lib/waitpid.c

   1 /* Emulate waitpid on systems that just have wait.
   2    Copyright 1994, 1995, 1998, 1999, 2007 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 3, 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    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  18
  19 #if HAVE_CONFIG_H
  20 # include <config.h>
  21 #endif
  22
  23 #include <sys/types.h>
  24 #include <sys/stat.h>
  25
  26 #include <errno.h>
  27 #ifndef errno
  28 extern int errno;
  29 #endif
  30
  31 #define WAITPID_CHILDREN 8
  32 static pid_t waited_pid[WAITPID_CHILDREN];
  33 static int waited_status[WAITPID_CHILDREN];
  34
  35 pid_t
  36 waitpid (pid_t pid, int *stat_loc, int options)
  37 {
  38   int i;
  39   pid_t p;
  40
  41   if (!options && (pid == -1 || 0 < pid))
  42     {
  43       /* If we have already waited for this child, return it immediately.  */
  44       for (i = 0;  i < WAITPID_CHILDREN;  i++)
  45         {
  46           p = waited_pid[i];
  47           if (p && (p == pid || pid == -1))
  48             {
  49               waited_pid[i] = 0;
  50               goto success;
  51             }
  52         }
  53
  54       /* The child has not returned yet; wait for it, accumulating status.  */
  55       for (i = 0;  i < WAITPID_CHILDREN;  i++)
  56         if (! waited_pid[i])
  57           {
  58             p = wait (&waited_status[i]);
  59             if (p < 0)
  60               return p;
  61             if (p == pid || pid == -1)
  62               goto success;
  63             waited_pid[i] = p;
  64           }
  65     }
  66
  67   /* We cannot emulate this wait call, e.g. because of too many children.  */
  68   errno = EINVAL;
  69   return -1;
  70
  71 success:
  72   if (stat_loc)
  73     *stat_loc = waited_status[i];
  74   return p;
  75 }