Linux nice Command

Linux Command Manual

The Linux nice command executes a program with a modified priority. If no program is specified, it prints the current scheduling priority. The default adjustment is 10, with a range from -20 (highest priority) to 19 (lowest priority).

Usage: All users.

Syntax

nice [-n adjustment] [-adjustment] [--adjustment=adjustment] [--help] [--version] [command [arg...]]

Parameter Description:

-n adjustment, -adjustment, --adjustment=adjustment all increase the original priority by adjustment.
--help displays help information.
--version displays version information.

Example

Setting the priority of a program while running:

# vi & //run in background
[1] 15297
# nice vi & //set default priority
[2] 15298

[1]+ Stopped         vi
# nice -n 19 vi & //set priority to 19
[3] 15299

[2]+ Stopped         nice vi
# nice -n -20 vi & //set priority to -20
[4] 15300

[3]+ Stopped         nice -n 19 vi
# ps -l //display processes
F S  UID  PID PPID C PRI NI ADDR SZ WCHAN TTY     TIME CMD
4 S   0 15278 15212 0 80  0 - 1208 wait  pts/2  00:00:00 bash
0 T   0 15297 15278 0 80  0 - 2687 signal pts/2  00:00:00 vi
0 T   0 15298 15278 0 90 10 - 2687 signal pts/2  00:00:00 vi
0 T   0 15299 15278 1 99 19 - 2687 signal pts/2  00:00:00 vi
4 T   0 15300 15278 3 60 -20 - 2687 signal pts/2  00:00:00 vi
4 R   0 15301 15278 0 80  0 -  625 -   pts/2  00:00:00 ps

[4]+ Stopped         nice -n -20 vi

Increase the priority of ls by 1 and execute:

nice -n 1 ls

Increase the priority of ls by 10 and execute:

nice ls

Note: Priority is a parameter used by the operating system to decide CPU allocation. Linux uses a 'round-robin' algorithm for CPU scheduling. The higher the priority, the more CPU time the process may receive.

Linux Command Manual

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