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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |CONFORMING TO |SEE ALSO |COLOPHON | |
CAP_CLEAR(3) Linux Programmer's ManualCAP_CLEAR(3)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
#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.
These functions work on a capability state held in working storage. Acap_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 asCAP_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 areCAP_EFFECTIVE,CAP_INHERITABLEorCAP_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 areCAP_CLEAR(0) orCAP_SET(1).cap_clear() initializes the capability state in working storage identified bycap_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 bycap_p and places it in the location pointed to byvalue_p.cap_set_flag() sets the flag,flag, of each capability in the arraycaps in the capability state identified bycap_p tovalue. 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 ofmemcmp(), returns zero if the two capability sets are identical. A positive returnvalue indicates there is a difference between them. The returnedvalue carries further information about thecap_flag_tflag differences. Specifically, the macroCAP_DIFFERS(value,flag) evaluates to non-zero if the returnedvalue differs in itsflag 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.
cap_clear(),cap_clear_flag(),cap_get_flag()cap_set_flag() andcap_compare() return zero on success, and -1 on failure. Other return values forcap_compare() are described above. The functioncap_max_bits() returns a numeric value of typecap_value_tthat is one larger than the largest actual value known to the running kernel. On failure,errno is set toEINVAL, indicating that one of the arguments is invalid.
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() andcap_max_bits().
libcap(3),cap_copy_ext(3),cap_from_text(3),cap_get_file(3),cap_get_proc(3),cap_init(3),capabilities(7)
This page is part of thelibcap (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 isnot part of the original manual page), send a mail to man-pages@man7.org 2022-10-16CAP_CLEAR(3)Pages that refer to this page:cap_copy_ext(3), cap_from_text(3), cap_get_file(3), cap_get_proc(3), cap_init(3), libcap(3), capabilities(7)
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