CAP_CLEAR(3) Linux Programmer's Manual CAP_CLEAR(3)
NAME
cap_clear, cap_clear_flag, cap_get_flag, cap_set_flag, cap_fill_flag,
cap_fill, cap_compare - capability data object manipulation
SYNOPSIS
#include <sys/capability.h>
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_fill_flag(cap_t cap_p, cap_flag_t to,
const cap_t ref, cap_flag_t from);
int cap_fill(cap_t cap_p, cap_flag_t to, cap_flag_t from);
int cap_compare(cap_t cap_a, cap_t cap_b);
cap_value_t cap_max_bits();
Link with -lcap.
DESCRIPTION
These functions work on a capability state held in working storage. A
cap_t holds information about the capabilities in each of the three
flags, 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 ca-
pability dimensions). 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_SET (1).
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,
caps.
cap_fill_flag() fills the to flag of one capability set, with the val-
ues in the from flag of a reference capability set.
cap_fill() fills the to flag values by copying all of the from flag
values.
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 indicates there is a difference between them. The
returned value carries further information about the cap_flag_t flag
differences. Specifically, the macro CAP_DIFFERS (value, flag) evalu-
ates to non-zero if the returned value differs in its flag components.
cap_max_bits() returns the number of capability values known to the
running kernel. This may differ from libcap's list known at compilation
time. Unnamed, at compilation time, capabilites can be referred to nu-
merically and libcap will handle them appropriately. Note, the running
kernel wins and it gets to define what "all" capabilities means.
RETURN VALUE
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. The function
cap_max_bits() returns a numeric value of type cap_value_t that is one
larger than the largest actual value known to the running kernel.
On failure, errno is set to EINVAL, indicating that one of the argu-
ments is invalid.
CONFORMING TO
These functions are mostly as per specified in the withdrawn POSIX.1e
draft specification. The following are Linux extensions: cap_fill(),
cap_fill_flag(), cap_clear_flag(), cap_compare() and cap_max_bits().
SEE ALSO
libcap(3), cap_copy_ext(3), cap_from_text(3), cap_get_file(3),
cap_get_proc(3), cap_init(3), capabilities(7)
2021-10-01 CAP_CLEAR(3)
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