Increment the process priority
value for the shell or for command by n.
The higher the priority value,
the lower the priority of a process, and the slower it runs.
When given, command is always
run in a subshell, and the restrictions placed on commands in simple if
If command is omitted, nice
increments the value for the current shell. If no increment is specified,
nice sets the process priority value to 4.
The range of process priority
values is from -20 to 20. Values of n outside this range set the value
to the lower, or to the higher boundary, respectively.
+n = Increment the
process priority value by n.
-n = Decrement by
n. This argument can be used only by the privileged user.