CAP_CLEAR(3) Linux Programmer's Manual CAP_CLEAR(3)NAME
cap_clear, cap_clear_flag, cap_get_flag, cap_set_flag, cap_compare -
capability data object manipulation
int cap_clear(cap_t cap_p);
int cap_clear_flag(cap_t cap_p, cap_flag_t flag);
int cap_get_flag(cap_t cap_p, cap_value_t cap,
cap_flag_t flag, cap_flag_value_t *value_p);
int cap_set_flag(cap_t cap_p, cap_flag_t flag, int ncap,
const cap_value_t *caps, cap_flag_value_t value);
int cap_compare(cap_t cap_a, cap_t cap_b);
Link with -lcap.
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 identi‐
fied by cap_p so that all capability flags are cleared.
cap_clear_flag() clears all of the capabilities of the specified capa‐
bility 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 argu‐
ment, ncap, is used to specify the number of capabilities in the array,
cap_compare() compares two full capability sets and, in the spirit of
memcmp(), returns zero if the two capability sets are identical. A pos‐
itive return value, status, indicates there is a difference between
them. The returned value carries further information about which of
three sets, cap_flag_t flag, differ. Specifically, the macro CAP_DIF‐
FERS (status, flag) evaluates to non-zero if the returned status dif‐
fers in its flag components.
RETURN VALUEcap_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 argu‐
ments is invalid.
These functions are as per the withdrawn POSIX.1e draft specification.
cap_clear_flag() and cap_compare() are Linux extensions.
SEE ALSOlibcap(3), cap_copy_ext(3), cap_from_text(3), cap_get_file(3),
cap_get_proc(3), cap_init(3), capabilities(7)