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



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	speci-
       fied 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 thread-
       ing implementation.  See nptl(7) for details.

EXAMPLE
       The program below blocks some signals in the main thread, and then cre-
       ates  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
       This  page  is  part of release 4.10 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest	  version     of     this    page,    can    be	   found    at
       https://www.kernel.org/doc/man-pages/.



Linux				  2015-08-08		    PTHREAD_SIGMASK(3)