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:mod:`tempfile` --- Generate temporary files and directories
============================================================
.. sectionauthor:: Zack Weinberg <zack@codesourcery.com>
.. module:: tempfile
:synopsis: Generate temporary files and directories.
.. index::
pair: temporary; file name
pair: temporary; file
This module generates temporary files and directories. It works on all
supported platforms.
In version 2.3 of Python, this module was overhauled for enhanced security. It
now provides three new functions, :func:`NamedTemporaryFile`, :func:`mkstemp`,
and :func:`mkdtemp`, which should eliminate all remaining need to use the
insecure :func:`mktemp` function. Temporary file names created by this module
no longer contain the process ID; instead a string of six random characters is
used.
Also, all the user-callable functions now take additional arguments which allow
direct control over the location and name of temporary files. It is no longer
necessary to use the global *tempdir* and *template* variables. To maintain
backward compatibility, the argument order is somewhat odd; it is recommended to
use keyword arguments for clarity.
The module defines the following user-callable functions:
.. function:: TemporaryFile([mode='w+b'[, bufsize=-1[, suffix[, prefix[, dir]]]]])
Return a file (or file-like) object that can be used as a temporary storage
area. The file is created using :func:`mkstemp`. It will be destroyed as soon
as it is closed (including an implicit close when the object is garbage
collected). Under Unix, the directory entry for the file is removed immediately
after the file is created. Other platforms do not support this; your code
should not rely on a temporary file created using this function having or not
having a visible name in the file system.
The *mode* parameter defaults to ``'w+b'`` so that the file created can be read
and written without being closed. Binary mode is used so that it behaves
consistently on all platforms without regard for the data that is stored.
*bufsize* defaults to ``-1``, meaning that the operating system default is used.
The *dir*, *prefix* and *suffix* parameters are passed to :func:`mkstemp`.
.. function:: NamedTemporaryFile([mode='w+b'[, bufsize=-1[, suffix[, prefix[, dir[, delete]]]]]])
This function operates exactly as :func:`TemporaryFile` does, except that the
file is guaranteed to have a visible name in the file system (on Unix, the
directory entry is not unlinked). That name can be retrieved from the
:attr:`name` member of the file object. Whether the name can be used to open
the file a second time, while the named temporary file is still open, varies
across platforms (it can be so used on Unix; it cannot on Windows NT or later).
If *delete* is true (the default), the file is deleted as soon as it is closed.
.. function:: SpooledTemporaryFile([max_size=0, [mode='w+b'[, bufsize=-1[, suffix[, prefix[, dir]]]]]])
This function operates exactly as :func:`TemporaryFile` does, except that data
is spooled in memory until the file size exceeds *max_size*, or until the file's
:func:`fileno` method is called, at which point the contents are written to disk
and operation proceeds as with :func:`TemporaryFile`.
The resulting file has one additional method, :func:`rollover`, which causes the
file to roll over to an on-disk file regardless of its size.
.. function:: mkstemp([suffix[, prefix[, dir[, text]]]])
Creates a temporary file in the most secure manner possible. There are no
race conditions in the file's creation, assuming that the platform properly
implements the :const:`os.O_EXCL` flag for :func:`os.open`. The file is
readable and writable only by the creating user ID. If the platform uses
permission bits to indicate whether a file is executable, the file is
executable by no one. The file descriptor is not inherited by child
processes.
Unlike :func:`TemporaryFile`, the user of :func:`mkstemp` is responsible for
deleting the temporary file when done with it.
If *suffix* is specified, the file name will end with that suffix, otherwise
there will be no suffix. :func:`mkstemp` does not put a dot between the file
name and the suffix; if you need one, put it at the beginning of *suffix*.
If *prefix* is specified, the file name will begin with that prefix; otherwise,
a default prefix is used.
If *dir* is specified, the file will be created in that directory; otherwise,
a default directory is used. The default directory is chosen from a
platform-dependent list, but the user of the application can control the
directory location by setting the *TMPDIR*, *TEMP* or *TMP* environment
variables. There is thus no guarantee that the generated filename will have
any nice properties, such as not requiring quoting when passed to external
commands via ``os.popen()``.
If *text* is specified, it indicates whether to open the file in binary mode
(the default) or text mode. On some platforms, this makes no difference.
:func:`mkstemp` returns a tuple containing an OS-level handle to an open file
(as would be returned by :func:`os.open`) and the absolute pathname of that
file, in that order.
.. function:: mkdtemp([suffix[, prefix[, dir]]])
Creates a temporary directory in the most secure manner possible. There are no
race conditions in the directory's creation. The directory is readable,
writable, and searchable only by the creating user ID.
The user of :func:`mkdtemp` is responsible for deleting the temporary directory
and its contents when done with it.
The *prefix*, *suffix*, and *dir* arguments are the same as for :func:`mkstemp`.
:func:`mkdtemp` returns the absolute pathname of the new directory.
.. function:: mktemp([suffix[, prefix[, dir]]])
.. deprecated:: 2.3
Use :func:`mkstemp` instead.
Return an absolute pathname of a file that did not exist at the time the call is
made. The *prefix*, *suffix*, and *dir* arguments are the same as for
:func:`mkstemp`.
.. warning::
Use of this function may introduce a security hole in your program. By the time
you get around to doing anything with the file name it returns, someone else may
have beaten you to the punch.
The module uses two global variables that tell it how to construct a temporary
name. They are initialized at the first call to any of the functions above.
The caller may change them, but this is discouraged; use the appropriate
function arguments, instead.
.. data:: tempdir
When set to a value other than ``None``, this variable defines the default value
for the *dir* argument to all the functions defined in this module.
If ``tempdir`` is unset or ``None`` at any call to any of the above functions,
Python searches a standard list of directories and sets *tempdir* to the first
one which the calling user can create files in. The list is:
#. The directory named by the :envvar:`TMPDIR` environment variable.
#. The directory named by the :envvar:`TEMP` environment variable.
#. The directory named by the :envvar:`TMP` environment variable.
#. A platform-specific location:
* On Windows, the directories :file:`C:\\TEMP`, :file:`C:\\TMP`,
:file:`\\TEMP`, and :file:`\\TMP`, in that order.
* On all other platforms, the directories :file:`/tmp`, :file:`/var/tmp`, and
:file:`/usr/tmp`, in that order.
#. As a last resort, the current working directory.
.. function:: gettempdir()
Return the directory currently selected to create temporary files in. If
:data:`tempdir` is not ``None``, this simply returns its contents; otherwise,
the search described above is performed, and the result returned.
.. data:: template
.. deprecated:: 2.0
Use :func:`gettempprefix` instead.
When set to a value other than ``None``, this variable defines the prefix of the
final component of the filenames returned by :func:`mktemp`. A string of six
random letters and digits is appended to the prefix to make the filename unique.
On Windows, the default prefix is :file:`~T`; on all other systems it is
:file:`tmp`.
Older versions of this module used to require that ``template`` be set to
``None`` after a call to :func:`os.fork`; this has not been necessary since
version 1.5.2.
.. function:: gettempprefix()
Return the filename prefix used to create temporary files. This does not
contain the directory component. Using this function is preferred over reading
the *template* variable directly.
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