mirror of https://github.com/mkerrisk/man-pages
98 lines
3.0 KiB
Plaintext
98 lines
3.0 KiB
Plaintext
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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.TH "NICE" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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.\" nice
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.SH NAME
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nice \- change the nice value of a process
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.SH SYNOPSIS
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.LP
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\fB#include <unistd.h>
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.br
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.sp
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int nice(int\fP \fIincr\fP\fB); \fP
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\fB
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.br
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\fP
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.SH DESCRIPTION
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.LP
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The \fInice\fP() function shall add the value of \fIincr\fP to the
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nice value of the calling process. A process' nice value is
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a non-negative number for which a more positive value shall result
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in less favorable scheduling.
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.LP
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A maximum nice value of 2*{NZERO}-1 and a minimum nice value of 0
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shall be imposed by the system. Requests for values above or
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below these limits shall result in the nice value being set to the
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corresponding limit. Only a process with appropriate privileges
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can lower the nice value.
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.LP
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Calling the \fInice\fP() function has no effect on the priority of
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processes or threads with policy SCHED_FIFO or SCHED_RR. The
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effect on processes or threads with other scheduling policies is implementation-defined.
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.LP
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The nice value set with \fInice\fP() shall be applied to the process.
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If the process is multi-threaded, the nice value shall
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affect all system scope threads in the process.
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.LP
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As -1 is a permissible return value in a successful situation, an
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application wishing to check for error situations should set
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\fIerrno\fP to 0, then call \fInice\fP(), and if it returns -1, check
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to see whether \fIerrno\fP is non-zero.
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.SH RETURN VALUE
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.LP
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Upon successful completion, \fInice\fP() shall return the new nice
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value -{NZERO}. Otherwise, -1 shall be returned, the
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process' nice value shall not be changed, and \fIerrno\fP shall be
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set to indicate the error.
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.SH ERRORS
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.LP
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The \fInice\fP() function shall fail if:
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.TP 7
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.B EPERM
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The \fIincr\fP argument is negative and the calling process does not
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have appropriate privileges.
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.sp
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.LP
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\fIThe following sections are informative.\fP
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.SH EXAMPLES
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.SS Changing the Nice Value
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.LP
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The following example adds the value of the \fIincr\fP argument, -20,
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to the nice value of the calling process.
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.sp
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.RS
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.nf
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\fB#include <unistd.h>
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\&...
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int incr = -20;
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int ret;
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.sp
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ret = nice(incr);
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\fP
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.fi
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.RE
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.SH APPLICATION USAGE
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.LP
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None.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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\fIgetpriority\fP() , \fIsetpriority\fP() , the Base Definitions
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volume of IEEE\ Std\ 1003.1-2001, \fI<limits.h>\fP, \fI<unistd.h>\fP
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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