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DESCRIPTION
The external nice command executes a specified command at a lower CPU priority than normal. Thus its name is derived from the fact the command is being nice to the rest of the users. The lower your priority the slower your program runs and the longer it takes to complete.
The super- user can increase the priority of a command by using nice . Instead of specifying - n, a -- n is given.
The nice value of a process can be viewed using the ps -l command. The NI column displays the nice value. The higher the value the lower the CPU priority (the slower the process executes).
COMMAND FORMAT
Following is the general format of the nice command.
nice [ -n ] command [ options ] [ arguments ]
Options
The following option may be used to control how nice functions.
- n | Decreases the scheduling priority by the value of n. The value of n can be from 1 to 19. |
If you do not specify a number, 10 is used. |
Arguments
The following arguments may be passed to the nice command.
command | The name of any command you normally execute. This command s process ID is assigned a lower priority level. |
options | The options to be used by the command. |
arguments | The arguments to be used by the command. |
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C shell |
The C shell uses a + to lower your CPU priority and a “ to increase it. The nice command is an internal command. |
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DIAGNOSTICS AND BUGS
If you specify a number greater than 19, 19 is used.
RETURN CODES
The exit status of command is returned.
APPLICATIONS
The nice command is beneficial in controlling the use of the CPU. If you are running large jobs, such as document formatting or other various CPU hogs, you should use nice . These CPU and/or IO intense jobs slow down the interactive jobs unless you lower their priority. This allows you to process large CPU intensive jobs while continuing to perform interactive tasks without as much delay.
TYPICAL OPERATION
In this activity you use the nice command to lower the priority of a command. Then you check the priority by using the ps command. Begin at the shell prompt.
cj> ps -l F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME COMD 1 R 60 4947 4771 14 181 20 bedc81 820 tty3p3 0:00 ps 1 S 60 4771 1 0 168 20 a02ea0 500 1abd6a0 tty3p3 0:02 ksh 1 S 60 4945 4771 3 148 30 594ab0 392 897380 tty3p3 0:03 find
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