sysdeps/unix/nice.c

   1 /* Copyright (C) 1992, 1996, 1997, 2001, 2002 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <unistd.h>
  21 #include <sys/resource.h>
  22
  23 /* Increment the scheduling priority of the calling process by INCR.
  24    The superuser may use a negative INCR to decrement the priority.  */
  25 int
  26 nice (int incr)
  27 {
  28   int save;
  29   int prio;
  30   int result;
  31
  32   /* -1 is a valid priority, so we use errno to check for an error.  */
  33   save = errno;
  34   __set_errno (0);
  35   prio = getpriority (PRIO_PROCESS, 0);
  36   if (prio == -1)
  37     {
  38       if (errno != 0)
  39         return -1;
  40       else
  41         __set_errno (save);
  42     }
  43
  44   prio += incr;
  45   if (prio < PRIO_MIN)
  46     prio = PRIO_MIN;
  47   else if (prio >= PRIO_MAX)
  48     prio = PRIO_MAX - 1;
  49   result = setpriority (PRIO_PROCESS, 0, prio);
  50   if (result != -1)
  51     return getpriority (PRIO_PROCESS, 0);
  52   else
  53     return -1;
  54
  55 }