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.TH PTHREAD_JOIN 3C "Mar 23, 2005"
.SH NAME
pthread_join \- wait for thread termination
.SH SYNOPSIS
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... -lpthread [ \fIlibrary\fR... ]
#include <pthread.h>

\fBint\fR \fBpthread_join\fR(\fBpthread_t\fR \fIthread\fR, \fBvoid **\fR\fIstatus\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBpthread_join()\fR function suspends processing of the calling thread
until the target \fIthread\fR completes. \fIthread\fR must be a member of the
current process and it cannot be a detached thread. See
\fBpthread_create\fR(3C).
.sp
.LP
If two or more threads wait for the same thread to complete, all will suspend
processing until the thread has terminated, and then one thread will return
successfully and the others will return with an error of \fBESRCH\fR. The
\fBpthread_join()\fR function will not block processing of the calling thread
if the target \fIthread\fR has already terminated.
.sp
.LP
If a \fBpthread_join()\fR call returns successfully with a non-null
\fIstatus\fR argument, the value passed to \fBpthread_exit\fR(3C) by the
terminating thread will be placed in the location referenced by \fIstatus\fR.
.sp
.LP
If the \fBpthread_join()\fR calling thread is cancelled, then the target
\fIthread\fR will remain joinable by \fBpthread_join()\fR. However, the calling
thread may set up a cancellation cleanup handler on \fIthread\fR prior to the
join call, which may detach the target \fIthread\fR by calling
\fBpthread_detach\fR(3C). See \fBpthread_detach\fR(3C) and
\fBpthread_cancel\fR(3C).
.SH RETURN VALUES
.sp
.LP
If successful, \fBpthread_join()\fR returns \fB0\fR. Otherwise, an error number
is returned to indicate the error.
.SH ERRORS
.sp
.ne 2
.na
\fB\fBEDEADLK\fR\fR
.ad
.RS 11n
A joining deadlock would occur, such as when a thread attempts to wait for
itself.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 11n
The thread corresponding to the given thread ID is a detached thread.
.RE

.sp
.ne 2
.na
\fB\fBESRCH\fR\fR
.ad
.RS 11n
No thread could be found corresponding to the given thread ID.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR pthread_cancel (3C),
.BR pthread_create (3C),
.BR pthread_detach (3C),
.BR pthread_exit (3C),
.BR wait (3C),
.BR attributes (7),
.BR standards (7)
.SH NOTES
.sp
.LP
The pthread_join(3C) function must specify the \fIthread\fR \fBID\fR for whose
termination it will wait.
.sp
.LP
Calling \fBpthread_join()\fR also "detaches" the thread; that is,
\fBpthread_join()\fR includes the effect of the \fBpthread_detach()\fR
function. If a thread were to be cancelled when blocked in
\fBpthread_join()\fR, an explicit detach would have to be performed in the
cancellation cleanup handler. The \fBpthread_detach()\fR function exists
primarily for this purpose.