From: Scott Gasch Date: Thu, 9 Feb 2023 23:34:50 +0000 (-0800) Subject: Adds CreateFileWithMode helper to create a new file with a given X-Git-Url: https://wannabe.guru.org/gitweb/?a=commitdiff_plain;h=b7780427c0a5c82406a093e0a08272e1e7117c1b;p=pyutils.git Adds CreateFileWithMode helper to create a new file with a given mode more easily. --- diff --git a/src/pyutils/files/file_utils.py b/src/pyutils/files/file_utils.py index 4412a41..8c3351f 100644 --- a/src/pyutils/files/file_utils.py +++ b/src/pyutils/files/file_utils.py @@ -312,7 +312,7 @@ def create_path_if_not_exist(path, on_error=None) -> None: .. warning:: - Files are created with mode 0x0777 (i.e. world read/writeable). + Files are created with mode 0o0777 (i.e. world read/writeable). >>> import uuid >>> import os @@ -1192,7 +1192,6 @@ class FileWriter(contextlib.AbstractContextManager): print("This is a test!", file=w) time.sleep(2) print("This is only a test...", file=w) - """ def __init__(self, filename: str) -> None: @@ -1221,6 +1220,65 @@ class FileWriter(contextlib.AbstractContextManager): return False +class CreateFileWithMode(contextlib.AbstractContextManager): + """This helper context manager can be used instead of the typical + pattern for creating a file if you want to ensure that the file + created is a particular permission mode upon creation. + + Python's open doesn't support this; you need to set the os.umask + and then create a descriptor to open via os.open, see below. + + >>> import os + >>> filename = f'/tmp/CreateFileWithModeTest.{os.getpid()}' + >>> with CreateFileWithMode(filename, mode=0o600) as wf: + ... print('This is a test', file=wf) + >>> result = os.stat(filename) + + Note: there is a high order bit set in this that is S_IFREG indicating + that the file is a "normal file". Clear it with the mask. + + >>> print(f'{result.st_mode & 0o7777:o}') + 600 + >>> with open(filename, 'r') as rf: + ... contents = rf.read() + >>> contents + 'This is a test\\n' + >>> remove(filename) + """ + + def __init__(self, filename: str, mode=0o600) -> None: + """ + Args: + filename: path of the file to create. It must not already + exist or we raise an Exception. + mode: the UNIX-style octal mode with which to create the + filename. + """ + self.filename = filename + self.mode = mode & 0o7777 + self.handle: Optional[TextIO] = None + self.old_umask = os.umask(0) + + def __enter__(self) -> TextIO: + if does_file_exist(self.filename): + raise Exception( + f"{self.filename} already exists; it must not to use this class" + ) + descriptor = os.open( + path=self.filename, + flags=(os.O_WRONLY | os.O_CREAT | os.O_TRUNC), + mode=self.mode, + ) + self.handle = open(descriptor, "w") + return self.handle + + def __exit__(self, exc_type, exc_val, exc_tb) -> Literal[False]: + os.umask(self.old_umask) + if self.handle is not None: + self.handle.close() + return False + + if __name__ == "__main__": import doctest