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.
If the calling process contains more than one thread or
lightweight process (i.e., the
process is multi-threaded) this function shall apply to all threads or
lightweight processes in the calling process.
Security Restrictions
Some or all of the actions associated with this system call are subject to
compartmental restrictions. See
compartments(5)
for more information about compartmentalization on systems that support
that feature.
Compartmental restrictions can be overridden if the process possesses the
PRIV_COMMALLOWED
privilege (COMMALLOWED).
Processes owned by the superuser may not have this privilege.
Processes owned by any user may have this privilege, depending on system
configuration.
Some or all of the actions associated with this system call require the
PRIV_OWNER
(OWNER) and/or the
PRIV_LIMIT
(LIMIT) privileges.
Processes owned by the superuser will have these privileges.
Processes owned by other users may have privilege(s), depending on system
configuration. See
privileges(5)
for more information about privileged access on
systems that support fine-grained privileges.
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.
STANDARDS CONFORMANCE
nice(): AES, SVID2, SVID3, XPG2, XPG3, XPG4
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