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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 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 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  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 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 .

IEEE/The Open Group                  2003                             NICE(3P)