python/lib/Lib/posixpath.py - platform/tools/idea - Git at Google

 """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

 __all__ = ["normcase","isabs","join","splitdrive","split","splitext",
            "basename","dirname","commonprefix","getsize","getmtime",
            "getatime","getctime","islink","exists","lexists","isdir","isfile",
            "walk","expanduser","expandvars","normpath","abspath",
            "samefile",
            "curdir","pardir","sep","pathsep","defpath","altsep","extsep",
            "devnull","realpath","supports_unicode_filenames"]

 # 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"""
     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):
     """Split the extension from a pathname.  Extension is everything from the
     last dot to the end.  Returns "(root, ext)", either part may be empty."""
     i = p.rfind('.')
     if i<=p.rfind('/'):
         return p, ''
     else:
         return p[:i], p[i:]


 # 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.

 def basename(p):
     """Returns the final component of a pathname"""
     return split(p)[1]


 # Return the head (dirname) part of a path.

 def dirname(p):
     """Returns the directory component of a pathname"""
     return split(p)[0]


 # Return the longest prefix of all list elements.

 def commonprefix(m):
     "Given a list of pathnames, returns the longest common leading component"
     if not m: return ''
     s1 = min(m)
     s2 = max(m)
     n = min(len(s1), len(s2))
     for i in xrange(n):
         if s1[i] != s2[i]:
             return s1[:i]
     return s1[:n]

 # Get size, mtime, atime of files.

 def getsize(filename):
     """Return the size of a file, reported by os.stat()."""
     return os.stat(filename).st_size

 def getmtime(filename):
     """Return the last modification time of a file, reported by os.stat()."""
     return os.stat(filename).st_mtime

 def getatime(filename):
     """Return the last access time of a file, reported by os.stat()."""
     return os.stat(filename).st_atime

 def getctime(filename):
     """Return the metadata change time of a file, reported by os.stat()."""
     return os.stat(filename).st_ctime

 # 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)


 # Does a path exist?
 # This is false for dangling symbolic links.

 def exists(path):
     """Test whether a path exists.  Returns False for broken symbolic links"""
     try:
         st = os.stat(path)
     except os.error:
         return False
     return True


 # 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


 # Is a path a directory?
 # This follows symbolic links, so both islink() and isdir() can be true
 # for the same path.

 def isdir(path):
     """Test whether a path is a directory"""
     try:
         st = os.stat(path)
     except os.error:
         return False
     return stat.S_ISDIR(st.st_mode)


 # Is a path a regular file?
 # This follows symbolic links, so both islink() and isfile() can be true
 # for the same path.

 def isfile(path):
     """Test whether a path is a regular file"""
     try:
         st = os.stat(path)
     except os.error:
         return False
     return stat.S_ISREG(st.st_mode)


 # Are two filenames really pointing to the same file?

 if not os._native_posix:
     import java.io.File
     import java.io.IOException
     from org.python.core.Py import newString

     def samefile(f1, f2):
         """Test whether two pathnames reference the same actual file"""
         canon1 = newString(java.io.File(_ensure_str(f1)).getCanonicalPath())
         canon2 = newString(java.io.File(_ensure_str(f2)).getCanonicalPath())
         return canon1 == canon2
 else:
     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)


 # XXX: Jython currently lacks fstat
 if hasattr(os, 'fstat'):
     # 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)

     __all__.append("sameopenfile")


 # XXX: Pure Java stat lacks st_ino/st_dev
 if os._native_posix:
     # 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

     __all__.extend(["samestat", "ismount"])


 # 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."""

     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:
             return path
         else:
             userhome = os.environ['HOME']
     else:
         # XXX: Jython lacks the pwd module: '~user' isn't supported
         return path
     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)


 if not os._native_posix:
     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).
         """
         try:
             return newString(java.io.File(abspath(path)).getCanonicalPath())
         except java.io.IOException:
             return None
 else:
     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


 def _ensure_str(obj):
     """Ensure obj is a string, otherwise raise a TypeError"""
     if isinstance(obj, basestring):
         return obj
     raise TypeError('coercing to Unicode: need string or buffer, %s found' % \
                         _type_name(obj))


 def _type_name(obj):
     """Determine the appropriate type name of obj for display"""
     TPFLAGS_HEAPTYPE = 1 << 9
     type_name = ''
     obj_type = type(obj)
     is_heap = obj_type.__flags__ & TPFLAGS_HEAPTYPE == TPFLAGS_HEAPTYPE
     if not is_heap and obj_type.__module__ != '__builtin__':
         type_name = '%s.' % obj_type.__module__
     type_name += obj_type.__name__
     return type_name

 supports_unicode_filenames = False
	"""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

	__all__ = ["normcase","isabs","join","splitdrive","split","splitext",
	"basename","dirname","commonprefix","getsize","getmtime",
	"getatime","getctime","islink","exists","lexists","isdir","isfile",
	"walk","expanduser","expandvars","normpath","abspath",
	"samefile",
	"curdir","pardir","sep","pathsep","defpath","altsep","extsep",
	"devnull","realpath","supports_unicode_filenames"]

	# 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"""
	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):
	"""Split the extension from a pathname. Extension is everything from the
	last dot to the end. Returns "(root, ext)", either part may be empty."""
	i = p.rfind('.')
	if i<=p.rfind('/'):
	return p, ''
	else:
	return p[:i], p[i:]


	# 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.

	def basename(p):
	"""Returns the final component of a pathname"""
	return split(p)[1]


	# Return the head (dirname) part of a path.

	def dirname(p):
	"""Returns the directory component of a pathname"""
	return split(p)[0]


	# Return the longest prefix of all list elements.

	def commonprefix(m):
	"Given a list of pathnames, returns the longest common leading component"
	if not m: return ''
	s1 = min(m)
	s2 = max(m)
	n = min(len(s1), len(s2))
	for i in xrange(n):
	if s1[i] != s2[i]:
	return s1[:i]
	return s1[:n]

	# Get size, mtime, atime of files.

	def getsize(filename):
	"""Return the size of a file, reported by os.stat()."""
	return os.stat(filename).st_size

	def getmtime(filename):
	"""Return the last modification time of a file, reported by os.stat()."""
	return os.stat(filename).st_mtime

	def getatime(filename):
	"""Return the last access time of a file, reported by os.stat()."""
	return os.stat(filename).st_atime

	def getctime(filename):
	"""Return the metadata change time of a file, reported by os.stat()."""
	return os.stat(filename).st_ctime

	# 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)


	# Does a path exist?
	# This is false for dangling symbolic links.

	def exists(path):
	"""Test whether a path exists. Returns False for broken symbolic links"""
	try:
	st = os.stat(path)
	except os.error:
	return False
	return True


	# 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


	# Is a path a directory?
	# This follows symbolic links, so both islink() and isdir() can be true
	# for the same path.

	def isdir(path):
	"""Test whether a path is a directory"""
	try:
	st = os.stat(path)
	except os.error:
	return False
	return stat.S_ISDIR(st.st_mode)


	# Is a path a regular file?
	# This follows symbolic links, so both islink() and isfile() can be true
	# for the same path.

	def isfile(path):
	"""Test whether a path is a regular file"""
	try:
	st = os.stat(path)
	except os.error:
	return False
	return stat.S_ISREG(st.st_mode)


	# Are two filenames really pointing to the same file?

	if not os._native_posix:
	import java.io.File
	import java.io.IOException
	from org.python.core.Py import newString

	def samefile(f1, f2):
	"""Test whether two pathnames reference the same actual file"""
	canon1 = newString(java.io.File(_ensure_str(f1)).getCanonicalPath())
	canon2 = newString(java.io.File(_ensure_str(f2)).getCanonicalPath())
	return canon1 == canon2
	else:
	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)


	# XXX: Jython currently lacks fstat
	if hasattr(os, 'fstat'):
	# 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)

	__all__.append("sameopenfile")


	# XXX: Pure Java stat lacks st_ino/st_dev
	if os._native_posix:
	# 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

	__all__.extend(["samestat", "ismount"])


	# 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."""

	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:
	return path
	else:
	userhome = os.environ['HOME']
	else:
	# XXX: Jython lacks the pwd module: '~user' isn't supported
	return path
	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)


	if not os._native_posix:
	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).
	"""
	try:
	return newString(java.io.File(abspath(path)).getCanonicalPath())
	except java.io.IOException:
	return None
	else:
	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


	def _ensure_str(obj):
	"""Ensure obj is a string, otherwise raise a TypeError"""
	if isinstance(obj, basestring):
	return obj
	raise TypeError('coercing to Unicode: need string or buffer, %s found' % \
	_type_name(obj))


	def _type_name(obj):
	"""Determine the appropriate type name of obj for display"""
	TPFLAGS_HEAPTYPE = 1 << 9
	type_name = ''
	obj_type = type(obj)
	is_heap = obj_type.__flags__ & TPFLAGS_HEAPTYPE == TPFLAGS_HEAPTYPE
	if not is_heap and obj_type.__module__ != '__builtin__':
	type_name = '%s.' % obj_type.__module__
	type_name += obj_type.__name__
	return type_name

	supports_unicode_filenames = False