1997-02-27 07:32:31 +00:00
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.\"
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1997-09-15 19:15:26 +00:00
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.\" $Id: sigblock.2,v 1.2 1997/09/15 19:15:26 gdr Exp $
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1997-02-27 07:32:31 +00:00
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.\"
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.TH SIGBLOCK 2 "19 January 1997" GNO "System Calls"
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.SH NAME
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.BR sigblock,
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.BR sigmask
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\- temporarily block signals
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.SH SYNOPSIS
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#include <signal.h>
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.sp 1
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long
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\fBsigblock\fR(long \fImask\fR);
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.br
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#define \fBsigmask\fR(\fIsignum\fR)
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.SH DESCRIPTION
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.BR sigblock
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1997-09-15 19:15:26 +00:00
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is used to temporarily block the reception of signals. The input parameter
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1997-02-27 07:32:31 +00:00
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.IR mask
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is a bit vector that specifies which signals are to be blocked; a 1 in bit
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.I n
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will block signal
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.IR n +1.
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The
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.IR mask
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is bitwise-or'd with the current signal mask to create the new
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signal mask.
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.LP
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.BR sigmask
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is a macro that can be used to calculate signal masks for
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.BR sigsetmask .
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It takes a signal number
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.IR signum ,
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as listed in
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.BR signal (2),
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as an argument and returns a mask corresponding to that signal.
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.LP
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If a signal is sent to a process but is blocked, the event is recorded
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for later release by
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.BR sigsetmask (2).
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blocked signals are not stacked; further occurrences of a blocked signal
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will overwrite any previous pending signal of the same
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.IR signum .
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.LP
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It is not possible to block
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.BR SIGKILL ,
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.BR SIGCONT ,
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or
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.BR SIGSTOP .
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This restriction is silently enforced by the kernel.
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.SH RETURN VALUE
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The previous value of the signal mask is returned.
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.SH SEE ALSO
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.BR kill (2),
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.BR sigsetmask (2),
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.BR signal (2)
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