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 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 applica-
ble 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 request-
ing 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 Vari-
ables 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 pro-
cesses in a system have priorities that are comparable. Scheduling
policy extensions such as the realtime priorities in the System Inter-
faces volume of IEEE Std 1003.1-2001 make the notion of a single under-
lying priority for all scheduling policies problematic. Some implemen-
tations may implement the nice-related features to affect all processes
on the system, others to affect just the general time-sharing activi-
ties 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 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 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 individ-
ual 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 original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 RENICE(1P)
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