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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13   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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15       sigprocmask(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE
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DESCRIPTION

18       sigprocmask()  is  used  to  fetch and/or change the signal mask of the
19       calling thread.  The signal mask is the set of signals  whose  delivery
20       is  currently  blocked  for  the  caller  (see  also signal(7) for more
21       details).
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23       The behavior of the call is dependent on the value of how, as follows.
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25       SIG_BLOCK
26              The set of blocked signals is the union of the current  set  and
27              the set argument.
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29       SIG_UNBLOCK
30              The  signals  in set are removed from the current set of blocked
31              signals.  It is permissible to attempt to unblock a signal which
32              is not blocked.
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34       SIG_SETMASK
35              The set of blocked signals is set to the argument set.
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37       If  oldset is non-NULL, the previous value of the signal mask is stored
38       in oldset.
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40       If set is NULL, then  the  signal  mask  is  unchanged  (i.e.,  how  is
41       ignored),  but  the  current  value  of the signal mask is nevertheless
42       returned in oldset (if it is not NULL).
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44       The use of sigprocmask() is unspecified in a multithreaded process; see
45       pthread_sigmask(3).
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RETURN VALUE

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

51       EINVAL The value specified in how was invalid.
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CONFORMING TO

54       POSIX.1-2001.
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NOTES

57       It  is not possible to block SIGKILL or SIGSTOP.  Attempts to do so are
58       silently ignored.
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60       Each of the threads in a process has its own signal mask.
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62       A child created via fork(2) inherits a  copy  of  its  parent's  signal
63       mask; the signal mask is preserved across execve(2).
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65       If  SIGBUS,  SIGFPE,  SIGILL,  or  SIGSEGV are generated while they are
66       blocked, the result is undefined, unless the signal  was  generated  by
67       kill(2), sigqueue(2), or raise(3).
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69       See sigsetops(3) for details on manipulating signal sets.
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SEE ALSO

72       kill(2), pause(2), sigaction(2), signal(2), sigpending(2), sigqueue(2),
73       sigsuspend(2), pthread_sigmask(3), sigsetops(3), signal(7)
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COLOPHON

76       This page is part of release 3.25 of the Linux  man-pages  project.   A
77       description  of  the project, and information about reporting bugs, can
78       be found at http://www.kernel.org/doc/man-pages/.
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82Linux                             2008-10-17                    SIGPROCMASK(2)
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