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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() 

""" 

from sage.misc.misc import SAGE_TMP 

tmp = tempfile.mkdtemp(prefix=name, suffix=ext, dir=str(SAGE_TMP)) 

name = os.path.abspath(tmp) 

return name + os.sep 

 

 

################################################################# 

# 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() 

""" 

from sage.misc.misc import SAGE_TMP 

handle, tmp = tempfile.mkstemp(prefix=name, suffix=ext, dir=str(SAGE_TMP)) 

os.close(handle) 

name = os.path.abspath(tmp) 

return name 

 

 

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 

""" 

import sage.plot.plot 

if sage.plot.plot.EMBEDDED_MODE: 

# Don't use this unsafe function except in the notebook, #15515 

i = 0 

while os.path.exists('sage%d%s'%(i,ext)): 

i += 1 

filename = 'sage%d%s'%(i,ext) 

return filename 

else: 

from sage.misc.superseded import deprecation 

deprecation(17234,'use tmp_filename instead') 

return tmp_filename(ext=ext) 

 

 

################################################################# 

# 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) 

/ 

""" 

self.target = os.path.realpath(target_filename) 

self.tmpdir = os.path.dirname(self.target) 

self.append = append 

# Remove umask bits from mode 

umask = os.umask(0); os.umask(umask) 

self.mode = mode & (~umask) 

 

# '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 

self.binary = six.PY2 if binary is None else binary 

self.kwargs = kwargs 

 

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 

""" 

 

fd, name = tempfile.mkstemp(dir=self.tmpdir) 

self.tempname = os.path.abspath(name) 

 

rmode = 'r' + ('b' if self.binary else '') 

wmode = 'w+' + ('b' if self.binary else '') 

 

try: 

self.tempfile = io.open(name, wmode, **self.kwargs) 

except Exception: 

# Some invalid arguments were passed to io.open 

os.unlink(name) 

raise 

finally: 

os.close(fd) 

 

os.chmod(name, self.mode) 

if self.append: 

try: 

with io.open(self.target, rmode, **self.kwargs) as f: 

r = f.read() 

except IOError: 

pass 

else: 

self.tempfile.write(r) 

 

return self.tempfile 

 

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. 

if not self.tempfile.closed: 

self.tempfile.flush() 

os.fsync(self.tempfile.fileno()) 

self.tempfile.close() 

 

if exc_type is None: 

# Success: move temporary file to target file 

try: 

os.rename(self.tempname, self.target) 

except OSError: 

os.unlink(self.target) 

os.rename(self.tempname, self.target) 

else: 

# Failure: delete temporary file 

os.unlink(self.tempname)