lib/areadlink.c

   1 /* areadlink.c -- readlink wrapper to return the link name in malloc'd storage
   2    Unlike xreadlink and xreadlink_with_size, don't ever call exit.
   3
   4    Copyright (C) 2001, 2003-2007, 2009-2019 Free Software Foundation, Inc.
   5
   6    This program is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 /* Written by Jim Meyering <jim@meyering.net>
  20    and Bruno Haible <bruno@clisp.org>.  */
  21
  22 #include <config.h>
  23
  24 /* Specification.  */
  25 #include "areadlink.h"
  26
  27 #include "careadlinkat.h"
  28
  29 #include <stdlib.h>
  30 #include <unistd.h>
  31
  32 /* Get the symbolic link value of FILENAME and put it into BUFFER, with
  33    size BUFFER_SIZE.  This function acts like readlink but has
  34    readlinkat's signature.  */
  35 static ssize_t
  36 careadlinkatcwd (int fd, char const *filename, char *buffer,
  37                  size_t buffer_size)
  38 {
  39   /* FD must be AT_FDCWD here, otherwise the caller is using this
  40      function in contexts it was not meant for.  */
  41   if (fd != AT_FDCWD)
  42     abort ();
  43   return readlink (filename, buffer, buffer_size);
  44 }
  45
  46 /* Call readlink to get the symbolic link value of FILENAME.
  47    Return a pointer to that NUL-terminated string in malloc'd storage.
  48    If readlink fails, return NULL and set errno.
  49    If allocation fails, or if the link value is longer than SIZE_MAX :-),
  50    return NULL and set errno to ENOMEM.  */
  51
  52 char *
  53 areadlink (char const *filename)
  54 {
  55   return careadlinkat (AT_FDCWD, filename, NULL, 0, NULL, careadlinkatcwd);
  56 }