sysdeps/unix/nice.c

   1 /* Copyright (C) 1992, 1996, 1997, 2001, 2002, 2006
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  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 nice (int incr)
  28 {
  29   int save;
  30   int prio;
  31   int result;
  32
  33   /* -1 is a valid priority, so we use errno to check for an error.  */
  34   save = errno;
  35   __set_errno (0);
  36   prio = getpriority (PRIO_PROCESS, 0);
  37   if (prio == -1)
  38     {
  39       if (errno != 0)
  40         return -1;
  41       else
  42         __set_errno (save);
  43     }
  44
  45   result = setpriority (PRIO_PROCESS, 0, prio + incr);
  46   if (result == -1)
  47     {
  48       if (errno == EACCES)
  49         errno = EPERM;
  50       return -1;
  51     }
  52   return getpriority (PRIO_PROCESS, 0);
  53 }