cpython/Lib/posixpath.py

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# Module 'path' -- common operations on POSIX pathnames
import posix
import stat
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# 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):
return s
# Return wheter a path is absolute.
# Trivial in Posix, harder on the Mac or MS-DOS.
def isabs(s):
return s[:1] == '/'
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# Join two pathnames.
# Ignore the first part if the second 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, b):
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if b[:1] == '/': return b
if a == '' or a[-1:] == '/': return a + b
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# Note: join('x', '') returns 'x/'; is this what we want?
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return a + '/' + b
# Split a path in head (empty or ending in '/') and tail (no '/').
# The tail will be empty if the path ends in '/'.
# It is always true that head + tail == p; also join(head, tail) == p.
# Note that because head ends in '/', if you want to find all components
# of a path by repeatedly getting the head, you will have to strip off
# the trailing '/' yourself (another function should be defined to
# split an entire path into components.)
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def split(p):
head, tail = '', ''
for c in p:
tail = tail + c
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if c == '/':
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head, tail = head + tail, ''
return head, tail
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# Split a path in root and extension.
# The extension is everything starting at the first dot in the last
# pathname component; the root is everything before that.
# It is always true that root + ext == p.
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def splitext(p):
root, ext = '', ''
for c in p:
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if c == '/':
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root, ext = root + ext + c, ''
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elif c == '.' or ext:
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ext = ext + c
else:
root = root + c
return root, ext
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# Return the tail (basename) part of a path.
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def basename(p):
return split(p)[1]
# Return the longest prefix of all list elements.
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def commonprefix(m):
if not m: return ''
prefix = m[0]
for item in m:
for i in range(len(prefix)):
if prefix[:i+1] <> item[:i+1]:
prefix = prefix[:i]
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if i == 0: return ''
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break
return prefix
# Is a path a symbolic link?
# This will always return false on systems where posix.lstat doesn't exist.
def islink(path):
try:
st = posix.lstat(path)
except (posix.error, AttributeError):
return 0
return stat.S_ISLNK(st[stat.ST_MODE])
# Does a path exist?
# This is false for dangling symbolic links.
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def exists(path):
try:
st = posix.stat(path)
except posix.error:
return 0
return 1
# Is a path a posix directory?
# This follows symbolic links, so both islink() and isdir() can be true
# for the same path.
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def isdir(path):
try:
st = posix.stat(path)
except posix.error:
return 0
return stat.S_ISDIR(st[stat.ST_MODE])
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# Is a path a regulat file?
# This follows symbolic links, so both islink() and isdir() can be true
# for the same path.
def isfile(path):
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try:
st = posix.stat(path)
except posix.error:
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return 0
return stat.S_ISREG(st[stat.ST_MODE])
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# Are two filenames really pointing to the same file?
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def samefile(f1, f2):
s1 = posix.stat(f1)
s2 = posix.stat(f2)
return samestat(s1, s2)
# Are two open files really referencing the same file?
# (Not necessarily the same file descriptor!)
# XXX Oops, posix.fstat() doesn't exist yet!
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def sameopenfile(fp1, fp2):
s1 = posix.fstat(fp1)
s2 = posix.fstat(fp2)
return samestat(s1, s2)
# Are two stat buffers (obtained from stat, fstat or lstat)
# describing the same file?
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def samestat(s1, s2):
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return s1[stat.ST_INO] == s2[stat.ST_INO] and \
s1[stat.ST_DEV] == s2[stat.STD_DEV]
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# Subroutine and global data used by ismount().
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_mounts = []
def _getmounts():
import commands, string
mounts = []
data = commands.getoutput('/etc/mount')
lines = string.splitfields(data, '\n')
for line in lines:
words = string.split(line)
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if len(words) >= 3 and words[1] == 'on':
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mounts.append(words[2])
return mounts
# Is a path a mount point?
# This only works for normalized paths,
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# and only if the mount table as printed by /etc/mount is correct.
# It tries to make relative paths absolute by prefixing them with the
# current directory, but it won't normalize arguments containing '../'
# or symbolic links.
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def ismount(path):
if not isabs(path):
path = join(posix.getcwd(), path)
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if not _mounts:
_mounts[:] = _getmounts()
return path in _mounts
# 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
# files files (and subdirectories etc.) in the directory.
# 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):
try:
names = posix.listdir(top)
except posix.error:
return
func(arg, top, names)
exceptions = ('.', '..')
for name in names:
if name not in exceptions:
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name = join(top, name)
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if isdir(name):
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):
if path[:1] <> '~':
return path
i, n = 1, len(path)
while i < n and path[i] <> '/':
i = i+1
if i == 1:
if not posix.environ.has_key('HOME'):
return path
userhome = posix.environ['HOME']
else:
import pwd
try:
pwent = pwd.getpwnam(path[1:i])
except KeyError:
return path
userhome = pwent[5]
return userhome + path[i:]