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



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

NAME
       nice -- invoke a utility with an altered nice value

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

DESCRIPTION
       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
       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
       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
       Not used.

INPUT FILES
       None.

ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of nice:

       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).

       LC__MESSAGES
                 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.

ASYNCHRONOUS EVENTS
       Default.

STDOUT
       Not used.

STDERR
       The standard error shall be used only for diagnostic messages.

OUTPUT FILES
       None.

EXTENDED DESCRIPTION
       None.

EXIT STATUS
       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.

CONSEQUENCES OF ERRORS
       Default.

       The following sections are informative.

APPLICATION USAGE
       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 reason.

EXAMPLES
       None.

RATIONALE
       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 ----11 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 --00 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'' message.

       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 POSIX.1-2017.

       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.

FUTURE DIRECTIONS
       None.

SEE ALSO
       Chapter _2, Shell Command Language, renice

       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()

COPYRIGHT
       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 http://www.opengroup.org/unix/online.html .

       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
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                              NICE(1)
