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 || os
.IsPathSeparator(path
[r
+1])):
123 case path
[r
] == '.' && path
[r
+1] == '.' && (r
+2 == n || os
.IsPathSeparator(path
[r
+2])):
124 // .. element: remove to last separator
130 for out
.w
> dotdot
&& !os
.IsPathSeparator(out
.index(out
.w
)) {
134 // cannot backtrack, but not rooted, so append .. element.
136 out
.append(Separator
)
143 // real path element.
144 // add slash if needed
145 if rooted
&& out
.w
!= 1 ||
!rooted
&& out
.w
!= 0 {
146 out
.append(Separator
)
149 for ; r
< n
&& !os
.IsPathSeparator(path
[r
]); r
++ {
155 // Turn empty string into "."
160 return FromSlash(out
.string())
163 // ToSlash returns the result of replacing each separator character
164 // in path with a slash ('/') character. Multiple separators are
165 // replaced by multiple slashes.
166 func ToSlash(path
string) string {
167 if Separator
== '/' {
170 return strings
.ReplaceAll(path
, string(Separator
), "/")
173 // FromSlash returns the result of replacing each slash ('/') character
174 // in path with a separator character. Multiple slashes are replaced
175 // by multiple separators.
176 func FromSlash(path
string) string {
177 if Separator
== '/' {
180 return strings
.ReplaceAll(path
, "/", string(Separator
))
183 // SplitList splits a list of paths joined by the OS-specific ListSeparator,
184 // usually found in PATH or GOPATH environment variables.
185 // Unlike strings.Split, SplitList returns an empty slice when passed an empty
187 func SplitList(path
string) []string {
188 return splitList(path
)
191 // Split splits path immediately following the final Separator,
192 // separating it into a directory and file name component.
193 // If there is no Separator in path, Split returns an empty dir
194 // and file set to path.
195 // The returned values have the property that path = dir+file.
196 func Split(path
string) (dir
, file
string) {
197 vol
:= VolumeName(path
)
199 for i
>= len(vol
) && !os
.IsPathSeparator(path
[i
]) {
202 return path
[:i
+1], path
[i
+1:]
205 // Join joins any number of path elements into a single path,
206 // separating them with an OS specific Separator. Empty elements
207 // are ignored. The result is Cleaned. However, if the argument
208 // list is empty or all its elements are empty, Join returns
210 // On Windows, the result will only be a UNC path if the first
211 // non-empty element is a UNC path.
212 func Join(elem
...string) string {
216 // Ext returns the file name extension used by path.
217 // The extension is the suffix beginning at the final dot
218 // in the final element of path; it is empty if there is
220 func Ext(path
string) string {
221 for i
:= len(path
) - 1; i
>= 0 && !os
.IsPathSeparator(path
[i
]); i
-- {
229 // EvalSymlinks returns the path name after the evaluation of any symbolic
231 // If path is relative the result will be relative to the current directory,
232 // unless one of the components is an absolute symbolic link.
233 // EvalSymlinks calls Clean on the result.
234 func EvalSymlinks(path
string) (string, error
) {
235 return evalSymlinks(path
)
238 // Abs returns an absolute representation of path.
239 // If the path is not absolute it will be joined with the current
240 // working directory to turn it into an absolute path. The absolute
241 // path name for a given file is not guaranteed to be unique.
242 // Abs calls Clean on the result.
243 func Abs(path
string) (string, error
) {
247 func unixAbs(path
string) (string, error
) {
249 return Clean(path
), nil
251 wd
, err
:= os
.Getwd()
255 return Join(wd
, path
), nil
258 // Rel returns a relative path that is lexically equivalent to targpath when
259 // joined to basepath with an intervening separator. That is,
260 // Join(basepath, Rel(basepath, targpath)) is equivalent to targpath itself.
261 // On success, the returned path will always be relative to basepath,
262 // even if basepath and targpath share no elements.
263 // An error is returned if targpath can't be made relative to basepath or if
264 // knowing the current working directory would be necessary to compute it.
265 // Rel calls Clean on the result.
266 func Rel(basepath
, targpath
string) (string, error
) {
267 baseVol
:= VolumeName(basepath
)
268 targVol
:= VolumeName(targpath
)
269 base
:= Clean(basepath
)
270 targ
:= Clean(targpath
)
271 if sameWord(targ
, base
) {
274 base
= base
[len(baseVol
):]
275 targ
= targ
[len(targVol
):]
278 } else if base
== "" && volumeNameLen(baseVol
) > 2 /* isUNC */ {
279 // Treat any targetpath matching `\\host\share` basepath as absolute path.
280 base
= string(Separator
)
283 // Can't use IsAbs - `\a` and `a` are both relative in Windows.
284 baseSlashed
:= len(base
) > 0 && base
[0] == Separator
285 targSlashed
:= len(targ
) > 0 && targ
[0] == Separator
286 if baseSlashed
!= targSlashed ||
!sameWord(baseVol
, targVol
) {
287 return "", errors
.New("Rel: can't make " + targpath
+ " relative to " + basepath
)
289 // Position base[b0:bi] and targ[t0:ti] at the first differing elements.
292 var b0
, bi
, t0
, ti
int
294 for bi
< bl
&& base
[bi
] != Separator
{
297 for ti
< tl
&& targ
[ti
] != Separator
{
300 if !sameWord(targ
[t0
:ti
], base
[b0
:bi
]) {
312 if base
[b0
:bi
] == ".." {
313 return "", errors
.New("Rel: can't make " + targpath
+ " relative to " + basepath
)
316 // Base elements left. Must go up before going down.
317 seps
:= strings
.Count(base
[b0
:bl
], string(Separator
))
322 buf
:= make([]byte, size
)
324 for i
:= 0; i
< seps
; i
++ {
326 copy(buf
[n
+1:], "..")
331 copy(buf
[n
+1:], targ
[t0
:])
333 return string(buf
), nil
335 return targ
[t0
:], nil
338 // SkipDir is used as a return value from WalkFuncs to indicate that
339 // the directory named in the call is to be skipped. It is not returned
340 // as an error by any function.
341 var SkipDir error
= fs
.SkipDir
343 // WalkFunc is the type of the function called by Walk to visit each
344 // file or directory.
346 // The path argument contains the argument to Walk as a prefix.
347 // That is, if Walk is called with root argument "dir" and finds a file
348 // named "a" in that directory, the walk function will be called with
351 // The directory and file are joined with Join, which may clean the
352 // directory name: if Walk is called with the root argument "x/../dir"
353 // and finds a file named "a" in that directory, the walk function will
354 // be called with argument "dir/a", not "x/../dir/a".
356 // The info argument is the fs.FileInfo for the named path.
358 // The error result returned by the function controls how Walk continues.
359 // If the function returns the special value SkipDir, Walk skips the
360 // current directory (path if info.IsDir() is true, otherwise path's
361 // parent directory). Otherwise, if the function returns a non-nil error,
362 // Walk stops entirely and returns that error.
364 // The err argument reports an error related to path, signaling that Walk
365 // will not walk into that directory. The function can decide how to
366 // handle that error; as described earlier, returning the error will
367 // cause Walk to stop walking the entire tree.
369 // Walk calls the function with a non-nil err argument in two cases.
371 // First, if an os.Lstat on the root directory or any directory or file
372 // in the tree fails, Walk calls the function with path set to that
373 // directory or file's path, info set to nil, and err set to the error
376 // Second, if a directory's Readdirnames method fails, Walk calls the
377 // function with path set to the directory's path, info, set to an
378 // fs.FileInfo describing the directory, and err set to the error from
380 type WalkFunc
func(path
string, info fs
.FileInfo
, err error
) error
382 var lstat
= os
.Lstat
// for testing
384 // walkDir recursively descends path, calling walkDirFn.
385 func walkDir(path
string, d fs
.DirEntry
, walkDirFn fs
.WalkDirFunc
) error
{
386 if err
:= walkDirFn(path
, d
, nil); err
!= nil ||
!d
.IsDir() {
387 if err
== SkipDir
&& d
.IsDir() {
388 // Successfully skipped directory.
394 dirs
, err
:= readDir(path
)
396 // Second call, to report ReadDir error.
397 err
= walkDirFn(path
, d
, err
)
403 for _
, d1
:= range dirs
{
404 path1
:= Join(path
, d1
.Name())
405 if err
:= walkDir(path1
, d1
, walkDirFn
); err
!= nil {
415 // walk recursively descends path, calling walkFn.
416 func walk(path
string, info fs
.FileInfo
, walkFn WalkFunc
) error
{
418 return walkFn(path
, info
, nil)
421 names
, err
:= readDirNames(path
)
422 err1
:= walkFn(path
, info
, err
)
423 // If err != nil, walk can't walk into this directory.
424 // err1 != nil means walkFn want walk to skip this directory or stop walking.
425 // Therefore, if one of err and err1 isn't nil, walk will return.
426 if err
!= nil || err1
!= nil {
427 // The caller's behavior is controlled by the return value, which is decided
428 // by walkFn. walkFn may ignore err and return nil.
429 // If walkFn returns SkipDir, it will be handled by the caller.
430 // So walk should return whatever walkFn returns.
434 for _
, name
:= range names
{
435 filename
:= Join(path
, name
)
436 fileInfo
, err
:= lstat(filename
)
438 if err
:= walkFn(filename
, fileInfo
, err
); err
!= nil && err
!= SkipDir
{
442 err
= walk(filename
, fileInfo
, walkFn
)
444 if !fileInfo
.IsDir() || err
!= SkipDir
{
453 // WalkDir walks the file tree rooted at root, calling fn for each file or
454 // directory in the tree, including root.
456 // All errors that arise visiting files and directories are filtered by fn:
457 // see the fs.WalkDirFunc documentation for details.
459 // The files are walked in lexical order, which makes the output deterministic
460 // but requires WalkDir to read an entire directory into memory before proceeding
461 // to walk that directory.
463 // WalkDir does not follow symbolic links.
464 func WalkDir(root
string, fn fs
.WalkDirFunc
) error
{
465 info
, err
:= os
.Lstat(root
)
467 err
= fn(root
, nil, err
)
469 err
= walkDir(root
, &statDirEntry
{info
}, fn
)
477 type statDirEntry
struct {
481 func (d
*statDirEntry
) Name() string { return d
.info
.Name() }
482 func (d
*statDirEntry
) IsDir() bool { return d
.info
.IsDir() }
483 func (d
*statDirEntry
) Type() fs
.FileMode
{ return d
.info
.Mode().Type() }
484 func (d
*statDirEntry
) Info() (fs
.FileInfo
, error
) { return d
.info
, nil }
486 // Walk walks the file tree rooted at root, calling fn for each file or
487 // directory in the tree, including root.
489 // All errors that arise visiting files and directories are filtered by fn:
490 // see the WalkFunc documentation for details.
492 // The files are walked in lexical order, which makes the output deterministic
493 // but requires Walk to read an entire directory into memory before proceeding
494 // to walk that directory.
496 // Walk does not follow symbolic links.
498 // Walk is less efficient than WalkDir, introduced in Go 1.16,
499 // which avoids calling os.Lstat on every visited file or directory.
500 func Walk(root
string, fn WalkFunc
) error
{
501 info
, err
:= os
.Lstat(root
)
503 err
= fn(root
, nil, err
)
505 err
= walk(root
, info
, fn
)
513 // readDir reads the directory named by dirname and returns
514 // a sorted list of directory entries.
515 func readDir(dirname
string) ([]fs
.DirEntry
, error
) {
516 f
, err
:= os
.Open(dirname
)
520 dirs
, err
:= f
.ReadDir(-1)
525 sort
.Slice(dirs
, func(i
, j
int) bool { return dirs
[i
].Name() < dirs
[j
].Name() })
529 // readDirNames reads the directory named by dirname and returns
530 // a sorted list of directory entry names.
531 func readDirNames(dirname
string) ([]string, error
) {
532 f
, err
:= os
.Open(dirname
)
536 names
, err
:= f
.Readdirnames(-1)
545 // Base returns the last element of path.
546 // Trailing path separators are removed before extracting the last element.
547 // If the path is empty, Base returns ".".
548 // If the path consists entirely of separators, Base returns a single separator.
549 func Base(path
string) string {
553 // Strip trailing slashes.
554 for len(path
) > 0 && os
.IsPathSeparator(path
[len(path
)-1]) {
555 path
= path
[0 : len(path
)-1]
557 // Throw away volume name
558 path
= path
[len(VolumeName(path
)):]
559 // Find the last element
561 for i
>= 0 && !os
.IsPathSeparator(path
[i
]) {
567 // If empty now, it had only slashes.
569 return string(Separator
)
574 // Dir returns all but the last element of path, typically the path's directory.
575 // After dropping the final element, Dir calls Clean on the path and trailing
576 // slashes are removed.
577 // If the path is empty, Dir returns ".".
578 // If the path consists entirely of separators, Dir returns a single separator.
579 // The returned path does not end in a separator unless it is the root directory.
580 func Dir(path
string) string {
581 vol
:= VolumeName(path
)
583 for i
>= len(vol
) && !os
.IsPathSeparator(path
[i
]) {
586 dir
:= Clean(path
[len(vol
) : i
+1])
587 if dir
== "." && len(vol
) > 2 {
594 // VolumeName returns leading volume name.
595 // Given "C:\foo\bar" it returns "C:" on Windows.
596 // Given "\\host\share\foo" it returns "\\host\share".
597 // On other platforms it returns "".
598 func VolumeName(path
string) string {
599 return path
[:volumeNameLen(path
)]