1NICE(1P) POSIX Programmer's Manual NICE(1P)
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6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 nice — invoke a utility with an altered nice value
13
15 nice [-n increment] utility [argument...]
16
18 The nice utility shall invoke a utility, requesting that it be run with
19 a different nice value (see the Base Definitions volume of
20 POSIX.1‐2017, Section 3.244, Nice Value). With no options, the exe‐
21 cuted utility shall be run with a nice value that is some implementa‐
22 tion-defined quantity greater than or equal to the nice value of the
23 current process. If the user lacks appropriate privileges to affect the
24 nice value in the requested manner, the nice utility shall not affect
25 the nice value; in this case, a warning message may be written to stan‐
26 dard error, but this shall not prevent the invocation of utility or
27 affect the exit status.
28
30 The nice utility shall conform to the Base Definitions volume of
31 POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.
32 The following option is supported:
34 -n increment
36 A positive or negative decimal integer which shall have the
37 same effect on the execution of the utility as if the utility
38 had called the nice() function with the numeric value of the
39 increment option-argument.
40
42 The following operands shall be supported:
43 utility The name of a utility that is to be invoked. If the utility
45 operand names any of the special built-in utilities in Sec‐
46 tion 2.14, Special Built-In Utilities, the results are unde‐
47 fined.
48 argument Any string to be supplied as an argument when invoking the
50 utility named by the utility operand.
51
53 Not used.
54
56 None.
57
59 The following environment variables shall affect the execution of nice:
60 LANG Provide a default value for the internationalization vari‐
62 ables that are unset or null. (See the Base Definitions vol‐
63 ume of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
64 ables for the precedence of internationalization variables
65 used to determine the values of locale categories.)
66 LC_ALL If set to a non-empty string value, override the values of
68 all the other internationalization variables.
69 LC_CTYPE Determine the locale for the interpretation of sequences of
71 bytes of text data as characters (for example, single-byte as
72 opposed to multi-byte characters in arguments).
73 LC_MESSAGES
75 Determine the locale that should be used to affect the format
76 and contents of diagnostic messages written to standard
77 error.
78 NLSPATH Determine the location of message catalogs for the processing
80 of LC_MESSAGES.
81 PATH Determine the search path used to locate the utility to be
83 invoked. See the Base Definitions volume of POSIX.1‐2017,
84 Chapter 8, Environment Variables.
85
87 Default.
88
90 Not used.
91
93 The standard error shall be used only for diagnostic messages.
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96 None.
97
99 None.
100
102 If utility is invoked, the exit status of nice shall be the exit status
103 of utility; otherwise, the nice utility shall exit with one of the fol‐
104 lowing values:
105 1‐125 An error occurred in the nice utility.
107 126 The utility specified by utility was found but could not be
109 invoked.
110 127 The utility specified by utility could not be found.
112
114 Default.
115 The following sections are informative.
117
119 The only guaranteed portable uses of this utility are:
120 nice utility
122 Run utility with the default higher or equal nice value.
123 nice -n <positive integer> utility
125 Run utility with a higher nice value.
126 On some implementations they have no discernible effect on the invoked
128 utility and on some others they are exactly equivalent.
129 Historical systems have frequently supported the <positive integer> up
131 to 20. Since there is no error penalty associated with guessing a num‐
132 ber that is too high, users without access to the system conformance
133 document (to see what limits are actually in place) could use the his‐
134 torical 1 to 20 range or attempt to use very large numbers if the job
135 should be truly low priority.
136 The nice value of a process can be displayed using the command:
138 ps -o nice
141 The command, env, nice, nohup, time, and xargs utilities have been
143 specified to use exit code 127 if an error occurs so that applications
144 can distinguish ``failure to find a utility'' from ``invoked utility
145 exited with an error indication''. The value 127 was chosen because it
146 is not commonly used for other meanings; most utilities use small val‐
147 ues for ``normal error conditions'' and the values above 128 can be
148 confused with termination due to receipt of a signal. The value 126 was
149 chosen in a similar manner to indicate that the utility could be found,
150 but not invoked. Some scripts produce meaningful error messages differ‐
151 entiating the 126 and 127 cases. The distinction between exit codes 126
152 and 127 is based on KornShell practice that uses 127 when all attempts
153 to exec the utility fail with [ENOENT], and uses 126 when any attempt
154 to exec the utility fails for any other reason.
155
157 None.
158
160 The 4.3 BSD version of nice does not check whether increment is a valid
161 decimal integer. The command nice -x utility, for example, would be
162 treated the same as the command nice --1 utility. If the user does not
163 have appropriate privileges, this results in a ``permission denied''
164 error. This is considered a bug.
165 When a user without appropriate privileges gives a negative increment,
167 System V treats it like the command nice -0 utility, while 4.3 BSD
168 writes a ``permission denied'' message and does not run the utility.
169 The standard specifies the System V behavior together with an optional
170 BSD-style ``permission denied'' message.
171 The C shell has a built-in version of nice that has a different inter‐
173 face from the one described in this volume of POSIX.1‐2017.
174 The term ``utility'' is used, rather than ``command'', to highlight the
176 fact that shell compound commands, pipelines, and so on, cannot be
177 used. Special built-ins also cannot be used. However, ``utility''
178 includes user application programs and shell scripts, not just utili‐
179 ties defined in this volume of POSIX.1‐2017.
180 Historical implementations of nice provide a nice value range of 40 or
182 41 discrete steps, with the default nice value being the midpoint of
183 that range. By default, they raise the nice value of the executed util‐
184 ity by 10.
185 Some historical documentation states that the increment value must be
187 within a fixed range. This is misleading; the valid increment values on
188 any invocation are determined by the current process nice value, which
189 is not always the default.
190 The definition of nice value is not intended to suggest that all pro‐
192 cesses in a system have priorities that are comparable. Scheduling pol‐
193 icy extensions such as the realtime priorities in the System Interfaces
194 volume of POSIX.1‐2017 make the notion of a single underlying priority
195 for all scheduling policies problematic. Some implementations may
196 implement the nice-related features to affect all processes on the sys‐
197 tem, others to affect just the general time-sharing activities implied
198 by this volume of POSIX.1‐2017, and others may have no effect at all.
199 Because of the use of ``implementation-defined'' in nice and renice, a
200 wide range of implementation strategies are possible.
201 Earlier versions of this standard allowed a -increment option. This
203 form is no longer specified by POSIX.1‐2008 but may be present in some
204 implementations.
205
207 None.
208
210 Chapter 2, Shell Command Language, renice
211 The Base Definitions volume of POSIX.1‐2017, Section 3.244, Nice Value,
213 Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guide‐
214 lines
215 The System Interfaces volume of POSIX.1‐2017, nice()
217
219 Portions of this text are reprinted and reproduced in electronic form
220 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
221 table Operating System Interface (POSIX), The Open Group Base Specifi‐
222 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
223 Electrical and Electronics Engineers, Inc and The Open Group. In the
224 event of any discrepancy between this version and the original IEEE and
225 The Open Group Standard, the original IEEE and The Open Group Standard
226 is the referee document. The original Standard can be obtained online
227 at http://www.opengroup.org/unix/online.html .
228 Any typographical or formatting errors that appear in this page are
230 most likely to have been introduced during the conversion of the source
231 files to man page format. To report such errors, see https://www.ker‐
232 nel.org/doc/man-pages/reporting_bugs.html .
233IEEE/The Open Group 2017 NICE(1P)