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.Dd $Mdocdate: June 5 2013 $ .Dt NICE 3 .Os .Sh NAME .Nm nice .Nd change process scheduling priority .Sh SYNOPSIS n unistd.h .Ft int .Fn nice "int incr" .Sh DESCRIPTION f -symbolic This interface is obsoleted by .Xr setpriority 2 . .Ef
p The .Fn nice function adds the value specified in .Fa incr to the scheduling priority of the invoking process.
p .Fa incr is an integer such that the resulting scheduling priority is within the range -20 to 20. Priority values outside this range are truncated to the appropriate limit. The default priority is 0; lower priorities cause more favorable scheduling. Only the superuser may lower priorities.
p Children inherit the priority of their parent processes via .Xr fork 2 . .Sh RETURN VALUES On success, .Fn nice returns the new priority. On error, it returns -1.
p Since .Fn nice can legitimately return the value -1, it is necessary to clear the external variable .Va errno prior to the call, then check it afterward to determine if a -1 is an error or a legitimate value. .Sh ERRORS .Fn nice has the same failure conditions as .Xr setpriority 2 . .Sh SEE ALSO .Xr nice 1 , .Xr fork 2 , .Xr setpriority 2 , .Xr renice 8 .Sh HISTORY A .Fn nice system call first appeared in .At v3 . It has accepted an .Fa incr argument since .At v4 .