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       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.


       nice — change the nice value of a process


       #include <unistd.h>

       int nice(int incr);


       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.


       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.


       The nice() function shall fail if:

       EPERM  The  incr  argument  is  negative and the calling process does not have appropriate

       The following sections are informative.


   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);








       exec, getpriority()

       The Base Definitions volume of POSIX.1‐2017, <limits.h>, <unistd.h>


       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 .

       Any  typographical  or  formatting errors that appear in this page are most likely to have
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