Python | os.umask () method

Python Methods and Functions | umask

os.umask() in Python is used to set the current numeric value umask and get the previous value umask .

umask denotes the user file creation mode mask . This is used to determine the permissions on newly created files or directories.

Syntax: os.umask (mask)

Parameter:
mask : An integer value denoting a valid umask value.

Return Type: This method sets the current umask value and returns an integer value which represents the previous umask value.

Code # 1 : Using the os.umask () method

# Python program to explain the os.umask () method

 
# import of the os module

import os

 
# mask
# 18 decimal
# equals 0o022 octal

mask = 18

 
# Set the current mask value
# and get the previous one
# mask value

umask = os.umask (mask)

 

 
# Print
# current and previous
# mask value

print ( "Current umask:" , mask)

print ( "Previo us umask: " , umask) 

Exit :

 Current umask: 18 Previous umask: 54 

Code # 2: Transfer octal value to as a parameter in the os.umask () method

# Python program to explain the os.umask () method

 
# import of the os module

import os

 
# Octal value for umask
# octal value 0o777
# 511 decimal

mask = 0o777

  
# Set the current mask value
# and get the previous one
# mask value

umask = os.umask (mask)

 

 
# Print
# current and previous
# mask value

print ( "Current umask:" , mask)

print ( "Previous umask:" , umask) 

Exit:

 Current umask: 511 Previous umask: 18 




Python | os.umask () method: StackOverflow Questions

Answer #1

Looks like this is new as of Python 3.4 - pathlib.

from pathlib import Path

Path("path/to/file.txt").touch()

This will create a file.txt at the path.

--

Path.touch(mode=0o777, exist_ok=True)

Create a file at this given path. If mode is given, it is combined with the process’ umask value to determine the file mode and access flags. If the file already exists, the function succeeds if exist_ok is true (and its modification time is updated to the current time), otherwise FileExistsError is raised.

Answer #2

There are many fiddly things to take care of when becoming a well-behaved daemon process:

  • prevent core dumps (many daemons run as root, and core dumps can contain sensitive information)

  • behave correctly inside a chroot gaol

  • set UID, GID, working directory, umask, and other process parameters appropriately for the use case

  • relinquish elevated suid, sgid privileges

  • close all open file descriptors, with exclusions depending on the use case

  • behave correctly if started inside an already-detached context, such as init, inetd, etc.

  • set up signal handlers for sensible daemon behaviour, but also with specific handlers determined by the use case

  • redirect the standard streams stdin, stdout, stderr since a daemon process no longer has a controlling terminal

  • handle a PID file as a cooperative advisory lock, which is a whole can of worms in itself with many contradictory but valid ways to behave

  • allow proper cleanup when the process is terminated

  • actually become a daemon process without leading to zombies

Some of these are standard, as described in canonical Unix literature (Advanced Programming in the UNIX Environment, by the late W. Richard Stevens, Addison-Wesley, 1992). Others, such as stream redirection and PID file handling, are conventional behaviour most daemon users would expect but that are less standardised.

All of these are covered by the PEP 3143 “Standard daemon process library” specification. The python-daemon reference implementation works on Python 2.7 or later, and Python 3.2 or later.

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