GNU Info

(fileutils.info)Umask and Protection

---

Prev: Multiple Changes Up: Symbolic Modes

---

Enter node , (file) or (file)node

The Umask and Protection
------------------------

   If the USERS part of a symbolic mode is omitted, it defaults to `a'
(affect all users), except that any permissions that are _set_ in the
system variable `umask' are _not affected_.  The value of `umask' can
be set using the `umask' command.  Its default value varies from system
to system.

   Omitting the USERS part of a symbolic mode is generally not useful
with operations other than `+'.  It is useful with `+' because it
allows you to use `umask' as an easily customizable protection against
giving away more permission to files than you intended to.

   As an example, if `umask' has the value 2, which removes write
permission for users who are not in the file's group, then the mode:

     +w

adds permission to write to the file to its owner and to other users who
are in the file's group, but _not_ to other users.  In contrast, the
mode:

     a+w

ignores `umask', and _does_ give write permission for the file to all
users.