sigprocmask(2)

1SIGPROCMASK(2)             Linux Programmer's Manual            SIGPROCMASK(2)
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NAME

6       sigprocmask - examine and change blocked signals
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SYNOPSIS

9       #include <signal.h>
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11       int sigprocmask(int how, const sigset_t *set, sigset_t *oldset);
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DESCRIPTION

14       sigprocmask()  is  used to change the signal mask, the set of currently
15       blocked signals.  The behaviour of the call is dependent on  the  value
16       of how, as follows.
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18              SIG_BLOCK
19                     The  set  of  blocked signals is the union of the current
20                     set and the set argument.
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22              SIG_UNBLOCK
23                     The signals in set are removed from the  current  set  of
24                     blocked  signals.   It  is  legal to attempt to unblock a
25                     signal which is not blocked.
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27              SIG_SETMASK
28                     The set of blocked signals is set to the argument set.
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30       If oldset is non-null, the previous value of the signal mask is  stored
31       in oldset.
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33       If  set  is  NULL,  then  the  signal  mask  is unchanged (i.e., how is
34       ignored), but the current value of  the  signal  mask  is  nevertheless
35       returned in oldset (it is not NULL).
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37       The use of sigprocmask() is unspecified in a multithreaded process; see
38       pthread_sigmask(3).
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RETURN VALUE

41       sigprocmask() returns 0 on success and -1 on error.
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ERRORS

44       EINVAL The value specified in how was invalid.
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NOTES

47       It is not possible to block SIGKILL or SIGSTOP.  Attempts to do so  are
48       silently ignored.
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50       If  SIGBUS,  SIGFPE,  SIGILL,  or  SIGSEGV are generated while they are
51       blocked, the result is undefined, unless the signal  was  generated  by
52       the kill(2), sigqueue(2), or raise(3).
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54       See sigsetops(3) for details on manipulating signal sets.
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CONFORMING TO

57       POSIX.1-2001.
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