#define _GNU_SOURCE
#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.
The pthread_tryjoin_np() function performs a non-blocking 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 */
};
 
pthread_timedjoin_np() can in addition fail with the following error:
pthread_timedjoin_np() never returns the error EINTR.
    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 */
    }