sysdeps/unix/sysv/linux/getpriority.c

   1 /* getpriority for Linux.
   2    Copyright (C) 1996-2019 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <sys/resource.h>
  21
  22 #include <sysdep.h>
  23 #include <sys/syscall.h>
  24
  25 /* The return value of getpriority syscall is biased by this value
  26    to avoid returning negative values.  */
  27 #define PZERO 20
  28
  29 /* Return the highest priority of any process specified by WHICH and WHO
  30    (see above); if WHO is zero, the current process, process group, or user
  31    (as specified by WHO) is used.  A lower priority number means higher
  32    priority.  Priorities range from PRIO_MIN to PRIO_MAX.  */
  33
  34 int
  35 __getpriority (enum __priority_which which, id_t who)
  36 {
  37   int res;
  38
  39   res = INLINE_SYSCALL (getpriority, 2, (int) which, who);
  40   if (res >= 0)
  41     res = PZERO - res;
  42   return res;
  43 }
  44 libc_hidden_def (__getpriority)
  45 weak_alias (__getpriority, getpriority)