NICE(3V) — C LIBRARY FUNCTIONS

NAME

nice − change nice value of a process

SYNOPSIS

int nice(incr)

DESCRIPTION

The nice value of the process is changed by incr. Positive nice values get less service than normal. See nice(1) for a discussion of the relationship of nice value and scheduling priority.

A nice value of 10 is recommended to users who wish to execute long-running programs without undue impact on system performance.

Negative increments are illegal, except when specified by the super-user. The nice value is limited to the range −20 (most urgent) to 19 (least). Requests for values above or below these limits result in the nice value being set to the corresponding limit.

The nice value of a process is passed to a child process by fork(2V). For a privileged process to return to normal nice value from an unknown state, nice() should be called successively with arguments −40 (goes to nice value −20 because of truncation), 20 (to get to 0), then 0 (to maintain compatibility with previous versions of this call).

SYSTEM V DESCRIPTION

The maximum allowed value for incr is 40 (least urgent).

RETURN VALUES

nice() returns:

0 on success.

−1 on failure and sets errno to indicate the error.

SYSTEM V RETURN VALUES

nice() returns the new nice value on success. On failure, it returns −1 and sets errno to indicate the error.

ERRORS

The nice value is not changed if:

EACCES The value of incr specified was negative, and the effective user ID is not super-user.

SYSTEM V ERRORS