'\" et

.TH NICE "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"

.SH 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.

.SH NAME

nice

\(em change the nice value of a process

.SH SYNOPSIS

.LP

.nf

#include <unistd.h>

.P

int nice(int \fIincr\fP);

.fi

.SH DESCRIPTION

The

\fInice\fR()

function shall add the value of

.IR 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 scheduling.

.P

A maximum nice value of 2*{NZERO}\(mi1 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.

.P

Calling the

\fInice\fR()

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.

.P

The nice value set with

\fInice\fR()

shall be applied to the process. If the process is multi-threaded,

the nice value shall affect all system scope threads in the process.

.P

As \(mi1 is a permissible return value in a successful situation, an

application wishing to check for error situations should set

.IR errno

to 0, then call

\fInice\fR(),

and if it returns \(mi1, check to see whether

.IR errno

is non-zero.

.SH "RETURN VALUE"

Upon successful completion,

\fInice\fR()

shall return the new nice value \(mi{NZERO}.

Otherwise, \(mi1 shall be returned, the nice value of the process

shall not be changed, and

.IR errno

shall be set to indicate the error.

.SH ERRORS

The

\fInice\fR()

function shall fail if:

.TP

.BR EPERM

The

.IR incr

argument is negative and the calling process does not have appropriate

privileges.

.LP

.IR "The following sections are informative."

.SH EXAMPLES

.SS "Changing the Nice Value"

.P

The following example adds the value of the

.IR incr

argument, \(mi20, to the nice value of the calling process.

.sp

.RS 4

.nf

\fB

#include <unistd.h>

\&...

int incr = -20;

int ret;

.P

ret = nice(incr);

.fi \fR

.P

.RE

.SH "APPLICATION USAGE"

None.

.SH RATIONALE

None.

.SH "FUTURE DIRECTIONS"

None.

.SH "SEE ALSO"

.IR "\fIexec\fR\^",

.IR "\fIgetpriority\fR\^(\|)"

.P

The Base Definitions volume of POSIX.1\(hy2008,

.IR "\fB<limits.h>\fP",

.IR "\fB<unistd.h>\fP"

.SH 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

Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .