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1 | """Common operations on Posix pathnames. |
2 | ||
3 | Instead of importing this module directly, import os and refer to | |
4 | this module as os.path. The "os.path" name is an alias for this | |
5 | module on Posix systems; on other systems (e.g. Mac, Windows), | |
6 | os.path provides the same operations in a manner specific to that | |
7 | platform, and is an alias to another module (e.g. macpath, ntpath). | |
8 | ||
9 | Some of this can actually be useful on non-Posix systems too, e.g. | |
10 | for manipulation of the pathname component of URLs. | |
11 | """ | |
12 | ||
13 | import os | |
14 | import stat | |
15 | ||
16 | __all__ = ["normcase","isabs","join","splitdrive","split","splitext", | |
17 | "basename","dirname","commonprefix","getsize","getmtime", | |
18 | "getatime","getctime","islink","exists","lexists","isdir","isfile", | |
19 | "ismount","walk","expanduser","expandvars","normpath","abspath", | |
20 | "samefile","sameopenfile","samestat", | |
21 | "curdir","pardir","sep","pathsep","defpath","altsep","extsep", | |
22 | "devnull","realpath","supports_unicode_filenames"] | |
23 | ||
24 | # strings representing various path-related bits and pieces | |
25 | curdir = '.' | |
26 | pardir = '..' | |
27 | extsep = '.' | |
28 | sep = '/' | |
29 | pathsep = ':' | |
30 | defpath = ':/bin:/usr/bin' | |
31 | altsep = None | |
32 | devnull = '/dev/null' | |
33 | ||
34 | # Normalize the case of a pathname. Trivial in Posix, string.lower on Mac. | |
35 | # On MS-DOS this may also turn slashes into backslashes; however, other | |
36 | # normalizations (such as optimizing '../' away) are not allowed | |
37 | # (another function should be defined to do that). | |
38 | ||
39 | def normcase(s): | |
40 | """Normalize case of pathname. Has no effect under Posix""" | |
41 | return s | |
42 | ||
43 | ||
44 | # Return whether a path is absolute. | |
45 | # Trivial in Posix, harder on the Mac or MS-DOS. | |
46 | ||
47 | def isabs(s): | |
48 | """Test whether a path is absolute""" | |
49 | return s.startswith('/') | |
50 | ||
51 | ||
52 | # Join pathnames. | |
53 | # Ignore the previous parts if a part is absolute. | |
54 | # Insert a '/' unless the first part is empty or already ends in '/'. | |
55 | ||
56 | def join(a, *p): | |
57 | """Join two or more pathname components, inserting '/' as needed""" | |
58 | path = a | |
59 | for b in p: | |
60 | if b.startswith('/'): | |
61 | path = b | |
62 | elif path == '' or path.endswith('/'): | |
63 | path += b | |
64 | else: | |
65 | path += '/' + b | |
66 | return path | |
67 | ||
68 | ||
69 | # Split a path in head (everything up to the last '/') and tail (the | |
70 | # rest). If the path ends in '/', tail will be empty. If there is no | |
71 | # '/' in the path, head will be empty. | |
72 | # Trailing '/'es are stripped from head unless it is the root. | |
73 | ||
74 | def split(p): | |
75 | """Split a pathname. Returns tuple "(head, tail)" where "tail" is | |
76 | everything after the final slash. Either part may be empty.""" | |
77 | i = p.rfind('/') + 1 | |
78 | head, tail = p[:i], p[i:] | |
79 | if head and head != '/'*len(head): | |
80 | head = head.rstrip('/') | |
81 | return head, tail | |
82 | ||
83 | ||
84 | # Split a path in root and extension. | |
85 | # The extension is everything starting at the last dot in the last | |
86 | # pathname component; the root is everything before that. | |
87 | # It is always true that root + ext == p. | |
88 | ||
89 | def splitext(p): | |
90 | """Split the extension from a pathname. Extension is everything from the | |
91 | last dot to the end. Returns "(root, ext)", either part may be empty.""" | |
92 | i = p.rfind('.') | |
93 | if i<=p.rfind('/'): | |
94 | return p, '' | |
95 | else: | |
96 | return p[:i], p[i:] | |
97 | ||
98 | ||
99 | # Split a pathname into a drive specification and the rest of the | |
100 | # path. Useful on DOS/Windows/NT; on Unix, the drive is always empty. | |
101 | ||
102 | def splitdrive(p): | |
103 | """Split a pathname into drive and path. On Posix, drive is always | |
104 | empty.""" | |
105 | return '', p | |
106 | ||
107 | ||
108 | # Return the tail (basename) part of a path. | |
109 | ||
110 | def basename(p): | |
111 | """Returns the final component of a pathname""" | |
112 | return split(p)[1] | |
113 | ||
114 | ||
115 | # Return the head (dirname) part of a path. | |
116 | ||
117 | def dirname(p): | |
118 | """Returns the directory component of a pathname""" | |
119 | return split(p)[0] | |
120 | ||
121 | ||
122 | # Return the longest prefix of all list elements. | |
123 | ||
124 | def commonprefix(m): | |
125 | "Given a list of pathnames, returns the longest common leading component" | |
126 | if not m: return '' | |
127 | s1 = min(m) | |
128 | s2 = max(m) | |
129 | n = min(len(s1), len(s2)) | |
130 | for i in xrange(n): | |
131 | if s1[i] != s2[i]: | |
132 | return s1[:i] | |
133 | return s1[:n] | |
134 | ||
135 | # Get size, mtime, atime of files. | |
136 | ||
137 | def getsize(filename): | |
138 | """Return the size of a file, reported by os.stat().""" | |
139 | return os.stat(filename).st_size | |
140 | ||
141 | def getmtime(filename): | |
142 | """Return the last modification time of a file, reported by os.stat().""" | |
143 | return os.stat(filename).st_mtime | |
144 | ||
145 | def getatime(filename): | |
146 | """Return the last access time of a file, reported by os.stat().""" | |
147 | return os.stat(filename).st_atime | |
148 | ||
149 | def getctime(filename): | |
150 | """Return the metadata change time of a file, reported by os.stat().""" | |
151 | return os.stat(filename).st_ctime | |
152 | ||
153 | # Is a path a symbolic link? | |
154 | # This will always return false on systems where os.lstat doesn't exist. | |
155 | ||
156 | def islink(path): | |
157 | """Test whether a path is a symbolic link""" | |
158 | try: | |
159 | st = os.lstat(path) | |
160 | except (os.error, AttributeError): | |
161 | return False | |
162 | return stat.S_ISLNK(st.st_mode) | |
163 | ||
164 | ||
165 | # Does a path exist? | |
166 | # This is false for dangling symbolic links. | |
167 | ||
168 | def exists(path): | |
169 | """Test whether a path exists. Returns False for broken symbolic links""" | |
170 | try: | |
171 | st = os.stat(path) | |
172 | except os.error: | |
173 | return False | |
174 | return True | |
175 | ||
176 | ||
177 | # Being true for dangling symbolic links is also useful. | |
178 | ||
179 | def lexists(path): | |
180 | """Test whether a path exists. Returns True for broken symbolic links""" | |
181 | try: | |
182 | st = os.lstat(path) | |
183 | except os.error: | |
184 | return False | |
185 | return True | |
186 | ||
187 | ||
188 | # Is a path a directory? | |
189 | # This follows symbolic links, so both islink() and isdir() can be true | |
190 | # for the same path. | |
191 | ||
192 | def isdir(path): | |
193 | """Test whether a path is a directory""" | |
194 | try: | |
195 | st = os.stat(path) | |
196 | except os.error: | |
197 | return False | |
198 | return stat.S_ISDIR(st.st_mode) | |
199 | ||
200 | ||
201 | # Is a path a regular file? | |
202 | # This follows symbolic links, so both islink() and isfile() can be true | |
203 | # for the same path. | |
204 | ||
205 | def isfile(path): | |
206 | """Test whether a path is a regular file""" | |
207 | try: | |
208 | st = os.stat(path) | |
209 | except os.error: | |
210 | return False | |
211 | return stat.S_ISREG(st.st_mode) | |
212 | ||
213 | ||
214 | # Are two filenames really pointing to the same file? | |
215 | ||
216 | def samefile(f1, f2): | |
217 | """Test whether two pathnames reference the same actual file""" | |
218 | s1 = os.stat(f1) | |
219 | s2 = os.stat(f2) | |
220 | return samestat(s1, s2) | |
221 | ||
222 | ||
223 | # Are two open files really referencing the same file? | |
224 | # (Not necessarily the same file descriptor!) | |
225 | ||
226 | def sameopenfile(fp1, fp2): | |
227 | """Test whether two open file objects reference the same file""" | |
228 | s1 = os.fstat(fp1) | |
229 | s2 = os.fstat(fp2) | |
230 | return samestat(s1, s2) | |
231 | ||
232 | ||
233 | # Are two stat buffers (obtained from stat, fstat or lstat) | |
234 | # describing the same file? | |
235 | ||
236 | def samestat(s1, s2): | |
237 | """Test whether two stat buffers reference the same file""" | |
238 | return s1.st_ino == s2.st_ino and \ | |
239 | s1.st_dev == s2.st_dev | |
240 | ||
241 | ||
242 | # Is a path a mount point? | |
243 | # (Does this work for all UNIXes? Is it even guaranteed to work by Posix?) | |
244 | ||
245 | def ismount(path): | |
246 | """Test whether a path is a mount point""" | |
247 | try: | |
248 | s1 = os.stat(path) | |
249 | s2 = os.stat(join(path, '..')) | |
250 | except os.error: | |
251 | return False # It doesn't exist -- so not a mount point :-) | |
252 | dev1 = s1.st_dev | |
253 | dev2 = s2.st_dev | |
254 | if dev1 != dev2: | |
255 | return True # path/.. on a different device as path | |
256 | ino1 = s1.st_ino | |
257 | ino2 = s2.st_ino | |
258 | if ino1 == ino2: | |
259 | return True # path/.. is the same i-node as path | |
260 | return False | |
261 | ||
262 | ||
263 | # Directory tree walk. | |
264 | # For each directory under top (including top itself, but excluding | |
265 | # '.' and '..'), func(arg, dirname, filenames) is called, where | |
266 | # dirname is the name of the directory and filenames is the list | |
267 | # of files (and subdirectories etc.) in the directory. | |
268 | # The func may modify the filenames list, to implement a filter, | |
269 | # or to impose a different order of visiting. | |
270 | ||
271 | def walk(top, func, arg): | |
272 | """Directory tree walk with callback function. | |
273 | ||
274 | For each directory in the directory tree rooted at top (including top | |
275 | itself, but excluding '.' and '..'), call func(arg, dirname, fnames). | |
276 | dirname is the name of the directory, and fnames a list of the names of | |
277 | the files and subdirectories in dirname (excluding '.' and '..'). func | |
278 | may modify the fnames list in-place (e.g. via del or slice assignment), | |
279 | and walk will only recurse into the subdirectories whose names remain in | |
280 | fnames; this can be used to implement a filter, or to impose a specific | |
281 | order of visiting. No semantics are defined for, or required of, arg, | |
282 | beyond that arg is always passed to func. It can be used, e.g., to pass | |
283 | a filename pattern, or a mutable object designed to accumulate | |
284 | statistics. Passing None for arg is common.""" | |
285 | ||
286 | try: | |
287 | names = os.listdir(top) | |
288 | except os.error: | |
289 | return | |
290 | func(arg, top, names) | |
291 | for name in names: | |
292 | name = join(top, name) | |
293 | try: | |
294 | st = os.lstat(name) | |
295 | except os.error: | |
296 | continue | |
297 | if stat.S_ISDIR(st.st_mode): | |
298 | walk(name, func, arg) | |
299 | ||
300 | ||
301 | # Expand paths beginning with '~' or '~user'. | |
302 | # '~' means $HOME; '~user' means that user's home directory. | |
303 | # If the path doesn't begin with '~', or if the user or $HOME is unknown, | |
304 | # the path is returned unchanged (leaving error reporting to whatever | |
305 | # function is called with the expanded path as argument). | |
306 | # See also module 'glob' for expansion of *, ? and [...] in pathnames. | |
307 | # (A function should also be defined to do full *sh-style environment | |
308 | # variable expansion.) | |
309 | ||
310 | def expanduser(path): | |
311 | """Expand ~ and ~user constructions. If user or $HOME is unknown, | |
312 | do nothing.""" | |
313 | if not path.startswith('~'): | |
314 | return path | |
315 | i = path.find('/', 1) | |
316 | if i < 0: | |
317 | i = len(path) | |
318 | if i == 1: | |
319 | if 'HOME' not in os.environ: | |
320 | import pwd | |
321 | userhome = pwd.getpwuid(os.getuid()).pw_dir | |
322 | else: | |
323 | userhome = os.environ['HOME'] | |
324 | else: | |
325 | import pwd | |
326 | try: | |
327 | pwent = pwd.getpwnam(path[1:i]) | |
328 | except KeyError: | |
329 | return path | |
330 | userhome = pwent.pw_dir | |
331 | if userhome.endswith('/'): | |
332 | i += 1 | |
333 | return userhome + path[i:] | |
334 | ||
335 | ||
336 | # Expand paths containing shell variable substitutions. | |
337 | # This expands the forms $variable and ${variable} only. | |
338 | # Non-existent variables are left unchanged. | |
339 | ||
340 | _varprog = None | |
341 | ||
342 | def expandvars(path): | |
343 | """Expand shell variables of form $var and ${var}. Unknown variables | |
344 | are left unchanged.""" | |
345 | global _varprog | |
346 | if '$' not in path: | |
347 | return path | |
348 | if not _varprog: | |
349 | import re | |
350 | _varprog = re.compile(r'\$(\w+|\{[^}]*\})') | |
351 | i = 0 | |
352 | while True: | |
353 | m = _varprog.search(path, i) | |
354 | if not m: | |
355 | break | |
356 | i, j = m.span(0) | |
357 | name = m.group(1) | |
358 | if name.startswith('{') and name.endswith('}'): | |
359 | name = name[1:-1] | |
360 | if name in os.environ: | |
361 | tail = path[j:] | |
362 | path = path[:i] + os.environ[name] | |
363 | i = len(path) | |
364 | path += tail | |
365 | else: | |
366 | i = j | |
367 | return path | |
368 | ||
369 | ||
370 | # Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A/B. | |
371 | # It should be understood that this may change the meaning of the path | |
372 | # if it contains symbolic links! | |
373 | ||
374 | def normpath(path): | |
375 | """Normalize path, eliminating double slashes, etc.""" | |
376 | if path == '': | |
377 | return '.' | |
378 | initial_slashes = path.startswith('/') | |
379 | # POSIX allows one or two initial slashes, but treats three or more | |
380 | # as single slash. | |
381 | if (initial_slashes and | |
382 | path.startswith('//') and not path.startswith('///')): | |
383 | initial_slashes = 2 | |
384 | comps = path.split('/') | |
385 | new_comps = [] | |
386 | for comp in comps: | |
387 | if comp in ('', '.'): | |
388 | continue | |
389 | if (comp != '..' or (not initial_slashes and not new_comps) or | |
390 | (new_comps and new_comps[-1] == '..')): | |
391 | new_comps.append(comp) | |
392 | elif new_comps: | |
393 | new_comps.pop() | |
394 | comps = new_comps | |
395 | path = '/'.join(comps) | |
396 | if initial_slashes: | |
397 | path = '/'*initial_slashes + path | |
398 | return path or '.' | |
399 | ||
400 | ||
401 | def abspath(path): | |
402 | """Return an absolute path.""" | |
403 | if not isabs(path): | |
404 | path = join(os.getcwd(), path) | |
405 | return normpath(path) | |
406 | ||
407 | ||
408 | # Return a canonical path (i.e. the absolute location of a file on the | |
409 | # filesystem). | |
410 | ||
411 | def realpath(filename): | |
412 | """Return the canonical path of the specified filename, eliminating any | |
413 | symbolic links encountered in the path.""" | |
414 | if isabs(filename): | |
415 | bits = ['/'] + filename.split('/')[1:] | |
416 | else: | |
417 | bits = [''] + filename.split('/') | |
418 | ||
419 | for i in range(2, len(bits)+1): | |
420 | component = join(*bits[0:i]) | |
421 | # Resolve symbolic links. | |
422 | if islink(component): | |
423 | resolved = _resolve_link(component) | |
424 | if resolved is None: | |
425 | # Infinite loop -- return original component + rest of the path | |
426 | return abspath(join(*([component] + bits[i:]))) | |
427 | else: | |
428 | newpath = join(*([resolved] + bits[i:])) | |
429 | return realpath(newpath) | |
430 | ||
431 | return abspath(filename) | |
432 | ||
433 | ||
434 | def _resolve_link(path): | |
435 | """Internal helper function. Takes a path and follows symlinks | |
436 | until we either arrive at something that isn't a symlink, or | |
437 | encounter a path we've seen before (meaning that there's a loop). | |
438 | """ | |
439 | paths_seen = [] | |
440 | while islink(path): | |
441 | if path in paths_seen: | |
442 | # Already seen this path, so we must have a symlink loop | |
443 | return None | |
444 | paths_seen.append(path) | |
445 | # Resolve where the link points to | |
446 | resolved = os.readlink(path) | |
447 | if not isabs(resolved): | |
448 | dir = dirname(path) | |
449 | path = normpath(join(dir, resolved)) | |
450 | else: | |
451 | path = normpath(resolved) | |
452 | return path | |
453 | ||
454 | supports_unicode_filenames = False |