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 (con-
       sult 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 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>

COPYRIGHT
       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, Copy-
       right (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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                      NICE(3P)