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 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(3POSIX)