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os.umask

os — process

Set the file-creation mode mask and return the previous value.

Syntax

os.umask(mask)

There is no way to read the mask without changing it: the usual idiom is old = os.umask(0); os.umask(old). The mask is process-wide, and between the two calls another thread may create a file with a zero mask. The mask removes permissions rather than setting them: with umask 022 a file created with 0o666 ends up 0o644.

Examples

import os
old = os.umask(0o022)
os.umask(old)
print(isinstance(old, int))   # → True

See also

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