cap_get_file(3) — Linux manual page


CAP_GET_FILE(3)         Linux Programmer's Manual        CAP_GET_FILE(3)

NAME         top

       cap_get_file, cap_set_file, cap_get_fd, cap_set_fd,
       cap_get_nsowner, cap_set_nsowner - capability manipulation on

SYNOPSIS         top

       #include <sys/capability.h>

       cap_t cap_get_file(const char *path_p);
       int cap_set_file(const char *path_p, cap_t cap_p);
       cap_t cap_get_fd(int fd);
       int cap_set_fd(int fd, cap_t caps);
       uid_t cap_get_nsowner(cap_t caps);
       int cap_set_nsowner(cap_t caps, uid_t rootuid);

       Link with -lcap.

DESCRIPTION         top

       cap_get_file() and cap_get_fd() allocate a capability state in
       working storage and set it to represent the capability state of
       the pathname pointed to by path_p or the file open on descriptor
       fd.  These functions return a pointer to the newly created
       capability state.  The effects of reading the capability state
       from any file other than a regular file is undefined.  The caller
       should free any releasable memory, when the capability state in
       working storage is no longer required, by calling cap_free() with
       the used cap_t as an argument.

       cap_set_file() and cap_set_fd() set the values for all capability
       flags for all capabilities for the pathname pointed to by path_p
       or the file open on descriptor fd, with the capability state
       identified by cap_p.  The new capability state of the file is
       completely determined by the contents of cap_p.  A NULL value for
       cap_p is used to indicate that capabilities for the file should
       be deleted.  For these functions to succeed, the calling process
       must have the CAP_SETFCAP capability in its effective set and
       either the effective user ID of the process must match the file
       owner or the calling process must have the CAP_FOWNER capability
       in its effective capability set.  The effects of writing the
       capability state to any file type other than a regular file are

       A capability set held in memory can be associated with the root
       user ID in use in a specific user namespace. It is possible to
       get and set this value (in the memory copy) with
       cap_get_nsowner() and cap_set_nsowner() respectively. The root
       user ID is ignored by the libcap library in all cases other than
       when the capability is written to a file. Only if the value is
       non-zero will the library attempt to include it in the written
       file capability set.

RETURN VALUE         top

       cap_get_file() and cap_get_fd() return a non-NULL value on
       success, and NULL on failure.

       cap_set_file() and cap_set_fd() return zero on success, and -1 on

       On failure, errno is set to EACCES, EBADFD, ENAMETOOLONG, ENOENT,

CONFORMING TO         top

       These functions are specified by withdrawn POSIX.1e draft

NOTES         top

       Support for file capabilities is provided on Linux since version

       On Linux, the file Effective set is a single bit.  If it is
       enabled, then all Permitted capabilities are enabled in the
       Effective set of the calling process when the file is executed;
       otherwise, no capabilities are enabled in the process's Effective
       set following an execve(2).  Because the file Effective set is a
       single bit, if any capability is enabled in the Effective set of
       the cap_t given to cap_set_file() or cap_set_fd(), then all
       capabilities whose Permitted or Inheritable flag is enabled must
       also have the Effective flag enabled.  Conversely, if the
       Effective bit is enabled on a file, then the cap_t returned by
       cap_get_file() and cap_get_fd() will have the Effective flag
       enabled for each capability that has the Permitted or Inheritable
       flag enabled.

SEE ALSO         top

       libcap(3), cap_clear(3), cap_copy_ext(3), cap_from_text(3),
       cap_get_proc(3), cap_init(3), capabilities(7), user_namespaces(7)

COLOPHON         top

       This page is part of the libcap (capabilities commands and
       library) project.  Information about the project can be found at
       ⟨⟩.  If you
       have a bug report for this manual page, send it to (please put "libcap" in the Subject line).
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on
       2024-06-14.  (At that time, the date of the most recent commit
       that was found in the repository was 2024-05-18.)  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

                               2022-10-16                CAP_GET_FILE(3)

Pages that refer to this page: cap_clear(3)cap_copy_ext(3)cap_from_text(3)cap_get_proc(3)cap_init(3)libcap(3)capabilities(7)getcap(8)setcap(8)