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.1‐2008, Section 3.240, 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.1‐2008, 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

       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.1‐2008, Section 8.2, Internationalization
                 Variables for the precedence of internationalization
                 variables used to determine the values of locale

       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.1‐2008,
                 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

         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 reason.

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'' 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.1‐2008.

       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.1‐2008.

       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.1‐2008 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.1‐2008, 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.1‐2008, Section 3.240, Nice
       Value, Chapter 8, Environment Variables, Section 12.2, Utility Syntax

       The System Interfaces volume of POSIX.1‐2008, nice(3p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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                 2013                            NICE(1P)

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