Caution: This version of this document is no longer maintained. For the latest documentation, see


Run a program at an altered priority (POSIX)


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


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

Runs on:



Deprecated. This is the historical method of specifying the amount to adjust the current priority by. Specifying -1 lowers the priority by one, while specifying --1 boosts the priority by one.
-n prioritylevels
Specify the amount to adjust the current priority by when running the command. The command is run at a priority level of the current priority minus prioritylevels.
command [arguments]...
The command to run at the altered priority.


The nice utility invokes the specified command with a modified priority, usually making the command behave “more nicely” towards competing processes.

If no prioritylevels option is specified, the program is invoked at a priority that's 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's subtracted from the parent's current priority and the program is invoked at the resultant priority. If the resulting priority isn't a valid priority, nice writes a diagnostic message to the standard error and exits with a status of 1.

If you enter: nice:
A positive value (e.g. -n2 or -n+2) Lowers the priority of the program, making it “nice”
A negative value (e.g. -n-2) Raises the priority of the program, making it “mean”

You can adjust the priority as follows:

If you're: You can change to any priority:
A non-root user From 1 to 63
root From 1 to 255

You can change the range of privileged priorities with the -P option for procnto.


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:

Invalid command-line parameters were given or the user requested an invalid priority.
The command specified didn't exist.
The command couldn't be started for some other reason.


In contrast to other operating systems, the QNX Neutrino 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 Neutrino is of a “whole” priority level. For example, where the following has a marginal effect on the execution of myprog on some operating systems:

nice -n5 myprog

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

See also:

on, renice, slay