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



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may dif-
       fer (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 -n increment [-g | -p | -u] ID ...

DESCRIPTION
       The renice utility shall request that the nice values (see the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 3.239, 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 corre-
       sponding 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 privi-
       leges.

OPTIONS
       The renice utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2,  Utility
       Syntax Guidelines.

       The following options shall be supported:

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

       -u     Interpret  all  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 IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables for  the  prece-
              dence 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  exam-
              ple, 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 writ-
              ten 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  the
           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 noth-
       ing 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
       IEEE Std 1003.1-2001  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 IEEE Std 1003.1-2001, 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 under-
       stand 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()/ set-
       priority() 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 por-
       tion of the BSD documentation), the standard developers considered that it was very useful for  individual  end
       users to control their own processes.

FUTURE DIRECTIONS
       None.

SEE ALSO
       nice()

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Stan-
       dard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base  Specifica-
       tions  Issue  6,  Copyright (C) 2001-2003 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 Stan-
       dard,  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 .



IEEE/The Open Group                  2003                           RENICE(1P)