pthread_sigmask(3)

1pthread_sigmask(3)         Library Functions Manual         pthread_sigmask(3)
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NAME

6       pthread_sigmask - examine and change mask of blocked signals
7

LIBRARY

9       POSIX threads library (libpthread, -lpthread)
10

SYNOPSIS

12       #include <signal.h>
13
14       int pthread_sigmask(int how, const sigset_t *set, sigset_t *oldset);
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16   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
17
18       pthread_sigmask():
19           _POSIX_C_SOURCE >= 199506L || _XOPEN_SOURCE >= 500
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DESCRIPTION

22       The  pthread_sigmask()  function  is just like sigprocmask(2), with the
23       difference that its use in multithreaded programs is explicitly  speci‐
24       fied by POSIX.1.  Other differences are noted in this page.
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26       For  a description of the arguments and operation of this function, see
27       sigprocmask(2).
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RETURN VALUE

30       On success, pthread_sigmask() returns 0; on error, it returns an  error
31       number.
32

ERRORS

34       See sigprocmask(2).
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ATTRIBUTES

37       For  an  explanation  of  the  terms  used  in  this  section,  see at‐
38       tributes(7).
39
40       ┌────────────────────────────────────────────┬───────────────┬─────────┐
41       │Interface                                   │ Attribute     │ Value   │
42       ├────────────────────────────────────────────┼───────────────┼─────────┤
43       │pthread_sigmask()                           │ Thread safety │ MT-Safe │
44       └────────────────────────────────────────────┴───────────────┴─────────┘
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STANDARDS

47       POSIX.1-2008.
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HISTORY

50       POSIX.1-2001.
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NOTES

53       A new thread inherits a copy of its creator's signal mask.
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55       The glibc pthread_sigmask() function silently ignores attempts to block
56       the  two real-time signals that are used internally by the NPTL thread‐
57       ing implementation.  See nptl(7) for details.
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EXAMPLES

60       The program below blocks some signals in the main thread, and then cre‐
61       ates  a  dedicated  thread  to fetch those signals via sigwait(3).  The
62       following shell session demonstrates its use:
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64           $ ./a.out &
65           [1] 5423
66           $ kill -QUIT %1
67           Signal handling thread got signal 3
68           $ kill -USR1 %1
69           Signal handling thread got signal 10
70           $ kill -TERM %1
71           [1]+  Terminated              ./a.out
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73   Program source
74
75       #include <errno.h>
76       #include <pthread.h>
77       #include <signal.h>
78       #include <stdio.h>
79       #include <stdlib.h>
80       #include <unistd.h>
81
82       /* Simple error handling functions */
83
84       #define handle_error_en(en, msg) \
85               do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)
86
87       static void *
88       sig_thread(void *arg)
89       {
90           sigset_t *set = arg;
91           int s, sig;
92
93           for (;;) {
94               s = sigwait(set, &sig);
95               if (s != 0)
96                   handle_error_en(s, "sigwait");
97               printf("Signal handling thread got signal %d\n", sig);
98           }
99       }
100
101       int
102       main(void)
103       {
104           pthread_t thread;
105           sigset_t set;
106           int s;
107
108           /* Block SIGQUIT and SIGUSR1; other threads created by main()
109              will inherit a copy of the signal mask. */
110
111           sigemptyset(&set);
112           sigaddset(&set, SIGQUIT);
113           sigaddset(&set, SIGUSR1);
114           s = pthread_sigmask(SIG_BLOCK, &set, NULL);
115           if (s != 0)
116               handle_error_en(s, "pthread_sigmask");
117
118           s = pthread_create(&thread, NULL, &sig_thread, &set);
119           if (s != 0)
120               handle_error_en(s, "pthread_create");
121
122           /* Main thread carries on to create other threads and/or do
123              other work. */
124
125           pause();            /* Dummy pause so we can test program */
126       }
127