nice(2) manual page
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nice - change priority of a process
#include <unistd.h>
int
nice(int incr);
nice() allows a process to change its priority.
The invoking process must be in a scheduling class that supports the
nice() system call. The priocntl function is a more general interface to
scheduler functions.
nice() adds the value of incr to the nice value of
the calling process. A process’s nice value is a non-negative number for which
a more positive value results in lower CPU
priority.
A maximum nice value
of 39 and a minimum nice value of 0 are imposed by the system. (The default
nice value is 20.) Requests for values above or below these limits result
in the nice value being set to the corresponding limit.
Upon
successful completion, nice() returns the new nice value minus 20. Otherwise,
a value of -1 is returned and errno is set to indicate the error.
nice()
fails if one or more of the following are true:
- EINVAL
- nice() is called
by a process in a scheduling class other than time-sharing.
- EPERM
- incr is
negative or greater than 40 and the effective user id of the calling process
is not super-user.
nice(1)
, exec(2)
, priocntl(2)
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