nice(2)
NAME
nice − change priority of a process
SYNOPSIS
#include <unistd.h>
int nice(int priority_change);
DESCRIPTION
nice() adds the value of priority_change to the nice value of the calling process. A process’s nice value is a positive 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. Requests for values above or below these limits result in the nice value being set to the corresponding limit.
RETURN VALUE
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.
Note that nice() assumes a user process priority value of 20. If a user having appropriate privileges has changed the user process priority value to something less than 20, certain values for priority_change can cause nice() to return −1, which is indistinguishable from an error return.
ERRORS
[EPERM] nice() fails and does not change the nice value if priority_change is negative or greater than 40, and the effective user ID of the calling process is not a user having appropriate privileges.
SEE ALSO
STANDARDS CONFORMANCE
nice(): AES, SVID2, XPG2, XPG3, XPG4
Hewlett-Packard Company — HP-UX Release 9.0: August 1992