readlink(2)                   System Calls Manual                  readlink(2)

<?><?><?>
       readlink, readlinkat - <?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?>

LIBRARY
       Standard C library (libc, -lc)

<?><?><?><?><?><?><?><?><?>
       #include <unistd.h>

       ssize_t readlink(const char *restrict pathname, char *restrict buf,
                        size_t bufsiz);

       #include <fcntl.h>            /* <?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?> AT_* */
       #include <unistd.h>

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

   <?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?>
   <?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?> <?><?><?> glibc
   (<?><?>. feature_test_macros(7)):

       readlink():
           _XOPEN_SOURCE >= 500 || _POSIX_C_SOURCE >= 200112L
               || /* glibc <= 2.19: */ _BSD_SOURCE

       readlinkat():
           <?><?><?><?><?><?><?> <?> glibc 2.10:
               _POSIX_C_SOURCE >= 200809L
           <?><?> glibc 2.10:
               _ATFILE_SOURCE

<?><?><?><?><?><?><?><?>
       readlink()  places the contents of the symbolic link pathname in the
       buffer buf, which has size bufsiz.  readlink()  does not append a
       terminating null byte to buf.  It will (silently) truncate the contents
       (to a length of bufsiz characters), in case the buffer is too small to
       hold all of the contents.

   readlinkat()
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?> readlinkat()
       <?><?><?><?><?><?><?><?> <?><?><?><?><?> <?><?><?>
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?> readlink(), <?><?>
       <?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?>,
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?>.

       <?><?><?><?> <?> pathname <?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?>, <?><?> <?><?>
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?>, <?><?> <?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?> dirfd (<?> <?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>, <?><?><?>
       <?><?><?> <?><?><?><?><?><?><?><?> <?> readlink()).

       <?><?><?><?> <?> pathname <?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?> <?> dirfd
       <?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?> AT_FDCWD, <?><?> pathname
       <?><?><?><?><?><?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?> (<?><?><?>
       readlink()).

       <?><?><?><?> <?> pathname <?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?> <?><?><?><?>, <?><?> dirfd
       <?><?><?><?><?><?><?><?><?><?><?><?>.

       <?><?><?><?><?><?><?> <?> Linux .6.39, pathname <?><?><?><?><?>
       <?><?><?><?> <?><?><?><?><?><?> <?><?><?><?><?><?><?>; <?><?><?>
       <?><?><?><?> <?><?><?><?><?> <?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?> <?> <?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?>, <?><?> <?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?> dirfd (<?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?> <?> <?><?><?><?><?><?><?>
       <?><?><?><?><?><?> open(2) <?> <?><?><?><?><?><?><?> O_PATH <?>
       O_NOFOLLOW).

       <?><?><?><?><?><?><?><?> <?> openat(2) <?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?> readlinkat().

<?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?> <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?>
       <?><?><?> <?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?> <?><?><?><?>,
       <?><?><?><?><?><?><?><?><?><?> <?> buf (<?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?> bufsiz, <?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?>). <?>
       <?><?><?><?><?><?> <?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?> -1, <?> errno
       <?><?><?><?><?><?><?><?><?><?><?><?><?><?><?> <?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>.

<?><?><?><?><?><?>
       EACCES <?> <?><?><?><?><?> <?><?> <?><?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?> <?><?><?><?> <?><?>
              <?><?><?><?><?><?><?><?> <?><?><?><?><?> (<?><?>.
              <?><?><?><?><?> path_resolution(7).

       EBADF  (readlinkat())  pathname is relative but dirfd is neither
              AT_FDCWD nor a valid file descriptor.

       EFAULT buf <?><?><?><?><?><?><?> <?><?> <?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?><?><?><?><?>,
              <?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>.

       EINVAL <?><?><?><?><?><?><?><?> bufsiz <?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?>.

       EINVAL <?><?><?><?><?><?><?><?><?> <?><?><?><?> (<?>. <?>.,
              <?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?>
              <?><?><?><?><?> <?><?><?><?><?> pathname) <?><?>
              <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?>.

       EIO    <?><?><?> <?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?> <?><?><?><?><?>-<?><?><?><?><?><?>.

       ELOOP  <?><?> <?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?>
              pathname <?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?>
              <?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?>.

       ENAMETOOLONG
              <?><?><?><?><?><?><?> <?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?> pathname
              <?><?><?> <?><?><?> <?><?><?><?><?>.

       ENOENT <?><?><?><?><?><?><?><?><?> <?><?><?><?> <?><?>
              <?><?><?><?><?><?><?><?><?><?>.

       ENOMEM <?><?><?><?><?><?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?> <?><?><?><?>.

       ENOTDIR
              <?><?><?><?><?><?><?><?><?> <?> <?><?><?><?><?><?><?><?>
              <?><?><?><?> <?><?> <?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?><?>.

       ENOTDIR
              (readlinkat())  <?><?><?><?><?><?><?><?> pathname
              <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?><?><?>
              <?><?><?><?> <?> dirfd <?><?><?><?><?><?><?><?>
              <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?>,
              <?><?><?><?><?><?><?><?><?><?><?> <?><?> <?><?><?><?>, <?>
              <?><?> <?><?> <?><?><?><?><?><?><?>.

<?><?><?><?><?><?><?><?><?>
       POSIX.1-2008.

<?><?><?><?><?><?><?>
       readlink()
              4.4BSD (first appeared in 4.2BSD), POSIX.1-2001, POSIX.1-2008.

       readlinkat()
              POSIX.1-2008.  Linux 2.6.16, glibc 2.4.

       Up to and including glibc 2.4, the return type of readlink()  was
       declared as int.  Nowadays, the return type is declared as ssize_t, as
       (newly) required in POSIX.1-2001.

   glibc
       <?> <?><?><?><?><?><?> <?><?><?><?><?>, <?><?><?> readlinkat()
       <?><?><?><?><?><?><?><?><?><?><?>, <?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?> glibc <?><?><?><?><?><?><?><?><?><?> readlink().
       <?><?><?><?> pathname <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?>, <?><?> glibc
       <?><?><?><?><?><?><?><?> <?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?> <?>
       /proc/self/fd, <?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?>
       dirfd.

<?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?> <?> <?><?><?><?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?> <?><?><?><?><?> <?><?> <?><?><?><?><?><?><?>
       <?><?><?> <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?>.
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?> <?><?><?><?><?><?>
       <?><?><?><?><?> <?><?><?><?><?><?><?><?> <?><?><?>
       <?><?><?><?><?><?><?><?> stat.st_size,
       <?><?><?><?><?><?><?><?><?><?><?><?> <?><?> <?><?><?><?><?><?>
       <?><?><?><?><?><?><?> lstat(2). <?><?><?><?><?><?>,
       <?><?><?><?><?><?><?><?><?><?> <?><?><?><?>,
       <?><?><?><?><?><?><?><?><?><?> readlink() <?> readlinkat(),
       <?><?><?><?><?><?> <?><?><?><?> <?><?><?><?><?><?><?><?><?>, <?><?><?>
       <?><?><?> <?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?>,
       <?><?><?> <?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?> <?><?> <?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?> <?><?><?><?><?><?><?><?>.
       <?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?> <?><?><?> readlink() <?> readlinkat()
       <?><?><?><?><?> <?><?><?><?><?><?><?> <?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?> <?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?><?>, <?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?>, <?><?><?><?><?> <?><?><?>
       <?><?><?><?><?><?><?> <?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?> PATH_MAX, <?><?>
       <?><?><?><?><?><?><?><?> POSIX <?><?><?> <?><?><?><?>
       <?><?><?><?><?><?><?><?><?> <?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?>, <?><?><?> <?><?><?>
       <?><?><?><?><?><?><?><?><?><?> , <?><?><?><?> <?><?><?><?><?><?><?>
       <?><?> <?><?><?><?><?> <?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?>.

<?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?>, <?><?><?><?><?><?><?><?><?><?><?> readlink(), <?><?>
       <?><?><?><?><?><?><?><?><?><?>,
       <?><?><?><?><?><?><?><?><?><?><?><?><?><?><?> lstat(2), <?><?><?>
       <?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?> <?><?><?><?><?><?><?><?>
       PATH_MAX, <?><?><?><?> lstat(2) <?><?><?><?><?><?>
       <?><?><?><?><?><?><?> <?><?><?><?><?><?>.

       #include <limits.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/stat.h>
       #include <unistd.h>

       int
       main(int argc, char *argv[])
       {
           char         *buf;
           ssize_t      nbytes, bufsiz;
           struct stat  sb;

           if (argc != 2) {
               fprintf(stderr, "Usage: %s <pathname>\n", argv[0]);
               exit(EXIT_FAILURE);
           }

           if (lstat(argv[1], &sb) == -1) {
               perror("lstat");
               exit(EXIT_FAILURE);
           }

           /* Add one to the link size, so that we can determine whether
              the buffer returned by readlink() was truncated. */

           bufsiz = sb.st_size + 1;

           /* Some magic symlinks under (for example) /proc and /sys
              report 'st_size' as zero. In that case, take PATH_MAX as
              a "good enough" estimate. */

           if (sb.st_size == 0)
               bufsiz = PATH_MAX;

           buf = malloc(bufsiz);
           if (buf == NULL) {
               perror("malloc");
               exit(EXIT_FAILURE);
           }

           nbytes = readlink(argv[1], buf, bufsiz);
           if (nbytes == -1) {
               perror("readlink");
               exit(EXIT_FAILURE);
           }

           /* Print only 'nbytes' of 'buf', as it doesn't contain a terminating
              null byte ('\0'). */
           printf("'%s' points to '%.*s'\n", argv[1], (int) nbytes, buf);

           /* If the return value was equal to the buffer size, then
              the link target was larger than expected (perhaps because the
              target was changed between the call to lstat() and the call to
              readlink()). Warn the user that the returned target may have
              been truncated. */

           if (nbytes == bufsiz)
               printf("(Returned buffer may have been truncated)\n");

           free(buf);
           exit(EXIT_SUCCESS);
       }

<?><?>. <?><?><?><?><?>
       readlink(1), lstat(2), stat(2), symlink(2), realpath(3),
       path_resolution(7), symlink(7)

<?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?> <?><?><?><?><?><?><?> <?><?><?><?>
       <?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?> <?><?><?>
       <?><?><?><?><?><?> aereiae <aereiae@gmail.com>, Azamat Hackimov
       <azamat.hackimov@gmail.com>, Dmitriy S. Seregin <dseregin@59.ru>,
       Katrin Kutepova <blackkatelv@gmail.com>, Lockal <lockalsash@gmail.com>,
       Yuri Kozlov <yuray@komyakino.ru>, <?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?> <?> <?><?><?><?> <?><?><?><?><?><?>
       <pavia00@gmail.com>

       <?><?><?><?> <?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?><?><?>;
       <?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?> GNU
       <?><?><?><?><?><?> 3 <https://www.gnu.org/licenses/gpl-3.0.html>
       <?><?><?> <?><?><?><?><?> <?><?><?><?><?><?><?>, <?><?><?><?><?>
       <?><?><?><?><?><?> <?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?>. <?><?> <?><?>
       <?><?><?><?><?> <?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?><?><?><?><?>.

       <?><?><?><?> <?><?> <?><?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?>
       <?> <?><?><?><?><?><?><?><?> <?><?><?><?> <?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?><?><?><?><?><?>, <?><?><?><?><?><?><?><?><?><?>,
       <?><?><?><?><?><?><?><?><?> <?><?><?><?><?><?><?><?><?><?><?>
       <?><?><?><?><?><?> <?><?> <man-pages-ru-talks@lists.sourceforge.net>.

Linux man-pages 6.06    1 <?><?><?><?><?><?> 2023 <?>.             readlink(2)