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pthread_sigmask

Section: C Library Functions (3)
Updated: 202-0-21
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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	M-Safe

STANDARDS

POSIX.-2008.

HISTORY

POSIX.-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 rea-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 <err.h> #include <errno.h> #include <pthread.h> #include <signal.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> /* Simple error handling functions */ static void * sig_thread(void *arg) {
    sigset_t *set = arg;
    int s, sig;
    for (;;) {
        s = sigwait(set, &sig);
        if (s != 0)
            errc(EXIT_FAILURE, s, "sigwait");
        printf("Signal handling thread got signal %d[rs]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)
        errc(EXIT_FAILURE, s, "pthread_sigmask");
    s = pthread_create(&thread, NULL, &sig_thread, &set);
    if (s != 0)
        errc(EXIT_FAILURE, s, "pthread_create");
    /* Main thread carries on to create other threads and/or do
       other work.  */
    pause();            /* Dummy pause so we can test program */ }

Index

Program source

SEE ALSO