libiberty/fdmatch.c

   1 /* Compare two open file descriptors to see if they refer to the same file.
   2    Copyright (C) 1991 Free Software Foundation, Inc.
   3
   4 This file is part of the libiberty library.
   5 Libiberty is free software; you can redistribute it and/or
   6 modify it under the terms of the GNU Library General Public
   7 License as published by the Free Software Foundation; either
   8 version 2 of the License, or (at your option) any later version.
   9
  10 Libiberty 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 Library General Public License for more details.
  14
  15 You should have received a copy of the GNU Library General Public
  16 License along with libiberty; see the file COPYING.LIB.  If
  17 not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18 Boston, MA 02111-1307, USA.  */
  19
  20
  21 /*
  22
  23 NAME
  24
  25         fdmatch -- see if two file descriptors refer to same file
  26
  27 SYNOPSIS
  28
  29         int fdmatch (int fd1, int fd2)
  30
  31 DESCRIPTION
  32
  33         Check to see if two open file descriptors refer to the same file.
  34         This is useful, for example, when we have an open file descriptor
  35         for an unnamed file, and the name of a file that we believe to
  36         correspond to that fd.  This can happen when we are exec'd with
  37         an already open file (stdout for example) or from the SVR4 /proc
  38         calls that return open file descriptors for mapped address spaces.
  39         All we have to do is open the file by name and check the two file
  40         descriptors for a match, which is done by comparing major&minor
  41         device numbers and inode numbers.
  42
  43 BUGS
  44
  45         (FIXME: does this work for networks?)
  46         It works for NFS, which assigns a device number to each mount.
  47
  48 */
  49
  50 #include "ansidecl.h"
  51 #include "libiberty.h"
  52 #include <sys/types.h>
  53 #include <sys/stat.h>
  54
  55 int fdmatch (fd1, fd2)
  56         int fd1;
  57         int fd2;
  58 {
  59   struct stat sbuf1;
  60   struct stat sbuf2;
  61
  62   if ((fstat (fd1, &sbuf1) == 0) &&
  63       (fstat (fd2, &sbuf2) == 0) &&
  64       (sbuf1.st_dev == sbuf2.st_dev) &&
  65       (sbuf1.st_ino == sbuf2.st_ino))
  66     {
  67       return (1);
  68     }
  69   else
  70     {
  71       return (0);
  72     }
  73 }