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346 lines
8.3 KiB
Python
346 lines
8.3 KiB
Python
# Module 'dospath' -- common operations on DOS pathnames
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import os
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import stat
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import string
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# Normalize the case of a pathname.
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# On MS-DOS it maps the pathname to lowercase, turns slashes into
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# backslashes.
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# Other normalizations (such as optimizing '../' away) are not allowed
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# (this is done by normpath).
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# Previously, this version mapped invalid consecutive characters to a
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# single '_', but this has been removed. This functionality should
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# possibly be added as a new function.
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def normcase(s):
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res, s = splitdrive(s)
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for c in s:
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if c in '/\\':
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res = res + os.sep
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else:
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res = res + c
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return string.lower(res)
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# Return wheter a path is absolute.
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# Trivial in Posix, harder on the Mac or MS-DOS.
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# For DOS it is absolute if it starts with a slash or backslash (current
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# volume), or if a pathname after the volume letter and colon starts with
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# a slash or backslash.
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def isabs(s):
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s = splitdrive(s)[1]
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return s != '' and s[:1] in '/\\'
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# Join two pathnames.
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# 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 isabs(b): return b
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if a == '' or a[-1:] in '/\\': return a + b
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# Note: join('x', '') returns 'x/'; is this what we want?
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return a + os.sep + b
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# Split a path in a drive specification (a drive letter followed by a
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# colon) and the path specification.
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# It is always true that drivespec + pathspec == p
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def splitdrive(p):
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if p[1:2] == ':':
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return p[0:2], p[2:]
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return '', p
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# Split a path in head (everything up to the last '/') and tail (the
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# rest). If the original path ends in '/' but is not the root, this
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# '/' is stripped. After the trailing '/' is stripped, the invariant
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# join(head, tail) == p holds.
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# The resulting head won't end in '/' unless it is the root.
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def split(p):
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d, p = splitdrive(p)
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slashes = ''
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while p and p[-1:] in '/\\':
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slashes = slashes + p[-1]
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p = p[:-1]
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if p == '':
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p = p + slashes
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head, tail = '', ''
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for c in p:
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tail = tail + c
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if c in '/\\':
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head, tail = head + tail, ''
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slashes = ''
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while head and head[-1:] in '/\\':
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slashes = slashes + head[-1]
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head = head[:-1]
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if head == '':
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head = head + slashes
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return d + head, tail
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# Split a path in root and extension.
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# The extension is everything starting at the first 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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root, ext = '', ''
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for c in p:
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if c in '/\\':
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root, ext = root + ext + c, ''
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elif c == '.' or ext:
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ext = ext + c
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else:
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root = root + c
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return root, ext
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# Return the tail (basename) part of a path.
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def basename(p):
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return split(p)[1]
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# Return the head (dirname) part of a path.
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def dirname(p):
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return split(p)[0]
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# Return the longest prefix of all list elements.
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def commonprefix(m):
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if not m: return ''
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prefix = m[0]
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for item in m:
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for i in range(len(prefix)):
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if prefix[:i+1] <> item[:i+1]:
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prefix = prefix[:i]
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if i == 0: return ''
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break
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return prefix
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# Is a path a symbolic link?
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# This will always return false on systems where posix.lstat doesn't exist.
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def islink(path):
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return false
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# Does a path exist?
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# This is false for dangling symbolic links.
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def exists(path):
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try:
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st = os.stat(path)
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except os.error:
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return 0
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return 1
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# Is a path a dos directory?
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# This follows symbolic links, so both islink() and isdir() can be true
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# for the same path.
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def isdir(path):
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try:
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st = os.stat(path)
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except os.error:
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return 0
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return stat.S_ISDIR(st[stat.ST_MODE])
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# Is a path a regular file?
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# This follows symbolic links, so both islink() and isdir() can be true
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# for the same path.
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def isfile(path):
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try:
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st = os.stat(path)
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except os.error:
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return 0
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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):
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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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# XXX THIS IS BROKEN UNDER DOS! ST_INO seems to indicate number of reads?
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def sameopenfile(fp1, fp2):
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s1 = os.fstat(fp1.fileno())
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s2 = os.fstat(fp2.fileno())
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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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return s1[stat.ST_INO] == s2[stat.ST_INO] and \
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s1[stat.ST_DEV] == s2[stat.ST_DEV]
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# Is a path a mount point?
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# XXX This degenerates in: 'is this the root?' on DOS
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def ismount(path):
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return isabs(splitdrive(path)[1])
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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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# files 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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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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exceptions = ('.', '..')
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for name in names:
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if name not in exceptions:
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name = join(top, name)
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if isdir(name):
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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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if path[:1] <> '~':
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return path
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i, n = 1, len(path)
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while i < n and path[i] not in '/\\':
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i = i+1
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if i == 1:
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if not os.environ.has_key('HOME'):
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return path
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userhome = os.environ['HOME']
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else:
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return path
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return userhome + path[i:]
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# Expand paths containing shell variable substitutions.
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# The following rules apply:
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# - no expansion within single quotes
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# - no escape character, except for '$$' which is translated into '$'
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# - ${varname} is accepted.
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# - varnames can be made out of letters, digits and the character '_'
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# XXX With COMMAND.COM you can use any characters in a variable name,
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# XXX except '^|<>='.
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varchars = string.letters + string.digits + '_-'
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def expandvars(path):
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if '$' not in path:
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return path
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res = ''
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index = 0
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pathlen = len(path)
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while index < pathlen:
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c = path[index]
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if c == '\'': # no expansion within single quotes
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path = path[index + 1:]
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pathlen = len(path)
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try:
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index = string.index(path, '\'')
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res = res + '\'' + path[:index + 1]
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except string.index_error:
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res = res + path
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index = pathlen -1
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elif c == '$': # variable or '$$'
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if path[index + 1:index + 2] == '$':
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res = res + c
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index = index + 1
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elif path[index + 1:index + 2] == '{':
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path = path[index+2:]
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pathlen = len(path)
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try:
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index = string.index(path, '}')
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var = path[:index]
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if os.environ.has_key(var):
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res = res + os.environ[var]
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except string.index_error:
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res = res + path
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index = pathlen - 1
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else:
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var = ''
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index = index + 1
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c = path[index:index + 1]
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while c != '' and c in varchars:
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var = var + c
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index = index + 1
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c = path[index:index + 1]
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if os.environ.has_key(var):
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res = res + os.environ[var]
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if c != '':
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res = res + c
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else:
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res = res + c
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index = index + 1
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return res
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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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# Also, components of the path are silently truncated to 8+3 notation.
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def normpath(path):
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path = normcase(path)
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prefix, path = splitdrive(path)
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while path[:1] == os.sep:
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prefix = prefix + os.sep
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path = path[1:]
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comps = string.splitfields(path, os.sep)
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i = 0
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while i < len(comps):
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if comps[i] == '.':
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del comps[i]
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elif comps[i] == '..' and i > 0 and \
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comps[i-1] not in ('', '..'):
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del comps[i-1:i+1]
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i = i-1
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elif comps[i] == '' and i > 0 and comps[i-1] <> '':
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del comps[i]
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elif '.' in comps[i]:
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comp = string.splitfields(comps[i], '.')
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comps[i] = comp[0][:8] + '.' + comp[1][:3]
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i = i+1
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elif len(comps[i]) > 8:
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comps[i] = comps[i][:8]
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i = i+1
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else:
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i = i+1
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# If the path is now empty, substitute '.'
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if not prefix and not comps:
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comps.append('.')
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return prefix + string.joinfields(comps, os.sep)
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