nice.2

UNIX v6源代码 这几乎是最经典的unix版本 unix操作系统设计和莱昂氏unix源代码分析都是用的该版

.th NICE II 8/5/73
.sh NAME
nice \*- set program priority
.sh SYNOPSIS
(nice = 34.)
.br
(priority in r0)
.br
.ft B
sys nice
.s3
nice(priority)
.ft R
.sh DESCRIPTION
The scheduling
.it priority
of the process is changed to the argument.
Positive priorities get less
service than normal; 0 is default.
Only the super-user may specify a negative priority.
The valid range of
.it priority
is 20 to \*-220.
The value of 4 is recommended to users
who wish to execute long-running programs
without flak from the administration.
.s3
The effect of this call is
passed to a child process by the
.it fork
system call.
The effect can be cancelled by
another call to
.it nice
with a
.it priority
of 0.
.s3
The actual running priority of a
process is the
.it priority
argument plus a number that
ranges from 100 to 119 depending on the
cpu usage of the process.
.sh "SEE ALSO"
nice (I)
.sh DIAGNOSTICS
The error bit
(c-bit)
is set if the user requests a
.it priority
outside the range of 0 to 20
and is not the super-user.