/Doc/library/tempfile.rst
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1 2:mod:`tempfile` --- Generate temporary files and directories 3============================================================ 4 5.. sectionauthor:: Zack Weinberg <zack@codesourcery.com> 6 7 8.. module:: tempfile 9 :synopsis: Generate temporary files and directories. 10 11 12.. index:: 13 pair: temporary; file name 14 pair: temporary; file 15 16This module generates temporary files and directories. It works on all 17supported platforms. 18 19In version 2.3 of Python, this module was overhauled for enhanced security. It 20now provides three new functions, :func:`NamedTemporaryFile`, :func:`mkstemp`, 21and :func:`mkdtemp`, which should eliminate all remaining need to use the 22insecure :func:`mktemp` function. Temporary file names created by this module 23no longer contain the process ID; instead a string of six random characters is 24used. 25 26Also, all the user-callable functions now take additional arguments which 27allow direct control over the location and name of temporary files. It is 28no longer necessary to use the global *tempdir* and *template* variables. 29To maintain backward compatibility, the argument order is somewhat odd; it 30is recommended to use keyword arguments for clarity. 31 32The module defines the following user-callable functions: 33 34 35.. function:: TemporaryFile([mode='w+b'[, bufsize=-1[, suffix=''[, prefix='tmp'[, dir=None]]]]]) 36 37 Return a file-like object that can be used as a temporary storage area. 38 The file is created using :func:`mkstemp`. It will be destroyed as soon 39 as it is closed (including an implicit close when the object is garbage 40 collected). Under Unix, the directory entry for the file is removed 41 immediately after the file is created. Other platforms do not support 42 this; your code should not rely on a temporary file created using this 43 function having or not having a visible name in the file system. 44 45 The *mode* parameter defaults to ``'w+b'`` so that the file created can 46 be read and written without being closed. Binary mode is used so that it 47 behaves consistently on all platforms without regard for the data that is 48 stored. *bufsize* defaults to ``-1``, meaning that the operating system 49 default is used. 50 51 The *dir*, *prefix* and *suffix* parameters are passed to :func:`mkstemp`. 52 53 The returned object is a true file object on POSIX platforms. On other 54 platforms, it is a file-like object whose :attr:`file` attribute is the 55 underlying true file object. This file-like object can be used in a 56 :keyword:`with` statement, just like a normal file. 57 58 59.. function:: NamedTemporaryFile([mode='w+b'[, bufsize=-1[, suffix=''[, prefix='tmp'[, dir=None[, delete=True]]]]]]) 60 61 This function operates exactly as :func:`TemporaryFile` does, except that 62 the file is guaranteed to have a visible name in the file system (on 63 Unix, the directory entry is not unlinked). That name can be retrieved 64 from the :attr:`name` member of the file object. Whether the name can be 65 used to open the file a second time, while the named temporary file is 66 still open, varies across platforms (it can be so used on Unix; it cannot 67 on Windows NT or later). If *delete* is true (the default), the file is 68 deleted as soon as it is closed. 69 70 The returned object is always a file-like object whose :attr:`file` 71 attribute is the underlying true file object. This file-like object can 72 be used in a :keyword:`with` statement, just like a normal file. 73 74 .. versionadded:: 2.3 75 76 .. versionadded:: 2.6 77 The *delete* parameter. 78 79 80.. function:: SpooledTemporaryFile([max_size=0, [mode='w+b'[, bufsize=-1[, suffix=''[, prefix='tmp'[, dir=None]]]]]]) 81 82 This function operates exactly as :func:`TemporaryFile` does, except that 83 data is spooled in memory until the file size exceeds *max_size*, or 84 until the file's :func:`fileno` method is called, at which point the 85 contents are written to disk and operation proceeds as with 86 :func:`TemporaryFile`. 87 88 The resulting file has one additional method, :func:`rollover`, which 89 causes the file to roll over to an on-disk file regardless of its size. 90 91 The returned object is a file-like object whose :attr:`_file` attribute 92 is either a :class:`StringIO` object or a true file object, depending on 93 whether :func:`rollover` has been called. This file-like object can be 94 used in a :keyword:`with` statement, just like a normal file. 95 96 .. versionadded:: 2.6 97 98 99.. function:: mkstemp([suffix=''[, prefix='tmp'[, dir=None[, text=False]]]]) 100 101 Creates a temporary file in the most secure manner possible. There are 102 no race conditions in the file's creation, assuming that the platform 103 properly implements the :const:`os.O_EXCL` flag for :func:`os.open`. The 104 file is readable and writable only by the creating user ID. If the 105 platform uses permission bits to indicate whether a file is executable, 106 the file is executable by no one. The file descriptor is not inherited 107 by child processes. 108 109 Unlike :func:`TemporaryFile`, the user of :func:`mkstemp` is responsible 110 for deleting the temporary file when done with it. 111 112 If *suffix* is specified, the file name will end with that suffix, 113 otherwise there will be no suffix. :func:`mkstemp` does not put a dot 114 between the file name and the suffix; if you need one, put it at the 115 beginning of *suffix*. 116 117 If *prefix* is specified, the file name will begin with that prefix; 118 otherwise, a default prefix is used. 119 120 If *dir* is specified, the file will be created in that directory; 121 otherwise, a default directory is used. The default directory is chosen 122 from a platform-dependent list, but the user of the application can 123 control the directory location by setting the *TMPDIR*, *TEMP* or *TMP* 124 environment variables. There is thus no guarantee that the generated 125 filename will have any nice properties, such as not requiring quoting 126 when passed to external commands via ``os.popen()``. 127 128 If *text* is specified, it indicates whether to open the file in binary 129 mode (the default) or text mode. On some platforms, this makes no 130 difference. 131 132 :func:`mkstemp` returns a tuple containing an OS-level handle to an open 133 file (as would be returned by :func:`os.open`) and the absolute pathname 134 of that file, in that order. 135 136 .. versionadded:: 2.3 137 138 139.. function:: mkdtemp([suffix=''[, prefix='tmp'[, dir=None]]]) 140 141 Creates a temporary directory in the most secure manner possible. There 142 are no race conditions in the directory's creation. The directory is 143 readable, writable, and searchable only by the creating user ID. 144 145 The user of :func:`mkdtemp` is responsible for deleting the temporary 146 directory and its contents when done with it. 147 148 The *prefix*, *suffix*, and *dir* arguments are the same as for 149 :func:`mkstemp`. 150 151 :func:`mkdtemp` returns the absolute pathname of the new directory. 152 153 .. versionadded:: 2.3 154 155 156.. function:: mktemp([suffix=''[, prefix='tmp'[, dir=None]]]) 157 158 .. deprecated:: 2.3 159 Use :func:`mkstemp` instead. 160 161 Return an absolute pathname of a file that did not exist at the time the 162 call is made. The *prefix*, *suffix*, and *dir* arguments are the same 163 as for :func:`mkstemp`. 164 165 .. warning:: 166 167 Use of this function may introduce a security hole in your program. By 168 the time you get around to doing anything with the file name it returns, 169 someone else may have beaten you to the punch. :func:`mktemp` usage can 170 be replaced easily with :func:`NamedTemporaryFile`, passing it the 171 ``delete=False`` parameter:: 172 173 >>> f = NamedTemporaryFile(delete=False) 174 >>> f 175 <open file '<fdopen>', mode 'w+b' at 0x384698> 176 >>> f.name 177 '/var/folders/5q/5qTPn6xq2RaWqk+1Ytw3-U+++TI/-Tmp-/tmpG7V1Y0' 178 >>> f.write("Hello World!\n") 179 >>> f.close() 180 >>> os.unlink(f.name) 181 >>> os.path.exists(f.name) 182 False 183 184The module uses two global variables that tell it how to construct a 185temporary name. They are initialized at the first call to any of the 186functions above. The caller may change them, but this is discouraged; use 187the appropriate function arguments, instead. 188 189 190.. data:: tempdir 191 192 When set to a value other than ``None``, this variable defines the 193 default value for the *dir* argument to all the functions defined in this 194 module. 195 196 If ``tempdir`` is unset or ``None`` at any call to any of the above 197 functions, Python searches a standard list of directories and sets 198 *tempdir* to the first one which the calling user can create files in. 199 The list is: 200 201 #. The directory named by the :envvar:`TMPDIR` environment variable. 202 203 #. The directory named by the :envvar:`TEMP` environment variable. 204 205 #. The directory named by the :envvar:`TMP` environment variable. 206 207 #. A platform-specific location: 208 209 * On RiscOS, the directory named by the :envvar:`Wimp$ScrapDir` environment 210 variable. 211 212 * On Windows, the directories :file:`C:\\TEMP`, :file:`C:\\TMP`, 213 :file:`\\TEMP`, and :file:`\\TMP`, in that order. 214 215 * On all other platforms, the directories :file:`/tmp`, :file:`/var/tmp`, and 216 :file:`/usr/tmp`, in that order. 217 218 #. As a last resort, the current working directory. 219 220 221.. function:: gettempdir() 222 223 Return the directory currently selected to create temporary files in. If 224 :data:`tempdir` is not ``None``, this simply returns its contents; otherwise, 225 the search described above is performed, and the result returned. 226 227 .. versionadded:: 2.3 228 229 230.. data:: template 231 232 .. deprecated:: 2.0 233 Use :func:`gettempprefix` instead. 234 235 When set to a value other than ``None``, this variable defines the prefix of the 236 final component of the filenames returned by :func:`mktemp`. A string of six 237 random letters and digits is appended to the prefix to make the filename unique. 238 The default prefix is :file:`tmp`. 239 240 Older versions of this module used to require that ``template`` be set to 241 ``None`` after a call to :func:`os.fork`; this has not been necessary since 242 version 1.5.2. 243 244 245.. function:: gettempprefix() 246 247 Return the filename prefix used to create temporary files. This does not 248 contain the directory component. Using this function is preferred over reading 249 the *template* variable directly. 250 251 .. versionadded:: 1.5.2 252