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"""
Move a file in the safest way possible::
>>> from django.core.files.move import file_move_save
>>> file_move_save("/tmp/old_file", "/tmp/new_file")
"""
import os
from django.core.files import locks
__all__ = ['file_move_safe']
try:
import shutil
file_move = shutil.move
except ImportError:
file_move = os.rename
def file_move_safe(old_file_name, new_file_name, chunk_size = 1024*64, allow_overwrite=False):
"""
Moves a file from one location to another in the safest way possible.
First, try using ``shutils.move``, which is OS-dependent but doesn't break
if moving across filesystems. Then, try ``os.rename``, which will break
across filesystems. Finally, streams manually from one file to another in
pure Python.
If the destination file exists and ``allow_overwrite`` is ``False``, this
function will throw an ``IOError``.
"""
# There's no reason to move if we don't have to.
if old_file_name == new_file_name:
return
if not allow_overwrite and os.path.exists(new_file_name):
raise IOError("Cannot overwrite existing file '%s'." % new_file_name)
try:
file_move(old_file_name, new_file_name)
return
except OSError:
# This will happen with os.rename if moving to another filesystem
pass
# If the built-in didn't work, do it the hard way.
new_file = open(new_file_name, 'wb')
locks.lock(new_file, locks.LOCK_EX)
old_file = open(old_file_name, 'rb')
current_chunk = None
while current_chunk != '':
current_chunk = old_file.read(chunk_size)
new_file.write(current_chunk)
new_file.close()
old_file.close()
os.remove(old_file_name)
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