Increases or decreases process priority relative to the process current priority by the amount of the argument. This function is nonreentrant. Format #include <unistd.h> int nice (int increment);
1 – Argument
increment As a positive argument, decreases priority; as a negative argument, increases priority. Issuing nice(0) restores the base priority. The resulting priority cannot be less than 1, or greater than the process's base priority. If it is, the nice function quietly does nothing.
2 – Description
When a process calls the vfork function, the resulting child inherits the parent's priority. With the DECC$ALLOW_UNPRIVILEGED_NICE feature logical enabled, the nice function exhibits its legacy behavior of not checking the privilege of the calling process (that is, any user may lower the nice value to increase process priorities). Also, when the caller sets a priority above MAX_PRIORITY, the nice value is set to the base priority. With DECC$ALLOW_UNPRIVILEGED_NICE disabled, the nice function conforms to the X/Open standard of checking the privilege of the calling process (only users with ALTPRI privilege can lower the nice value to increase process priorities), and when the caller sets a priority above MAX_PRIORITY, the nice value is set to MAX_ PRIORITY. See also vfork.
3 – Return Values
0 Indicates success. -1 Indicates failure.