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1. Preface
Temporary files are usually used to save data that cannot be saved in memory, or to pass to data that must be read from the file. external program. Generally we will generate a unique file name in the /tmp directory, but creating temporary files safely is not that simple and needs to follow many rules. Never try to do this yourself, instead use library functions to do it. Also be careful to clean up temporary files.
The biggest problem caused by temporary files is that the file name can be predicted, allowing malicious users to predict the temporary file name and create soft links to hijack the temporary file.
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##2. Introduction to the tempfile module
The module generally used to create temporary files is tempfile. The commonly used functions of this module library are the following:3. Example introduction
The following methods introduce safe and unsafe ways to create temporary files.3.1 Incorrect example:
Incorrect 1:
import os import tempfile # This will most certainly put you at risk tmp = os.path.join(tempfile.gettempdir(), filename) if not os.path.exists(tmp): with open(tmp, "w") file: file.write("defaults")
Incorrect 2:
import os import tempfile open(tempfile.mktemp(), "w")
Incorrect 3:
filename = "{}/{}.tmp".format(tempfile.gettempdir(), os.getpid()) open(filename, "w")
3.2 Correct example
Correct 1:
fd, path = tempfile.mkstemp() try: with os.fdopen(fd, 'w') as tmp: # do stuff with temp file tmp.write('stuff') finally: os.remove(path)
Correct 2:
# 句柄关闭,文件即删除 with tempfile.TemporaryFile() as tmp: # Do stuff with tmp tmp.write('stuff')
Correct 3:
tmp = tempfile.NamedTemporaryFile(delete=True) try: # do stuff with temp tmp.write('stuff') finally: tmp.close() # 文件关闭即删除
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