sysdeps/posix/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, see
  17    <http://www.gnu.org/licenses/>.  */
  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   result = setpriority (PRIO_PROCESS, 0, prio + incr);
  45   if (result == -1)
  46     {
  47       if (errno == EACCES)
  48         errno = EPERM;
  49       return -1;
  50     }
  51   return getpriority (PRIO_PROCESS, 0);
  52 }