NAME

       pthread_sigmask - examine and change mask of blocked signals

SYNOPSIS

       #include <signal.h>

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

       Compile and link with -pthread.

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

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008.

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.

EXAMPLE

       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 <pthread.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <unistd.h>
       #include <signal.h>
       #include <errno.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(int argc, char *argv[])
       {
           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, (void *) &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_create(3),   pthread_kill(3),    sigsetops(3),
       pthreads(7), signal(7)

COLOPHON

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