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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 (con-
sult 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 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 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 Variables for the precedence of international-
ization 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 stan-
dard 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 clar-
ity, 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 compara-
ble. 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 imple-
mentations may implement the nice-related features to affect all processes on the system, others to affect just the gen-
eral 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 nice and renice, a wide range of implementation strategies are possi-
ble.

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.

FUTURE DIRECTIONS
None.