renice(1posix)
NAME
renice --- set nice values of running processes
SYNOPSIS
renice [g|p|u] n increment ID...
DESCRIPTION
The renice utility shall request that the nice values (see the Base Definitions volume of POSIX.12008, Section 3.240, 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
POSIX.12008, Section 12.2, Utility Syntax Guidelines, except for
Guideline 9.
The following options shall be supported:
g Interpret the following 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 the following operands as unsigned decimal integer
process IDs. The p option is the default if no options are
specified.
u Interpret the following 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 POSIX.12008, 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 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 POSIX.12008 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 POSIX.12008, 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 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
individual end users to control their own processes.
Earlier versions of this standard allowed the following forms in the
SYNOPSIS:
renice nice_value[p] pid...[g gid...][p pid...][u user...]
renice nice_value g gid...[g gid...]p pid...][u user...]
renice nice_value u user...[g gid...]p pid...][u user...]
These forms are no longer specified by POSIX.12008 but may be present
in some implementations.
FUTURE DIRECTIONS
None.
SEE ALSO
nice The Base Definitions volume of POSIX.12008, Section 3.240, Nice Value, Chapter 8, Environment Variables, Section 12.2, Utility Syntax Guidelines
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html . Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .
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