NAME

nice - change nice value of a process

 SYNOPSIS

#include <unistd.h>

int nice(int incr);

 DESCRIPTION

The nice() function adds the value of incr to the nice value of the calling process. A process' nice value is a non-negative number for which a more positive value results in less favourable scheduling.

A maximum nice value of 2 * {NZERO} -1 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. Only a process with appropriate privileges can lower the nice value.

Calling the nice() function has no effect on the priority of processes or threads with policy SCHED_FIFO or SCHED_RR. The effect on processes or threads with other scheduling policies is implementation-dependent.

The nice value set with nice() is applied to the process. If the process is multi-threaded, the nice value affects all system scope threads in the process.

 RETURN VALUE

Upon successful completion, nice() returns the new nice value minus {NZERO}. Otherwise, -1 is returned, the process' nice value is not changed, and errno is set to indicate the error.

 ERRORS

The nice() function will fail if:

[EPERM]

The incr argument is negative and the calling process does not have appropriate privileges.

 EXAMPLES

None.

 APPLICATION USAGE

As -1 is a permissible return value in a successful situation, an application wishing to check for error situations should set errno to 0, then call nice(), and if it returns -1, check to see if errno is non-zero.

 FUTURE DIRECTIONS

None.

 SEE ALSO

<limits.h>, <unistd.h>.

DERIVATION

Derived from Issue 1 of the SVID.