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  -  capability
       manipulation on files

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);

       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

       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
       effective capability, CAP_SETFCAP, enabled and either the effective
       user ID of the process must match the file owner or the calling
       process must have the CAP_FOWNER flag in its effective capability
       set.  The effects of writing the capability state to any file type
       other than a regular file are undefined.

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       These functions are specified by withdrawn POSIX.1e draft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)

COLOPHON         top

       This page is part of the libcap (capabilities commands and library)
       project.  Information about the project can be found at 
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                                 2008-05-11                  CAP_GET_FILE(3)