nice — change process priority
#include <unistd.h>
int
nice( |
int | inc) ; |
nice
() adds inc
to the nice value for the
calling process. (A higher nice value means a low priority.)
Only the superuser may specify a negative increment, or
priority increase. The range for nice values is described in
getpriority(2).
On success, the new nice value is returned (but see NOTES
below). On error, −1 is returned, and errno
is set appropriately.
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).)
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.
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.
nice(1), fork(2), getpriority(2), setpriority(2), capabilities(7), renice(8)
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