oracular (3) nice.3posix.gz

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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>


       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 .