sysdeps/posix/nice.c

   1 /* Copyright (C) 1992-2021 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, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <unistd.h>
  20 #include <sys/resource.h>
  21
  22 /* Increment the scheduling priority of the calling process by INCR.
  23    The superuser may use a negative INCR to decrement the priority.  */
  24 int
  25 nice (int incr)
  26 {
  27   int save;
  28   int prio;
  29   int result;
  30
  31   /* -1 is a valid priority, so we use errno to check for an error.  */
  32   save = errno;
  33   __set_errno (0);
  34   prio = __getpriority (PRIO_PROCESS, 0);
  35   if (prio == -1)
  36     {
  37       if (errno != 0)
  38         return -1;
  39     }
  40
  41   result = __setpriority (PRIO_PROCESS, 0, prio + incr);
  42   if (result == -1)
  43     {
  44       if (errno == EACCES)
  45         __set_errno (EPERM);
  46       return -1;
  47     }
  48
  49   __set_errno (save);
  50   return __getpriority (PRIO_PROCESS, 0);
  51 }