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



NAME
       sigprocmask - examine and change blocked signals

SYNOPSIS
       #include <signal.h>

       int sigprocmask(int how, const sigset_t *set, sigset_t *oldset);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       sigprocmask(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE

DESCRIPTION
       sigprocmask()  is  used to fetch and/or change the signal mask of the calling thread.  The signal mask is the set of sig-
       nals whose delivery is currently blocked for the caller (see also signal(7) for more details).

       The behavior of the call is dependent on the value of how, as follows.

       SIG_BLOCK
              The set of blocked signals is the union of the current set and the set argument.

       SIG_UNBLOCK
              The signals in set are removed from the current set of blocked signals.  It is permissible to attempt to unblock a
              signal which is not blocked.

       SIG_SETMASK
              The set of blocked signals is set to the argument set.

       If oldset is non-NULL, the previous value of the signal mask is stored in oldset.

       If  set  is  NULL,  then the signal mask is unchanged (i.e., how is ignored), but the current value of the signal mask is
       nevertheless returned in oldset (if it is not NULL).

       The use of sigprocmask() is unspecified in a multithreaded process; see pthread_sigmask(3).

RETURN VALUE
       sigprocmask() returns 0 on success and -1 on error.

ERRORS
       EINVAL The value specified in how was invalid.

CONFORMING TO
       POSIX.1-2001.

NOTES
       It is not possible to block SIGKILL or SIGSTOP.  Attempts to do so are silently ignored.

       Each of the threads in a process has its own signal mask.

       A child created via fork(2) inherits a copy of its parent's signal mask; the signal mask is preserved across execve(2).

       If SIGBUS, SIGFPE, SIGILL, or SIGSEGV are generated while they are blocked, the result is undefined,  unless  the  signal
       was generated by kill(2), sigqueue(2), or raise(3).

       See sigsetops(3) for details on manipulating signal sets.

SEE ALSO
       kill(2),  pause(2), sigaction(2), signal(2), sigpending(2), sigqueue(2), sigsuspend(2), pthread_sigmask(3), sigsetops(3),
       signal(7)

COLOPHON
       This page is part of release 3.25 of the Linux man-pages project.  A description of the project,  and  information  about
       reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.



Linux                                                      2008-10-17                                             SIGPROCMASK(2)