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Linux 2.6 - man page for renice (linux section 1posix)

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

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  implementa-
       tion-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 privi-
       leges to do so for the specified process. If the user lacks appropriate privileges to per-
       form 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 op-
	      erand,  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, Inter-
	      nationalization 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 interna-
	      tionalization 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 argu-
	      ments).

       LC_MESSAGES
	      Determine the locale that should be used to affect the format and contents of diag-
	      nostic 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 pro-
       cesses 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 others may have no effect at all. Because of the use of "imple-
       mentation-defined" in nice and renice, a wide range of implementation strategies are  pos-
       sible.

       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  intro-
       duced  the  concepts  of  process and thread scheduling priorities that were totally unaf-
       fected 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.

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 Technology  --  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 orig-
       inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group			       2003					RENICE(P)


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