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.1‐2008, <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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .