.\"
.\" $Id: sigsetmask.2,v 1.1 1997/02/27 07:32:16 gdr Exp $
.\"
.TH SIGSETMASK 2 "19 January 1997" GNO "System Calls"
.SH NAME
.BR sigsetmask
\- set signal mask
.SH SYNOPSIS
#include <signal.h>
.sp 1
long
\fBsigsetmask\fR(long \fImask\fR);
.br
#define \fBsigmask\fR(\fIsignum\fR)
.SH DESCRIPTION
.BR sigsetmask
is usually used to restore signal masks after modifications by 
.BR sigblock .
The parameter mask is the absolute value to which the process signal
mask will be set.  (Compare to
.BR sigblock ,
which adds the argument to the set of blocked signals.)
.LP
If there are pending instances of signals which become unblocked by the 
.BR sigsetmask
call, they are 'released' into the system signal queue and their 'pending'
status is cleared.  The system signal queue is maintained by the kernel
null process, and is used in situations where signals could not normally
be sent (such as in interrupt handlers).
.LP
.BR sigmask
is a macro that can be used to calculate signal masks for 
.BR sigsetmask .
It takes a signal number, as listed in 
.BR signal (2),
as an argument and returns a mask corresponding to that signal.
.SH "RETURN VALUE"
The previous value of the signal mask is returned from
.BR sigsetmask .
.SH CAVEATS
If somehow the process re-blocks a signal released by 
.BR sigsetmask
before the system signal queue processes it, it will be blocked and marked
as pending.  This can happen if a signal handler makes a 
.BR sigblock
call.
.SH SEE ALSO
.BR kill (2), 
.BR sigblock (2),
.BR signal (2)