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.TH PTHREAD_TRYJOIN_NP 3 2021-03-22 "Linux" "Linux Programmer's Manual"
.SH NAME
pthread_tryjoin_np, pthread_timedjoin_np \- try to join with a
terminated thread
.SH SYNOPSIS
.nf
.BR "#define _GNU_SOURCE" "             /* See feature_test_macros(7) */"
.B #include <pthread.h>
.PP
.BI "int pthread_tryjoin_np(pthread_t " thread ", void **" retval );
.BI "int pthread_timedjoin_np(pthread_t " thread ", void **" retval ,
.BI "                         const struct timespec *" abstime );
.fi
.PP
Compile and link with \fI\-pthread\fP.
.SH DESCRIPTION
These functions operate in the same way as
.BR pthread_join (3),
except for the differences described on this page.
.PP
The
.BR pthread_tryjoin_np ()
function performs a nonblocking join with the thread
.IR thread ,
returning the exit status of the thread in
.IR *retval .
If
.I thread
has not yet terminated, then instead of blocking, as is done by
.BR pthread_join (3),
the call returns an error.
.PP
The
.BR pthread_timedjoin_np ()
function performs a join-with-timeout.
If
.I thread
has not yet terminated,
then the call blocks until a maximum time, specified in
.IR abstime ,
measured against the
.BR CLOCK_REALTIME
clock.
If the timeout expires before
.I thread
terminates,
the call returns an error.
The
.I abstime
argument is a structure of the following form,
specifying an absolute time measured since the Epoch (see
.BR time (2)):
.PP
.in +4n
.EX
struct timespec {
    time_t tv_sec;     /* seconds */
    long   tv_nsec;    /* nanoseconds */
};
.EE
.in
.SH RETURN VALUE
On success,
these functions return 0;
on error, they return an error number.
.SH ERRORS
These functions can fail with the same errors as
.BR pthread_join (3).
.BR pthread_tryjoin_np ()
can in addition fail with the following error:
.TP
.B EBUSY
.I thread
had not yet terminated at the time of the call.
.PP
.BR pthread_timedjoin_np ()
can in addition fail with the following errors:
.TP
.BR ETIMEDOUT
The call timed out before
.I thread
terminated.
.TP
.BR EINVAL
.I abstime
value is invalid
.RI ( tv_sec
is less than 0 or
.IR tv_nsec
is greater than 1e9).
.PP
.BR pthread_timedjoin_np ()
never returns the error
.BR EINTR .
.SH VERSIONS
These functions first appeared in glibc in version 2.3.3.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR pthread_tryjoin_np (),
.BR pthread_timedjoin_np ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
These functions are nonstandard GNU extensions;
hence the suffix "_np" (nonportable) in the names.
.SH EXAMPLES
The following code waits to join for up to 5 seconds:
.PP
.in +4n
.EX
struct timespec ts;
int s;

\&...

if (clock_gettime(CLOCK_REALTIME, &ts) == \-1) {
    /* Handle error */
}

ts.tv_sec += 5;

s = pthread_timedjoin_np(thread, NULL, &ts);
if (s != 0) {
    /* Handle error */
}
.EE
.in
.SH BUGS
The
.BR pthread_timedjoin_np ()
function measures time by internally calculating a relative sleep interval
that is then measured against the
.BR CLOCK_MONOTONIC
clock instead of the
.BR CLOCK_REALTIME
clock.
Consequently, the timeout is unaffected by discontinuous changes to the
.BR CLOCK_REALTIME
clock.
.SH SEE ALSO
.BR clock_gettime (2),
.BR pthread_exit (3),
.BR pthread_join (3),
.BR pthreads (7)