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