1  /* getpriority for Linux.
       2     Copyright (C) 1996-2023 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)