glibc/sysvipc/ftok.c

/* Copyright (C) 1995, 1996 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995.

The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.

The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Library General Public License for more details.

You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB.  If
not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

#include <sys/ipc.h>
#include <sys/stat.h>

key_t
ftok (pathname, proj_id)
     char *pathname;
     char proj_id;
{
  struct stat st;
  key_t key;

  if (__stat (pathname, &st) < 0)
    return (key_t) -1;

  key = (st.st_ino & 0xffff) | ((st.st_dev & 0xff) << 16) | (proj_id << 24);

  return key;
}