.\" $OpenBSD: pthread_setspecific.3,v 1.13 2017/01/27 15:47:47 schwarze Exp $
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.\" Copyright (c) 1996 John Birrell <jb@cimlogic.com.au>.
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.\" $FreeBSD: pthread_setspecific.3,v 1.5 1999/08/28 00:03:11 peter Exp $
.\"
.Dd $Mdocdate: January 27 2017 $
.Dt PTHREAD_SETSPECIFIC 3
.Os
.Sh NAME
.Nm pthread_setspecific
.Nd set a thread-specific data value
.Sh SYNOPSIS
.In pthread.h
.Ft int
.Fn pthread_setspecific "pthread_key_t key" "const void *value"
.Sh DESCRIPTION
The
.Fn pthread_setspecific
function associates a thread-specific value with a
.Fa key
obtained via a previous call to
.Fn pthread_key_create .
Different threads may bind different values to the same key.
These values are
typically pointers to blocks of dynamically allocated memory that have been
reserved for use by the calling thread.
.Pp
The effect of calling
.Fn pthread_setspecific
with a key value not obtained from
.Fn pthread_key_create
or after
.Fa key
has been deleted with
.Fn pthread_key_delete
is undefined.
.Pp
.Fn pthread_setspecific
may be called from a thread-specific data destructor function; however, this
may result in lost storage or infinite loops.
.Sh RETURN VALUES
If successful, the
.Fn pthread_setspecific
function will return zero.
Otherwise an error number will be returned to indicate the error.
.Sh ERRORS
.Fn pthread_setspecific
will fail if:
.Bl -tag -width Er
.It Bq Er ENOMEM
Insufficient memory exists to associate the value with the
.Fa key .
.It Bq Er EINVAL
The
.Fa key
value is invalid.
.El
.Sh SEE ALSO
.Xr pthread_getspecific 3 ,
.Xr pthread_key_create 3 ,
.Xr pthread_key_delete 3
.Sh STANDARDS
.Fn pthread_setspecific
conforms to
.St -p1003.1-96 .