reads: []readStep{
  4063  				{bufSize: 512, retN: 100, retErr: io.EOF},
  4064  			},
  4065  		},
  4066  		{
  4067  			name:     "returning-error",
  4068  			statSize: 1000,
  4069  			wantSize: 50,
  4070  			wantErr:  errFoo,
  4071  			reads: []readStep{
  4072  				{bufSize: 1001, retN: 25, retErr: nil},
  4073  				{retN: 25, retErr: errFoo},
  4074  			},
  4075  		},
  4076  		{
  4077  			name:     "proc-file",
  4078  			statSize: 0,
  4079  			wantSize: 1023,
  4080  			reads: []readStep{
  4081  				{bufSize: 512, retN: 512, retErr: nil},
  4082  				{retN: 511, retErr: io.EOF},
  4083  			},
  4084  		},
  4085  		{
  4086  			name:     "plan9-iproute-file", // Issue 72080
  4087  			statSize: 0,
  4088  			wantSize: 1032,
  4089  			reads: []readStep{
  4090  				{bufSize: 512, retN: 511, retErr: nil},
  4091  				{retN: 511, retErr: nil},
  4092  				{retN: 10, retErr: io.EOF},
  4093  			},
  4094  		},
  4095  	}
  4096  	for _, tt := range tests {
  4097  		t.Run(tt.name, func(t *testing.T) {
  4098  			remain := tt.reads
  4099  			i := -1
  4100  			got, err := ExportReadFileContents(tt.statSize, func(buf []byte) (int, error) {
  4101  				i++
  4102  				t.Logf("read[%d] with buf size %d", i, len(buf))
  4103  				if len(remain) == 0 {
  4104  					t.Fatalf("unexpected read of length %d after %d expected reads", len(buf), len(tt.reads))
  4105  				}
  4106  				if tt.statSize == 0 && len(buf) < 512 {
  4107  					// Issue 72080: readFileContents should not do /proc reads with buffers
  4108  					// smaller than 512.
  4109  					t.Fatalf("read[%d] with buf size %d; want at least 512 for 0-sized file", i, len(buf))
  4110  				}
  4111  				step := remain[0]
  4112  				remain = remain[1:]
  4113  				if step.bufSize != 0 && len(buf) != step.bufSize {
  4114  					t.Fatalf("read[%d] has buffer size %d; want %d", i, len(buf), step.bufSize)
  4115  				}
  4116  				return step.retN, step.retErr
  4117  			})
  4118  			if len(remain) > 0 {
  4119  				t.Fatalf("expected %d reads, got %d", len(tt.reads), i+1)
  4120  			}
  4121  			if fmt.Sprint(err) != fmt.Sprint(tt.wantErr) {
  4122  				t.Errorf("got error %v; want %v", err, tt.wantErr)
  4123  			}
  4124  			if len(got) != tt.wantSize {
  4125  				t.Errorf("got size %d; want %d", len(got), tt.wantSize)
  4126  			}
  4127  		})
  4128  	}
  4129  }
  4130  

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