lib/rename.c

   1 /* BSD compatible rename and directory rename function for System V.
   2    Copyright (C) 1988, 1990 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 #if HAVE_CONFIG_H
  19 # include <config.h>
  20 #endif
  21
  22 #include <sys/types.h>
  23 #include <sys/stat.h>
  24 #include <errno.h>
  25 #ifndef errno
  26 extern int errno;
  27 #endif
  28
  29 #if STAT_MACROS_BROKEN
  30 # undef S_ISDIR
  31 #endif
  32
  33 #if !defined(S_ISDIR) && defined(S_IFDIR)
  34 # define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
  35 #endif
  36
  37 /* Rename file FROM to file TO.
  38    Return 0 if successful, -1 if not. */
  39
  40 int
  41 rename (from, to)
  42      char *from;
  43      char *to;
  44 {
  45   struct stat from_stats, to_stats;
  46   int pid, status;
  47
  48   if (stat (from, &from_stats))
  49     return -1;
  50
  51   /* Be careful not to unlink `from' if it happens to be equal to `to' or
  52      (on filesystems that silently truncate filenames after 14 characters)
  53      if `from' and `to' share the significant characters. */
  54   if (stat (to, &to_stats))
  55     {
  56       if (errno != ENOENT)
  57         return -1;
  58     }
  59   else
  60     {
  61       if ((from_stats.st_dev == to_stats.st_dev)
  62           && (from_stats.st_ino == to_stats.st_ino))
  63         /* `from' and `to' designate the same file on that filesystem. */
  64         return 0;
  65
  66       if (unlink (to) && errno != ENOENT)
  67         return -1;
  68     }
  69
  70 #ifdef MVDIR
  71
  72 /* If MVDIR is defined, it should be the full filename of a setuid root
  73    program able to link and unlink directories.  If MVDIR is not defined,
  74    then the capability of renaming directories may be missing.  */
  75
  76   if (S_ISDIR (from_stats.st_mode))
  77     {
  78       /* Need a setuid root process to link and unlink directories. */
  79       pid = fork ();
  80       switch (pid)
  81         {
  82         case -1:                /* Error. */
  83           error (1, errno, "cannot fork");
  84
  85         case 0:                 /* Child. */
  86           execl (MVDIR, "mvdir", from, to, (char *) 0);
  87           error (255, errno, "cannot run `%s'", MVDIR);
  88
  89         default:                /* Parent. */
  90           while (wait (&status) != pid)
  91             /* Do nothing. */ ;
  92
  93           errno = 0;            /* mvdir printed the system error message. */
  94           if (status)
  95             return -1;
  96         }
  97     }
  98   else
  99
 100 #endif /* MVDIR */
 101
 102     {
 103       if (link (from, to))
 104         return -1;
 105       if (unlink (from) && errno != ENOENT)
 106         {
 107           unlink (to);
 108           return -1;
 109         }
 110     }
 111   return 0;
 112 }