These functions work on a capability state held in working storage.
A cap_t holds information about the capabilities in each of the three
sets, Permitted, Inheritable, and Effective. Each capability in a
set may be clear (disabled, 0) or set (enabled, 1).
These functions work with the following data types:
cap_value_t identifies a capability, such as CAP_CHOWN.
cap_flag_t identifies one of the three flags associated with a
capability (i.e., it identifies one of the three
capability sets). Valid values for this type are
CAP_EFFECTIVE, CAP_INHERITABLE or CAP_PERMITTED.
cap_flag_value_t identifies the setting of a particular capability
flag (i.e, the value of a capability in a set).
Valid values for this type are CAP_CLEAR (0) or
cap_clear() initializes the capability state in working storage
identified by cap_p so that all capability flags are cleared.
cap_clear_flag() clears all of the capabilities of the specified
capability flag, flag.
cap_get_flag() obtains the current value of the capability flag,
flag, of the capability, cap, from the capability state identified by
cap_p and places it in the location pointed to by value_p.
cap_set_flag() sets the flag, flag, of each capability in the array
caps in the capability state identified by cap_p to value. The
argument, ncap, is used to specify the number of capabilities in the
cap_compare() compares two full capability sets and, in the spirit of
memcmp(), returns zero if the two capability sets are identical. A
positive return value, status, indicates there is a difference
between them. The returned value carries further information about
which of three sets, cap_flag_tflag, differ. Specifically, the macro
CAP_DIFFERS (status, flag) evaluates to non-zero if the returned
status differs in its flag components.
cap_clear(), cap_clear_flag(), cap_get_flag() cap_set_flag() and
cap_compare() return zero on success, and -1 on failure. Other return
values for cap_compare() are described above.
On failure, errno is set to EINVAL, indicating that one of the
arguments is invalid.
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