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 differ (consult the correspond-
       ing 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 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 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 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 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 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 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 oth-
       ers 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 prior-
       ity", 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. Contin-
       uing  to use the term "system scheduling priority'' would have incorrectly suggested that these utilities and functions were indeed affect-
       ing 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.

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, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications 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 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 .

IEEE
/The Open Group						       2003								RENICE(1P)