The enum class type perm_options is a bitmask type ([bitmask.types]) that specifies bitmask constants used to control the semantics of permissions operations, with the meanings listed in Table 126. The bitmask constants are bitmask elements. In Table 126 perm denotes a value of type perms passed to permissions.
| Name | Meaning |
| replace | permissions shall replace the file's permission bits with perm |
| add | permissions shall replace the file's permission bits with the bitwise OR of perm and the file's current permission bits. |
| remove | permissions shall replace the file's permission bits with the bitwise AND of the complement of perm and the file's current permission bits. |
| nofollow | permissions shall change the permissions of a symbolic link itself rather than the permissions of the file the link resolves to. |