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# -*- coding: utf-8 -*- """ Temporary file handling
AUTHORS:
- Volker Braun, Jeroen Demeyer (2012-10-18): move these functions here from sage/misc/misc.py and make them secure, see :trac:`13579`.
- Jeroen Demeyer (2013-03-17): add :class:`atomic_write`, see :trac:`14292`. """
#***************************************************************************** # Copyright (C) 2012 Volker Braun <vbraun@stp.dias.ie> # Copyright (C) 2012 Jeroen Demeyer <jdemeyer@cage.ugent.be> # # Distributed under the terms of the GNU General Public License (GPL) # as published by the Free Software Foundation; either version 2 of # the License, or (at your option) any later version. # http://www.gnu.org/licenses/ #***************************************************************************** from __future__ import print_function
import io import os import tempfile import atexit import six
def delete_tmpfiles(): """ Remove the directory ``SAGE_TMP``.
TESTS:
This is automatically run when Sage exits, test this by running a separate session of Sage::
sage: from sage.tests.cmdline import test_executable sage: child_SAGE_TMP, err, ret = test_executable(["sage", "-c", "print(SAGE_TMP)"]) sage: err, ret ('', 0) sage: os.path.exists(child_SAGE_TMP) # indirect doctest False
The parent directory should exist::
sage: parent_SAGE_TMP = os.path.normpath(child_SAGE_TMP + '/..') sage: os.path.isdir(parent_SAGE_TMP) True """ import shutil from sage.misc.misc import SAGE_TMP shutil.rmtree(str(SAGE_TMP), ignore_errors=True)
# Run when Python shuts down atexit.register(delete_tmpfiles)
################################################################# # temporary directory #################################################################
def tmp_dir(name="dir_", ext=""): r""" Create and return a temporary directory in ``$HOME/.sage/temp/hostname/pid/``
The temporary directory is deleted automatically when Sage exits.
INPUT:
- ``name`` -- (default: ``"dir_"``) A prefix for the directory name.
- ``ext`` -- (default: ``""``) A suffix for the directory name.
OUTPUT:
The absolute path of the temporary directory created, with a trailing slash (or whatever the path separator is on your OS).
EXAMPLES::
sage: from sage.misc.sage_ostools import restore_cwd sage: d = tmp_dir('dir_testing_', '.extension') sage: d # random output '/home/username/.sage/temp/hostname/7961/dir_testing_XgRu4p.extension/' sage: with restore_cwd(d): ....: f = open('file_inside_d', 'w')
Temporary directories are unaccessible by other users::
sage: os.stat(d).st_mode & 0o077 0 sage: f.close() """
################################################################# # temporary filename #################################################################
def tmp_filename(name="tmp_", ext=""): r""" Create and return a temporary file in ``$HOME/.sage/temp/hostname/pid/``
The temporary file is deleted automatically when Sage exits.
.. warning::
If you need a particular file extension always use ``tmp_filename(ext=".foo")``, this will ensure that the file does not yet exist. If you were to use ``tmp_filename()+".foo"``, then you might overwrite an existing file!
INPUT:
- ``name`` -- (default: ``"tmp_"``) A prefix for the file name.
- ``ext`` -- (default: ``""``) A suffix for the file name. If you want a filename extension in the usual sense, this should start with a dot.
OUTPUT:
The absolute path of the temporary file created.
EXAMPLES::
sage: fn = tmp_filename('just_for_testing_', '.extension') sage: fn # random '/home/username/.sage/temp/hostname/8044/just_for_testing_tVVHsn.extension' sage: f = open(fn, 'w')
Temporary files are unaccessible by other users::
sage: os.stat(fn).st_mode & 0o077 0 sage: f.close() """
def graphics_filename(ext='.png'): """ Deprecated SageNB graphics filename
You should just use :meth:`tmp_filename`.
When run from the Sage notebook, return the next available canonical filename for a plot/graphics file in the current working directory. Otherwise, return a temporary file inside ``SAGE_TMP``.
INPUT:
- ``ext`` -- (default: ``".png"``) A file extension (including the dot) for the filename.
OUTPUT:
The path of the temporary file created. In the notebook, this is a filename without path in the current directory. Otherwise, this an absolute path.
EXAMPLES::
sage: from sage.misc.temporary_file import graphics_filename sage: print(graphics_filename()) # random, typical filename for sagenb sage0.png
TESTS:
When doctesting, this returns instead a random temporary file. We check that it's a file inside ``SAGE_TMP`` and that the extension is correct::
sage: fn = graphics_filename(ext=".jpeg") sage: fn.startswith(str(SAGE_TMP)) True sage: fn.endswith('.jpeg') True """ # Don't use this unsafe function except in the notebook, #15515 else:
################################################################# # write to a temporary file and move it in place ################################################################# class atomic_write(object): """ Write to a given file using a temporary file and then rename it to the target file. This renaming should be atomic on modern operating systems. Therefore, this class can be used to avoid race conditions when a file might be read while it is being written. It also avoids having partially written files due to exceptions or crashes.
This is to be used in a ``with`` statement, where a temporary file is created when entering the ``with`` and is moved in place of the target file when exiting the ``with`` (if no exceptions occured).
INPUT:
- ``target_filename`` -- the name of the file to be written. Normally, the contents of this file will be overwritten.
- ``append`` -- (boolean, default: False) if True and ``target_filename`` is an existing file, then copy the current contents of ``target_filename`` to the temporary file when entering the ``with`` statement. Otherwise, the temporary file is initially empty.
- ``mode`` -- (default: ``0o666``) mode bits for the file. The temporary file is created with mode ``mode & ~umask`` and the resulting file will also have these permissions (unless the mode bits of the file were changed manually). (Not to be confused with the file opening mode.)
- ``binary`` -- (boolean, default: True on Python 2, False on Python 3) the underlying file is opened in binary mode. If False then it is opened in text mode and an encoding with which to write the file may be supplied.
- ``**kwargs`` -- additional keyword arguments passed to the underlying `io.open` call.
EXAMPLES::
sage: from sage.misc.temporary_file import atomic_write sage: target_file = tmp_filename() sage: with open(target_file, 'w') as f: ....: _ = f.write("Old contents") sage: with atomic_write(target_file) as f: ....: _ = f.write("New contents") ....: f.flush() ....: with open(target_file, 'r') as f2: ....: f2.read() 'Old contents' sage: with open(target_file, 'r') as f: ....: f.read() 'New contents'
The name of the temporary file can be accessed using ``f.name``. It is not a problem to close and re-open the temporary file::
sage: from sage.misc.temporary_file import atomic_write sage: target_file = tmp_filename() sage: with open(target_file, 'w') as f: ....: _ = f.write("Old contents") sage: with atomic_write(target_file) as f: ....: f.close() ....: with open(f.name, 'w') as f2: ....: _ = f2.write("Newer contents") sage: with open(target_file, 'r') as f: ....: f.read() 'Newer contents'
If an exception occurs while writing the file, the target file is not touched::
sage: with atomic_write(target_file) as f: ....: _ = f.write("Newest contents") ....: raise RuntimeError Traceback (most recent call last): ... RuntimeError sage: with open(target_file, 'r') as f: ....: f.read() 'Newer contents'
Some examples of using the ``append`` option. Note that the file is never opened in "append" mode, it is possible to overwrite existing data::
sage: target_file = tmp_filename() sage: with atomic_write(target_file, append=True) as f: ....: _ = f.write("Hello") sage: with atomic_write(target_file, append=True) as f: ....: _ = f.write(" World") sage: with open(target_file, 'r') as f: ....: f.read() 'Hello World' sage: with atomic_write(target_file, append=True) as f: ....: _ = f.seek(0) ....: _ = f.write("HELLO") sage: with open(target_file, 'r') as f: ....: f.read() 'HELLO World'
If the target file is a symbolic link, the link is kept and the target of the link is written to::
sage: link_to_target = os.path.join(tmp_dir(), "templink") sage: os.symlink(target_file, link_to_target) sage: with atomic_write(link_to_target) as f: ....: _ = f.write("Newest contents") sage: with open(target_file, 'r') as f: ....: f.read() 'Newest contents'
We check the permission bits of the new file. Note that the old permissions do not matter::
sage: os.chmod(target_file, 0o600) sage: _ = os.umask(0o022) sage: with atomic_write(target_file) as f: ....: pass sage: '{:#o}'.format(os.stat(target_file).st_mode & 0o777) '0o644' sage: _ = os.umask(0o077) sage: with atomic_write(target_file, mode=0o777) as f: ....: pass sage: '{:#o}'.format(os.stat(target_file).st_mode & 0o777) '0o700'
Test writing twice to the same target file. The outermost ``with`` "wins"::
sage: with open(target_file, 'w') as f: ....: _ = f.write('>>> ') sage: with atomic_write(target_file, append=True) as f, \ ....: atomic_write(target_file, append=True) as g: ....: _ = f.write("AAA"); f.close() ....: _ = g.write("BBB"); g.close() sage: with open(target_file, 'r') as f: ....: f.read() '>>> AAA'
Supplying an encoding means we're writing the file in "text mode" (in the same sense as `io.open`) and so we must write unicode strings::
sage: target_file = tmp_filename() sage: with atomic_write(target_file, binary=False, ....: encoding='utf-8') as f: ....: _ = f.write(u'Hélas') sage: import io sage: with io.open(target_file, encoding='utf-8') as f: ....: print(f.read()) Hélas
Supplying an encoding in binary mode (or other arguments that don't make sense to `io.open` in binary mode) is an error::
sage: writer = atomic_write(target_file, binary=True, ....: encoding='utf-8') sage: with writer as f: ....: _ = f.write(u'Hello') Traceback (most recent call last): ... ValueError: binary mode doesn't take an encoding argument sage: os.path.exists(writer.tempname) False """ def __init__(self, target_filename, append=False, mode=0o666, binary=None, **kwargs): """ TESTS::
sage: from sage.misc.temporary_file import atomic_write sage: link_to_target = os.path.join(tmp_dir(), "templink") sage: os.symlink("/foobar", link_to_target) sage: aw = atomic_write(link_to_target) sage: print(aw.target) /foobar sage: print(aw.tmpdir) / """ # Remove umask bits from mode
# 'binary' mode is the default on Python 2, whereas 'text' mode is the # default on Python 3--this reflects consistent handling of the default # str type on the two platforms
def __enter__(self): """ Create and return a temporary file in ``self.tmpdir`` (normally the same directory as the target file).
If ``self.append``, then copy the current contents of ``self.target`` to the temporary file.
OUTPUT: a file returned by :func:`tempfile.NamedTemporaryFile`.
TESTS::
sage: from sage.misc.temporary_file import atomic_write sage: aw = atomic_write(tmp_filename()) sage: with aw as f: ....: os.path.dirname(aw.target) == os.path.dirname(f.name) True """
# Some invalid arguments were passed to io.open finally:
except IOError: pass else:
def __exit__(self, exc_type, exc_val, exc_tb): """ If the ``with`` block was successful, move the temporary file to the target file. Otherwise, delete the temporary file.
TESTS:
Check that the temporary file is deleted if there was an exception::
sage: from sage.misc.temporary_file import atomic_write sage: with atomic_write(tmp_filename()) as f: ....: tempname = f.name ....: raise RuntimeError Traceback (most recent call last): ... RuntimeError sage: os.path.exists(tempname) False """ # Flush the file contents to disk (to be safe even if the # system crashes) and close the file.
# Success: move temporary file to target file except OSError: os.unlink(self.target) os.rename(self.tempname, self.target) else: # Failure: delete temporary file |