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