Linux cli command pthread_sigmask

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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).

InterfaceAttributeValue

pthread_sigmask()

Thread safetyMT-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

“, 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)

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