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.\" $FreeBSD: src/lib/libpthread/man/pthread_attr.3,v 1.11 2002/09/16 19:29:28 mini Exp $
.\"
.Dd July 9, 2010
.Dt PTHREAD_ATTR 3
.Os
.Sh NAME
.Nm pthread_attr_init ,
.Nm pthread_attr_destroy
.Nd thread attribute operations
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_attr_init "pthread_attr_t *attr"
.Ft int
.Fn pthread_attr_destroy "pthread_attr_t *attr"
.Sh DESCRIPTION
Thread attributes are used to specify parameters to
.Fn pthread_create .
One attribute object can be used in multiple calls to
.Fn pthread_create ,
with or without modifications between the calls.
The
.Vt pthread_attr_t
type is an opaque representation of the thread attributes;
any access to the object other than via the described
.Fn pthread_attr_*
functions may result in undefined behavior.
.Pp
The
.Fn pthread_attr_init
function initializes
.Fa attr
with the default thread attributes used in the implementation.
Depending on the implementation, undefined behavior may follow
if an uninitialized thread attribute object is used with some of
the thread attribute functions.
It is therefore a good practice to always use
.Fn pthread_attr_init ,
even if this might be unnecessary.
Undefined behavior may also follow if an already initialized
.Fa attr
is used with
.Fn pthread_attr_init .
.Pp
When the attribute object is no longer needed,
it should be destroyed by using
.Fn pthread_attr_destroy .
The function has no effect on threads that
were created by using a given attribute object.
A destroyed
.Fa attr
can be reinitialized using
.Fn pthread_attr_init ,
but all other actions with the destroyed object are unspecified.
.Pp
The following standard thread attribute functions are available:
.Bl -column -offset indent "pthread_attr_getinheritsched " "XXX"
.It Sy Function Ta Sy Description
.It Xr pthread_attr_getdetachstate 3 Ta thread detach state
.It Xr pthread_attr_getguardsize 3 Ta thread guard size
.It Xr pthread_attr_getinheritsched 3 Ta inherit scheduler attribute
.It Xr pthread_attr_getschedparam 3 Ta thread scheduling parameter
.It Xr pthread_attr_getschedpolicy 3 Ta thread scheduling policy
.It Xr pthread_attr_getscope 3 Ta thread contention scope
.It Xr pthread_attr_getstack 3 Ta thread stack
.It Xr pthread_attr_getstacksize 3 Ta thread stack size
.It Xr pthread_attr_getstackaddr 3 Ta thread stack address
.El
.Pp
Each listed
.Fn pthread_attr_get*
function has a
.Fn pthread_attr_set*
counterpart.
In addition, the following
.Nx
specific extensions are available:
.Bl -column -offset indent "pthread_attr_getinheritsched " "XXX"
.It Sy Function Ta Sy Description
.It Xr pthread_attr_get_np 3 Ta attributes of a running thread
.It Xr pthread_attr_getname_np 3 Ta descriptive name of an attribute
.El
.Sh RETURN VALUES
If successful, these functions return 0.
Otherwise, an error number is returned to indicate the error.
.Sh ERRORS
No errors are defined for
.Fn pthread_attr_init
and
.Fn pthread_attr_destroy .
.Sh SEE ALSO
.Xr pthread_create 3 ,
.Xr pthread_join 3
.Sh STANDARDS
Both
.Fn pthread_attr_init
and
.Fn pthread_attr_destroy
conform to
.St -p1003.1-2001 .