1/* Copyright (C) 1992-2024 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. */
24int
25nice (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}
52

source code of glibc/sysdeps/posix/nice.c