nice - 改變進程的優先級

內容簡介

#include <unistd.h>

int nice(int inc**);**

描述

nice () 增加 inc 爲調用進程的nice值 . (A higher nice value means a low priority.) Only the super user may specify a negative increment, or priority increase. The range for nice values is described in  getpriority (2).

返回值

On success, the new nice value is returned (but see NOTES below). On error, -1 is returned, and  errno  is set appropriately.

錯誤

標籤

描述

EPERM

The calling process attempted to increase its priority by supplying a negative inc but has insufficient privileges. Under Linux the CAP_SYS_NICE capability is required. (But see the discussion of the RLIMIT_NICE resource limit in setrlimit(2).)

遵循於

SVr4, 4.3BSD, POSIX.1-2001. However, the Linux and (g)libc (earlier than glibc 2.2.4) return value is nonstandard, see below. SVr4 documents an additional EINVAL error code.

注意

SUSv2 and POSIX.1-2001 specify that  nice () should return the new nice value. However, the Linux syscall and the  nice () library function provided in older versions of (g)libc (earlier than glibc 2.2.4) return 0 on success. The new nice value can be found using getpriority (2).

Since glibc 2.2.4, nice() is implemented as a library function that calls getpriority(2) to obtain the new nice value to be returned to the caller. With this implementation, a successful call can legitimately return -1. To reliably detect an error, set errno to 0 before the call, and check its value when nice() returns -1.

另請參閱

• nice (1)

• fork (2)

• getpriority (2)

• setpriority (2)

• renice (8)