lib/waitpid.c

   1 /* Emulate waitpid on systems that just have wait.
   2    Copyright 1994, 1995, 1998, 1999 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; see the file COPYING.
  16    If not, write to the Free Software Foundation,
  17    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  18
  19 #if HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 #include <errno.h>
  24 #ifndef errno
  25 extern int errno;
  26 #endif
  27
  28 #define WAITPID_CHILDREN 8
  29 static pid_t waited_pid[WAITPID_CHILDREN];
  30 static int waited_status[WAITPID_CHILDREN];
  31
  32 pid_t
  33 waitpid (pid_t pid, int *stat_loc, int options)
  34 {
  35   int i;
  36   pid_t p;
  37
  38   if (!options && (pid == -1 || 0 < pid))
  39     {
  40       /* If we have already waited for this child, return it immediately.  */
  41       for (i = 0;  i < WAITPID_CHILDREN;  i++)
  42         {
  43           p = waited_pid[i];
  44           if (p && (p == pid || pid == -1))
  45             {
  46               waited_pid[i] = 0;
  47               goto success;
  48             }
  49         }
  50
  51       /* The child has not returned yet; wait for it, accumulating status.  */
  52       for (i = 0;  i < WAITPID_CHILDREN;  i++)
  53         if (! waited_pid[i])
  54           {
  55             p = wait (&waited_status[i]);
  56             if (p < 0)
  57               return p;
  58             if (p == pid || pid == -1)
  59               goto success;
  60             waited_pid[i] = p;
  61           }
  62     }
  63
  64   /* We cannot emulate this wait call, e.g. because of too many children.  */
  65   errno = EINVAL;
  66   return -1;
  67
  68 success:
  69   if (stat_loc)
  70     *stat_loc = waited_status[i];
  71   return p;
  72 }