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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 nice value of a process is a non-negative number
       for which a more positive value shall result in less favorable schedul-
       ing.
       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 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.1-2008, <limits.h>, <unistd.h>
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri-
       cal  and  Electronics  Engineers,  Inc  and  The  Open Group.  (This is
       POSIX.1-2008 with the 2013 Technical Corrigendum  1  applied.)  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.unix.org/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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                             NICE(3P)