sysdeps/unix/nice.c

   1 /* Copyright (C) 1992 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 Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 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 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ansidecl.h>
  20 #include <errno.h>
  21 #include <unistd.h>
  22 #include <sys/resource.h>
  23
  24 /* Increment the scheduling priority of the calling process by INCR.
  25    The superuser may use a negative INCR to decrement the priority.  */
  26 int
  27 DEFUN(nice, (incr), int incr)
  28 {
  29   int save;
  30   int prio;
  31
  32   /* -1 is a valid priority, so we use errno to check for an error.  */
  33   save = errno;
  34   errno = 0;
  35   prio = getpriority (PRIO_PROCESS, 0);
  36   if (prio == -1)
  37     {
  38       if (errno != 0)
  39         return -1;
  40       else
  41         errno = save;
  42     }
  43
  44   return setpriority (PRIO_PROCESS, 0, prio + incr);
  45 }