support/xreadlink.c

   1 /* Error-checking, allocating wrapper for readlink.
   2    Copyright (C) 2017-2018 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <scratch_buffer.h>
  20 #include <support/check.h>
  21 #include <support/support.h>
  22 #include <xunistd.h>
  23
  24 char *
  25 xreadlink (const char *path)
  26 {
  27   struct scratch_buffer buf;
  28   scratch_buffer_init (&buf);
  29
  30   while (true)
  31     {
  32       ssize_t count = readlink (path, buf.data, buf.length);
  33       if (count < 0)
  34         FAIL_EXIT1 ("readlink (\"%s\"): %m", path);
  35       if (count < buf.length)
  36         {
  37           char *result = xstrndup (buf.data, count);
  38           scratch_buffer_free (&buf);
  39           return result;
  40         }
  41       if (!scratch_buffer_grow (&buf))
  42         FAIL_EXIT1 ("scratch_buffer_grow in xreadlink");
  43     }
  44 }