NAME

       pthread_sigmask - examine and change mask of blocked signals

LIBRARY

       POSIX threads library (libpthread, -lpthread)

SYNOPSIS

       #include <signal.h>

       int pthread_sigmask(int how, const sigset_t *set, sigset_t *oldset);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       pthread_sigmask():
           _POSIX_C_SOURCE >= 199506L || _XOPEN_SOURCE >= 500

DESCRIPTION

       The  pthread_sigmask()  function is just like sigprocmask(2), with the difference that its
       use in multithreaded programs is explicitly specified by POSIX.1.  Other  differences  are
       noted in this page.

       For a description of the arguments and operation of this function, see sigprocmask(2).

RETURN VALUE

       On success, pthread_sigmask() returns 0; on error, it returns an error number.

ERRORS

       See sigprocmask(2).

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌───────────────────────────────────────────────────────────────┬───────────────┬─────────┐
       │Interface                                                      │ Attribute     │ Value   │
       ├───────────────────────────────────────────────────────────────┼───────────────┼─────────┤
       │pthread_sigmask()                                              │ Thread safety │ MT-Safe │
       └───────────────────────────────────────────────────────────────┴───────────────┴─────────┘

STANDARDS

       POSIX.1-2008.

HISTORY

       POSIX.1-2001.

NOTES

       A new thread inherits a copy of its creator's signal mask.

       The  glibc pthread_sigmask() function silently ignores attempts to block the two real-time
       signals that are used internally by the NPTL threading implementation.   See  nptl(7)  for
       details.

EXAMPLES

       The  program  below  blocks  some signals in the main thread, and then creates a dedicated
       thread to fetch those signals via sigwait(3).  The following  shell  session  demonstrates
       its use:

           $ ./a.out &
           [1] 5423
           $ kill -QUIT %1
           Signal handling thread got signal 3
           $ kill -USR1 %1
           Signal handling thread got signal 10
           $ kill -TERM %1
           [1]+  Terminated              ./a.out

   Program source

       #include <errno.h>
       #include <pthread.h>
       #include <signal.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>

       /* Simple error handling functions */

       #define handle_error_en(en, msg) \
               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

       static void *
       sig_thread(void *arg)
       {
           sigset_t *set = arg;
           int s, sig;

           for (;;) {
               s = sigwait(set, &sig);
               if (s != 0)
                   handle_error_en(s, "sigwait");
               printf("Signal handling thread got signal %d\n", sig);
           }
       }

       int
       main(void)
       {
           pthread_t thread;
           sigset_t set;
           int s;

           /* Block SIGQUIT and SIGUSR1; other threads created by main()
              will inherit a copy of the signal mask. */

           sigemptyset(&set);
           sigaddset(&set, SIGQUIT);
           sigaddset(&set, SIGUSR1);
           s = pthread_sigmask(SIG_BLOCK, &set, NULL);
           if (s != 0)
               handle_error_en(s, "pthread_sigmask");

           s = pthread_create(&thread, NULL, &sig_thread, &set);
           if (s != 0)
               handle_error_en(s, "pthread_create");

           /* Main thread carries on to create other threads and/or do
              other work. */

           pause();            /* Dummy pause so we can test program */
       }

SEE ALSO

       sigaction(2),      sigpending(2),      sigprocmask(2),      pthread_attr_setsigmask_np(3),
       pthread_create(3), pthread_kill(3), sigsetops(3), pthreads(7), signal(7)