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

       int readlinkat(int dirfd, const char *pathname,
                      char *buf, size_t bufsiz);

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

           Since glibc 2.10:
               _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:

       The readlinkat() system call operates in exactly the same way as  read-
       link(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 readlink(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 readlink(2)).

       If pathname is absolute, then dirfd is ignored.

       Since Linux 2.6.39, pathname can be an empty string, in which case  the
       call  operates  on  the  file referred to by dirfd (which may have been
       obtained using the open(2) O_PATH flag).  In this case, dirfd can refer
       to any type of file, not just a directory.

       On success, readlinkat() returns the number of bytes placed in buf.  On
       error, -1 is returned and errno is set to indicate the error.

       The same errors that occur for readlink(2) can  also  occur  for  read-
       linkat().  The following additional errors can occur for readlinkat():

       EBADF  dirfd is not a valid file descriptor.

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

       readlinkat() was added to Linux in kernel 2.6.16; library  support  was
       This  page  is  part of release 3.54 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at

Linux                             2013-07-31                     READLINKAT(2)
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