NetBSD/lib/libpthread/pthread_getspecific.3

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.\" $FreeBSD: src/lib/libpthread/man/pthread_getspecific.3,v 1.11 2002/09/16 19:29:28 mini Exp $
.\"
.Dd July 9, 2010
.Dt PTHREAD_GETSPECIFIC 3
.Os
.Sh NAME
.Nm pthread_getspecific
.Nd thread-specific data value
.Sh LIBRARY
.Lb libpthread
.Sh SYNOPSIS
.In pthread.h
.Ft void *
.Fn pthread_getspecific "pthread_key_t key"
.Ft int
.Fn pthread_setspecific "pthread_key_t key" "const void *value"
.Sh DESCRIPTION
The
.Fn pthread_getspecific
function returns the value currently bound to the specified
.Fa key
on behalf of the calling thread.
Conversely, the
.Fn pthread_setspecific
function associates a thread-specific value with a
.Fa key
obtained via a previous call to
.Xr pthread_key_create 3 .
Different threads have different values bound to each key.
These values are typically pointers to blocks of dynamically
allocated memory that have been reserved for use by the calling thread.
.Pp
Undefined behavior may follow if either function is called with a
.Fa key
value not obtained from
.Xr pthread_key_create 3 ,
or if the call is made after
.Fa key
has been deleted with
.Xr pthread_key_delete 3 .
It is possible to call either function from
a thread-specific data destructor function.
Note however that this is not well defined for the
.Fn pthread_setspecific
function;
lost storage or infinite loops may occur.
.Sh RETURN VALUES
The
.Fn pthread_getspecific
function will return the thread-specific data value associated with the given
.Fa key .
If no thread-specific data value is associated with
.Fa key ,
then the value
.Dv NULL
is returned.
If successful, the
.Fn pthread_setspecific
function will return zero.
Otherwise an error number will be returned to
indicate the error.
.Sh ERRORS
No errors are defined for either function.
.Sh SEE ALSO
.Xr pthread_key_create 3
.Sh STANDARDS
These functions conform to
.St -p1003.1-2001 .