lib/lstat.c

   1 /* Work around the bug in some systems whereby lstat succeeds when
   2    given the zero-length file name argument.  The lstat from SunOS4.1.4
   3    has this bug.
   4    Copyright (C) 1997-2000 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 2, or (at your option)
   9    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, write to the Free Software Foundation,
  18    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 /* written by Jim Meyering */
  21
  22 #include <config.h>
  23
  24 #include <sys/types.h>
  25 #include <sys/stat.h>
  26 #include <errno.h>
  27 #ifndef errno
  28 extern int errno;
  29 #endif
  30
  31 #ifdef STAT_MACROS_BROKEN
  32 # undef S_ISLNK
  33 #endif
  34 #if !defined(S_ISLNK) && defined(S_IFLNK)
  35 # define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
  36 #endif
  37
  38 char *xmalloc ();
  39
  40 /* lstat works different on Linux and Solaris systems.  POSIX (see
  41    `pathname resolution' in the glossary) requires that programs like `ls'
  42    take into consideration the fact that FILE has a trailing slash when
  43    FILE is a symbolic link.  On Linux systems, the lstat function already
  44    has the desired semantics (in treating `lstat("symlink/",sbuf)' just like
  45    `lstat("symlink/.",sbuf)', but on Solaris it does not.
  46
  47    If FILE has a trailing slash and specifies a symbolic link,
  48    then append a `.' to FILE and call lstat a second time.  */
  49
  50 static int
  51 slash_aware_lstat (const char *file, struct stat *sbuf)
  52 {
  53   size_t len;
  54   char *new_file;
  55
  56   int lstat_result = lstat (file, sbuf);
  57
  58   if (lstat_result != 0 || !S_ISLNK (sbuf->st_mode))
  59     return lstat_result;
  60
  61   len = strlen (file);
  62   if (file[len - 1] != '/')
  63     return lstat_result;
  64
  65   /* FILE refers to a symbolic link and the name ends with a slash.
  66      Append a `.' to FILE and repeat the lstat call.  */
  67
  68   /* Add one for the `.' we might have to append, and one more
  69      for the trailing NUL.  */
  70   new_file = xmalloc (len + 1 + 1);
  71   memcpy (new_file, file, len);
  72   new_file[len] = '.';
  73   new_file[len + 1] = 0;
  74
  75   lstat_result = lstat (new_file, sbuf);
  76   free (new_file);
  77
  78   return lstat_result;
  79 }
  80
  81 /* This is a wrapper for lstat(2).
  82    If FILE is the empty string, fail with errno == ENOENT.
  83    Otherwise, return the result of calling the real lstat.
  84
  85    This works around the bug in some systems whereby lstat succeeds when
  86    given the zero-length file name argument.  The lstat from SunOS4.1.4
  87    has this bug.  */
  88
  89 /* This function also provides a version of lstat with consistent semantics
  90    when FILE specifies a symbolic link and has a trailing slash.  */
  91
  92 int
  93 rpl_lstat (const char *file, struct stat *sbuf)
  94 {
  95   if (file && *file == 0)
  96     {
  97       errno = ENOENT;
  98       return -1;
  99     }
 100
 101   return slash_aware_lstat (file, sbuf);
 102 }