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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 process' nice
       value 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 process' nice value 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
       getpriority()  ,  setpriority()  ,  the  Base  Definitions  volume  of  IEEE Std 1003.1-2001, <limits.h>,
       <unistd.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard  for  Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003 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 .