nice

QNX SDP8.0Utilities ReferenceUtilities

Run a program at an altered priority (POSIX)

Syntax:

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

Deprecated: 

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

Runs on:

QNX OS

Options:

-prioritylevels
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.

Description:

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's 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.

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 didn't exist.
127
The command couldn't be started for some other reason.

Caveats:

In contrast to other operating systems, the QNX OS 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 OS 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 OS it lowers the priority of myprog by five full priority levels, and could have a significant effect on myprog's execution time.

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