/Lib/posixpath.py
Python | 404 lines | 401 code | 0 blank | 3 comment | 0 complexity | d38ff07e283797a93085b258ab853733 MD5 | raw file
- """Common operations on Posix pathnames.
-
- Instead of importing this module directly, import os and refer to
- this module as os.path. The "os.path" name is an alias for this
- module on Posix systems; on other systems (e.g. Mac, Windows),
- os.path provides the same operations in a manner specific to that
- platform, and is an alias to another module (e.g. macpath, ntpath).
-
- Some of this can actually be useful on non-Posix systems too, e.g.
- for manipulation of the pathname component of URLs.
- """
-
- import os
- import stat
- import genericpath
- import warnings
- from genericpath import *
-
- __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
- "basename","dirname","commonprefix","getsize","getmtime",
- "getatime","getctime","islink","exists","lexists","isdir","isfile",
- "ismount","walk","expanduser","expandvars","normpath","abspath",
- "samefile","sameopenfile","samestat",
- "curdir","pardir","sep","pathsep","defpath","altsep","extsep",
- "devnull","realpath","supports_unicode_filenames","relpath"]
-
- # strings representing various path-related bits and pieces
- curdir = '.'
- pardir = '..'
- extsep = '.'
- sep = '/'
- pathsep = ':'
- defpath = ':/bin:/usr/bin'
- altsep = None
- devnull = '/dev/null'
-
- # Normalize the case of a pathname. Trivial in Posix, string.lower on Mac.
- # On MS-DOS this may also turn slashes into backslashes; however, other
- # normalizations (such as optimizing '../' away) are not allowed
- # (another function should be defined to do that).
-
- def normcase(s):
- """Normalize case of pathname. Has no effect under Posix"""
- return s
-
-
- # Return whether a path is absolute.
- # Trivial in Posix, harder on the Mac or MS-DOS.
-
- def isabs(s):
- """Test whether a path is absolute"""
- return s.startswith('/')
-
-
- # Join pathnames.
- # Ignore the previous parts if a part is absolute.
- # Insert a '/' unless the first part is empty or already ends in '/'.
-
- def join(a, *p):
- """Join two or more pathname components, inserting '/' as needed.
- If any component is an absolute path, all previous path components
- will be discarded."""
- path = a
- for b in p:
- if b.startswith('/'):
- path = b
- elif path == '' or path.endswith('/'):
- path += b
- else:
- path += '/' + b
- return path
-
-
- # Split a path in head (everything up to the last '/') and tail (the
- # rest). If the path ends in '/', tail will be empty. If there is no
- # '/' in the path, head will be empty.
- # Trailing '/'es are stripped from head unless it is the root.
-
- def split(p):
- """Split a pathname. Returns tuple "(head, tail)" where "tail" is
- everything after the final slash. Either part may be empty."""
- i = p.rfind('/') + 1
- head, tail = p[:i], p[i:]
- if head and head != '/'*len(head):
- head = head.rstrip('/')
- return head, tail
-
-
- # Split a path in root and extension.
- # The extension is everything starting at the last dot in the last
- # pathname component; the root is everything before that.
- # It is always true that root + ext == p.
-
- def splitext(p):
- return genericpath._splitext(p, sep, altsep, extsep)
- splitext.__doc__ = genericpath._splitext.__doc__
-
- # Split a pathname into a drive specification and the rest of the
- # path. Useful on DOS/Windows/NT; on Unix, the drive is always empty.
-
- def splitdrive(p):
- """Split a pathname into drive and path. On Posix, drive is always
- empty."""
- return '', p
-
-
- # Return the tail (basename) part of a path, same as split(path)[1].
-
- def basename(p):
- """Returns the final component of a pathname"""
- i = p.rfind('/') + 1
- return p[i:]
-
-
- # Return the head (dirname) part of a path, same as split(path)[0].
-
- def dirname(p):
- """Returns the directory component of a pathname"""
- i = p.rfind('/') + 1
- head = p[:i]
- if head and head != '/'*len(head):
- head = head.rstrip('/')
- return head
-
-
- # Is a path a symbolic link?
- # This will always return false on systems where os.lstat doesn't exist.
-
- def islink(path):
- """Test whether a path is a symbolic link"""
- try:
- st = os.lstat(path)
- except (os.error, AttributeError):
- return False
- return stat.S_ISLNK(st.st_mode)
-
- # Being true for dangling symbolic links is also useful.
-
- def lexists(path):
- """Test whether a path exists. Returns True for broken symbolic links"""
- try:
- st = os.lstat(path)
- except os.error:
- return False
- return True
-
-
- # Are two filenames really pointing to the same file?
-
- def samefile(f1, f2):
- """Test whether two pathnames reference the same actual file"""
- s1 = os.stat(f1)
- s2 = os.stat(f2)
- return samestat(s1, s2)
-
-
- # Are two open files really referencing the same file?
- # (Not necessarily the same file descriptor!)
-
- def sameopenfile(fp1, fp2):
- """Test whether two open file objects reference the same file"""
- s1 = os.fstat(fp1)
- s2 = os.fstat(fp2)
- return samestat(s1, s2)
-
-
- # Are two stat buffers (obtained from stat, fstat or lstat)
- # describing the same file?
-
- def samestat(s1, s2):
- """Test whether two stat buffers reference the same file"""
- return s1.st_ino == s2.st_ino and \
- s1.st_dev == s2.st_dev
-
-
- # Is a path a mount point?
- # (Does this work for all UNIXes? Is it even guaranteed to work by Posix?)
-
- def ismount(path):
- """Test whether a path is a mount point"""
- try:
- s1 = os.lstat(path)
- s2 = os.lstat(join(path, '..'))
- except os.error:
- return False # It doesn't exist -- so not a mount point :-)
- dev1 = s1.st_dev
- dev2 = s2.st_dev
- if dev1 != dev2:
- return True # path/.. on a different device as path
- ino1 = s1.st_ino
- ino2 = s2.st_ino
- if ino1 == ino2:
- return True # path/.. is the same i-node as path
- return False
-
-
- # Directory tree walk.
- # For each directory under top (including top itself, but excluding
- # '.' and '..'), func(arg, dirname, filenames) is called, where
- # dirname is the name of the directory and filenames is the list
- # of files (and subdirectories etc.) in the directory.
- # The func may modify the filenames list, to implement a filter,
- # or to impose a different order of visiting.
-
- def walk(top, func, arg):
- """Directory tree walk with callback function.
-
- For each directory in the directory tree rooted at top (including top
- itself, but excluding '.' and '..'), call func(arg, dirname, fnames).
- dirname is the name of the directory, and fnames a list of the names of
- the files and subdirectories in dirname (excluding '.' and '..'). func
- may modify the fnames list in-place (e.g. via del or slice assignment),
- and walk will only recurse into the subdirectories whose names remain in
- fnames; this can be used to implement a filter, or to impose a specific
- order of visiting. No semantics are defined for, or required of, arg,
- beyond that arg is always passed to func. It can be used, e.g., to pass
- a filename pattern, or a mutable object designed to accumulate
- statistics. Passing None for arg is common."""
- warnings.warnpy3k("In 3.x, os.path.walk is removed in favor of os.walk.")
- try:
- names = os.listdir(top)
- except os.error:
- return
- func(arg, top, names)
- for name in names:
- name = join(top, name)
- try:
- st = os.lstat(name)
- except os.error:
- continue
- if stat.S_ISDIR(st.st_mode):
- walk(name, func, arg)
-
-
- # Expand paths beginning with '~' or '~user'.
- # '~' means $HOME; '~user' means that user's home directory.
- # If the path doesn't begin with '~', or if the user or $HOME is unknown,
- # the path is returned unchanged (leaving error reporting to whatever
- # function is called with the expanded path as argument).
- # See also module 'glob' for expansion of *, ? and [...] in pathnames.
- # (A function should also be defined to do full *sh-style environment
- # variable expansion.)
-
- def expanduser(path):
- """Expand ~ and ~user constructions. If user or $HOME is unknown,
- do nothing."""
- if not path.startswith('~'):
- return path
- i = path.find('/', 1)
- if i < 0:
- i = len(path)
- if i == 1:
- if 'HOME' not in os.environ:
- import pwd
- userhome = pwd.getpwuid(os.getuid()).pw_dir
- else:
- userhome = os.environ['HOME']
- else:
- import pwd
- try:
- pwent = pwd.getpwnam(path[1:i])
- except KeyError:
- return path
- userhome = pwent.pw_dir
- userhome = userhome.rstrip('/')
- return userhome + path[i:]
-
-
- # Expand paths containing shell variable substitutions.
- # This expands the forms $variable and ${variable} only.
- # Non-existent variables are left unchanged.
-
- _varprog = None
-
- def expandvars(path):
- """Expand shell variables of form $var and ${var}. Unknown variables
- are left unchanged."""
- global _varprog
- if '$' not in path:
- return path
- if not _varprog:
- import re
- _varprog = re.compile(r'\$(\w+|\{[^}]*\})')
- i = 0
- while True:
- m = _varprog.search(path, i)
- if not m:
- break
- i, j = m.span(0)
- name = m.group(1)
- if name.startswith('{') and name.endswith('}'):
- name = name[1:-1]
- if name in os.environ:
- tail = path[j:]
- path = path[:i] + os.environ[name]
- i = len(path)
- path += tail
- else:
- i = j
- return path
-
-
- # Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A/B.
- # It should be understood that this may change the meaning of the path
- # if it contains symbolic links!
-
- def normpath(path):
- """Normalize path, eliminating double slashes, etc."""
- if path == '':
- return '.'
- initial_slashes = path.startswith('/')
- # POSIX allows one or two initial slashes, but treats three or more
- # as single slash.
- if (initial_slashes and
- path.startswith('//') and not path.startswith('///')):
- initial_slashes = 2
- comps = path.split('/')
- new_comps = []
- for comp in comps:
- if comp in ('', '.'):
- continue
- if (comp != '..' or (not initial_slashes and not new_comps) or
- (new_comps and new_comps[-1] == '..')):
- new_comps.append(comp)
- elif new_comps:
- new_comps.pop()
- comps = new_comps
- path = '/'.join(comps)
- if initial_slashes:
- path = '/'*initial_slashes + path
- return path or '.'
-
-
- def abspath(path):
- """Return an absolute path."""
- if not isabs(path):
- path = join(os.getcwd(), path)
- return normpath(path)
-
-
- # Return a canonical path (i.e. the absolute location of a file on the
- # filesystem).
-
- def realpath(filename):
- """Return the canonical path of the specified filename, eliminating any
- symbolic links encountered in the path."""
- if isabs(filename):
- bits = ['/'] + filename.split('/')[1:]
- else:
- bits = [''] + filename.split('/')
-
- for i in range(2, len(bits)+1):
- component = join(*bits[0:i])
- # Resolve symbolic links.
- if islink(component):
- resolved = _resolve_link(component)
- if resolved is None:
- # Infinite loop -- return original component + rest of the path
- return abspath(join(*([component] + bits[i:])))
- else:
- newpath = join(*([resolved] + bits[i:]))
- return realpath(newpath)
-
- return abspath(filename)
-
-
- def _resolve_link(path):
- """Internal helper function. Takes a path and follows symlinks
- until we either arrive at something that isn't a symlink, or
- encounter a path we've seen before (meaning that there's a loop).
- """
- paths_seen = []
- while islink(path):
- if path in paths_seen:
- # Already seen this path, so we must have a symlink loop
- return None
- paths_seen.append(path)
- # Resolve where the link points to
- resolved = os.readlink(path)
- if not isabs(resolved):
- dir = dirname(path)
- path = normpath(join(dir, resolved))
- else:
- path = normpath(resolved)
- return path
-
- supports_unicode_filenames = False
-
- def relpath(path, start=curdir):
- """Return a relative version of a path"""
-
- if not path:
- raise ValueError("no path specified")
-
- start_list = abspath(start).split(sep)
- path_list = abspath(path).split(sep)
-
- # Work out how much of the filepath is shared by start and path.
- i = len(commonprefix([start_list, path_list]))
-
- rel_list = [pardir] * (len(start_list)-i) + path_list[i:]
- if not rel_list:
- return curdir
- return join(*rel_list)