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PROLOG

       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

       renice — set nice values of running processes

SYNOPSIS

       renice [−g|−p|−u] −n increment ID...

DESCRIPTION

       The  renice  utility shall request that the nice values (see the Base Definitions volume of POSIX.1‐2008,
       Section 3.240, Nice Value) of one or more running  processes  be  changed.  By  default,  the  applicable
       processes  are  specified  by  their process IDs. When a process group is specified (see −g), the request
       shall apply to all processes in the process group.

       The nice value shall be bounded in an implementation-defined manner.  If the  requested  increment  would
       raise  or  lower  the  nice  value of the executed utility beyond implementation-defined limits, then the
       limit whose value was exceeded shall be used.

       When a user is reniced, the request applies to all processes whose saved set-user-ID matches the user  ID
       corresponding to the user.

       Regardless  of  which options are supplied or any other factor, renice shall not alter the nice values of
       any process unless the user requesting such a  change  has  appropriate  privileges  to  do  so  for  the
       specified  process. If the user lacks appropriate privileges to perform the requested action, the utility
       shall return an error status.

       The saved set-user-ID of the user's process shall be checked instead of its effective user ID when renice
       attempts to determine the user ID of the process in order to determine whether the user  has  appropriate
       privileges.

OPTIONS

       The  renice  utility  shall conform to the Base Definitions volume of POSIX.1‐2008, Section 12.2, Utility
       Syntax Guidelines, except for Guideline 9.

       The following options shall be supported:

       −g        Interpret the following operands as unsigned decimal integer process group IDs.

       −n increment
                 Specify how the nice value of the specified  process  or  processes  is  to  be  adjusted.  The
                 increment  option-argument  is  a  positive  or  negative decimal integer that shall be used to
                 modify the nice value of the specified process or processes.

                 Positive increment values shall cause a lower nice value. Negative increment values may require
                 appropriate privileges and shall cause a higher nice value.

       −p        Interpret the following operands as unsigned decimal integer process IDs. The −p option is  the
                 default if no options are specified.

       −u        Interpret  the  following  operands  as  users.  If a user exists with a user name equal to the
                 operand, then the user ID of that user is used in further processing. Otherwise, if the operand
                 represents an unsigned decimal integer, it shall be used as the numeric user ID of the user.

OPERANDS

       The following operands shall be supported:

       ID        A process ID, process group ID, or user name/user ID, depending on the option selected.

STDIN

       Not used.

INPUT FILES

       None.

ENVIRONMENT VARIABLES

       The following environment variables shall affect the execution of renice:

       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 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.

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

       The following exit values shall be returned:

        0    Successful completion.

       >0    An error occurred.

CONSEQUENCES OF ERRORS

       Default.

       The following sections are informative.

APPLICATION USAGE

       None.

EXAMPLES

        1. Adjust the nice value so that process IDs 987 and 32 would have a lower nice value:

               renice −n 5 −p 987 32

        2. Adjust  the  nice  value so that group IDs 324 and 76 would have a higher nice value, if the user has
           appropriate privileges to do so:

               renice −n −4 −g 324 76

        3. Adjust the nice value so that numeric user ID 8 and user sas would have a lower nice value:

               renice −n 4 −u 8 sas

       Useful nice value increments on historical systems include 19 or 20 (the affected processes run only when
       nothing else in the system attempts to run) and any negative number (to make processes run faster).

RATIONALE

The gid, pid, and user specifications do not fit either the definition of operand or option-argument.
However, for clarity, they have been included in the OPTIONS section, rather than the OPERANDS section.

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.

Originally, this utility was written in the historical manner, using the term ``nice value''. This was
always a point of concern with users because it was never intuitively obvious what this meant. With a
newer version of renice, which used the term ``system scheduling priority'', it was hoped that novice
users could better understand what this utility was meant to do. Also, it would be easier to document
what the utility was meant to do. Unfortunately, the addition of the POSIX realtime scheduling
capabilities introduced the concepts of process and thread scheduling priorities that were totally
unaffected by the nice/renice utilities or the nice()/setpriority() functions. Continuing to use the term
``system scheduling priority'' would have incorrectly suggested that these utilities and functions were
indeed affecting these realtime priorities. It was decided to revert to the historical term ``nice
value'' to reference this unrelated process attribute.

Although this utility has use by system administrators (and in fact appears in the system administration
portion of the BSD documentation), the standard developers considered that it was very useful for
individual end users to control their own processes.

Earlier versions of this standard allowed the following forms in the SYNOPSIS:

renice nice_value[−p] pid...[−g gid...][−p pid...][−u user...]
renice nice_value −g gid...[−g gid...]−p pid...][−u user...]
renice nice_value −u user...[−g gid...]−p pid...][−u user...]

These forms are no longer specified by POSIX.1‐2008 but may be present in some implementations.

FUTURE DIRECTIONS

       None.

COPYRIGHT

       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
       http://www.unix.org/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                                   2013                                        RENICE(1POSIX)