`nice`

Run a program at an altered priority (POSIX)

Syntax:

nice [-nprioritylevels] command [arguments]...

Deprecated:

nice [-prioritylevels] command [arguments]...

Options:

-prioritylevels: Deprecated. This is the historical method of specifying the amount to adjust the current priority by. Specifying -1 ("one") would lower the priority by one, while specifying --1 ("one") would boost the priority by one.
-n prioritylevels: Specify the amount to adjust the current priority by when running the command. The command will be run at a priority level of the current_priority minus prioritylevels. The lowest priority allowed is priority 1. The highest for non-root users is 19; 29 for root. (To increase priority specify a negative number for prioritylevels.)
command [arguments]...: The command to run at the altered priority.

Description:

The nice utility invokes the specified command with a modified priority, usually making the command behave "nicer" towards competing processes.

If no prioritylevels option is specified, the program is invoked at a priority that is one level lower than the parent's current priority (i.e. it is invoked with a "nice increment" of 1).

If a prioritylevels option is specified, it is subtracted from the parent's current priority and the program is invoked at the resultant priority. If the resulting priority is not a valid priority, nice will write a diagnostic message to the standard error and will exit with an exit status of 1.

If you enter:	`nice` will:
a positive value (e.g. `-n2` or `-n+2`)	lower the priority of the program, making it "nice"
a negative value (e.g. `-n-2`)	raise the priority of the program, making it "mean"

Users may adjust the priority as follows:

If you're:	You can change to any priority:
a normal user	from 1 to 19
`root`	from 1 to 29

Examples:

Run make at one priority lower than the parent's priority (be nice):

    nice make application

Run make at two priorities lower than the parent's priority (be nicer):

    nice -n2 make application

Run make at two priorities higher than the parent's priority (be mean):

    nice -n-2 make application

Exit status:

If the operation is successful, the exit status of the invoked command is returned. If an error occurs, the exit status is as follows:

1: Invalid command-line parameters were given or the user requested an invalid priority.
126: The command specified did not exist.
127: The command could not be started for some other reason.

Caveats:

In contrast to other operating systems, the QNX interpretation of the nice value substantially affects the priority of the process. Rather than representing a fraction of a priority, the granularity of the nice value in QNX is of a "whole" priority level. For example, where the following would have a marginal effect on the execution of myprog on some operating systems:

    nice -n5 myprog

on QNX it would lower the priority of myprog by five full priority levels, and could have a significant effect on myprog's execution time.