NICE(3P) POSIX Programmer's Manual NICE(3P)
PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAME
nice -- change the nice value of a process
SYNOPSIS
#include <unistd.h>
int nice(int incr);
DESCRIPTION
The nice() function shall add the value of incr to the nice value of
the calling process. A nice value of a process is a non-negative number
for which a more positive value shall result in less favorable schedul-
ing.
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 lim-
its 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.
RETURN VALUE
Upon successful completion, nice() shall return the new nice value
-{NZERO}. Otherwise, -1 shall be returned, the nice value of the
process shall not be changed, and errno shall be set to indicate the
error.
ERRORS
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.
EXAMPLES
Changing the Nice Value
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);
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
exec, getpriority()
The Base Definitions volume of POSIX.1-2008, <limits.h>, <unistd.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker-
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 NICE(3P)