Originální popis anglicky:
nice - change the nice value of a process
Návod, kniha: POSIX Programmer's Manual
#include <unistd.h>
int nice(int
incr);
The
nice() function shall add the value of
incr to the nice value
of the calling process. A process' nice value is a non-negative number for
which a more positive value shall result in less favorable scheduling.
A maximum nice value of 2*{NZERO}-1 and a minimum nice value of 0 shall be
imposed by the system. Requests for values above or below these limits shall
result in the nice value being set to the corresponding limit. Only a process
with appropriate privileges can lower the nice value.
Calling the
nice() function has no effect on the priority of processes or
threads with policy SCHED_FIFO or SCHED_RR. The effect on processes or threads
with other scheduling policies is implementation-defined.
The nice value set with
nice() shall be applied to the process. If the
process is multi-threaded, the nice value shall affect all system scope
threads in the process.
As -1 is a permissible return value in a successful situation, an application
wishing to check for error situations should set
errno to 0, then call
nice(), and if it returns -1, check to see whether
errno is
non-zero.
Upon successful completion,
nice() shall return the new nice value
-{NZERO}. Otherwise, -1 shall be returned, the process' nice value shall not
be changed, and
errno shall be set to indicate the error.
The
nice() function shall fail if:
- EPERM
- The incr argument is negative and the calling
process does not have appropriate privileges.
The following sections are informative.
The following example adds the value of the
incr argument, -20, to the
nice value of the calling process.
#include <unistd.h>
...
int incr = -20;
int ret;
ret = nice(incr);
None.
None.
None.
getpriority() ,
setpriority() , the Base Definitions volume of
IEEE Std 1003.1-2001,
<limits.h>,
<unistd.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
