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 correspond-
       ing 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 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 pro-
       cesses 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 process' nice value 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

       getpriority(), setpriority(), the Base Definitions volume of IEEE Std 1003.1-2001, <limits.h>, <unistd.h>

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- 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 .

IEEE
/The Open Group						       2003								  NICE(3P)