1  /* Copyright (C) 1992-2023 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  }