41 lines
1.4 KiB
Python
41 lines
1.4 KiB
Python
# Copyright 2011, VMware, Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
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# implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import os
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import tempfile
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def replace_file(file_name, data, file_mode=0o644):
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"""Replaces the contents of file_name with data in a safe manner.
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First write to a temp file and then rename. Since POSIX renames are
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atomic, the file is unlikely to be corrupted by competing writes.
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We create the tempfile on the same device to ensure that it can be renamed.
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:param file_name: Path to the file to replace.
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:param data: The data to write to the file.
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:param file_mode: The mode to use for the replaced file.
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:returns: None.
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"""
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base_dir = os.path.dirname(os.path.abspath(file_name))
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with tempfile.NamedTemporaryFile('w+',
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dir=base_dir,
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delete=False) as tmp_file:
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tmp_file.write(data)
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os.chmod(tmp_file.name, file_mode)
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os.rename(tmp_file.name, file_name)
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