NICE(3)                    POSIX Programmer's Manual                   NICE(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

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
       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 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.1-2017, <limits.h>, <unistd.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 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 .

       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 .



IEEE/The Open Group                  2017                              NICE(3)
