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NAME

       faccessat - check user's permissions of a file relative to a directory file descriptor

SYNOPSIS

       #include <fcntl.h> /* Definition of AT_* constants */
       #include <unistd.h>

       int faccessat(int dirfd, const char *pathname, int mode, int flags);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       faccessat():
           Since glibc 2.10:
               _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:
               _ATFILE_SOURCE

DESCRIPTION

       The  faccessat() system call operates in exactly the same way as access(2), except for the
       differences described in this manual page.

       If the pathname given in pathname is relative, then it  is  interpreted  relative  to  the
       directory  referred  to  by the file descriptor dirfd (rather than relative to the current
       working directory of the  calling  process,  as  is  done  by  access(2)  for  a  relative
       pathname).

       If  pathname  is  relative  and  dirfd  is  the  special  value AT_FDCWD, then pathname is
       interpreted relative to the  current  working  directory  of  the  calling  process  (like
       access(2)).

       If pathname is absolute, then dirfd is ignored.

       flags is constructed by ORing together zero or more of the following values:

       AT_EACCESS
              Perform  access  checks  using  the  effective  user  and  group  IDs.  By default,
              faccessat() uses the real IDs (like access(2)).

       AT_SYMLINK_NOFOLLOW
              If pathname is a symbolic link, do not dereference it: instead  return  information
              about the link itself.

RETURN VALUE

       On  success,  (all  requested permissions granted) faccessat() returns 0.  On error, -1 is
       returned and errno is set to indicate the error.

ERRORS

       The same errors that occur for access(2) can also occur for  faccessat().   The  following
       additional errors can occur for faccessat():

       EBADF  dirfd is not a valid file descriptor.

       EINVAL Invalid flag specified in flags.

       ENOTDIR
              pathname  is relative and dirfd is a file descriptor referring to a file other than
              a directory.

VERSIONS

       faccessat() was added to Linux in kernel 2.6.16.

CONFORMING TO

       POSIX.1-2008.

NOTES

       See openat(2) for an explanation of the need for faccessat().

       Warning: faccessat() is subject to the same kinds of races as access(2) and euidaccess(3).

   Glibc Notes
       The AT_EACCESS and AT_SYMLINK_NOFOLLOW flags are actually  implemented  within  the  glibc
       wrapper  function  for  faccessat().   If  either  of  these flags are specified, then the
       wrapper function employs fstatat(2) to determine access permissions.

SEE ALSO

       access(2), openat(2), euidaccess(3), credentials(7), path_resolution(7), symlink(7)

COLOPHON

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       project,  and information about reporting bugs, can be found at http://man7.org/linux/man-
       pages/.