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       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.


       nice — invoke a utility with an altered nice value


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


       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.


       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.


       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.


       Not used.




       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.1‐2008,  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

                 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.




       Not used.


       The standard error shall be used only for diagnostic messages.






       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




       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.




       Chapter 2, Shell Command Language, renice

       The Base Definitions volume  of  POSIX.1‐2008,  Section  3.240,  Nice  Value,  Chapter  8,
       Environment Variables, Section 12.2, Utility Syntax Guidelines

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


       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 .

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