изменить приоритет процесса (change process priority)
Имя (Name)
nice - change process priority
Синопсис (Synopsis)
#include <unistd.h>
int nice(int inc);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
nice():
_XOPEN_SOURCE
|| /* Since glibc 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
Описание (Description)
nice() adds inc to the nice value for the calling thread. (A
higher nice value means a lower priority.)
The range of the nice value is +19 (low priority) to -20 (high
priority). Attempts to set a nice value outside the range are
clamped to the range.
Traditionally, only a privileged process could lower the nice
value (i.e., set a higher priority). However, since Linux
2.6.12, an unprivileged process can decrease the nice value of a
target process that has a suitable RLIMIT_NICE soft limit; see
getrlimit(2) for details.
Возвращаемое значение (Return value)
On success, the new nice value is returned (but see NOTES below).
On error, -1 is returned, and errno is set to indicate the error.
A successful call can legitimately return -1. To detect an
error, set errno to 0 before the call, and check whether it is
nonzero after nice() returns -1.
Ошибки (Error)
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).)
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008, SVr4, 4.3BSD. However, the raw
system call and (g)libc (earlier than glibc 2.2.4) return value
is nonstandard, see below.
Примечание (Note)
For further details on the nice value, see sched(7).
Note: the addition of the "autogroup" feature in Linux 2.6.38
means that the nice value no longer has its traditional effect in
many circumstances. For details, see sched(7).
C library/kernel differences
POSIX.1 specifies that nice() should return the new nice value.
However, the raw Linux system call returns 0 on success.
Likewise, the nice() wrapper function provided in glibc 2.2.3 and
earlier returns 0 on success.
Since glibc 2.2.4, the nice() wrapper function provided by glibc
provides conformance to POSIX.1 by calling getpriority(2) to
obtain the new nice value, which is then returned to the caller.
Смотри также (See also)
nice(1), renice(1), fork(2), getpriority(2), getrlimit(2),
setpriority(2), capabilities(7), sched(7)
