1 .\" Copyright (c) 1992 Drew Eckhardt <drew@cs.colorado.edu>, March 28, 1992
3 .\" %%%LICENSE_START(VERBATIM)
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25 .\" Modified by Michael Haardt <michael@moria.de>
26 .\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu>
27 .\" Modified 1996-11-04 by Eric S. Raymond <esr@thyrsus.com>
28 .\" Modified 2001-06-04 by aeb
29 .\" Modified 2004-05-27 by Michael Kerrisk <mtk.manpages@gmail.com>
31 .TH NICE 2 2016-12-12 "Linux" "Linux Programmer's Manual"
33 nice \- change process priority
35 .B #include <unistd.h>
37 .BI "int nice(int " inc );
40 Feature Test Macro Requirements for glibc (see
41 .BR feature_test_macros (7)):
46 || /* Since glibc 2.19: */ _DEFAULT_SOURCE
47 || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
52 to the nice value for the calling thread.
53 (A higher nice value means a low priority.)
55 The range of the nice value is +19 (low priority) to \-20 (high priority).
56 Attempts to set a nice value outside the range are clamped to the range.
58 Traditionally, only a privileged process could lower the nice value
59 (i.e., set a higher priority).
60 However, since Linux 2.6.12, an unprivileged process can decrease
61 the nice value of a target process that has a suitable
67 On success, the new nice value is returned (but see NOTES below).
68 On error, \-1 is returned, and
72 A successful call can legitimately return \-1.
73 To detect an error, set
75 to 0 before the call, and check whether it is nonzero after
81 The calling process attempted to increase its priority by
84 but has insufficient privileges.
87 capability is required.
88 (But see the discussion of the
93 POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD.
94 However, the raw system call and (g)libc
95 (earlier than glibc 2.2.4) return value is nonstandard, see below.
96 .\" SVr4 documents an additional
100 For further details on the nice value, see
104 the addition of the "autogroup" feature in Linux 2.6.38 means that
105 the nice value no longer has its traditional effect in many circumstances.
109 .SS C library/kernel differences
110 POSIX.1 specifies that
112 should return the new nice value.
113 However, the raw Linux system call returns 0 on success.
116 wrapper function provided in glibc 2.2.3 and earlier returns 0 on success.
118 Since glibc 2.2.4, the
120 wrapper function provided by glibc provides conformance to POSIX.1 by calling
122 to obtain the new nice value, which is then returned to the caller.
130 .BR capabilities (7),