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 capability 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  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 array, caps.

       cap_fill_flag()  fills the to flag of one capability set, with the values 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 positive 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) evaluates
       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 numerically 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 arguments 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)