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, 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 .