CAP_CLEAR
Section: Linux Programmer's Manual (3)
Updated: 202-1-16
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NAME
cap_clear, cap_clear_flag, cap_get_flag, cap_set_flag, cap_fill_flag, cap_fill, cap_compare, cap_max_bits - 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 no-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)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- CONFORMING TO
-
- SEE ALSO
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