PTHREAD_TRYJOIN_NP(3)                                                   Linux Programmer's Manual                                                  PTHREAD_TRYJOIN_NP(3)

NAME
       pthread_tryjoin_np, pthread_timedjoin_np - try to join with a terminated thread

SYNOPSIS
       #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.

DESCRIPTION
       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  ab‐
       stime,  measured against the CLOCK_REALTIME clock.  If the timeout expires before thread terminates, the call returns an error.  The abstime argument is a struc‐
       ture 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 */
           };

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

ERRORS
       These functions can fail with the same errors as pthread_join(3).  pthread_tryjoin_np() can in addition fail with the following error:

       EBUSY  thread had not yet terminated at the time of the call.

       pthread_timedjoin_np() can in addition fail with the following errors:

       EINVAL abstime value is invalid (tv_sec is less than 0 or tv_nsec is greater than 1e9).

       ETIMEDOUT
              The call timed out before thread terminated.

       pthread_timedjoin_np() never returns the error EINTR.

VERSIONS
       These functions first appeared in glibc in version 2.3.3.

ATTRIBUTES
       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 │
       └──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┴───────────────┴─────────┘

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

BUGS
       The pthread_timedjoin_np() function measures time by internally calculating a relative sleep interval that is then measured against the CLOCK_MONOTONIC clock in‐
       stead of the CLOCK_REALTIME clock.  Consequently, the timeout is unaffected by discontinuous changes to the CLOCK_REALTIME clock.

EXAMPLES
       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 */
           }

SEE ALSO
       clock_gettime(2), pthread_exit(3), pthread_join(3), pthreads(7)

Linux                                                                          2021-08-27                                                          PTHREAD_TRYJOIN_NP(3)