sigmask(2)                                                   sigmask(2)

  sigblock()

  NAME

    sigblock(), sigmask(), sigsetmask() - BSD4.3 compatibility signal
    functions

  SYNOPSIS

    #include 

    int sigblock (int mask)
    int sigmask (int signum)
    int sigsetmask (int mask)

  DESCRIPTION

    This interface is made obsolete by: sigprocmask(2).

    The sigblock(3) function adds the signals specified in mask to the set of
    signals currently being blocked from delivery. Signals are blocked if the
    corresponding bit in mask is a 1. The sigmask(2) function is provided to
    construct the mask for a given signum.

    It is not possible to block SIGKILL or SIGSTOP; this restriction is
    silently imposed by the system.

  RETURN VALUES

    The functions sigblock(3) and sigsetmask(3) return the previous set of
    masked signals.

    The sigmask(2) function returns a mask that can be used to block the
    signal signum.

  NOTES

    The sigblock(3) call is provided for compatibility with BSD 4.3 only;
    portable code should use sigprocmask(2).

    The declaration of these APIs is visible only when _ALL_SOURCE is defined.
    These routines are only viable while the total number of signals supported
    on INTERIX is less than 32. If more signals are supported, then the signal
    mask will no longer fit in an int.

  SEE ALSO

    kill(2)

    sigprocmask(2)

    sigaction(2)

    sigemptyset(3)

    signal(2)

  USAGE NOTES

    The following functions are thread safe: sigblock, sigsetmask. The sigmask
    function is not thread safe.

    None of these functions are async-signal safe.