pthread_tryjoin_np, pthread_timedjoin_np - try to join with a terminated thread

#define _GNU_SOURCE             /* See feature_test_macros(7) */
#include <pthread.h>
int pthread_tryjoin_np(pthread_t thread, void **retval);
int pthread_timedjoin_np(pthread_t thread, void **retval,
                         const struct timespec *abstime);
Compile and link with -pthread.

These functions operate in the same way as pthread_join(3), except for the differences described on this page.
The pthread_tryjoin_np() function performs a nonblocking join with the thread thread, returning the exit status of the thread in *retval. If thread has not yet terminated, then instead of blocking, as is done by pthread_join(3), the call returns an error.
The pthread_timedjoin_np() function performs a join-with-timeout. If thread has not yet terminated, then the call blocks until a maximum time, specified in abstime. If the timeout expires before thread terminates, the call returns an error. The abstime argument is a structure of the following form, specifying an absolute time measured since the Epoch (see time(2)):

struct timespec {
    time_t tv_sec;     /* seconds */
    long   tv_nsec;    /* nanoseconds */

On success, these functions return 0; on error, they return an error number.

These functions can fail with the same errors as pthread_join(3). pthread_tryjoin_np() can in addition fail with the following error:
thread had not yet terminated at the time of the call.
pthread_timedjoin_np() can in addition fail with the following errors:
The call timed out before thread terminated.
abstime value is invalid (tv_sec is less than 0 or tv_nsec is greater than 1e9).
pthread_timedjoin_np() never returns the error EINTR.

These functions first appeared in glibc in version 2.3.3.

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
pthread_tryjoin_np (), pthread_timedjoin_np () Thread safety MT-Safe

These functions are nonstandard GNU extensions; hence the suffix "_np" (nonportable) in the names.

The following code waits to join for up to 5 seconds:

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 */ }

clock_gettime(2), pthread_exit(3), pthread_join(3), pthreads(7)
2017-09-15 Linux