.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "RENICE" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" renice 
.SH 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.
.SH NAME
renice \- set nice values of running processes
.SH SYNOPSIS
.LP
\fBrenice -n\fP \fIincrement\fP \fB[\fP\fB-g | -p | -u\fP\fB]\fP \fIID\fP
\fB\&... \fP
.SH DESCRIPTION
.LP
The \fIrenice\fP 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 \fB-g\fP), the
request shall apply to all processes in the process group.
.LP
The nice value shall be bounded in an implementation-defined manner.
If the requested \fIincrement\fP 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.
.LP
When a user is \fIrenice\fPd, the request applies to all processes
whose saved set-user-ID matches the user ID corresponding to
the user.
.LP
Regardless of which options are supplied or any other factor, \fIrenice\fP
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.
.LP
The saved set-user-ID of the user's process shall be checked instead
of its effective user ID when \fIrenice\fP attempts to
determine the user ID of the process in order to determine whether
the user has appropriate privileges.
.SH OPTIONS
.LP
The \fIrenice\fP utility shall conform to the Base Definitions volume
of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
.LP
The following options shall be supported:
.TP 7
\fB-g\fP
Interpret all operands as unsigned decimal integer process group IDs.
.TP 7
\fB-n\ \fP \fIincrement\fP
Specify how the nice value of the specified process or processes is
to be adjusted. The \fIincrement\fP option-argument is a
positive or negative decimal integer that shall be used to modify
the nice value of the specified process or processes. 
.LP
Positive \fIincrement\fP values shall cause a lower nice value. Negative
\fIincrement\fP values may require appropriate
privileges and shall cause a higher nice value.
.TP 7
\fB-p\fP
Interpret all operands as unsigned decimal integer process IDs. The
\fB-p\fP option is the default if no options are
specified.
.TP 7
\fB-u\fP
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.
.sp
.SH OPERANDS
.LP
The following operands shall be supported:
.TP 7
\fIID\fP
A process ID, process group ID, or user name/user ID, depending on
the option selected.
.sp
.SH STDIN
.LP
Not used.
.SH INPUT FILES
.LP
None.
.SH ENVIRONMENT VARIABLES
.LP
The following environment variables shall affect the execution of
\fIrenice\fP:
.TP 7
\fILANG\fP
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.)
.TP 7
\fILC_ALL\fP
If set to a non-empty string value, override the values of all the
other internationalization variables.
.TP 7
\fILC_CTYPE\fP
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).
.TP 7
\fILC_MESSAGES\fP
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard
error.
.TP 7
\fINLSPATH\fP
Determine the location of message catalogs for the processing of \fILC_MESSAGES
\&.\fP 
.sp
.SH ASYNCHRONOUS EVENTS
.LP
Default.
.SH STDOUT
.LP
Not used.
.SH STDERR
.LP
The standard error shall be used only for diagnostic messages.
.SH OUTPUT FILES
.LP
None.
.SH EXTENDED DESCRIPTION
.LP
None.
.SH EXIT STATUS
.LP
The following exit values shall be returned:
.TP 7
\ 0
Successful completion.
.TP 7
>0
An error occurred.
.sp
.SH CONSEQUENCES OF ERRORS
.LP
Default.
.LP
\fIThe following sections are informative.\fP
.SH APPLICATION USAGE
.LP
None.
.SH EXAMPLES
.IP " 1." 4
Adjust the nice value so that process IDs 987 and 32 would have a
lower nice value:
.sp
.RS
.nf

\fBrenice -n 5 -p 987 32
\fP
.fi
.RE
.LP
.IP " 2." 4
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:
.sp
.RS
.nf

\fBrenice -n -4 -g 324 76
\fP
.fi
.RE
.LP
.IP " 3." 4
Adjust the nice value so that numeric user ID 8 and user \fBsas\fP
would have a lower nice value:
.sp
.RS
.nf

\fBrenice -n 4 -u 8 sas
\fP
.fi
.RE
.LP
.LP
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).
.SH RATIONALE
.LP
The \fIgid\fP, \fIpid\fP, and \fIuser\fP 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.
.LP
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 \fInice\fP-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 \fInice\fP and \fIrenice\fP,
a wide range of
implementation strategies are possible.
.LP
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 \fIrenice\fP, 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 \fInice\fP/ \fIrenice\fP
utilities or the \fInice\fP()/ \fIsetpriority\fP() 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.
.LP
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.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fInice\fP()
.SH 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 .
