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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.
See also:
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