nice(1p) — Linux manual page


NICE(1P)                POSIX Programmer's Manual               NICE(1P)

PROLOG         top

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME         top

       nice — invoke a utility with an altered nice value

SYNOPSIS         top

       nice [-n increment] utility [argument...]

DESCRIPTION         top

       The nice utility shall invoke a utility, requesting that it be
       run with a different nice value (see the Base Definitions volume
       of POSIX.1‐2017, Section 3.244, Nice Value).  With no options,
       the executed utility shall be run with a nice value that is some
       implementation-defined quantity greater than or equal to the nice
       value of the current process. If the user lacks appropriate
       privileges to affect the nice value in the requested manner, the
       nice utility shall not affect the nice value; in this case, a
       warning message may be written to standard error, but this shall
       not prevent the invocation of utility or affect the exit status.

OPTIONS         top

       The nice utility shall conform to the Base Definitions volume of
       POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.

       The following option is supported:

       -n increment
                 A positive or negative decimal integer which shall have
                 the same effect on the execution of the utility as if
                 the utility had called the nice() function with the
                 numeric value of the increment option-argument.

OPERANDS         top

       The following operands shall be supported:

       utility   The name of a utility that is to be invoked. If the
                 utility operand names any of the special built-in
                 utilities in Section 2.14, Special Built-In Utilities,
                 the results are undefined.

       argument  Any string to be supplied as an argument when invoking
                 the utility named by the utility operand.

STDIN         top

       Not used.

INPUT FILES         top



       The following environment variables shall affect the execution of

       LANG      Provide a default value for the internationalization
                 variables that are unset or null. (See the Base
                 Definitions volume of POSIX.1‐2017, Section 8.2,
                 Internationalization Variables for the precedence of
                 internationalization variables used to determine the
                 values of locale categories.)

       LC_ALL    If set to a non-empty string value, override the values
                 of all the other internationalization variables.

       LC_CTYPE  Determine the locale for the interpretation of
                 sequences of bytes of text data as characters (for
                 example, single-byte as opposed to multi-byte
                 characters in arguments).

                 Determine the locale that should be used to affect the
                 format and contents of diagnostic messages written to
                 standard error.

       NLSPATH   Determine the location of message catalogs for the
                 processing of LC_MESSAGES.

       PATH      Determine the search path used to locate the utility to
                 be invoked.  See the Base Definitions volume of
                 POSIX.1‐2017, Chapter 8, Environment Variables.



STDOUT         top

       Not used.

STDERR         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top




EXIT STATUS         top

       If utility is invoked, the exit status of nice shall be the exit
       status of utility; otherwise, the nice utility shall exit with
       one of the following values:

       1‐125   An error occurred in the nice utility.

         126   The utility specified by utility was found but could not
               be invoked.

         127   The utility specified by utility could not be found.



       The following sections are informative.


       The only guaranteed portable uses of this utility are:

       nice utility
             Run utility with the default higher or equal nice value.

       nice -n <positive integer> utility
             Run utility with a higher nice value.

       On some implementations they have no discernible effect on the
       invoked utility and on some others they are exactly equivalent.

       Historical systems have frequently supported the <positive
       integer> up to 20. Since there is no error penalty associated
       with guessing a number that is too high, users without access to
       the system conformance document (to see what limits are actually
       in place) could use the historical 1 to 20 range or attempt to
       use very large numbers if the job should be truly low priority.

       The nice value of a process can be displayed using the command:

           ps -o nice

       The command, env, nice, nohup, time, and xargs utilities have
       been specified to use exit code 127 if an error occurs so that
       applications can distinguish ``failure to find a utility'' from
       ``invoked utility exited with an error indication''. The value
       127 was chosen because it is not commonly used for other
       meanings; most utilities use small values for ``normal error
       conditions'' and the values above 128 can be confused with
       termination due to receipt of a signal. The value 126 was chosen
       in a similar manner to indicate that the utility could be found,
       but not invoked. Some scripts produce meaningful error messages
       differentiating the 126 and 127 cases. The distinction between
       exit codes 126 and 127 is based on KornShell practice that uses
       127 when all attempts to exec the utility fail with [ENOENT], and
       uses 126 when any attempt to exec the utility fails for any other

EXAMPLES         top


RATIONALE         top

       The 4.3 BSD version of nice does not check whether increment is a
       valid decimal integer. The command nice -x utility, for example,
       would be treated the same as the command nice --1 utility.  If
       the user does not have appropriate privileges, this results in a
       ``permission denied'' error.  This is considered a bug.

       When a user without appropriate privileges gives a negative
       increment, System V treats it like the command nice -0 utility,
       while 4.3 BSD writes a ``permission denied'' message and does not
       run the utility. The standard specifies the System V behavior
       together with an optional BSD-style ``permission denied''

       The C shell has a built-in version of nice that has a different
       interface from the one described in this volume of POSIX.1‐2017.

       The term ``utility'' is used, rather than ``command'', to
       highlight the fact that shell compound commands, pipelines, and
       so on, cannot be used. Special built-ins also cannot be used.
       However, ``utility'' includes user application programs and shell
       scripts, not just utilities defined in this volume of

       Historical implementations of nice provide a nice value range of
       40 or 41 discrete steps, with the default nice value being the
       midpoint of that range. By default, they raise the nice value of
       the executed utility by 10.

       Some historical documentation states that the increment value
       must be within a fixed range. This is misleading; the valid
       increment values on any invocation are determined by the current
       process nice value, which is not always the default.

       The definition of nice value is not intended to suggest that all
       processes in a system have priorities that are comparable.
       Scheduling policy extensions such as the realtime priorities in
       the System Interfaces volume of POSIX.1‐2017 make the notion of a
       single underlying priority for all scheduling policies
       problematic. Some implementations may implement the nice-related
       features to affect all processes on the system, others to affect
       just the general time-sharing activities implied by this volume
       of POSIX.1‐2017, and others may have no effect at all. Because of
       the use of ``implementation-defined'' in nice and renice, a wide
       range of implementation strategies are possible.

       Earlier versions of this standard allowed a -increment option.
       This form is no longer specified by POSIX.1‐2008 but may be
       present in some implementations.



SEE ALSO         top

       Chapter 2, Shell Command Language, renice(1p)

       The Base Definitions volume of POSIX.1‐2017, Section 3.244, Nice
       Value, Chapter 8, Environment Variables, Section 12.2, Utility
       Syntax Guidelines

       The System Interfaces volume of POSIX.1‐2017, nice(3p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see .

IEEE/The Open Group               2017                          NICE(1P)

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