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waitpid.c

/* Emulate waitpid on systems that just have wait.
   Copyright 1994, 1995, 1998, 1999 Free Software Foundation, Inc.

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

   This program 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 General Public License for more details.

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

#if HAVE_CONFIG_H
# include <config.h>
#endif

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

#include <errno.h>
#ifndef errno
extern int errno;
#endif

#define WAITPID_CHILDREN 8
static pid_t waited_pid[WAITPID_CHILDREN];
static int waited_status[WAITPID_CHILDREN];

pid_t
waitpid (pid_t pid, int *stat_loc, int options)
{
  int i;
  pid_t p;

  if (!options && (pid == -1 || 0 < pid))
    {
      /* If we have already waited for this child, return it immediately.  */
      for (i = 0;  i < WAITPID_CHILDREN;  i++)
      {
        p = waited_pid[i];
        if (p && (p == pid || pid == -1))
          {
            waited_pid[i] = 0;
            goto success;
          }
      }

      /* The child has not returned yet; wait for it, accumulating status.  */
      for (i = 0;  i < WAITPID_CHILDREN;  i++)
      if (! waited_pid[i])
        {
          p = wait (&waited_status[i]);
          if (p < 0)
            return p;
          if (p == pid || pid == -1)
            goto success;
          waited_pid[i] = p;
        }
    }

  /* We cannot emulate this wait call, e.g. because of too many children.  */
  errno = EINVAL;
  return -1;

success:
  if (stat_loc)
    *stat_loc = waited_status[i];
  return p;
}

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