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PROGRAM:

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.1‐2008, 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.1‐2008, 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.1‐2008, 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.1‐2008 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.1‐2008,
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.1‐2008 but may be present in some
implementations.

FUTURE DIRECTIONS

None.

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