From the description section of man 2 umask command, it says

For example, the following default ACL is equivalent to a umask of 022:


What's the significance of having another value which is a complement of UMASK instead of umask itself as an ACL value?

  • 1
    Because umask has always been, confusingly, the ones-complement of what it lets through. ACL is the same way as file modes. – ctrl-alt-delor Apr 19 '19 at 22:18
  • In that manpage it says that when the parent dir has a default ACL, the umask is ignored and goes on to explain what default ACL creates the same effect as a umask of 022 -- considering that, I have trouble understanding the point of your question. – mosvy Apr 19 '19 at 22:27
  • @ctrl-alt-delor why is it confusing that a bitmask is masking bits (turning them off)? I have a strange feeling of déjà-vu -- we already beat this horse to death. – mosvy Apr 19 '19 at 22:41
  • @mosvy thanks to you, I have come a long way to comprehend this concept. By default ACL equals ~umask, however I can no longer ask why because the umask (022 by default) is determined by Inode(s) specifications...way beyond my understanding (for now). I still don't understand why the default ACL (ACL value of the parent folder) is the complement of umask value (octal 022 by default), I guess it's for bits operations tricks?! – Jim-chriss Charles Apr 20 '19 at 20:20

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