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