Source file src/os/file.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 provides a platform-independent interface to operating system 6 // functionality. The design is Unix-like, although the error handling is 7 // Go-like; failing calls return values of type error rather than error numbers. 8 // Often, more information is available within the error. For example, 9 // if a call that takes a file name fails, such as Open or Stat, the error 10 // will include the failing file name when printed and will be of type 11 // *PathError, which may be unpacked for more information. 12 // 13 // The os interface is intended to be uniform across all operating systems. 14 // Features not generally available appear in the system-specific package syscall. 15 // 16 // Here is a simple example, opening a file and reading some of it. 17 // 18 // file, err := os.Open("file.go") // For read access. 19 // if err != nil { 20 // log.Fatal(err) 21 // } 22 // 23 // If the open fails, the error string will be self-explanatory, like 24 // 25 // open file.go: no such file or directory 26 // 27 // The file's data can then be read into a slice of bytes. Read and 28 // Write take their byte counts from the length of the argument slice. 29 // 30 // data := make([]byte, 100) 31 // count, err := file.Read(data) 32 // if err != nil { 33 // log.Fatal(err) 34 // } 35 // fmt.Printf("read %d bytes: %q\n", count, data[:count]) 36 // 37 // Note: The maximum number of concurrent operations on a File may be limited by 38 // the OS or the system. The number should be high, but exceeding it may degrade 39 // performance or cause other issues. 40 // 41 package os 42 43 import ( 44 "errors" 45 "internal/poll" 46 "internal/testlog" 47 "internal/unsafeheader" 48 "io" 49 "io/fs" 50 "runtime" 51 "syscall" 52 "time" 53 "unsafe" 54 ) 55 56 // Name returns the name of the file as presented to Open. 57 func (f *File) Name() string { return f.name } 58 59 // Stdin, Stdout, and Stderr are open Files pointing to the standard input, 60 // standard output, and standard error file descriptors. 61 // 62 // Note that the Go runtime writes to standard error for panics and crashes; 63 // closing Stderr may cause those messages to go elsewhere, perhaps 64 // to a file opened later. 65 var ( 66 Stdin = NewFile(uintptr(syscall.Stdin), "/dev/stdin") 67 Stdout = NewFile(uintptr(syscall.Stdout), "/dev/stdout") 68 Stderr = NewFile(uintptr(syscall.Stderr), "/dev/stderr") 69 ) 70 71 // Flags to OpenFile wrapping those of the underlying system. Not all 72 // flags may be implemented on a given system. 73 const ( 74 // Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified. 75 O_RDONLY int = syscall.O_RDONLY // open the file read-only. 76 O_WRONLY int = syscall.O_WRONLY // open the file write-only. 77 O_RDWR int = syscall.O_RDWR // open the file read-write. 78 // The remaining values may be or'ed in to control behavior. 79 O_APPEND int = syscall.O_APPEND // append data to the file when writing. 80 O_CREATE int = syscall.O_CREAT // create a new file if none exists. 81 O_EXCL int = syscall.O_EXCL // used with O_CREATE, file must not exist. 82 O_SYNC int = syscall.O_SYNC // open for synchronous I/O. 83 O_TRUNC int = syscall.O_TRUNC // truncate regular writable file when opened. 84 ) 85 86 // Seek whence values. 87 // 88 // Deprecated: Use io.SeekStart, io.SeekCurrent, and io.SeekEnd. 89 const ( 90 SEEK_SET int = 0 // seek relative to the origin of the file 91 SEEK_CUR int = 1 // seek relative to the current offset 92 SEEK_END int = 2 // seek relative to the end 93 ) 94 95 // LinkError records an error during a link or symlink or rename 96 // system call and the paths that caused it. 97 type LinkError struct { 98 Op string 99 Old string 100 New string 101 Err error 102 } 103 104 func (e *LinkError) Error() string { 105 return e.Op + " " + e.Old + " " + e.New + ": " + e.Err.Error() 106 } 107 108 func (e *LinkError) Unwrap() error { 109 return e.Err 110 } 111 112 // Read reads up to len(b) bytes from the File and stores them in b. 113 // It returns the number of bytes read and any error encountered. 114 // At end of file, Read returns 0, io.EOF. 115 func (f *File) Read(b []byte) (n int, err error) { 116 if err := f.checkValid("read"); err != nil { 117 return 0, err 118 } 119 n, e := f.read(b) 120 return n, f.wrapErr("read", e) 121 } 122 123 // ReadAt reads len(b) bytes from the File starting at byte offset off. 124 // It returns the number of bytes read and the error, if any. 125 // ReadAt always returns a non-nil error when n < len(b). 126 // At end of file, that error is io.EOF. 127 func (f *File) ReadAt(b []byte, off int64) (n int, err error) { 128 if err := f.checkValid("read"); err != nil { 129 return 0, err 130 } 131 132 if off < 0 { 133 return 0, &PathError{Op: "readat", Path: f.name, Err: errors.New("negative offset")} 134 } 135 136 for len(b) > 0 { 137 m, e := f.pread(b, off) 138 if e != nil { 139 err = f.wrapErr("read", e) 140 break 141 } 142 n += m 143 b = b[m:] 144 off += int64(m) 145 } 146 return 147 } 148 149 // ReadFrom implements io.ReaderFrom. 150 func (f *File) ReadFrom(r io.Reader) (n int64, err error) { 151 if err := f.checkValid("write"); err != nil { 152 return 0, err 153 } 154 n, handled, e := f.readFrom(r) 155 if !handled { 156 return genericReadFrom(f, r) // without wrapping 157 } 158 return n, f.wrapErr("write", e) 159 } 160 161 func genericReadFrom(f *File, r io.Reader) (int64, error) { 162 return io.Copy(onlyWriter{f}, r) 163 } 164 165 type onlyWriter struct { 166 io.Writer 167 } 168 169 // Write writes len(b) bytes from b to the File. 170 // It returns the number of bytes written and an error, if any. 171 // Write returns a non-nil error when n != len(b). 172 func (f *File) Write(b []byte) (n int, err error) { 173 if err := f.checkValid("write"); err != nil { 174 return 0, err 175 } 176 n, e := f.write(b) 177 if n < 0 { 178 n = 0 179 } 180 if n != len(b) { 181 err = io.ErrShortWrite 182 } 183 184 epipecheck(f, e) 185 186 if e != nil { 187 err = f.wrapErr("write", e) 188 } 189 190 return n, err 191 } 192 193 var errWriteAtInAppendMode = errors.New("os: invalid use of WriteAt on file opened with O_APPEND") 194 195 // WriteAt writes len(b) bytes to the File starting at byte offset off. 196 // It returns the number of bytes written and an error, if any. 197 // WriteAt returns a non-nil error when n != len(b). 198 // 199 // If file was opened with the O_APPEND flag, WriteAt returns an error. 200 func (f *File) WriteAt(b []byte, off int64) (n int, err error) { 201 if err := f.checkValid("write"); err != nil { 202 return 0, err 203 } 204 if f.appendMode { 205 return 0, errWriteAtInAppendMode 206 } 207 208 if off < 0 { 209 return 0, &PathError{Op: "writeat", Path: f.name, Err: errors.New("negative offset")} 210 } 211 212 for len(b) > 0 { 213 m, e := f.pwrite(b, off) 214 if e != nil { 215 err = f.wrapErr("write", e) 216 break 217 } 218 n += m 219 b = b[m:] 220 off += int64(m) 221 } 222 return 223 } 224 225 // Seek sets the offset for the next Read or Write on file to offset, interpreted 226 // according to whence: 0 means relative to the origin of the file, 1 means 227 // relative to the current offset, and 2 means relative to the end. 228 // It returns the new offset and an error, if any. 229 // The behavior of Seek on a file opened with O_APPEND is not specified. 230 // 231 // If f is a directory, the behavior of Seek varies by operating 232 // system; you can seek to the beginning of the directory on Unix-like 233 // operating systems, but not on Windows. 234 func (f *File) Seek(offset int64, whence int) (ret int64, err error) { 235 if err := f.checkValid("seek"); err != nil { 236 return 0, err 237 } 238 r, e := f.seek(offset, whence) 239 if e == nil && f.dirinfo != nil && r != 0 { 240 e = syscall.EISDIR 241 } 242 if e != nil { 243 return 0, f.wrapErr("seek", e) 244 } 245 return r, nil 246 } 247 248 // WriteString is like Write, but writes the contents of string s rather than 249 // a slice of bytes. 250 func (f *File) WriteString(s string) (n int, err error) { 251 var b []byte 252 hdr := (*unsafeheader.Slice)(unsafe.Pointer(&b)) 253 hdr.Data = (*unsafeheader.String)(unsafe.Pointer(&s)).Data 254 hdr.Cap = len(s) 255 hdr.Len = len(s) 256 return f.Write(b) 257 } 258 259 // Mkdir creates a new directory with the specified name and permission 260 // bits (before umask). 261 // If there is an error, it will be of type *PathError. 262 func Mkdir(name string, perm FileMode) error { 263 if runtime.GOOS == "windows" && isWindowsNulName(name) { 264 return &PathError{Op: "mkdir", Path: name, Err: syscall.ENOTDIR} 265 } 266 longName := fixLongPath(name) 267 e := ignoringEINTR(func() error { 268 return syscall.Mkdir(longName, syscallMode(perm)) 269 }) 270 271 if e != nil { 272 return &PathError{Op: "mkdir", Path: name, Err: e} 273 } 274 275 // mkdir(2) itself won't handle the sticky bit on *BSD and Solaris 276 if !supportsCreateWithStickyBit && perm&ModeSticky != 0 { 277 e = setStickyBit(name) 278 279 if e != nil { 280 Remove(name) 281 return e 282 } 283 } 284 285 return nil 286 } 287 288 // setStickyBit adds ModeSticky to the permission bits of path, non atomic. 289 func setStickyBit(name string) error { 290 fi, err := Stat(name) 291 if err != nil { 292 return err 293 } 294 return Chmod(name, fi.Mode()|ModeSticky) 295 } 296 297 // Chdir changes the current working directory to the named directory. 298 // If there is an error, it will be of type *PathError. 299 func Chdir(dir string) error { 300 if e := syscall.Chdir(dir); e != nil { 301 testlog.Open(dir) // observe likely non-existent directory 302 return &PathError{Op: "chdir", Path: dir, Err: e} 303 } 304 if log := testlog.Logger(); log != nil { 305 wd, err := Getwd() 306 if err == nil { 307 log.Chdir(wd) 308 } 309 } 310 return nil 311 } 312 313 // Open opens the named file for reading. If successful, methods on 314 // the returned file can be used for reading; the associated file 315 // descriptor has mode O_RDONLY. 316 // If there is an error, it will be of type *PathError. 317 func Open(name string) (*File, error) { 318 return OpenFile(name, O_RDONLY, 0) 319 } 320 321 // Create creates or truncates the named file. If the file already exists, 322 // it is truncated. If the file does not exist, it is created with mode 0666 323 // (before umask). If successful, methods on the returned File can 324 // be used for I/O; the associated file descriptor has mode O_RDWR. 325 // If there is an error, it will be of type *PathError. 326 func Create(name string) (*File, error) { 327 return OpenFile(name, O_RDWR|O_CREATE|O_TRUNC, 0666) 328 } 329 330 // OpenFile is the generalized open call; most users will use Open 331 // or Create instead. It opens the named file with specified flag 332 // (O_RDONLY etc.). If the file does not exist, and the O_CREATE flag 333 // is passed, it is created with mode perm (before umask). If successful, 334 // methods on the returned File can be used for I/O. 335 // If there is an error, it will be of type *PathError. 336 func OpenFile(name string, flag int, perm FileMode) (*File, error) { 337 testlog.Open(name) 338 f, err := openFileNolog(name, flag, perm) 339 if err != nil { 340 return nil, err 341 } 342 f.appendMode = flag&O_APPEND != 0 343 344 return f, nil 345 } 346 347 // lstat is overridden in tests. 348 var lstat = Lstat 349 350 // Rename renames (moves) oldpath to newpath. 351 // If newpath already exists and is not a directory, Rename replaces it. 352 // OS-specific restrictions may apply when oldpath and newpath are in different directories. 353 // If there is an error, it will be of type *LinkError. 354 func Rename(oldpath, newpath string) error { 355 return rename(oldpath, newpath) 356 } 357 358 // Many functions in package syscall return a count of -1 instead of 0. 359 // Using fixCount(call()) instead of call() corrects the count. 360 func fixCount(n int, err error) (int, error) { 361 if n < 0 { 362 n = 0 363 } 364 return n, err 365 } 366 367 // wrapErr wraps an error that occurred during an operation on an open file. 368 // It passes io.EOF through unchanged, otherwise converts 369 // poll.ErrFileClosing to ErrClosed and wraps the error in a PathError. 370 func (f *File) wrapErr(op string, err error) error { 371 if err == nil || err == io.EOF { 372 return err 373 } 374 if err == poll.ErrFileClosing { 375 err = ErrClosed 376 } 377 return &PathError{Op: op, Path: f.name, Err: err} 378 } 379 380 // TempDir returns the default directory to use for temporary files. 381 // 382 // On Unix systems, it returns $TMPDIR if non-empty, else /tmp. 383 // On Windows, it uses GetTempPath, returning the first non-empty 384 // value from %TMP%, %TEMP%, %USERPROFILE%, or the Windows directory. 385 // On Plan 9, it returns /tmp. 386 // 387 // The directory is neither guaranteed to exist nor have accessible 388 // permissions. 389 func TempDir() string { 390 return tempDir() 391 } 392 393 // UserCacheDir returns the default root directory to use for user-specific 394 // cached data. Users should create their own application-specific subdirectory 395 // within this one and use that. 396 // 397 // On Unix systems, it returns $XDG_CACHE_HOME as specified by 398 // https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if 399 // non-empty, else $HOME/.cache. 400 // On Darwin, it returns $HOME/Library/Caches. 401 // On Windows, it returns %LocalAppData%. 402 // On Plan 9, it returns $home/lib/cache. 403 // 404 // If the location cannot be determined (for example, $HOME is not defined), 405 // then it will return an error. 406 func UserCacheDir() (string, error) { 407 var dir string 408 409 switch runtime.GOOS { 410 case "windows": 411 dir = Getenv("LocalAppData") 412 if dir == "" { 413 return "", errors.New("%LocalAppData% is not defined") 414 } 415 416 case "darwin", "ios": 417 dir = Getenv("HOME") 418 if dir == "" { 419 return "", errors.New("$HOME is not defined") 420 } 421 dir += "/Library/Caches" 422 423 case "plan9": 424 dir = Getenv("home") 425 if dir == "" { 426 return "", errors.New("$home is not defined") 427 } 428 dir += "/lib/cache" 429 430 default: // Unix 431 dir = Getenv("XDG_CACHE_HOME") 432 if dir == "" { 433 dir = Getenv("HOME") 434 if dir == "" { 435 return "", errors.New("neither $XDG_CACHE_HOME nor $HOME are defined") 436 } 437 dir += "/.cache" 438 } 439 } 440 441 return dir, nil 442 } 443 444 // UserConfigDir returns the default root directory to use for user-specific 445 // configuration data. Users should create their own application-specific 446 // subdirectory within this one and use that. 447 // 448 // On Unix systems, it returns $XDG_CONFIG_HOME as specified by 449 // https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if 450 // non-empty, else $HOME/.config. 451 // On Darwin, it returns $HOME/Library/Application Support. 452 // On Windows, it returns %AppData%. 453 // On Plan 9, it returns $home/lib. 454 // 455 // If the location cannot be determined (for example, $HOME is not defined), 456 // then it will return an error. 457 func UserConfigDir() (string, error) { 458 var dir string 459 460 switch runtime.GOOS { 461 case "windows": 462 dir = Getenv("AppData") 463 if dir == "" { 464 return "", errors.New("%AppData% is not defined") 465 } 466 467 case "darwin", "ios": 468 dir = Getenv("HOME") 469 if dir == "" { 470 return "", errors.New("$HOME is not defined") 471 } 472 dir += "/Library/Application Support" 473 474 case "plan9": 475 dir = Getenv("home") 476 if dir == "" { 477 return "", errors.New("$home is not defined") 478 } 479 dir += "/lib" 480 481 default: // Unix 482 dir = Getenv("XDG_CONFIG_HOME") 483 if dir == "" { 484 dir = Getenv("HOME") 485 if dir == "" { 486 return "", errors.New("neither $XDG_CONFIG_HOME nor $HOME are defined") 487 } 488 dir += "/.config" 489 } 490 } 491 492 return dir, nil 493 } 494 495 // UserHomeDir returns the current user's home directory. 496 // 497 // On Unix, including macOS, it returns the $HOME environment variable. 498 // On Windows, it returns %USERPROFILE%. 499 // On Plan 9, it returns the $home environment variable. 500 func UserHomeDir() (string, error) { 501 env, enverr := "HOME", "$HOME" 502 switch runtime.GOOS { 503 case "windows": 504 env, enverr = "USERPROFILE", "%userprofile%" 505 case "plan9": 506 env, enverr = "home", "$home" 507 } 508 if v := Getenv(env); v != "" { 509 return v, nil 510 } 511 // On some geese the home directory is not always defined. 512 switch runtime.GOOS { 513 case "android": 514 return "/sdcard", nil 515 case "ios": 516 return "/", nil 517 } 518 return "", errors.New(enverr + " is not defined") 519 } 520 521 // Chmod changes the mode of the named file to mode. 522 // If the file is a symbolic link, it changes the mode of the link's target. 523 // If there is an error, it will be of type *PathError. 524 // 525 // A different subset of the mode bits are used, depending on the 526 // operating system. 527 // 528 // On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and 529 // ModeSticky are used. 530 // 531 // On Windows, only the 0200 bit (owner writable) of mode is used; it 532 // controls whether the file's read-only attribute is set or cleared. 533 // The other bits are currently unused. For compatibility with Go 1.12 534 // and earlier, use a non-zero mode. Use mode 0400 for a read-only 535 // file and 0600 for a readable+writable file. 536 // 537 // On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive, 538 // and ModeTemporary are used. 539 func Chmod(name string, mode FileMode) error { return chmod(name, mode) } 540 541 // Chmod changes the mode of the file to mode. 542 // If there is an error, it will be of type *PathError. 543 func (f *File) Chmod(mode FileMode) error { return f.chmod(mode) } 544 545 // SetDeadline sets the read and write deadlines for a File. 546 // It is equivalent to calling both SetReadDeadline and SetWriteDeadline. 547 // 548 // Only some kinds of files support setting a deadline. Calls to SetDeadline 549 // for files that do not support deadlines will return ErrNoDeadline. 550 // On most systems ordinary files do not support deadlines, but pipes do. 551 // 552 // A deadline is an absolute time after which I/O operations fail with an 553 // error instead of blocking. The deadline applies to all future and pending 554 // I/O, not just the immediately following call to Read or Write. 555 // After a deadline has been exceeded, the connection can be refreshed 556 // by setting a deadline in the future. 557 // 558 // If the deadline is exceeded a call to Read or Write or to other I/O 559 // methods will return an error that wraps ErrDeadlineExceeded. 560 // This can be tested using errors.Is(err, os.ErrDeadlineExceeded). 561 // That error implements the Timeout method, and calling the Timeout 562 // method will return true, but there are other possible errors for which 563 // the Timeout will return true even if the deadline has not been exceeded. 564 // 565 // An idle timeout can be implemented by repeatedly extending 566 // the deadline after successful Read or Write calls. 567 // 568 // A zero value for t means I/O operations will not time out. 569 func (f *File) SetDeadline(t time.Time) error { 570 return f.setDeadline(t) 571 } 572 573 // SetReadDeadline sets the deadline for future Read calls and any 574 // currently-blocked Read call. 575 // A zero value for t means Read will not time out. 576 // Not all files support setting deadlines; see SetDeadline. 577 func (f *File) SetReadDeadline(t time.Time) error { 578 return f.setReadDeadline(t) 579 } 580 581 // SetWriteDeadline sets the deadline for any future Write calls and any 582 // currently-blocked Write call. 583 // Even if Write times out, it may return n > 0, indicating that 584 // some of the data was successfully written. 585 // A zero value for t means Write will not time out. 586 // Not all files support setting deadlines; see SetDeadline. 587 func (f *File) SetWriteDeadline(t time.Time) error { 588 return f.setWriteDeadline(t) 589 } 590 591 // SyscallConn returns a raw file. 592 // This implements the syscall.Conn interface. 593 func (f *File) SyscallConn() (syscall.RawConn, error) { 594 if err := f.checkValid("SyscallConn"); err != nil { 595 return nil, err 596 } 597 return newRawConn(f) 598 } 599 600 // isWindowsNulName reports whether name is os.DevNull ('NUL') on Windows. 601 // True is returned if name is 'NUL' whatever the case. 602 func isWindowsNulName(name string) bool { 603 if len(name) != 3 { 604 return false 605 } 606 if name[0] != 'n' && name[0] != 'N' { 607 return false 608 } 609 if name[1] != 'u' && name[1] != 'U' { 610 return false 611 } 612 if name[2] != 'l' && name[2] != 'L' { 613 return false 614 } 615 return true 616 } 617 618 // DirFS returns a file system (an fs.FS) for the tree of files rooted at the directory dir. 619 // 620 // Note that DirFS("/prefix") only guarantees that the Open calls it makes to the 621 // operating system will begin with "/prefix": DirFS("/prefix").Open("file") is the 622 // same as os.Open("/prefix/file"). So if /prefix/file is a symbolic link pointing outside 623 // the /prefix tree, then using DirFS does not stop the access any more than using 624 // os.Open does. DirFS is therefore not a general substitute for a chroot-style security 625 // mechanism when the directory tree contains arbitrary content. 626 func DirFS(dir string) fs.FS { 627 return dirFS(dir) 628 } 629 630 func containsAny(s, chars string) bool { 631 for i := 0; i < len(s); i++ { 632 for j := 0; j < len(chars); j++ { 633 if s[i] == chars[j] { 634 return true 635 } 636 } 637 } 638 return false 639 } 640 641 type dirFS string 642 643 func (dir dirFS) Open(name string) (fs.File, error) { 644 if !fs.ValidPath(name) || runtime.GOOS == "windows" && containsAny(name, `\:`) { 645 return nil, &PathError{Op: "open", Path: name, Err: ErrInvalid} 646 } 647 f, err := Open(string(dir) + "/" + name) 648 if err != nil { 649 return nil, err // nil fs.File 650 } 651 return f, nil 652 } 653 654 func (dir dirFS) Stat(name string) (fs.FileInfo, error) { 655 if !fs.ValidPath(name) || runtime.GOOS == "windows" && containsAny(name, `\:`) { 656 return nil, &PathError{Op: "stat", Path: name, Err: ErrInvalid} 657 } 658 f, err := Stat(string(dir) + "/" + name) 659 if err != nil { 660 return nil, err 661 } 662 return f, nil 663 } 664 665 // ReadFile reads the named file and returns the contents. 666 // A successful call returns err == nil, not err == EOF. 667 // Because ReadFile reads the whole file, it does not treat an EOF from Read 668 // as an error to be reported. 669 func ReadFile(name string) ([]byte, error) { 670 f, err := Open(name) 671 if err != nil { 672 return nil, err 673 } 674 defer f.Close() 675 676 var size int 677 if info, err := f.Stat(); err == nil { 678 size64 := info.Size() 679 if int64(int(size64)) == size64 { 680 size = int(size64) 681 } 682 } 683 size++ // one byte for final read at EOF 684 685 // If a file claims a small size, read at least 512 bytes. 686 // In particular, files in Linux's /proc claim size 0 but 687 // then do not work right if read in small pieces, 688 // so an initial read of 1 byte would not work correctly. 689 if size < 512 { 690 size = 512 691 } 692 693 data := make([]byte, 0, size) 694 for { 695 if len(data) >= cap(data) { 696 d := append(data[:cap(data)], 0) 697 data = d[:len(data)] 698 } 699 n, err := f.Read(data[len(data):cap(data)]) 700 data = data[:len(data)+n] 701 if err != nil { 702 if err == io.EOF { 703 err = nil 704 } 705 return data, err 706 } 707 } 708 } 709 710 // WriteFile writes data to the named file, creating it if necessary. 711 // If the file does not exist, WriteFile creates it with permissions perm (before umask); 712 // otherwise WriteFile truncates it before writing, without changing permissions. 713 func WriteFile(name string, data []byte, perm FileMode) error { 714 f, err := OpenFile(name, O_WRONLY|O_CREATE|O_TRUNC, perm) 715 if err != nil { 716 return err 717 } 718 _, err = f.Write(data) 719 if err1 := f.Close(); err1 != nil && err == nil { 720 err = err1 721 } 722 return err 723 } 724