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.
5 // Package filepath implements utility routines for manipulating filename paths
6 // in a way compatible with the target operating system-defined file paths.
8 // The filepath package uses either forward slashes or backslashes,
9 // depending on the operating system. To process paths such as URLs
10 // that always use forward slashes regardless of the operating
11 // system, see the path package.
22 // A lazybuf is a lazily constructed path buffer.
23 // It supports append, reading previously appended bytes,
24 // and retrieving the final string. It does not allocate a buffer
25 // to hold the output until that output diverges from s.
34 func (b *lazybuf) index(i int) byte {
41 func (b *lazybuf) append(c byte) {
43 if b.w < len(b.path) && b.path[b.w] == c {
47 b.buf = make([]byte, len(b.path))
48 copy(b.buf, b.path[:b.w])
54 func (b *lazybuf) string() string {
56 return b.volAndPath[:b.volLen+b.w]
58 return b.volAndPath[:b.volLen] + string(b.buf[:b.w])
62 Separator = os.PathSeparator
63 ListSeparator = os.PathListSeparator
66 // Clean returns the shortest path name equivalent to path
67 // by purely lexical processing. It applies the following rules
68 // iteratively until no further processing can be done:
70 // 1. Replace multiple Separator elements with a single one.
71 // 2. Eliminate each . path name element (the current directory).
72 // 3. Eliminate each inner .. path name element (the parent directory)
73 // along with the non-.. element that precedes it.
74 // 4. Eliminate .. elements that begin a rooted path:
75 // that is, replace "/.." by "/" at the beginning of a path,
76 // assuming Separator is '/'.
78 // The returned path ends in a slash only if it represents a root directory,
79 // such as "/" on Unix or `C:\` on Windows.
81 // Finally, any occurrences of slash are replaced by Separator.
83 // If the result of this process is an empty string, Clean
84 // returns the string ".".
86 // See also Rob Pike, “Lexical File Names in Plan 9 or
87 // Getting Dot-Dot Right,”
88 // https://9p.io/sys/doc/lexnames.html
89 func Clean(path string) string {
91 volLen := volumeNameLen(path)
94 if volLen > 1 && originalPath[1] != ':' {
96 return FromSlash(originalPath)
98 return originalPath + "."
100 rooted := os.IsPathSeparator(path[0])
103 // reading from path; r is index of next byte to process.
104 // writing to buf; w is index of next byte to write.
105 // dotdot is index in buf where .. must stop, either because
106 // it is the leading slash or it is a leading ../../.. prefix.
108 out := lazybuf{path: path, volAndPath: originalPath, volLen: volLen}
111 out.append(Separator)
117 case os.IsPathSeparator(path[r]):
118 // empty path element
120 case path[r] == '.' && r+1 == n:
123 case path[r] == '.' && os.IsPathSeparator(path[r+1]):
127 for r < len(path) && os.IsPathSeparator(path[r]) {
130 if out.w == 0 && volumeNameLen(path[r:]) > 0 {
131 // When joining prefix "." and an absolute path on Windows,
132 // the prefix should not be removed.
135 case path[r] == '.' && path[r+1] == '.' && (r+2 == n || os.IsPathSeparator(path[r+2])):
136 // .. element: remove to last separator
142 for out.w > dotdot && !os.IsPathSeparator(out.index(out.w)) {
146 // cannot backtrack, but not rooted, so append .. element.
148 out.append(Separator)
155 // real path element.
156 // add slash if needed
157 if rooted && out.w != 1 || !rooted && out.w != 0 {
158 out.append(Separator)
161 for ; r < n && !os.IsPathSeparator(path[r]); r++ {
167 // Turn empty string into "."
172 return FromSlash(out.string())
175 // ToSlash returns the result of replacing each separator character
176 // in path with a slash ('/') character. Multiple separators are
177 // replaced by multiple slashes.
178 func ToSlash(path string) string {
179 if Separator == '/' {
182 return strings.ReplaceAll(path, string(Separator), "/")
185 // FromSlash returns the result of replacing each slash ('/') character
186 // in path with a separator character. Multiple slashes are replaced
187 // by multiple separators.
188 func FromSlash(path string) string {
189 if Separator == '/' {
192 return strings.ReplaceAll(path, "/", string(Separator))
195 // SplitList splits a list of paths joined by the OS-specific ListSeparator,
196 // usually found in PATH or GOPATH environment variables.
197 // Unlike strings.Split, SplitList returns an empty slice when passed an empty
199 func SplitList(path string) []string {
200 return splitList(path)
203 // Split splits path immediately following the final Separator,
204 // separating it into a directory and file name component.
205 // If there is no Separator in path, Split returns an empty dir
206 // and file set to path.
207 // The returned values have the property that path = dir+file.
208 func Split(path string) (dir, file string) {
209 vol := VolumeName(path)
211 for i >= len(vol) && !os.IsPathSeparator(path[i]) {
214 return path[:i+1], path[i+1:]
217 // Join joins any number of path elements into a single path,
218 // separating them with an OS specific Separator. Empty elements
219 // are ignored. The result is Cleaned. However, if the argument
220 // list is empty or all its elements are empty, Join returns
222 // On Windows, the result will only be a UNC path if the first
223 // non-empty element is a UNC path.
224 func Join(elem ...string) string {
228 // Ext returns the file name extension used by path.
229 // The extension is the suffix beginning at the final dot
230 // in the final element of path; it is empty if there is
232 func Ext(path string) string {
233 for i := len(path) - 1; i >= 0 && !os.IsPathSeparator(path[i]); i-- {
241 // EvalSymlinks returns the path name after the evaluation of any symbolic
243 // If path is relative the result will be relative to the current directory,
244 // unless one of the components is an absolute symbolic link.
245 // EvalSymlinks calls Clean on the result.
246 func EvalSymlinks(path string) (string, error) {
247 return evalSymlinks(path)
250 // Abs returns an absolute representation of path.
251 // If the path is not absolute it will be joined with the current
252 // working directory to turn it into an absolute path. The absolute
253 // path name for a given file is not guaranteed to be unique.
254 // Abs calls Clean on the result.
255 func Abs(path string) (string, error) {
259 func unixAbs(path string) (string, error) {
261 return Clean(path), nil
263 wd, err := os.Getwd()
267 return Join(wd, path), nil
270 // Rel returns a relative path that is lexically equivalent to targpath when
271 // joined to basepath with an intervening separator. That is,
272 // Join(basepath, Rel(basepath, targpath)) is equivalent to targpath itself.
273 // On success, the returned path will always be relative to basepath,
274 // even if basepath and targpath share no elements.
275 // An error is returned if targpath can't be made relative to basepath or if
276 // knowing the current working directory would be necessary to compute it.
277 // Rel calls Clean on the result.
278 func Rel(basepath, targpath string) (string, error) {
279 baseVol := VolumeName(basepath)
280 targVol := VolumeName(targpath)
281 base := Clean(basepath)
282 targ := Clean(targpath)
283 if sameWord(targ, base) {
286 base = base[len(baseVol):]
287 targ = targ[len(targVol):]
290 } else if base == "" && volumeNameLen(baseVol) > 2 /* isUNC */ {
291 // Treat any targetpath matching `\\host\share` basepath as absolute path.
292 base = string(Separator)
295 // Can't use IsAbs - `\a` and `a` are both relative in Windows.
296 baseSlashed := len(base) > 0 && base[0] == Separator
297 targSlashed := len(targ) > 0 && targ[0] == Separator
298 if baseSlashed != targSlashed || !sameWord(baseVol, targVol) {
299 return "", errors.New("Rel: can't make " + targpath + " relative to " + basepath)
301 // Position base[b0:bi] and targ[t0:ti] at the first differing elements.
304 var b0, bi, t0, ti int
306 for bi < bl && base[bi] != Separator {
309 for ti < tl && targ[ti] != Separator {
312 if !sameWord(targ[t0:ti], base[b0:bi]) {
324 if base[b0:bi] == ".." {
325 return "", errors.New("Rel: can't make " + targpath + " relative to " + basepath)
328 // Base elements left. Must go up before going down.
329 seps := strings.Count(base[b0:bl], string(Separator))
334 buf := make([]byte, size)
336 for i := 0; i < seps; i++ {
338 copy(buf[n+1:], "..")
343 copy(buf[n+1:], targ[t0:])
345 return string(buf), nil
347 return targ[t0:], nil
350 // SkipDir is used as a return value from WalkFuncs to indicate that
351 // the directory named in the call is to be skipped. It is not returned
352 // as an error by any function.
353 var SkipDir error = fs.SkipDir
355 // WalkFunc is the type of the function called by Walk to visit each
356 // file or directory.
358 // The path argument contains the argument to Walk as a prefix.
359 // That is, if Walk is called with root argument "dir" and finds a file
360 // named "a" in that directory, the walk function will be called with
363 // The directory and file are joined with Join, which may clean the
364 // directory name: if Walk is called with the root argument "x/../dir"
365 // and finds a file named "a" in that directory, the walk function will
366 // be called with argument "dir/a", not "x/../dir/a".
368 // The info argument is the fs.FileInfo for the named path.
370 // The error result returned by the function controls how Walk continues.
371 // If the function returns the special value SkipDir, Walk skips the
372 // current directory (path if info.IsDir() is true, otherwise path's
373 // parent directory). Otherwise, if the function returns a non-nil error,
374 // Walk stops entirely and returns that error.
376 // The err argument reports an error related to path, signaling that Walk
377 // will not walk into that directory. The function can decide how to
378 // handle that error; as described earlier, returning the error will
379 // cause Walk to stop walking the entire tree.
381 // Walk calls the function with a non-nil err argument in two cases.
383 // First, if an os.Lstat on the root directory or any directory or file
384 // in the tree fails, Walk calls the function with path set to that
385 // directory or file's path, info set to nil, and err set to the error
388 // Second, if a directory's Readdirnames method fails, Walk calls the
389 // function with path set to the directory's path, info, set to an
390 // fs.FileInfo describing the directory, and err set to the error from
392 type WalkFunc func(path string, info fs.FileInfo, err error) error
394 var lstat = os.Lstat // for testing
396 // walkDir recursively descends path, calling walkDirFn.
397 func walkDir(path string, d fs.DirEntry, walkDirFn fs.WalkDirFunc) error {
398 if err := walkDirFn(path, d, nil); err != nil || !d.IsDir() {
399 if err == SkipDir && d.IsDir() {
400 // Successfully skipped directory.
406 dirs, err := readDir(path)
408 // Second call, to report ReadDir error.
409 err = walkDirFn(path, d, err)
411 if err == SkipDir && d.IsDir() {
418 for _, d1 := range dirs {
419 path1 := Join(path, d1.Name())
420 if err := walkDir(path1, d1, walkDirFn); err != nil {
430 // walk recursively descends path, calling walkFn.
431 func walk(path string, info fs.FileInfo, walkFn WalkFunc) error {
433 return walkFn(path, info, nil)
436 names, err := readDirNames(path)
437 err1 := walkFn(path, info, err)
438 // If err != nil, walk can't walk into this directory.
439 // err1 != nil means walkFn want walk to skip this directory or stop walking.
440 // Therefore, if one of err and err1 isn't nil, walk will return.
441 if err != nil || err1 != nil {
442 // The caller's behavior is controlled by the return value, which is decided
443 // by walkFn. walkFn may ignore err and return nil.
444 // If walkFn returns SkipDir, it will be handled by the caller.
445 // So walk should return whatever walkFn returns.
449 for _, name := range names {
450 filename := Join(path, name)
451 fileInfo, err := lstat(filename)
453 if err := walkFn(filename, fileInfo, err); err != nil && err != SkipDir {
457 err = walk(filename, fileInfo, walkFn)
459 if !fileInfo.IsDir() || err != SkipDir {
468 // WalkDir walks the file tree rooted at root, calling fn for each file or
469 // directory in the tree, including root.
471 // All errors that arise visiting files and directories are filtered by fn:
472 // see the fs.WalkDirFunc documentation for details.
474 // The files are walked in lexical order, which makes the output deterministic
475 // but requires WalkDir to read an entire directory into memory before proceeding
476 // to walk that directory.
478 // WalkDir does not follow symbolic links.
479 func WalkDir(root string, fn fs.WalkDirFunc) error {
480 info, err := os.Lstat(root)
482 err = fn(root, nil, err)
484 err = walkDir(root, &statDirEntry{info}, fn)
492 type statDirEntry struct {
496 func (d *statDirEntry) Name() string { return d.info.Name() }
497 func (d *statDirEntry) IsDir() bool { return d.info.IsDir() }
498 func (d *statDirEntry) Type() fs.FileMode { return d.info.Mode().Type() }
499 func (d *statDirEntry) Info() (fs.FileInfo, error) { return d.info, nil }
501 // Walk walks the file tree rooted at root, calling fn for each file or
502 // directory in the tree, including root.
504 // All errors that arise visiting files and directories are filtered by fn:
505 // see the WalkFunc documentation for details.
507 // The files are walked in lexical order, which makes the output deterministic
508 // but requires Walk to read an entire directory into memory before proceeding
509 // to walk that directory.
511 // Walk does not follow symbolic links.
513 // Walk is less efficient than WalkDir, introduced in Go 1.16,
514 // which avoids calling os.Lstat on every visited file or directory.
515 func Walk(root string, fn WalkFunc) error {
516 info, err := os.Lstat(root)
518 err = fn(root, nil, err)
520 err = walk(root, info, fn)
528 // readDir reads the directory named by dirname and returns
529 // a sorted list of directory entries.
530 func readDir(dirname string) ([]fs.DirEntry, error) {
531 f, err := os.Open(dirname)
535 dirs, err := f.ReadDir(-1)
540 sort.Slice(dirs, func(i, j int) bool { return dirs[i].Name() < dirs[j].Name() })
544 // readDirNames reads the directory named by dirname and returns
545 // a sorted list of directory entry names.
546 func readDirNames(dirname string) ([]string, error) {
547 f, err := os.Open(dirname)
551 names, err := f.Readdirnames(-1)
560 // Base returns the last element of path.
561 // Trailing path separators are removed before extracting the last element.
562 // If the path is empty, Base returns ".".
563 // If the path consists entirely of separators, Base returns a single separator.
564 func Base(path string) string {
568 // Strip trailing slashes.
569 for len(path) > 0 && os.IsPathSeparator(path[len(path)-1]) {
570 path = path[0 : len(path)-1]
572 // Throw away volume name
573 path = path[len(VolumeName(path)):]
574 // Find the last element
576 for i >= 0 && !os.IsPathSeparator(path[i]) {
582 // If empty now, it had only slashes.
584 return string(Separator)
589 // Dir returns all but the last element of path, typically the path's directory.
590 // After dropping the final element, Dir calls Clean on the path and trailing
591 // slashes are removed.
592 // If the path is empty, Dir returns ".".
593 // If the path consists entirely of separators, Dir returns a single separator.
594 // The returned path does not end in a separator unless it is the root directory.
595 func Dir(path string) string {
596 vol := VolumeName(path)
598 for i >= len(vol) && !os.IsPathSeparator(path[i]) {
601 dir := Clean(path[len(vol) : i+1])
602 if dir == "." && len(vol) > 2 {
609 // VolumeName returns leading volume name.
610 // Given "C:\foo\bar" it returns "C:" on Windows.
611 // Given "\\host\share\foo" it returns "\\host\share".
612 // On other platforms it returns "".
613 func VolumeName(path string) string {
614 return path[:volumeNameLen(path)]