shell - Who can access a file with octal permissions "000" on Linux/UNIX?

Question

If a file has permissions 000, who or what can access the file? What can they do to it?

What, exactly, does 000 (---------) permissions on a file mean in practice?

Answer 1

root can do everything, others (with userid != 0) can't do anything. But anyone who has write access to the containing folder is allowed to delete the file. The owner can of course always change the flags and regain access anytime.

greybox:~ septi$ touch foo
greybox:~ septi$ chmod 000 foo
greybox:~ septi$ ls -l foo
----------  1 septi  staff  0 Apr  8 12:28 foo
greybox:~ septi$ cat foo
cat: foo: Permission denied
greybox:~ septi$ sudo ls -l foo
Password:
----------  1 septi  staff  0 Apr  8 12:28 foo
greybox:~ septi$