1NICE(P)                    POSIX Programmer's Manual                   NICE(P)
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NAME

6       nice - change the nice value of a process
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SYNOPSIS

9       #include <unistd.h>
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11       int nice(int incr);
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DESCRIPTION

15       The  nice()  function  shall add the value of incr to the nice value of
16       the calling process. A process' nice value is a non-negative number for
17       which a more positive value shall result in less favorable scheduling.
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19       A maximum nice value of 2*{NZERO}-1 and a minimum nice value of 0 shall
20       be imposed by the system. Requests for values above or below these lim‐
21       its  shall  result  in  the  nice  value being set to the corresponding
22       limit. Only a process with appropriate privileges can  lower  the  nice
23       value.
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25       Calling  the nice() function has no effect on the priority of processes
26       or threads with policy SCHED_FIFO or SCHED_RR. The effect on  processes
27       or threads with other scheduling policies is implementation-defined.
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29       The nice value set with nice() shall be applied to the process.  If the
30       process is multi-threaded, the nice value shall affect all system scope
31       threads in the process.
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33       As  -1  is  a  permissible  return  value in a successful situation, an
34       application wishing to check for error situations should set  errno  to
35       0,  then  call nice(), and if it returns -1, check to see whether errno
36       is non-zero.
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RETURN VALUE

39       Upon successful completion, nice() shall  return  the  new  nice  value
40       -{NZERO}.  Otherwise,  -1  shall  be  returned, the process' nice value
41       shall not be changed, and errno shall be set to indicate the error.
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ERRORS

44       The nice() function shall fail if:
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46       EPERM  The incr argument is negative and the calling process  does  not
47              have appropriate privileges.
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50       The following sections are informative.
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EXAMPLES

53   Changing the Nice Value
54       The  following example adds the value of the incr argument, -20, to the
55       nice value of the calling process.
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58              #include <unistd.h>
59              ...
60              int incr = -20;
61              int ret;
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64              ret = nice(incr);
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APPLICATION USAGE

67       None.
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RATIONALE

70       None.
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FUTURE DIRECTIONS

73       None.
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SEE ALSO

76       getpriority()  ,  setpriority()  ,  the  Base  Definitions  volume   of
77       IEEE Std 1003.1-2001, <limits.h>, <unistd.h>
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80       Portions  of  this text are reprinted and reproduced in electronic form
81       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
82       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
83       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
84       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
85       event of any discrepancy between this version and the original IEEE and
86       The  Open Group Standard, the original IEEE and The Open Group Standard
87       is the referee document. The original Standard can be  obtained  online
88       at http://www.opengroup.org/unix/online.html .
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92IEEE/The Open Group                  2003                              NICE(P)
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