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(fileutils.info)Changing Special Permissions

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Changing Special Permissions
----------------------------

   In addition to changing a file's read, write, and execute
permissions, you can change its special permissions.  Note: Mode
Structure, for a summary of these permissions.

   To change a file's permission to set the user ID on execution, use
`u' in the USERS part of the symbolic mode and `s' in the PERMISSIONS
part.

   To change a file's permission to set the group ID on execution, use
`g' in the USERS part of the symbolic mode and `s' in the PERMISSIONS
part.

   To change a file's permission to stay permanently on the swap device,
use `o' in the USERS part of the symbolic mode and `t' in the
PERMISSIONS part.

   For example, to add set user ID permission to a program, you can use
the mode:

     u+s

   To remove both set user ID and set group ID permission from it, you
can use the mode:

     ug-s

   To cause a program to be saved on the swap device, you can use the
mode:

     o+t

   Remember that the special permissions only affect files that are
executable, plus, on some systems, directories (on which they have
different meanings; Note: Mode Structure).  Also, the combinations
`u+t', `g+t', and `o+s' have no effect.

   The `=' operator is not very useful with special permissions; for
example, the mode:

     o=t

does cause the file to be saved on the swap device, but it also removes
all read, write, and execute permissions that users not in the file's
group might have had for it.