476 lines
14 KiB
Python
476 lines
14 KiB
Python
"""Temporary files.
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This module provides generic, low- and high-level interfaces for
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creating temporary files and directories. The interfaces listed
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as "safe" just below can be used without fear of race conditions.
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Those listed as "unsafe" cannot, and are provided for backward
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compatibility only.
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This module also provides some data items to the user:
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TMP_MAX - maximum number of names that will be tried before
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giving up.
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template - the default prefix for all temporary names.
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You may change this to control the default prefix.
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tempdir - If this is set to a string before the first use of
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any routine from this module, it will be considered as
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another candidate location to store temporary files.
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"""
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__all__ = [
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"NamedTemporaryFile", "TemporaryFile", # high level safe interfaces
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"mkstemp", "mkdtemp", # low level safe interfaces
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"mktemp", # deprecated unsafe interface
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"TMP_MAX", "gettempprefix", # constants
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"tempdir", "gettempdir"
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]
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# Imports.
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import os as _os
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import errno as _errno
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from random import Random as _Random
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if _os.name == 'mac':
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import Carbon.Folder as _Folder
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import Carbon.Folders as _Folders
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try:
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import fcntl as _fcntl
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except ImportError:
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def _set_cloexec(fd):
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pass
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else:
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def _set_cloexec(fd):
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try:
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flags = _fcntl.fcntl(fd, _fcntl.F_GETFD, 0)
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except IOError:
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pass
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else:
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# flags read successfully, modify
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flags |= _fcntl.FD_CLOEXEC
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_fcntl.fcntl(fd, _fcntl.F_SETFD, flags)
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try:
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import thread as _thread
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except ImportError:
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import dummy_thread as _thread
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_allocate_lock = _thread.allocate_lock
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_text_openflags = _os.O_RDWR | _os.O_CREAT | _os.O_EXCL
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if hasattr(_os, 'O_NOINHERIT'):
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_text_openflags |= _os.O_NOINHERIT
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if hasattr(_os, 'O_NOFOLLOW'):
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_text_openflags |= _os.O_NOFOLLOW
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_bin_openflags = _text_openflags
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if hasattr(_os, 'O_BINARY'):
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_bin_openflags |= _os.O_BINARY
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if hasattr(_os, 'TMP_MAX'):
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TMP_MAX = _os.TMP_MAX
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else:
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TMP_MAX = 10000
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template = "tmp"
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tempdir = None
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# Internal routines.
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_once_lock = _allocate_lock()
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if hasattr(_os, "lstat"):
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_stat = _os.lstat
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elif hasattr(_os, "stat"):
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_stat = _os.stat
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else:
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# Fallback. All we need is something that raises os.error if the
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# file doesn't exist.
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def _stat(fn):
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try:
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f = open(fn)
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except IOError:
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raise _os.error
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f.close()
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def _exists(fn):
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try:
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_stat(fn)
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except _os.error:
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return False
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else:
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return True
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class _RandomNameSequence:
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"""An instance of _RandomNameSequence generates an endless
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sequence of unpredictable strings which can safely be incorporated
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into file names. Each string is six characters long. Multiple
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threads can safely use the same instance at the same time.
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_RandomNameSequence is an iterator."""
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characters = ("abcdefghijklmnopqrstuvwxyz" +
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"ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
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"0123456789_")
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def __init__(self):
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self.mutex = _allocate_lock()
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self.rng = _Random()
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self.normcase = _os.path.normcase
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def __iter__(self):
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return self
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def next(self):
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m = self.mutex
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c = self.characters
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choose = self.rng.choice
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m.acquire()
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try:
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letters = [choose(c) for dummy in "123456"]
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finally:
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m.release()
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return self.normcase(''.join(letters))
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def _candidate_tempdir_list():
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"""Generate a list of candidate temporary directories which
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_get_default_tempdir will try."""
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dirlist = []
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# First, try the environment.
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for envname in 'TMPDIR', 'TEMP', 'TMP':
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dirname = _os.getenv(envname)
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if dirname: dirlist.append(dirname)
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# Failing that, try OS-specific locations.
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if _os.name == 'mac':
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try:
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fsr = _Folder.FSFindFolder(_Folders.kOnSystemDisk,
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_Folders.kTemporaryFolderType, 1)
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dirname = fsr.as_pathname()
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dirlist.append(dirname)
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except _Folder.error:
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pass
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elif _os.name == 'riscos':
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dirname = _os.getenv('Wimp$ScrapDir')
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if dirname: dirlist.append(dirname)
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elif _os.name == 'nt':
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dirlist.extend([ r'c:\temp', r'c:\tmp', r'\temp', r'\tmp' ])
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else:
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dirlist.extend([ '/tmp', '/var/tmp', '/usr/tmp' ])
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# As a last resort, the current directory.
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try:
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dirlist.append(_os.getcwd())
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except (AttributeError, _os.error):
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dirlist.append(_os.curdir)
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return dirlist
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def _get_default_tempdir():
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"""Calculate the default directory to use for temporary files.
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This routine should be called exactly once.
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We determine whether or not a candidate temp dir is usable by
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trying to create and write to a file in that directory. If this
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is successful, the test file is deleted. To prevent denial of
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service, the name of the test file must be randomized."""
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namer = _RandomNameSequence()
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dirlist = _candidate_tempdir_list()
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flags = _text_openflags
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for dir in dirlist:
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if dir != _os.curdir:
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dir = _os.path.normcase(_os.path.abspath(dir))
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# Try only a few names per directory.
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for seq in xrange(100):
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name = namer.next()
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filename = _os.path.join(dir, name)
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try:
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fd = _os.open(filename, flags, 0600)
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fp = _os.fdopen(fd, 'w')
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fp.write('blat')
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fp.close()
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_os.unlink(filename)
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del fp, fd
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return dir
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except (OSError, IOError), e:
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if e[0] != _errno.EEXIST:
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break # no point trying more names in this directory
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pass
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raise IOError, (_errno.ENOENT,
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("No usable temporary directory found in %s" % dirlist))
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_name_sequence = None
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def _get_candidate_names():
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"""Common setup sequence for all user-callable interfaces."""
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global _name_sequence
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if _name_sequence is None:
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_once_lock.acquire()
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try:
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if _name_sequence is None:
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_name_sequence = _RandomNameSequence()
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finally:
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_once_lock.release()
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return _name_sequence
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def _mkstemp_inner(dir, pre, suf, flags):
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"""Code common to mkstemp, TemporaryFile, and NamedTemporaryFile."""
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names = _get_candidate_names()
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for seq in xrange(TMP_MAX):
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name = names.next()
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file = _os.path.join(dir, pre + name + suf)
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try:
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fd = _os.open(file, flags, 0600)
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_set_cloexec(fd)
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return (fd, _os.path.abspath(file))
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except OSError, e:
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if e.errno == _errno.EEXIST:
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continue # try again
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raise
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raise IOError, (_errno.EEXIST, "No usable temporary file name found")
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# User visible interfaces.
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def gettempprefix():
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"""Accessor for tempdir.template."""
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return template
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tempdir = None
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def gettempdir():
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"""Accessor for tempdir.tempdir."""
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global tempdir
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if tempdir is None:
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_once_lock.acquire()
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try:
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if tempdir is None:
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tempdir = _get_default_tempdir()
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finally:
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_once_lock.release()
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return tempdir
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def mkstemp(suffix="", prefix=template, dir=None, text=False):
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"""mkstemp([suffix, [prefix, [dir, [text]]]])
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User-callable function to create and return a unique temporary
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file. The return value is a pair (fd, name) where fd is the
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file descriptor returned by os.open, and name is the filename.
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If 'suffix' is specified, the file name will end with that suffix,
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otherwise there will be no suffix.
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If 'prefix' is specified, the file name will begin with that prefix,
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otherwise a default prefix is used.
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If 'dir' is specified, the file will be created in that directory,
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otherwise a default directory is used.
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If 'text' is specified and true, the file is opened in text
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mode. Else (the default) the file is opened in binary mode. On
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some operating systems, this makes no difference.
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The file is readable and writable only by the creating user ID.
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If the operating system uses permission bits to indicate whether a
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file is executable, the file is executable by no one. The file
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descriptor is not inherited by children of this process.
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Caller is responsible for deleting the file when done with it.
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"""
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if dir is None:
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dir = gettempdir()
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if text:
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flags = _text_openflags
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else:
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flags = _bin_openflags
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return _mkstemp_inner(dir, prefix, suffix, flags)
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def mkdtemp(suffix="", prefix=template, dir=None):
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"""mkdtemp([suffix, [prefix, [dir]]])
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User-callable function to create and return a unique temporary
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directory. The return value is the pathname of the directory.
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Arguments are as for mkstemp, except that the 'text' argument is
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not accepted.
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The directory is readable, writable, and searchable only by the
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creating user.
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Caller is responsible for deleting the directory when done with it.
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"""
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if dir is None:
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dir = gettempdir()
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names = _get_candidate_names()
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for seq in xrange(TMP_MAX):
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name = names.next()
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file = _os.path.join(dir, prefix + name + suffix)
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try:
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_os.mkdir(file, 0700)
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return file
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except OSError, e:
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if e.errno == _errno.EEXIST:
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continue # try again
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raise
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raise IOError, (_errno.EEXIST, "No usable temporary directory name found")
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def mktemp(suffix="", prefix=template, dir=None):
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"""mktemp([suffix, [prefix, [dir]]])
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User-callable function to return a unique temporary file name. The
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file is not created.
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Arguments are as for mkstemp, except that the 'text' argument is
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not accepted.
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This function is unsafe and should not be used. The file name
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refers to a file that did not exist at some point, but by the time
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you get around to creating it, someone else may have beaten you to
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the punch.
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"""
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## from warnings import warn as _warn
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## _warn("mktemp is a potential security risk to your program",
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## RuntimeWarning, stacklevel=2)
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if dir is None:
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dir = gettempdir()
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names = _get_candidate_names()
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for seq in xrange(TMP_MAX):
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name = names.next()
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file = _os.path.join(dir, prefix + name + suffix)
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if not _exists(file):
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return file
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raise IOError, (_errno.EEXIST, "No usable temporary filename found")
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class _TemporaryFileWrapper:
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"""Temporary file wrapper
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This class provides a wrapper around files opened for
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temporary use. In particular, it seeks to automatically
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remove the file when it is no longer needed.
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"""
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def __init__(self, file, name, delete=True):
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self.file = file
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self.name = name
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self.close_called = False
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self.delete = delete
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def __getattr__(self, name):
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file = self.__dict__['file']
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a = getattr(file, name)
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if type(a) != type(0):
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setattr(self, name, a)
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return a
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# NT provides delete-on-close as a primitive, so we don't need
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# the wrapper to do anything special. We still use it so that
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# file.name is useful (i.e. not "(fdopen)") with NamedTemporaryFile.
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if _os.name != 'nt':
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# Cache the unlinker so we don't get spurious errors at
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# shutdown when the module-level "os" is None'd out. Note
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# that this must be referenced as self.unlink, because the
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# name TemporaryFileWrapper may also get None'd out before
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# __del__ is called.
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unlink = _os.unlink
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def close(self):
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if not self.close_called:
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self.close_called = True
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self.file.close()
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if self.delete:
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self.unlink(self.name)
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def __del__(self):
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self.close()
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def NamedTemporaryFile(mode='w+b', bufsize=-1, suffix="",
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prefix=template, dir=None, delete=True):
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"""Create and return a temporary file.
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Arguments:
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'prefix', 'suffix', 'dir' -- as for mkstemp.
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'mode' -- the mode argument to os.fdopen (default "w+b").
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'bufsize' -- the buffer size argument to os.fdopen (default -1).
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'delete' -- whether the file is deleted on close (default True).
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The file is created as mkstemp() would do it.
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Returns an object with a file-like interface; the name of the file
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is accessible as file.name. The file will be automatically deleted
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when it is closed unless the 'delete' argument is set to False.
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"""
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if dir is None:
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dir = gettempdir()
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if 'b' in mode:
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flags = _bin_openflags
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else:
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flags = _text_openflags
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# Setting O_TEMPORARY in the flags causes the OS to delete
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# the file when it is closed. This is only supported by Windows.
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if _os.name == 'nt' and delete:
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flags |= _os.O_TEMPORARY
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(fd, name) = _mkstemp_inner(dir, prefix, suffix, flags)
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file = _os.fdopen(fd, mode, bufsize)
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return _TemporaryFileWrapper(file, name, delete)
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if _os.name != 'posix' or _os.sys.platform == 'cygwin':
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# On non-POSIX and Cygwin systems, assume that we cannot unlink a file
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# while it is open.
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TemporaryFile = NamedTemporaryFile
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else:
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def TemporaryFile(mode='w+b', bufsize=-1, suffix="",
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prefix=template, dir=None):
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"""Create and return a temporary file.
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Arguments:
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'prefix', 'suffix', 'dir' -- as for mkstemp.
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'mode' -- the mode argument to os.fdopen (default "w+b").
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'bufsize' -- the buffer size argument to os.fdopen (default -1).
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The file is created as mkstemp() would do it.
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Returns an object with a file-like interface. The file has no
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name, and will cease to exist when it is closed.
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"""
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if dir is None:
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dir = gettempdir()
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if 'b' in mode:
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flags = _bin_openflags
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else:
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flags = _text_openflags
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(fd, name) = _mkstemp_inner(dir, prefix, suffix, flags)
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try:
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_os.unlink(name)
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return _os.fdopen(fd, mode, bufsize)
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except:
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_os.close(fd)
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raise
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