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| -rw-r--r-- | Doc/library/os.rst | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/Doc/library/os.rst b/Doc/library/os.rst index 7609580..dfc910b 100644 --- a/Doc/library/os.rst +++ b/Doc/library/os.rst @@ -1346,7 +1346,26 @@ Files and Directories Using :func:`access` to check if a user is authorized to e.g. open a file before actually doing so using :func:`open` creates a security hole, because the user might exploit the short time interval between checking - and opening the file to manipulate it. + and opening the file to manipulate it. It's preferable to use :term:`EAFP` + techniques. For example:: + + if os.access("myfile", os.R_OK): + with open("myfile") as fp: + return fp.read() + return "some default data" + + is better written as:: + + try: + fp = open("myfile") + except OSError as e: + if e.errno == errno.EACCESS: + return "some default data" + # Not a permission error. + raise + else: + with fp: + return fp.read() .. note:: |