pthread_sigmask(3) - Linux manual page (original) (raw)

pthreadsigmask(3) Library Functions Manual pthreadsigmask(3)

NAME top

   pthread_sigmask - examine and change mask of blocked signals

LIBRARY top

   POSIX threads library (_libpthread_, _-lpthread_)

SYNOPSIS top

   **#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 top

   The **pthread_sigmask**() function is just like [sigprocmask(2)](../man2/sigprocmask.2.html), 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)](../man2/sigprocmask.2.html).

RETURN VALUE top

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

ERRORS top

   See [sigprocmask(2)](../man2/sigprocmask.2.html).

ATTRIBUTES top

   For an explanation of the terms used in this section, see
   [attributes(7)](../man7/attributes.7.html).
   ┌──────────────────────────────────────┬───────────────┬─────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├──────────────────────────────────────┼───────────────┼─────────┤
   │ **pthread_sigmask**()                    │ Thread safety │ MT-Safe │
   └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS top

   POSIX.1-2008.

HISTORY top

   POSIX.1-2001.

NOTES top

   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)](../man7/nptl.7.html) for details.

EXAMPLES top

   The program below blocks some signals in the main thread, and then
   creates a dedicated thread to fetch those signals via [sigwait(3)](../man3/sigwait.3.html).
   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 top

   [sigaction(2)](../man2/sigaction.2.html), [sigpending(2)](../man2/sigpending.2.html), [sigprocmask(2)](../man2/sigprocmask.2.html),
   [pthread_attr_setsigmask_np(3)](../man3/pthread%5Fattr%5Fsetsigmask%5Fnp.3.html), [pthread_create(3)](../man3/pthread%5Fcreate.3.html), [pthread_kill(3)](../man3/pthread%5Fkill.3.html),
   [sigsetops(3)](../man3/sigsetops.3.html), [pthreads(7)](../man7/pthreads.7.html), [signal(7)](../man7/signal.7.html)

COLOPHON top

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   man-pages@man7.org

Linux man-pages 6.10 2024-07-23 pthreadsigmask(3)

Pages that refer to this page:sigprocmask(2), pthread_attr_setsigmask_np(3), pthread_create(3), pthread_kill(3), pthread_sigqueue(3), sd_event_add_child(3), sd_event_add_signal(3), sigset(3), sigwait(3), nptl(7), pthreads(7), signal(7), signal-safety(7)