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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | SEE ALSO | COLOPHON |
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CAP_COPY_EXT(3) Linux Programmer's Manual CAP_COPY_EXT(3)
cap_copy_ext, cap_size, cap_copy_int - capability state external
representation translation
#include <sys/capability.h>
ssize_t cap_size(cap_t cap_p);
ssize_t cap_copy_ext(void *ext_p, cap_t cap_p, ssize_t size);
cap_t cap_copy_int(const void * ext_p);
cap_t cap_copy_int_check(const void *cap_ext, ssize_t length);
Link with -lcap.
These functions translate between internal and external
representations of a capability state. The external
representation is an exportable, contiguous, persistent
representation of a capability state in user-managed space. The
internal representation is managed by the capability functions in
working storage.
cap_size() returns the total length (in bytes) that the capability
state in working storage identified by cap_p would require when
converted by cap_copy_ext(). This function is used primarily to
determine the amount of buffer space that must be provided to the
cap_copy_ext() function in order to hold the capability data
record created from cap_p.
cap_copy_ext() copies a capability state in working storage,
identified by cap_p, from system-managed space to user-managed
space (pointed to by ext_p) and returns the length of the
resulting data record. The size parameter represents the maximum
size, in bytes, of the resulting data record. The cap_copy_ext()
function will do any conversions necessary to convert the
capability state from the undefined internal format to an
exportable, contiguous, persistent data record. It is the
responsibility of the user to allocate a buffer large enough to
hold the copied data. The buffer length required to hold the
copied data may be obtained by a call to the cap_size() function.
cap_copy_int() copies a capability state from a capability data
record in user-managed space to a new capability state in working
storage, allocating any memory necessary, and returning a pointer
to the newly created capability state. The function initializes
the capability state and then copies the capability state from the
record pointed to by ext_p into the capability state, converting,
if necessary, the data from a contiguous, persistent format to an
opaque, internal format. Once copied into internal format, the
object can be manipulated by the capability state manipulation
functions (see cap_clear(3)). Note that the record pointed to by
ext_p must have been obtained from a previous, successful call to
cap_copy_ext() for this function to work successfully. The caller
should free any releasable memory, when the capability state in
working storage is no longer required, by calling cap_free() with
the cap_t as an argument.
cap_copy_int_check() performs the same operation as cap_copy_int()
but additionally checks that the provided external data's size is
not larger than the noted length.
cap_size() returns the length required to hold a capability data
record on success, and -1 on failure.
cap_copy_ext() returns the number of bytes placed in the user
managed space pointed to by ext_p on success, and -1 on failure.
cap_copy_int() and cap_copy_int_check() return a pointer to the
newly created capability state in working storage on success, and
NULL on failure.
On failure, errno is set to EINVAL, ENOMEM, or ERANGE.
These functions are specified in the withdrawn POSIX.1e draft
specification.
libcap(3), cap_clear(3), cap_from_text(3), cap_get_file(3),
cap_get_proc(3), cap_init(3), capabilities(7)
This page is part of the libcap (capabilities commands and
library) project. Information about the project can be found at
⟨https://git.kernel.org/pub/scm/libs/libcap/libcap.git/⟩. If you
have a bug report for this manual page, send it to
morgan@kernel.org (please put "libcap" in the Subject line). This
page was obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/libs/libcap/libcap.git/⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-10.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
2021-03-06 CAP_COPY_EXT(3)
Pages that refer to this page: cap_clear(3), cap_from_text(3), cap_get_file(3), cap_get_proc(3), cap_init(3), libcap(3), capabilities(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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